Elizium.Loopz.psm1

using module Elizium.Klassy;
using module Elizium.Krayola;
Set-StrictMode -Version 1.0

function Rename-Many {
  <#
  .NAME
    Rename-Many
 
  .SYNOPSIS
    Performs a bulk rename for all file system objects delivered through the pipeline,
  via regular expression replacement.
 
  .DESCRIPTION
    The user should assemble the candidate items from the file system, be they files or
  directories typically using Get-ChildItem, or can be any other function that delivers
  file systems items via the PowerShell pipeline. For each item in the pipeline,
  Rename-Many will perform a rename.
    Rename-Many is a powerful command and should be used with caution. Because of the
  potential of accidental misuse, a number of protections have been put in place:
 
  * By default, the command is locked. This means that the command will not actually
  perform any renames until it has been unlocked by the user. When locked, the command
  runs as though -WhatIf has been specified. There are indications in the output to show
  that the command is in a locked state (there is an indicator in the batch header and
  a 'Novice' indicator in the summary). To activate the command, the user needs to
  set the environment variable 'LOOPZ_REMY_LOCKED' to $false. The user should not
  unlock the command until they are comfortable with how to use this command properly
  and knows how to write regular expressions correctly. (See regex101.com)
 
  * An undo script is generated by default. If the user has invoked a rename operation
  by accident without specifying $WhatIf (or any other WhatIf equivalent like $Diagnose)
  then the user can execute the undo script to reverse the rename operation. The user
  should clearly do this immediately on recognising the error of their ways. In a panic,
  the user may terminate the command via ctrl-c. In this case, a partial undo script is
  still generated and should contain the undo operations for the renames that were
  performed up to the point of the termination request.
    The name of the undo script is based upon the current date and time and is displayed
  in the summary. (The user can, if they wish disable the undo feature if they don't want
  to have to manage the accumulation of undo scripts, by setting the environment variable
  LOOPZ_REMY_UNDO_DISABLED to $true)
 
  Another important point of note is that there are currently 3 modes of operation:
  'move', 'update' or 'cut':
  * 'move': requires an anchor, which may be an $Anchor pattern or
    either $Start or $End switches.
  * 'update': requires $With or $Paste without an anchor.
  * 'cut': no anchor or $With/$Paste specified, the $Pattern match is simply removed
    from the name.
 
  The following regular expression parameters:
  * $Pattern
  * $Anchor
  * $Copy
  can optionally have an occurrence value specified that can be used to select which
  match is active. In the case where a provided expression has multiple matches, the
  occurrence value can be used to single out which one. When no occurrence is specified,
  the default is the first match only. The occurrence for a parameter can be:
 
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
  * *: all occurrences. The wild card occurrence can only be used with 'update' or 'cut' operations
  (it doesn't make sense for example to 'move' all occurrences of a pattern to the anchor)
  The occurrence is specified after the regular expression eg:
  -Pattern '\w\d{2,3}', l
    which means match the Last occurrence of the expression.
  (Actually, an occurrence may be specified for $Include and $Exclude but there is no
  point in doing so because these patterns only provide a filtering function and play
  no part in the actual renaming process).
 
    A note about escaping. If a pattern needs to use an regular expression character as
  a literal, it must be escaped. There are multiple ways of doing this:
  * use the 'esc' function; eg: -Pattern $($esc('(\d{2})'))
  * use a leading ~; -Pattern '~(123)'
 
  The above 2 approaches escape the entire string. The second approach is more concise
  and avoids the necessary use of extra brackets and $.
  * use 'esc' alongside other string concatenation:
    eg: -Pattern $($esc('(123)') + '-(?<ccy>GBP|SEK)').
  This third method is required when the whole pattern should not be subjected to
  escaping.
 
  .PARAMETER Anchor
    Indicates that the rename operation will be a move of the token from its original point
  to the point indicated by Anchor. Anchor is a regular expression string applied to the
  pipeline item's name (after the $Pattern match has been removed). The $Pattern match that
  is removed is inserted at the position indicated by the anchor match in collaboration with
  the $Relation parameter.
 
  .PARAMETER Condition
    Provides another way of filtering pipeline items. This is not typically specified on the
  command line, rather it is meant for those wanting to build functionality on top of Rename-Many.
 
  .PARAMETER Context
    Provides another way of customising Rename-Many. This is not typically specified on the
  command line, rather it is meant for those wanting to build functionality on top of Rename-Many.
  $Context should be a PSCustomObject with the following note properties:
  * Title (default: 'Rename') the name used in the batch header.
  * ItemMessage (default: 'Rename Item') the operation name used for each renamed item.
  * SummaryMessage (default: 'Rename Summary') the name used in the batch summary.
  * Locked (default: 'LOOPZ_REMY_LOCKED) the name of the environment variable which controls
    the locking of the command.
  * DisabledEnVar (default: 'LOOPZ_REMY_UNDO_DISABLED') the name of the environment variable
    which controls if the undo script feature is disabled.
  * UndoDisabledEnVar (default: 'LOOPZ_REMY_UNDO_DISABLED') the name of the environment
    variable which determines if the Undo feature is disabled. This allows any other function
    built on top of Rename-Many to control the undo feature for itself independently of
    Rename-Many.
 
  .PARAMETER Copy
    Regular expression string applied to the pipeline item's name (after the $Pattern match
  has been removed), indicating a portion which should be copied and re-inserted (via the
  $Paste parameter; see $Paste or $With). Since this is a regular expression to be used in
  $Paste/$With, there is no value in the user specifying a static pattern, because that
  static string can just be defined in $Paste/$With. The value in the $Copy parameter comes
  when a generic pattern is defined eg \d{3} (is non static), specifies any 3 digits as
  opposed to say '123', which could be used directly in the $Paste/$With parameter without
  the need for $Copy. The match defined by $Copy is stored in special variable ${_c} and
  can be referenced as such from $Paste and $With.
 
  .PARAMETER Diagnose
    switch parameter that indicates the command should be run in WhatIf mode. When enabled
  it presents additional information that assists the user in correcting the un-expected
  results caused by an incorrect/un-intended regular expression. The current diagnosis
  will show the contents of named capture groups that they may have specified. When an item
  is not renamed (usually because of an incorrect regular expression), the user can use the
  diagnostics along side the 'Not Renamed' reason to track down errors. When $Diagnose has
  been specified, $WhatIf does not need to be specified.
 
  .PARAMETER Directory
    switch to indicate only Directory items in the pipeline will be processed. If neither
  this switch or the File switch are specified, then both File and Directory items
  are processed.
 
  .PARAMETER Drop
    A string parameter (only applicable to move operations, ie Anchor/Star/End) that defines
  what text is used to replace the Pattern match. So in this use-case, the user wants to
  move a particular token/pattern to another part of the name and at the same time drop a
  static string in the place where the $Pattern was removed from.
 
  .PARAMETER End
    Is another type of anchor used instead of $Anchor and specifies that the $Pattern match
  should be moved to the end of the new name.
 
  .PARAMETER Except
    Regular expression string applied to the original pipeline item's name (before the $Pattern
  match has been removed). Allows the user to exclude some items that have been fed in via the
  pipeline. Those items that match the exclusion are skipped during the rename batch.
 
  .PARAMETER File
    switch to indicate only File items in the pipeline will be processed. If neither
  this switch or the Directory switch are specified, then both File and Directory items
  are processed.
 
  .PARAMETER Include
    Regular expression string applied to the original pipeline item's name (before the $Pattern
  match has been removed). Allows the user to include some items that have been fed in via the
  pipeline. Only those items that match $Include pattern are included during the rename batch,
  the others are skipped. The value of the Include parameter comes when you want to define
  a pattern which pipeline items match, without it be removed from the original name, which is
  what happens with $Pattern. Eg, the user may want to specify the only items that should be
  considered a candidate to be renamed are those that match a particular pattern but doing so
  in $Pattern would simply remove that pattern. That may be ok, but if it's not, the user should
  specify a pattern in the $Include and use $Pattern for the match you do want to be moved
  (with Anchor/Start/End) or replaced (with $With/$Paste).
 
  .PARAMETER Paste
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $With parameter. When $Paste is defined, the $Anchor (if specified) is removed
  from the original name and needs to be be re-inserted using the special variable ${_a}. The
  other special variables that can be used inside a $Paste string is documented under the $With
  parameter.
    The $Paste string can specify a format that defines the replacement and since it removes the
  $Anchor, the $Relation is not applicable ($Relation and $Paste can't be used together).
 
  .PARAMETER Pattern
    Regular expression string that indicates which part of the pipeline items' name that
  either needs to be moved or replaced as part of bulk rename operation. Those characters
  in the name which match are removed from the name.
    The pattern can be followed by an occurrence indicator. As the $Pattern parameter is
  strictly speaking an array, the user can specify the occurrence after the regular
  expression eg:
    $Pattern '(?<code>\w\d{2})', l
 
    => This indicates that the last match should be captured into named group 'code'.
 
  .PARAMETER Relation
    Used in conjunction with the $Anchor parameter and can be set to either 'before' or
  'after' (the default). Defines the relationship of the $pattern match with the $Anchor
  match in the new name for the pipeline item.
 
  .PARAMETER Start
    Is another type of anchor used instead of $Anchor and specifies that the $Pattern match
  should be moved to the start of the new name.
 
  .PARAMETER Top
    A number indicating how many items to process. If it is known that the number of items
  that will be candidates to be renamed is large, the user can limit this is the first $Top
  number of items. This is typically used as an exploratory tool, to determine the effects
  of the rename operation.
 
  .PARAMETER Transform
    A script block which is given the chance to perform a modification to the finally named
  item. The transform is invoked prior to post-processing, so that the post-processing rules
  are not breached and the transform does not have to worry about breaking them. The transform
  function's signature is as follows:
 
  * Original: original item's name
  * Renamed: new name
  * CapturedPattern: pattern capture
 
  and should return the new name. If the transform does not change the name, it should return
  an empty string.
 
  .PARAMETER Whole
    Provides an alternative way to indicate that the regular expression parameters
  should be treated as a whole word (it just wraps the expression inside \b tokens).
  If set to '*', then it applies to all expression parameters otherwise a single letter
  can specify which of the parameters 'Whole' should be applied to. Valid values are:
 
  * 'p': $Pattern
  * 'a': $Anchor
  * 'c': $Copy
  * 'i': $Include
  * 'x': $Exclude
  * '*': All the above
  (NB: Currently, can't be set to more than 1 of the above items at a time)
 
  .PARAMETER With
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $Paste parameter. Defines what text is used as the replacement for the $Pattern
  match. Works in concert with $Relation (whereas $Paste does not). $With can reference special
  variables:
 
  * $0: the pattern match
  * ${_a}: the anchor match
  * ${_c}: the copy match
 
  When $Pattern contains named capture groups, these variables can also be referenced. Eg if the
  $Pattern is defined as '(?<day>\d{1,2})-(?<mon>\d{1,2})-(?<year>\d{4})', then the variables
  ${day}, ${mon} and ${year} also become available for use in $With or $Paste.
  Typically, $With is static text which is used to replace the $Pattern match and is inserted
  according to the Anchor match, (or indeed $Start or $End) and $Relation. When using $With,
  whatever is defined in the $Anchor match is not removed from the pipeline's name (this is
  different to how $Paste works).
    If neither $With or Paste have been specified, then the rename operation becomes a 'Cut'
  operation and will be indicated as such in the batch summary.
 
  .PARAMETER underscore
    The pipeline item which should either be an instance of FileInfo or DirectoryInfo.
 
  .EXAMPLE 1
  Move a static string before anchor (consider file items only):
  gci ... | Rename-Many -File -Pattern 'data' -Anchor 'loopz' -Relation 'before'
 
  .EXAMPLE 2
  Move last occurrence of whole-word static string before anchor:
  gci ... | Rename-Many -Pattern 'data',l -Anchor 'loopz' -Relation 'before' -Whole p
 
  .EXAMPLE 3
  Move a static string before anchor and drop (consider Directory items only):
  gci ... | Rename-Many -Directory -Pattern 'data' -Anchor 'loopz' -Relation 'before' -Drop '-'
 
  .EXAMPLE 4
  Update a static string using $With (consider file items only):
  gci ... | Rename-Many -File -Pattern 'data' -With 'info'
 
  .EXAMPLE 5
  Update last occurrence of whole-word static string using $With:
  gci ... | Rename-Many -Pattern 'data',l -With 'info' -Whole p
 
  .EXAMPLE 6
  Update a static string using $Paste:
  gci ... | Rename-Many -Pattern 'data' -Paste '_info_'
 
  .EXAMPLE 7
  Update last occurrence of whole-word static string using $Paste:
  gci ... | Rename-Many -Pattern 'data',l -Whole p -Paste '_info_'
 
  .EXAMPLE 8
  Move a match before anchor:
  gci ... | Rename-Many -Pattern '\d{2}-data' -Anchor 'loopz' -Relation 'before'
 
  .EXAMPLE 9
  Move last occurrence of whole-word static string before anchor:
  gci ... | Rename-Many -Pattern '\d{2}-data',l -Anchor 'loopz' -Relation 'before' -Whole p
 
  .EXAMPLE 10
  Move a match before anchor and drop:
  gci ... | Rename-Many -Pattern '\d{2}-data' -Anchor 'loopz' -Relation 'before' -Drop '-'
 
  .EXAMPLE 11
  Update a match using $With:
  gci ... | Rename-Many -Pattern '\d{2}-data' -With 'info'
 
  .EXAMPLE 12
  Update last occurrence of whole-word match using $With:
  gci ... | Rename-Many -Pattern '\d{2}-data',l -With 'info' -Whole p
 
  .EXAMPLE 13
  Update match contain named capture group using $With:
  gci ... | Rename-Many -Pattern '(?<day>\d{2})-(?<mon>\d{2})-(?<year>\d{2})'
    -With '(${year})-(${mon})-(${day})'
 
  .EXAMPLE 14
  Update 2nd occurrence of whole-word match using $Paste and preserve anchor:
  gci ... | Rename-Many -Pattern '\d{2}-data', l -Paste '${_a}_info_'
 
  .EXAMPLE 15
  Update match contain named capture group using $Paste and preserve the anchor:
  gci ... | Rename-Many -Pattern (?<day>\d{2})-(?<mon>\d{2})-(?<year>\d{2})
    -Paste '(${year})-(${mon})-(${day}) ${_a}'
 
  .EXAMPLE 16
  Update match contain named capture group using $Paste and preserve the anchor and copy
  whole last occurrence:
  gci ... | Rename-Many -Pattern (?<day>\d{2})-(?<mon>\d{2})-(?<year>\d{2})
    -Copy '[A-Z]{3}',l -Whole c -Paste 'CCY_${_c} (${year})-(${mon})-(${day}) ${_a}'
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSShouldProcess', '',
    Justification = 'WhatIf IS accessed and passed into Exchange')]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingEmptyCatchBlock', '')]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
  [CmdletBinding(SupportsShouldProcess, DefaultParameterSetName = 'ReplaceWith')]
  [Alias('remy')]
  param
  (
    # Defining parameter sets for File and Directory, just to ensure both of these switches
    # are mutually exclusive makes the whole parameter set definition exponentially more
    # complex. It's easier just to enforce this with a ValidateScript.
    #
    [Parameter()]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('Directory')); })]
    [switch]$File,

    [Parameter()]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('File')); })]
    [switch]$Directory,

    [Parameter(Mandatory, ValueFromPipeline = $true)]
    [System.IO.FileSystemInfo]$underscore,

    [Parameter()]
    [ValidateSet('p', 'a', 'c', 'i', 'x', '*')]
    [string]$Whole,

    [Parameter(Mandatory, Position = 0)]
    [ValidateScript( { { $(test-ValidPatternArrayParam -Arg $_ -AllowWildCard ) } })]
    [array]$Pattern,

    [Parameter(ParameterSetName = 'MoveToAnchor', Mandatory)]
    [ValidateScript( { $(test-ValidPatternArrayParam -Arg $_) })]
    [array]$Anchor,

    [Parameter(ParameterSetName = 'MoveToAnchor')]
    [ValidateSet('before', 'after')]
    [string]$Relation = 'after',

    [Parameter(ParameterSetName = 'MoveToAnchor')]
    [Parameter(ParameterSetName = 'ReplaceWith')]
    [ValidateScript( { { $(test-ValidPatternArrayParam -Arg $_) } })]
    [array]$Copy,

    [Parameter(ParameterSetName = 'ReplaceLiteralWith', Mandatory)]
    [string]$With,

    [Parameter()]
    [Alias('x')]
    [string]$Except = [string]::Empty,

    [Parameter()]
    [Alias('i')]
    [string]$Include,

    [Parameter()]
    [scriptblock]$Condition = ( { return $true; }),

    # Both Start & End are members of ReplaceWith, but they shouldn't be supplied at
    # the same time. So how to prevent this? Use ValidateScript instead.
    #
    [Parameter(ParameterSetName = 'ReplaceWith')]
    [Parameter(ParameterSetName = 'MoveToStart', Mandatory)]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('End')); })]
    [switch]$Start,

    [Parameter(ParameterSetName = 'ReplaceWith')]
    [Parameter(ParameterSetName = 'MoveToEnd', Mandatory)]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('Start')); })]
    [switch]$End,

    [Parameter()]
    [string]$Paste,

    [Parameter()]
    [PSCustomObject]$Context = $Loopz.Defaults.Remy.Context,

    [Parameter()]
    [switch]$Diagnose,

    [Parameter()]
    [string]$Drop,

    [Parameter()]
    [ValidateScript( { $_ -gt 0 } )]
    [int]$Top,

    [Parameter()]
    [scriptblock]$Transform
  )

  begin {
    Write-Debug ">>> Rename-Many [ParameterSet: '$($PSCmdlet.ParameterSetName)]' >>>";

    function get-fixedIndent {
      [OutputType([int])]
      param(
        [Parameter()]
        [hashtable]$Theme,

        [Parameter()]
        [string]$Message = [string]::Empty
      )
      [int]$indent = $Message.Length;

      # 1 2 3 4
      # 1234567890123456789012345678901234567890
      # [🏷️] Rename Item // ["No" => " 1",
      # |<-- fixed bit -->|
      #
      $indent += $Theme['MESSAGE-SUFFIX'].Length;
      $indent += $Theme['OPEN'].Length;
      $indent += $Theme['FORMAT'].Replace($Theme['KEY-PLACE-HOLDER'], "No").Replace(
        $Theme['VALUE-PLACE-HOLDER'], '999').Length;
      $indent += $Theme['SEPARATOR'].Length;
      return $indent;
    }

    [scriptblock]$doRenameFsItems = {
      [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
      param(
        [Parameter(Mandatory)]
        [System.IO.FileSystemInfo]$_underscore,

        [Parameter(Mandatory)]
        [int]$_index,

        [Parameter(Mandatory)]
        [hashtable]$_exchange,

        [Parameter(Mandatory)]
        [boolean]$_trigger
      )

      [boolean]$itemIsDirectory = ($_underscore.Attributes -band
        [System.IO.FileAttributes]::Directory) -eq [System.IO.FileAttributes]::Directory;

      $endAdapter = New-EndAdapter($_underscore);
      [string]$adjustedName = $endAdapter.GetAdjustedName();

      [string]$action = $_exchange['LOOPZ.REMY.ACTION'];

      [hashtable]$actionParameters = @{
        'Value'   = $adjustedName;
        'Pattern' = $_exchange['LOOPZ.REMY.PATTERN-REGEX'];
      }

      [boolean]$performDiagnosis = ($_exchange.ContainsKey('LOOPZ.DIAGNOSE') -and
        $_exchange['LOOPZ.DIAGNOSE']);

      $actionParameters['PatternOccurrence'] = $_exchange.ContainsKey('LOOPZ.REMY.PATTERN-OCC') `
        ? $_exchange['LOOPZ.REMY.PATTERN-OCC'] : 'f';

      if ($_exchange.ContainsKey('LOOPZ.REMY.COPY')) {
        $actionParameters['Copy'] = $_exchange['LOOPZ.REMY.COPY'];

        if ($_exchange.ContainsKey('LOOPZ.REMY.COPY-OCC')) {
          $actionParameters['CopyOccurrence'] = $_exchange['LOOPZ.REMY.COPY-OCC'];
        }
      }
      elseif ($_exchange.ContainsKey('LOOPZ.REMY.WITH')) {
        $actionParameters['With'] = $_exchange['LOOPZ.REMY.WITH'];
      }

      if ($_exchange.ContainsKey('LOOPZ.REMY.PASTE')) {
        $actionParameters['Paste'] = $_exchange['LOOPZ.REMY.PASTE']
      }

      if ($performDiagnosis) {
        $actionParameters['Diagnose'] = $_exchange['LOOPZ.DIAGNOSE']
      }

      if ($action -eq 'Move-Match') {
        if ($_exchange.ContainsKey('LOOPZ.REMY.ANCHOR')) {
          $actionParameters['Anchor'] = $_exchange['LOOPZ.REMY.ANCHOR'];
        }
        if ($_exchange.ContainsKey('LOOPZ.REMY.ANCHOR-OCC')) {
          $actionParameters['AnchorOccurrence'] = $_exchange['LOOPZ.REMY.ANCHOR-OCC'];
        }

        if ($_exchange.ContainsKey('LOOPZ.REMY.DROP')) {
          $actionParameters['Drop'] = $_exchange['LOOPZ.REMY.DROP'];
          $actionParameters['Marker'] = $_exchange['LOOPZ.REMY.MARKER'];
        }

        switch ($_exchange['LOOPZ.REMY.ANCHOR-TYPE']) {
          'MATCHED-ITEM' {
            if ($_exchange.ContainsKey('LOOPZ.REMY.RELATION')) {
              $actionParameters['Relation'] = $_exchange['LOOPZ.REMY.RELATION'];
            }
            break;
          }
          'START' {
            $actionParameters['Start'] = $true;
            break;
          }
          'END' {
            $actionParameters['End'] = $true;
            break;
          }
          default {
            throw "doRenameFsItems: encountered Invalid 'LOOPZ.REMY.ANCHOR-TYPE': '$AnchorType'";
          }
        }
      } # $action

      [line]$properties = [line]::new();
      [line[]]$lines = @();
      [hashtable]$signals = $_exchange['LOOPZ.SIGNALS'];

      # Perform Rename Action, then post process
      #
      [PSCustomObject]$actionResult = & $action @actionParameters;
      [string]$newItemName = $actionResult.Payload;

      if ($_exchange.ContainsKey('LOOPZ.REMY.TRANSFORM')) {
        [scriptblock]$transform = $_exchange['LOOPZ.REMY.TRANSFORM'];

        if ($transform) {
          [string]$transformed = $transform.InvokeReturnAsIs(
            $_underscore.Name, $newItemName, $actionResult.CapturedPattern);

          if (-not([string]::IsNullOrEmpty($transformed))) {
            $newItemName = $transformed;
          }
        }
      }

      $postResult = invoke-PostProcessing -InputSource $newItemName -Rules $Loopz.Rules.Remy `
        -Signals $signals;

      if ($postResult.Modified) {
        [couplet]$postSignal = Get-FormattedSignal -Name 'REMY.POST' `
          -Signals $signals -Value $postResult.Indication -CustomLabel $postResult.Label;
        $properties.append($postSignal);
        $newItemName = $postResult.TransformResult;
      }

      $newItemName = $endAdapter.GetNameWithExtension($newItemName);
      Write-Debug "Rename-Many; New Item Name: '$newItemName'";

      [boolean]$trigger = $false;
      [boolean]$affirm = $false;
      [boolean]$whatIf = $_exchange.ContainsKey('WHAT-IF') -and ($_exchange['WHAT-IF']);

      [string]$parent = $itemIsDirectory ? $_underscore.Parent.FullName : $_underscore.Directory.FullName;
      [boolean]$nameHasChanged = -not($_underscore.Name -ceq $newItemName);
      [string]$newItemFullPath = Join-Path -Path $parent -ChildPath $newItemName;
      [boolean]$clash = (Test-Path -LiteralPath $newItemFullPath) -and $nameHasChanged;
      [string]$fileSystemItemType = $itemIsDirectory ? 'Directory' : 'File';

      [PSCustomObject]$context = $_exchange['LOOPZ.REMY.CONTEXT'];
      [int]$maxItemMessageSize = $_exchange['LOOPZ.REMY.MAX-ITEM-MESSAGE-SIZE'];
      [string]$normalisedItemMessage = $Context.ItemMessage.replace(
        $Loopz.FsItemTypePlaceholder, $fileSystemItemType);

      [string]$messageLabel = if ($context.psobject.properties.match('ItemMessage') -and `
          -not([string]::IsNullOrEmpty($Context.ItemMessage))) {

        Get-PaddedLabel -Label $($Context.ItemMessage.replace(
            $Loopz.FsItemTypePlaceholder, $fileSystemItemType)) -Width $maxItemMessageSize;
      }
      else {
        $normalisedItemMessage;
      }

      [string]$signalName = $itemIsDirectory ? 'DIRECTORY-A' : 'FILE-A';
      [string]$message = Get-FormattedSignal -Name $signalName `
        -Signals $signals -CustomLabel $messageLabel -Format ' [{1}] {0}';

      [int]$indent = $_exchange['LOOPZ.REMY.FIXED-INDENT'] + $message.Length;
      $_exchange['LOOPZ.WH-FOREACH-DECORATOR.INDENT'] = $indent;
      $_exchange['LOOPZ.WH-FOREACH-DECORATOR.MESSAGE'] = $message;
      $_exchange['LOOPZ.WH-FOREACH-DECORATOR.PRODUCT-LABEL'] = $(Get-PaddedLabel -Label $(
          $fileSystemItemType) -Width 9);

      if ($nameHasChanged -and -not($clash)) {
        $trigger = $true;

        [UndoRename]$operant = $_exchange.ContainsKey('LOOPZ.REMY.UNDO') `
          ? $_exchange['LOOPZ.REMY.UNDO'] : $null;

        $product = rename-FsItem -From $_underscore -To $newItemName -WhatIf:$whatIf -UndoOperant $operant;
      }
      else {
        $product = $_underscore;
      }

      if ($trigger) {
        $null = $lines += (New-Line(
            New-Pair(@($_exchange['LOOPZ.REMY.FROM-LABEL'], $_underscore.Name))
          ));
      }
      else {
        if ($clash) {
          Write-Debug "!!! doRenameFsItems; path: '$newItemFullPath' already exists, rename skipped";
          [couplet]$clashSignal = Get-FormattedSignal -Name 'CLASH' `
            -Signals $signals -EmojiAsValue -EmojiOnlyFormat '{0}';
          $properties.append($clashSignal);
        }
        else {
          [couplet]$notActionedSignal = Get-FormattedSignal -Name 'NOT-ACTIONED' `
            -Signals $signals -EmojiAsValue -CustomLabel 'Not Renamed' -EmojiOnlyFormat '{0}';
          $properties.append($notActionedSignal);
        }
      }

      if (-not($actionResult.Success)) {
        [couplet]$failedSignal = Get-FormattedSignal -Name 'FAILED-A' `
          -Signals $signals -Value $actionResult.FailedReason;
        $properties.append($failedSignal);
      }

      # Do diagnostics
      #
      if ($performDiagnosis -and $actionResult.Diagnostics.Named -and
        ($actionResult.Diagnostics.Named.Count -gt 0)) {

        [string]$diagnosticEmoji = Get-FormattedSignal -Name 'DIAGNOSTICS' -Signals $signals `
          -EmojiOnly;

        [string]$captureEmoji = Get-FormattedSignal -Name 'CAPTURE' -Signals $signals `
          -EmojiOnly -EmojiOnlyFormat '[{0}]';

        foreach ($namedItem in $actionResult.Diagnostics.Named) {
          foreach ($namedKey in $namedItem.Keys) {
            [hashtable]$groups = $actionResult.Diagnostics.Named[$namedKey];
            [string[]]$diagnosticLines = @();

            foreach ($groupName in $groups.Keys) {
              [string]$captured = $groups[$groupName];
              [string]$compoundValue = "({0} <{1}>)='{2}'" -f $captureEmoji, $groupName, $captured;
              [string]$namedLabel = Get-PaddedLabel -Label ($diagnosticEmoji + $namedKey);

              $diagnosticLines += $compoundValue;
            }
            $null = $lines += (New-Line(
                New-Pair(@($namedLabel, $($diagnosticLines -join ', ')))
              ));
          }
        }
      }

      if ($whatIf) {
        [couplet]$whatIfSignal = Get-FormattedSignal -Name 'WHAT-IF' `
          -Signals $signals -EmojiAsValue -EmojiOnlyFormat '{0}';
        $properties.append($whatIfSignal);
      }

      [PSCustomObject]$result = [PSCustomObject]@{
        Product = $product;
      }

      $result | Add-Member -MemberType NoteProperty -Name 'Pairs' -Value $properties;

      if ($lines.Length -gt 0) {
        $result | Add-Member -MemberType NoteProperty -Name 'Lines' -Value $lines;
      }

      if ($trigger) {
        $result | Add-Member -MemberType NoteProperty -Name 'Trigger' -Value $true;
      }

      [boolean]$differsByCaseOnly = $newItemName.ToLower() -eq $_underscore.Name.ToLower();
      [boolean]$affirm = $trigger -and ($product) -and -not($differsByCaseOnly);
      if ($affirm) {
        $result | Add-Member -MemberType NoteProperty -Name 'Affirm' -Value $true;
      }

      return $result;
    } # doRenameFsItems

    [System.IO.FileSystemInfo[]]$collection = @();
  } # begin

  process {
    Write-Debug "=== Rename-Many [$($underscore.Name)] ===";

    $collection += $underscore;
  }

  end {
    Write-Debug '<<< Rename-Many <<<';

    [boolean]$locked = Get-IsLocked -Variable $(
      [string]::IsNullOrEmpty($Context.Locked) ? 'LOOPZ_REMY_LOCKED' : $Context.Locked
    );
    [boolean]$whatIf = $PSBoundParameters.ContainsKey('WhatIf') -or $locked;
    [PSCustomObject]$containers = @{
      Wide  = [line]::new();
      Props = [line]::new();
    }

    [string]$adjustedWhole = if ($PSBoundParameters.ContainsKey('Whole')) {
      $Whole.ToLower();
    }
    else {
      [string]::Empty;
    }

    [hashtable]$signals = $(Get-Signals);

    # RegEx/Occurrence parameters
    #
    [string]$patternExpression, [string]$patternOccurrence = Resolve-PatternOccurrence $Pattern

    Select-SignalContainer -Containers $containers -Name 'PATTERN' `
      -Value $patternExpression -Signals $signals;

    if ($PSBoundParameters.ContainsKey('Anchor')) {
      [string]$anchorExpression, [string]$anchorOccurrence = Resolve-PatternOccurrence $Anchor

      Select-SignalContainer -Containers $containers -Name 'REMY.ANCHOR' `
        -Value $anchorExpression -Signals $signals -CustomLabel $('Anchor ({0})' -f $Relation);
    }

    if ($PSBoundParameters.ContainsKey('Copy')) {
      [string]$copyExpression, [string]$copyOccurrence = Resolve-PatternOccurrence $Copy;

      Select-SignalContainer -Containers $containers -Name 'COPY-A' `
        -Value $copyExpression -Signals $signals;
    }
    elseif ($PSBoundParameters.ContainsKey('With')) {
      if (-not([string]::IsNullOrEmpty($With))) {

        Select-SignalContainer -Containers $containers -Name 'WITH' `
          -Value $With -Signals $signals;
      }
      elseif (-not($PSBoundParameters.ContainsKey('Paste'))) {

        Select-SignalContainer -Containers $containers -Name 'CUT-A' `
          -Value $patternExpression -Signals $signals -Force 'Props';
      }
    }

    if ($PSBoundParameters.ContainsKey('Include')) {
      [string]$includeExpression, [string]$includeOccurrence = Resolve-PatternOccurrence $Include;

      Select-SignalContainer -Containers $containers -Name 'INCLUDE' `
        -Value $includeExpression -Signals $signals;
    }

    if ($PSBoundParameters.ContainsKey('Diagnose')) {
      [string]$switchOnEmoji = $signals['SWITCH-ON'].Value;

      [couplet]$diagnosticsSignal = Get-FormattedSignal -Name 'DIAGNOSTICS' `
        -Signals $signals -Value $('[{0}]' -f $switchOnEmoji);

      $containers.Props.Line += $diagnosticsSignal;
    }

    [boolean]$doMoveToken = ($PSBoundParameters.ContainsKey('Anchor') -or
      $PSBoundParameters.ContainsKey('Start') -or $PSBoundParameters.ContainsKey('End'));

    if ($doMoveToken -and ($patternOccurrence -eq '*')) {
      [string]$errorMessage = "'Pattern' wildcard prohibited for move operation (Anchor/Start/End).`r`n";
      $errorMessage += "Please use a digit, 'f' (first) or 'l' (last) for Pattern Occurrence";
      Write-Error $errorMessage -ErrorAction Stop;
    }

    [boolean]$doCut = (
      -not($doMoveToken) -and
      -not($PSBoundParameters.ContainsKey('Copy')) -and
      -not($PSBoundParameters.ContainsKey('With')) -and
      -not($PSBoundParameters.ContainsKey('Paste'))
    )

    if ($doCut) {
      Select-SignalContainer -Containers $containers -Name 'CUT-A' `
        -Value $patternExpression -Signals $signals -Force 'Props';
    }

    if ($PSBoundParameters.ContainsKey('Paste')) {
      if (-not(Test-IsFileSystemSafe -Value $Paste)) {
        throw [System.ArgumentException]::new("Paste parameter ('$Paste') contains unsafe characters")
      }
      if (-not([string]::IsNullOrEmpty($Paste))) {
        Select-SignalContainer -Containers $containers -Name 'PASTE-A' `
          -Value $Paste -Signals $signals;
      }
    }

    [scriptblock]$getResult = {
      param($result)

      $result.GetType() -in @([System.IO.FileInfo], [System.IO.DirectoryInfo]) ? $result.Name : $result;
    }

    [regex]$patternRegEx = New-RegularExpression -Expression $patternExpression `
      -WholeWord:$(-not([string]::IsNullOrEmpty($adjustedWhole)) -and ($adjustedWhole -in @('*', 'p')));

    [string]$title = $Context.psobject.properties.match('Title') -and `
      -not([string]::IsNullOrEmpty($Context.Title)) `
      ? $Context.Title : 'Rename';

    if ($locked) {
      $title = Get-FormattedSignal -Name 'LOCKED' -Signals $signals `
        -Format '{1} {0} {1}' -CustomLabel $('Locked: ' + $title);
    }

    [int]$maxItemMessageSize = $Context.ItemMessage.replace(
      $Loopz.FsItemTypePlaceholder, 'Directory').Length;

    [string]$summaryMessage = $Context.psobject.properties.match('SummaryMessage') -and `
      -not([string]::IsNullOrEmpty($Context.SummaryMessage)) `
      ? $Context.SummaryMessage : 'Rename Summary';

    $summaryMessage = Get-FormattedSignal -Name 'SUMMARY-A' -Signals $signals -CustomLabel $summaryMessage;

    [hashtable]$theme = $(Get-KrayolaTheme);
    [Krayon]$krayon = New-Krayon -Theme $theme;

    [hashtable]$exchange = @{
      'LOOPZ.WH-FOREACH-DECORATOR.BLOCK'      = $doRenameFsItems;
      'LOOPZ.WH-FOREACH-DECORATOR.GET-RESULT' = $getResult;

      'LOOPZ.HEADER-BLOCK.CRUMB-SIGNAL'       = 'CRUMB-A';
      'LOOPZ.HEADER-BLOCK.LINE'               = $LoopzUI.DashLine;
      'LOOPZ.HEADER-BLOCK.MESSAGE'            = $title;

      'LOOPZ.SUMMARY-BLOCK.LINE'              = $LoopzUI.EqualsLine;
      'LOOPZ.SUMMARY-BLOCK.MESSAGE'           = $summaryMessage;

      'LOOPZ.REMY.PATTERN-REGEX'              = $patternRegEx;
      'LOOPZ.REMY.PATTERN-OCC'                = $patternOccurrence;
      'LOOPZ.REMY.CONTEXT'                    = $Context;
      'LOOPZ.REMY.MAX-ITEM-MESSAGE-SIZE'      = $maxItemMessageSize;
      'LOOPZ.REMY.FIXED-INDENT'               = $(get-fixedIndent -Theme $theme);
      'LOOPZ.REMY.FROM-LABEL'                 = Get-PaddedLabel -Label 'From' -Width 9;

      'LOOPZ.SIGNALS'                         = $signals;
      'LOOPZ.KRAYON'                           = $krayon;
    }
    $exchange['LOOPZ.REMY.ACTION'] = $doMoveToken ? 'Move-Match' : 'Update-Match';

    if ($PSBoundParameters.ContainsKey('Copy')) {
      [regex]$copyRegEx = New-RegularExpression -Expression $copyExpression `
        -WholeWord:$(-not([string]::IsNullOrEmpty($adjustedWhole)) -and ($adjustedWhole -in @('*', 'c')));

      $exchange['LOOPZ.REMY.COPY-OCC'] = $copyOccurrence;
      $exchange['LOOPZ.REMY.COPY'] = $copyRegEx;
    }
    elseif ($PSBoundParameters.ContainsKey('With')) {
      if (-not(Test-IsFileSystemSafe -Value $With)) {
        throw [System.ArgumentException]::new("With parameter ('$With') contains unsafe characters")
      }
      $exchange['LOOPZ.REMY.WITH'] = $With;
    }

    if ($PSBoundParameters.ContainsKey('Relation')) {
      $exchange['LOOPZ.REMY.RELATION'] = $Relation;
    }

    # NB: anchoredRegEx refers to whether -Start or -End anchors have been specified,
    # NOT the -Anchor pattern (when ANCHOR-TYPE = 'MATCHED-ITEM') itself.
    #
    [regex]$anchoredRegEx = $null;

    if ($PSBoundParameters.ContainsKey('Anchor')) {

      [regex]$anchorRegEx = New-RegularExpression -Expression $anchorExpression `
        -WholeWord:$(-not([string]::IsNullOrEmpty($adjustedWhole)) -and ($adjustedWhole -in @('*', 'a')));

      $exchange['LOOPZ.REMY.ANCHOR-OCC'] = $anchorOccurrence;
      $exchange['LOOPZ.REMY.ANCHOR-TYPE'] = 'MATCHED-ITEM';
      $exchange['LOOPZ.REMY.ANCHOR'] = $anchorRegEx;
    }
    elseif ($PSBoundParameters.ContainsKey('Start')) {

      Select-SignalContainer -Containers $containers -Name 'REMY.ANCHOR' `
        -Value $signals['SWITCH-ON'].Value -Signals $signals -CustomLabel 'Start' -Force 'Props';

      $exchange['LOOPZ.REMY.ANCHOR-TYPE'] = 'START';

      [regex]$anchoredRegEx = New-RegularExpression `
        -Expression $('^' + $patternExpression);
    }
    elseif ($PSBoundParameters.ContainsKey('End')) {

      Select-SignalContainer -Containers $containers -Name 'REMY.ANCHOR' `
        -Value $signals['SWITCH-ON'].Value -Signals $signals -CustomLabel 'End' -Force 'Props';

      $exchange['LOOPZ.REMY.ANCHOR-TYPE'] = 'END';

      [regex]$anchoredRegEx = New-RegularExpression `
        -Expression $($patternExpression + '$');
    }

    if ($PSBoundParameters.ContainsKey('Drop') -and -not([string]::IsNullOrEmpty($Drop))) {
      Select-SignalContainer -Containers $containers -Name 'REMY.DROP' `
        -Value $Drop -Signals $signals -Force 'Wide';

      $exchange['LOOPZ.REMY.DROP'] = $Drop;
      $exchange['LOOPZ.REMY.MARKER'] = $Loopz.Defaults.Remy.Marker;
    }

    if ($locked) {
      Select-SignalContainer -Containers $containers -Name 'NOVICE' `
        -Value $signals['SWITCH-ON'].Value -Signals $signals -Force 'Wide';
    }

    [boolean]$includeDefined = $PSBoundParameters.ContainsKey('Include');
    [regex]$includeRegEx = $includeDefined `
      ? (New-RegularExpression -Expression $includeExpression `
        -WholeWord:$(-not([string]::IsNullOrEmpty($adjustedWhole)) -and ($adjustedWhole -in @('*', 'i')))) `
      : $null;

    if ($PSBoundParameters.ContainsKey('Paste')) {
      $exchange['LOOPZ.REMY.PASTE'] = $Paste;
    }

    if ($PSBoundParameters.ContainsKey('Transform')) {
      $exchange['LOOPZ.REMY.TRANSFORM'] = $Transform;

      Select-SignalContainer -Containers $containers -Name 'TRANSFORM' `
        -Value $signals['SWITCH-ON'].Value -Signals $signals -Force 'Wide';
    }

    [PSCustomObject]$operantOptions = [PSCustomObject]@{
      ShortCode    = $Context.OperantShortCode;
      OperantName  = 'UndoRename';
      Shell        = 'PoShShell';
      BaseFilename = 'undo-rename';
      DisabledEnVar  = $Context.UndoDisabledEnVar;
    }
    [UndoRename]$operant = Initialize-ShellOperant -Options $operantOptions -DryRun:$whatIf;

    if ($operant) {
      $exchange['LOOPZ.REMY.UNDO'] = $operant;

      Select-SignalContainer -Containers $containers -Name 'REMY.UNDO' `
        -Value $operant.Shell.FullPath -Signals $signals -Force 'Wide';
    }
    else {
      Select-SignalContainer -Containers $containers -Name 'REMY.UNDO' `
        -Value $signals['SWITCH-OFF'].Value -Signals $signals -Force 'Wide';
    }

    if ($containers.Wide.Line.Length -gt 0) {
      $exchange['LOOPZ.SUMMARY-BLOCK.WIDE-ITEMS'] = $containers.Wide;
    }

    if ($containers.Props.Line.Length -gt 0) {
      $exchange['LOOPZ.SUMMARY.PROPERTIES'] = $containers.Props;
    }

    [scriptblock]$clientCondition = $Condition;
    [scriptblock]$compoundCondition = {
      param(
        [System.IO.FileSystemInfo]$pipelineItem
      )

      [boolean]$clientResult = $clientCondition.InvokeReturnAsIs($pipelineItem);
      [boolean]$isAlreadyAnchoredAt = $anchoredRegEx -and $anchoredRegEx.IsMatch($pipelineItem.Name);

      return $($clientResult -and -not($isAlreadyAnchoredAt));
    };

    [regex]$excludedRegEx = [string]::IsNullOrEmpty($Except) `
      ? $null : $(New-RegularExpression -Expression $Except);

    [scriptblock]$matchesPattern = {
      param(
        [System.IO.FileSystemInfo]$pipelineItem
      )
      # Inside the scope of this script block, $Condition is assigned to Invoke-ForeachFsItem's
      # version of the Condition parameter which is this scriptblock and thus results in a stack
      # overflow due to infinite recursion. We need to use a temporary variable so that
      # the client's Condition (Rename-Many) is not accidentally hidden.
      #
      [boolean]$isIncluded = $includeDefined ? $includeRegEx.IsMatch($pipelineItem.Name) : $true;
      return ($patternRegEx.IsMatch($pipelineItem.Name)) -and $isIncluded -and `
      ((-not($excludedRegEx)) -or -not($excludedRegEx.IsMatch($pipelineItem.Name))) -and `
        $compoundCondition.InvokeReturnAsIs($pipelineItem);
    }

    [hashtable]$parameters = @{
      'Condition' = $matchesPattern;
      'Exchange'  = $exchange;
      'Header'    = $LoopzHelpers.HeaderBlock;
      'Summary'   = $LoopzHelpers.SummaryBlock;
      'Block'     = $LoopzHelpers.WhItemDecoratorBlock;
    }

    if ($PSBoundParameters.ContainsKey('File')) {
      $parameters['File'] = $true;
    }
    elseif ($PSBoundParameters.ContainsKey('Directory')) {
      $parameters['Directory'] = $true;
    }

    if ($PSBoundParameters.ContainsKey('Top')) {
      $parameters['Top'] = $Top;
    }

    if ($whatIf -or $Diagnose.ToBool()) {
      $exchange['WHAT-IF'] = $true;
    }

    if ($Diagnose.ToBool()) {
      $exchange['LOOPZ.DIAGNOSE'] = $true;
    }

    try {
      $null = $collection | Invoke-ForeachFsItem @parameters;
    }
    catch {
      # ctrl-c doesn't invoke an exception, it just abandons processing,
      # ending up in the finally block.
      #
      Write-Host $_.Exception.StackTrace;
      Write-Error $_.Exception.Message;
    }
    finally {
      # catch ctrl-c
      if ($operant -and -not($whatIf)) {
        $operant.finalise();
      }
    }
  } # end
} # Rename-Many

function Select-Patterns {
  <#
  .NAME
    Select-Patterns
 
  .SYNOPSIS
    This is a simplified yet enhanced version of standard Select-String command (or
  the grep command on Linux/Unix/mac) that allows the user to run multiple searches
  which are chained together to produce its final result.
 
  .DESCRIPTION
    The main rationale for using this command ("greps" as in multiple grep invokes) instead
  of Select-String, is for the provision of multiple patterns. Now, Select-String does
  allow the user to provide multiple Patterns, but the result is a logical OR rather
  than an AND. greps uses AND by piping the result of each individual Pattern search to
  the next Pattern search so the result is those lines found that match all the patterns
  provided rather than all lines that match 1 or more of the patterns. The user can achieve
  OR functionality by using a | inside the same string; for example to find all lines
  that contain any of the patterns 'red', 'green' or 'blue', they could just use
  'red|green|blue'.
    At the end of the run, greps displays the full command (containing multiple pipeline
  legs, one for each pattern provided). If so required, the user can re-run the command
  by running the full command which is displayed and providing different parameters not
  directly supported by greps.
    'greps', does not currently support input from the pipeline. Perhaps this will be
  implemented in a future release.
    At some point in the future, it is intended to further enhance greps using a coloured
  output, whereby a colour is assigned to each pattern and that colour is used to render the
  result. So where the user has provided multiple patterns, currently, only the first pattern
  is highlighted in the result. With the coloured enhancement, the user will be able to see
  all pattern matches in the result with each match displayed in the corresponding allocated
  colour.
 
  .PARAMETER filter
    Defines which files are considered in the search. It can be a path with a wildcard or
  simply a wildcard. If its just a wildcard (eg *.txt), then files considered will be from
  the current directory only.
    The user can define a default filter in the environment as variable 'LOOPZ_GREPS_FILTER'
  which should be a glob such as '*.txt' to represent all text files. If no filter parameter
  is supplied to the greps invoke, then the filter is defined by the value of
  'LOOPZ_GREPS_FILTER'.
 
  .PARAMETER Patterns
    An array of patterns. The result shows all lines that match all the patterns specified.
  An individual pattern can be prefixed with a not op: '!', which means exclude those lines
  which match the subsequent pattern; it is a more succinct way of specifying the -NotMatch
  operator on Select-String. The '!' is not part of the pattern.
 
  .EXAMPLE 1
    Show lines in all .txt files in the current directory files that contain the patterns
  'red' and 'blue':
  greps red, blue *.txt
 
  .EXAMPLE 2
    Show lines in all .txt files in home directory that contain the patterns 'green lorry' and
  'yellow lorry':
  greps 'green lorry', 'yellow lorry' ~/*.txt
 
  .EXAMPLE 3
    Show lines in all files defined in environment as 'LOOPZ_GREPS_FILTER' that contains
  'foo' but not 'bar':
  greps foo, !bar
   
  #>

  [CmdletBinding()]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidUsingInvokeExpression', '')]
  [Alias("greps")]
  param
  (
    [parameter(Mandatory = $true, Position = 0)]
    [ValidateNotNullOrEmpty()]
    [String[]]$Patterns,

    [parameter(Position = 1)]
    [String]$Filter = $(Get-EnvironmentVariable -Variable 'LOOPZ_GREPS_FILTER' -Default './*.*')
  )
  function build-command {
    [OutputType([string])]
    param(
      [String]$Pattern,
      [String]$Filter,
      [Switch]$Pipe,
      [string]$NotOpSymbol = '!'
    )
    [string]$platform = Get-PlatformName;
    [string]$builder = [string]::Empty;

    if ($Pipe.ToBool()) {
      $builder += ' | ';
    }

    if ($platform -eq 'windows') {
      $builder += 'select-string ';
      if ($pattern.StartsWith($NotOpSymbol)) {
        $builder += ('-notmatch -pattern "{0}" ' -f $Pattern.Substring(1));
      }
      else {
        $builder += ('-pattern "{0}" ' -f $Pattern);
      }
    }
    else {
      $builder += 'grep ';
      if ($pattern.StartsWith($NotOpSymbol)) {
        $builder += ('-v -i "{0}" ' -f $Pattern.Substring(1));
      }
      else {
        $builder += ('-i "{0}" ' -f $Pattern);
      }
    }

    if (-not([string]::IsNullOrWhiteSpace($Filter))) {
      $builder += "$Filter ";
    }

    return $builder;
  } # build-command

  [string]$command = [string]::Empty;
  [int]$count = 0;

  foreach ($pat in $Patterns) {
    $count++;

    if ($count -eq 1) {
      $command = build-command -Pattern $Patterns[0] -Filter $Filter;
    }
    else {
      $segment = build-command -Pipe -Pattern $pat;
      $command += $segment;
    }
  }

  [hashtable]$signals = $(Get-Signals);
  [hashtable]$theme = $(Get-KrayolaTheme);
  [Krayon]$krayon = New-Krayon -Theme $theme;
  [couplet]$formattedSignal = Get-FormattedSignal -Name 'GREPS' -Value $command -Signals $signals;
  Invoke-Expression $command;

  $null = $krayon.blue().Text($formattedSignal.Key). `
    red().Text(' --> '). `
    green().Text($formattedSignal.Value);
}

function Show-Signals {
  <#
  .NAME
    Show-Signals
 
  .SYNOPSIS
    Shows all defined signals, including user defined signals.
 
  .DESCRIPTION
    User can override signal definitions in their profile, typically using the provided
  function Update-CustomSignals.
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidGlobalVars', '')]
  param(
    [Parameter()]
    [hashtable]$SourceSignals = $(Get-Signals),

    [Parameter()]
    [hashtable]$Custom = $global:Loopz.CustomSignals
  )
  $result = $SourceSignals;

  [hashtable]$collection = @{}
  $result.GetEnumerator() | ForEach-Object {

    $collection[$_.Key] = [PSCustomObject]@{
      Label  = $_.Value.Key;
      Icon   = $_.Value.Value;
      Length = $_.Value.Value.Length
    }
  }

  # result is array, because of the sort
  #
  $result = $collection.GetEnumerator() | Sort-Object -Property Name;

  return $result;
}

function Update-CustomSignals {
  param(
    [Parameter(Mandatory)]
    [hashtable]$Signals
  )

  if ($Signals -and ($Signals.Count -gt 0)) {
    if ($Loopz) {
      if (-not($Loopz.CustomSignals)) {
        $Loopz.CustomSignals = @{}
      }

      $Signals.GetEnumerator() | ForEach-Object {
        if ($_.Value -and ($_.Value -is [couplet])) {
          $Loopz.CustomSignals[$_.Key] = $_.Value;
        }
        else {
          Write-Warning "Loopz: Skipping custom signal('$($_.Key)'); not a valid couplet/pair: -->$($_.Value)<--";
        }
      }
    }
  }
}

function Format-Escape {
  <#
  .NAME
    Format-Escape
 
  .SYNOPSIS
    Escapes the regular expression specified. This is just a wrapper around the
  .net regex::escape method, but gives the user a much easier way to
  invoke it from the command line.
 
  .DESCRIPTION
    Various functions in Loopz have parameters that accept a regular expression. This
  function gives the user an easy way to escape the regex, without them having to do
  this manually themselves which could be tricky to get right depending on their
  requirements.
 
.PARAMETER Source
    The source string to escape.
 
  #>

  [Alias('esc')]
  [OutputType([string])]
  param(
    [Parameter(Position = 0, Mandatory)]$Source
  )
  [regex]::Escape($Source);
}

function Get-FormattedSignal {
  <#
  .NAME
    Get-FormattedSignal
 
  .SYNOPSIS
    Controls and standardises the way that signals are displayed.
 
  .DESCRIPTION
    This function enables the display of key/value pairs where the key includes
  an emoji. The value may also include the emoji depending on how the function
  is used.
    Generally, this function returns either a Pair object or a single string.
  The user can define a format string (or simply use the default) which controls
  how the signal is displayed. If the function is invoked without a Value, then
  a formatted string is returned, otherwise a pair object is returned.
 
  .PARAMETER CustomLabel
    An alternative label to display overriding the signal's defined label.
 
  .PARAMETER EmojiAsValue
    switch which changes the result so that the emoji appears as part of the
  value as opposed to the key.
 
  .PARAMETER EmojiOnly
    Changes what is returned, to be a single value only, formatted as EmojiOnlyFormat.
 
  .PARAMETER EmojiOnlyFormat
    When the switch EmojiOnly is enabled, EmojiOnlyFormat defines the format used to create
  the result. Should contain at least 1 occurrence of {1} representing the
  emoji.
 
  .PARAMETER Format
    A string defining the format defining how the signal is displayed. Should
  contain either {0} representing the signal's emoji or {1} the label. They
  can appear as many time as is required, but there should be at least either
  one of these.
 
  .PARAMETER Name
    The name of the signal
 
  .PARAMETER Signals
    The signals hashtable collection from which to select the signal from.
 
  .PARAMETER Value
    A string defining the Value displayed when the signal is a Key/Value pair.
 
  #>

  param(
    [Parameter(Mandatory)]
    [string]$Name,

    [Parameter()]
    [string]$Format = '[{1}] {0}', # 0=Label, 1=Emoji

    [Parameter()]
    [string]$Value,

    [Parameter()]
    [hashtable]$Signals = $(Get-Signals),

    [Parameter()]
    [string]$CustomLabel,

    [Parameter()]
    [string]$EmojiOnlyFormat = '[{0}] ',

    [Parameter()]
    [switch]$EmojiOnly,

    [Parameter()]
    [switch]$EmojiAsValue
  )

  [couplet]$signal = $Signals.ContainsKey($Name) `
    ? $Signals[$Name] `
    : $(New-Pair(@($("??? ({0})" -f $Name), $(Resolve-ByPlatform -Hash $Loopz.MissingSignal).Value)));

  [string]$label = ($PSBoundParameters.ContainsKey('CustomLabel') -and
    (-not([string]::IsNullOrEmpty($CustomLabel)))) ? $CustomLabel : $signal.Key;

  [string]$formatted = $EmojiOnly.ToBool() `
    ? $EmojiOnlyFormat -f $signal.Value : $Format -f $label, $signal.Value;

  $result = if ($PSBoundParameters.ContainsKey('Value')) {
    New-Pair($formatted, $Value);
  }
  elseif ($EmojiAsValue.ToBool()) {
    New-Pair($label, $($EmojiOnlyFormat -f $signal.Value));
  }
  else {
    $formatted;
  }

  return $result;
}

function Get-PaddedLabel {
  <#
  .NAME
    Get-PaddedLabel
 
  .SYNOPSIS
    Controls and standardises the way that signals are displayed.
 
  .DESCRIPTION
    Pads out a string with leading or trailing spaces depending on
  alignment.
 
  .PARAMETER Align
    Left or right alignment of the label.
 
  .PARAMETER Label
    The string to be padded
 
  .PARAMETER Width
    Size of the field into which the label is to be placed.
 
  #>

  [OutputType([string])]
  param(
    [Parameter()]
    [string]$Label,

    [Parameter()]
    [string]$Align = 'right',

    [Parameter()]
    [int]$Width
  )
  [int]$length = $Label.Length;

  [string]$result = if ($length -lt $Width) {
    [string]$padding = [string]::new(' ', $($Width - $length))
    ($Align -eq 'right') ? $($padding + $Label) : $($Label + $padding);
  } else {
    $Label;
  }

  $result;
}

function Get-Signals {
  <#
  .NAME
    Get-Signals
 
  .SYNOPSIS
    Returns a copy of the Signals hashtable.
 
  .DESCRIPTION
    The signals returned include the user defined signal overrides.
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidGlobalVars', '')]
  [OutputType([hashtable])]
  param(
    [Parameter()]
    [hashtable]$SourceSignals = $global:Loopz.Signals,

    [Parameter()]
    [hashtable]$Custom = $global:Loopz.CustomSignals
  )

  [hashtable]$result = $SourceSignals.Clone();

  if ($Custom -and ($Custom.Count -gt 0)) {
    $Custom.GetEnumerator() | ForEach-Object {
      try {
        $result[$_.Key] = $_.Value;
      }
      catch {
        Write-Error "Skipping custom signal: '$($_.Key)'";
      }
    }
  }

  return $result;
}
$global:LoopzHelpers = @{
  # Helper Script Blocks
  #
  WhItemDecoratorBlock = [scriptblock] {
    param(
      [Parameter(Mandatory)]
      $_underscore,

      [Parameter(Mandatory)]
      [int]$_index,

      [Parameter(Mandatory)]
      [hashtable]$_exchange,

      [Parameter(Mandatory)]
      [boolean]$_trigger
    )

    return Write-HostFeItemDecorator -Underscore $_underscore `
      -Index $_index `
      -Exchange $_exchange `
      -Trigger $_trigger
  } # WhItemDecoratorBlock

  HeaderBlock          = [scriptblock] {
    param(
      [hashtable]$Exchange = @{}
    )

    Show-Header -Exchange $Exchange;
  } # HeaderBlock

  SummaryBlock         = [scriptblock] {
    param(
      [int]$Count,
      [int]$Skipped,
      [int]$Errors,
      [boolean]$Triggered,
      [hashtable]$Exchange = @{}
    )

    Show-Summary -Count $Count -Skipped $Skipped `
      -Errors $Errors -Triggered $Triggered -Exchange $Exchange;
  } # SummaryBlock
}

# Session UI state
#
[int]$global:_LineLength = 121;
[int]$global:_SmallLineLength = 81;
#
$global:LoopzUI = [ordered]@{
  # Line definitions:
  #
  UnderscoreLine      = ([string]::new("_", $_LineLength));
  EqualsLine          = ([string]::new("=", $_LineLength));
  DotsLine            = ([string]::new(".", $_LineLength));
  DashLine            = ([string]::new("-", $_LineLength));
  LightDotsLine       = (([string]::new(".", (($_LineLength - 1) / 2))).Replace(".", ". ") + ".");
  LightDashLine       = (([string]::new("-", (($_LineLength - 1) / 2))).Replace("-", "- ") + "-");
  TildeLine           = ([string]::new("~", $_LineLength));

  SmallUnderscoreLine = ([string]::new("_", $_SmallLineLength));
  SmallEqualsLine     = ([string]::new("=", $_SmallLineLength));
  SmallDotsLine       = ([string]::new(".", $_SmallLineLength));
  SmallDashLine       = ([string]::new("-", $_SmallLineLength));
  SmallLightDotsLine  = (([string]::new(".", (($_SmallLineLength - 1) / 2))).Replace(".", ". ") + ".");
  SmallLightDashLine  = (([string]::new("-", (($_SmallLineLength - 1) / 2))).Replace("-", "- ") + "-");
  SmallTildeLine      = ([string]::new("~", $_SmallLineLength));
}

$global:Loopz = [PSCustomObject]@{
  InlineCodeToOption    = [hashtable]@{
    'm' = 'Multiline';
    'i' = 'IgnoreCase';
    'x' = 'IgnorePatternWhitespace';
    's' = 'Singleline';
    'n' = 'ExplicitCapture';
  }

  FsItemTypePlaceholder = '*{_fileSystemItemType}';

  SignalLabel           = 0;
  SignalEmoji           = 1;

  MissingSignal         = @{
    'windows' = (New-Pair(@('???', '🔻')));
    'linux'   = (New-Pair(@('???', '🔴')));
    'mac'     = (New-Pair(@('???', '🔺')));
  }

  # TODO:
  # - See
  # * https://devblogs.microsoft.com/commandline/windows-command-line-unicode-and-utf-8-output-text-buffer/
  # * https://stackoverflow.com/questions/49476326/displaying-unicode-in-powershell
  #
  DefaultSignals        = [ordered]@{
    # Operations
    #
    'CUT-A'        = (New-Pair(@('Cut', '✂️')));
    'CUT-B'        = (New-Pair(@('Cut', '🔪')));
    'COPY-A'       = (New-Pair(@('Copy', '🍒')));
    'COPY-B'       = (New-Pair(@('Copy', '🥒')));
    'MOVE-A'       = (New-Pair(@('Move', '🍺')));
    'MOVE-B'       = (New-Pair(@('Move', '🍻')));
    'PASTE-A'      = (New-Pair(@('Paste', '🌶️')));
    'PASTE-B'      = (New-Pair(@('Paste', '🥜')));
    'OVERWRITE-A'  = (New-Pair(@('Overwrite', '♻️')));
    'OVERWRITE-B'  = (New-Pair(@('Overwrite', '❗')));

    # Thingies
    #
    'DIRECTORY-A'  = (New-Pair(@('Directory', '📁')));
    'DIRECTORY-B'  = (New-Pair(@('Directory', '🗂️')));
    'FILE-A'       = (New-Pair(@('File', '🏷️')));
    'FILE-B'       = (New-Pair(@('File', '📝')));
    'PATTERN'      = (New-Pair(@('Pattern', '🛡️')));
    'WITH'         = (New-Pair(@('With', '🍑')));
    'CRUMB-A'      = (New-Pair(@('Crumb', '🎯')));
    'CRUMB-B'      = (New-Pair(@('Crumb', '🧿')));
    'CRUMB-C'      = (New-Pair(@('Crumb', '💎')));
    'SUMMARY-A'    = (New-Pair(@('Summary', '🔆')));
    'SUMMARY-B'    = (New-Pair(@('Summary', '✨')));
    'MESSAGE'      = (New-Pair(@('Message', '🗯️')));
    'CAPTURE'      = (New-Pair(@('Capture', '☂️')));

    # Media
    #
    'AUDIO'        = (New-Pair(@('Audio', '🎶')));
    'TEXT'         = (New-Pair(@('Text', '🆎')));
    'DOCUMENT'     = (New-Pair(@('Document', '📜')));
    'IMAGE'        = (New-Pair(@('Image', '🖼️')));
    'MOVIE'        = (New-Pair(@('Movie', '🎬')));

    # Indicators
    #
    'WHAT-IF'      = (New-Pair(@('WhatIf', '☑️')));
    'WARNING-A'    = (New-Pair(@('Warning', '⚠️')));
    'WARNING-B'    = (New-Pair(@('Warning', '👻')));
    'SWITCH-ON'    = (New-Pair(@('On', '✔️')));
    'SWITCH-OFF'   = (New-Pair(@('Off', '❌')));
    'OK-A'         = (New-Pair(@('🆗', '🚀')));
    'OK-B'         = (New-Pair(@('🆗', '🌟')));
    'BAD-A'        = (New-Pair(@('Bad', '💥')));
    'BAD-B'        = (New-Pair(@('Bad', '💢')));
    'PROHIBITED'   = (New-Pair(@('Prohibited', '🚫')));
    'INCLUDE'      = (New-Pair(@('Include', '💠')));
    'SOURCE'       = (New-Pair(@('Source', '🎀')));
    'DESTINATION'  = (New-Pair(@('Destination', '☀️')));
    'TRIM'         = (New-Pair(@('Trim', '🌊')));
    'MULTI-SPACES' = (New-Pair(@('Spaces', '❄️')));
    'DIAGNOSTICS'  = (New-Pair(@('Diagnostics', '🧪')));
    'LOCKED'       = (New-Pair(@('Locked', '🔐')));
    'NOVICE'       = (New-Pair(@('Novice', '🔰')));
    'TRANSFORM'    = (New-Pair(@('Transform', '🤖')));

    # Outcomes
    #
    'FAILED-A'     = (New-Pair(@('Failed', '☢️')));
    'FAILED-B'     = (New-Pair(@('Failed', '💩')));
    'SKIPPED-A'    = (New-Pair(@('Skipped', '💤')));
    'SKIPPED-B'    = (New-Pair(@('Skipped', '👾')));
    'ABORTED-A'    = (New-Pair(@('Aborted', '✖️')));
    'ABORTED-B'    = (New-Pair(@('Aborted', '👽')));
    'CLASH'        = (New-Pair(@('Clash', '📛')));
    'NOT-ACTIONED' = (New-Pair(@('Not Actioned', '⛔')));

    # Command Specific
    #
    'REMY.ANCHOR'  = (New-Pair(@('Anchor', '⚓')));
    'REMY.POST'    = (New-Pair(@('Post Process', '🌈')));
    'REMY.DROP'    = (New-Pair(@('Drop', '💧')));
    'REMY.UNDO'    = (New-Pair(@('Undo Rename', '❎')));
    'GREPS'        = (New-Pair(@('greps', '🔍')));
  }

  OverrideSignals       = @{ # Label, Emoji
    'windows' = @{
      # defaults based on windows, so there should be no need for overrides
    };

    'linux'   = @{
      # tbd
    };

    'mac'     = @{
      # tbd
    };
  }

  # DefaultSignals resolved into Signals by Initialize-Signals
  #
  Signals               = $null;

  # User defined signals, should be populated by profile
  #
  CustomSignals         = $null;

  Defaults              = [PSCustomObject]@{
    Remy = [PSCustomObject]@{
      Marker            = [char]0x2BC1;

      Context           = [PSCustomObject]@{
        Title             = 'Rename';
        ItemMessage       = 'Rename Item';
        SummaryMessage    = 'Rename Summary';
        Locked            = 'LOOPZ_REMY_LOCKED';
        UndoDisabledEnVar = 'LOOPZ_REMY_UNDO_DISABLED';
        OperantShortCode  = 'remy';
      }
    }
  }

  Rules                 = [PSCustomObject]@{
    Remy = [PSCustomObject]@{
      Trim   = @{
        'IsApplicable' = [scriptblock] {
          param([string]$_Input)
          $($_Input.StartsWith(' ') -or $_Input.EndsWith(' '));
        };

        'Transform'    = [scriptblock] {
          param([string]$_Input)
          $_Input.Trim();
        };
        'Signal'       = 'TRIM'
      }

      Spaces = @{
        'IsApplicable' = [scriptblock] {
          param([string]$_Input)
          $_Input -match "\s{2,}";
        };

        'Transform'    = [scriptblock] {
          param([string]$_Input)
          $_Input -replace "\s{2,}", ' '
        };
        'Signal'       = 'MULTI-SPACES'
      }
    }
  }

  InvalidCharacterSet   = [char[]]'<>:"/\|?*';
}

function Initialize-ShellOperant {
  <#
  .NAME
    Initialize-ShellOperant
 
  .SYNOPSIS
    Operant factory function.
 
  .DESCRIPTION
    By default all operant related files are stored somewhere inside the home path.
  Actually, a predefined subpath under home is used. This can be customised by the user
  by them defining an alternative path (in the environment as 'LOOPZ_PATH'). This
  alternative path can be relative or absolute. Relative paths are relative to the
  home directory.
    The options specify how the operant is created and must be a PSCustomObject with
  the following fields (examples provided inside brackets relate to Rename-Many command):
  - ShortCode ('remy'): a short string denoting the related command
  - OperantName ('UndoRename'): name of the operant class required
  - Shell ('PoShShell'): The type of shell that the command should be generated for. So
  for PowerShell the user would specify 'PoShShell' (which for the time being is the
  only shell supported).
  - BaseFilename ('undo-rename'): the core part of the file name which should reflect
  the nature of the operant (the operation, which ideally should be a verb noun pair
  but is not enforced)
  - DisabledEnVar ('LOOPZ_REMY_UNDO_DISABLED'): The environment variable used to disable
  this operant.
 
  .PARAMETER DryRun
    Similar to WhatIf, but by passing ShouldProcess process for custom handling of
  dry run scenario. DryRun should be set if WhatIf is enabled.
 
  .PARAMETER HomePath
      User's home directory. (This parameter does not need to be set by client, just
    used for testing purposes.)
 
  .PARAMETER Options
    (See command description for $Options field descriptions).
 
  .EXAMPLE 1
  Operant options for Rename-Many(remy) command
 
  [PSCustomObject]$operantOptions = [PSCustomObject]@{
    ShortCode = 'remy';
    OperantName = 'UndoRename';
    Shell = 'PoShShell';
    BaseFilename = 'undo-rename';
    DisabledEnVar = 'LOOPZ_REMY_UNDO_DISABLED';
  }
     
  #>

  [OutputType([Operant])]
  param(
    [Parameter()]
    [string]$HomePath = $(Resolve-Path "~"),

    [Parameter()]
    [PSCustomObject]$Options,

    [Parameter()]
    [switch]$DryRun
  )
  [string]$envUndoRenameDisabled = $(Get-EnvironmentVariable -Variable $Options.DisabledEnVar);

  try {
    [boolean]$isDisabled = if (-not([string]::IsNullOrEmpty($envUndoRenameDisabled))) {
      [System.Convert]::ToBoolean($envUndoRenameDisabled);
    }
    else {
      $false;
    }
  }
  catch {
    [boolean]$isDisabled = $false;
  }

  [Operant]$operant = if (-not($isDisabled)) {
    [string]$loopzPath = $(Get-EnvironmentVariable -Variable 'LOOPZ_PATH');
    [string]$subPath = ".loopz" + [System.IO.Path]::DirectorySeparatorChar + $($Options.ShortCode);
    if ([string]::IsNullOrEmpty($loopzPath)) {
      $loopzPath = Join-Path -Path $HomePath -ChildPath $subPath;
    }
    else {
      $loopzPath = [System.IO.Path]::IsPathRooted($loopzPath) `
        ? $(Join-Path -Path $loopzPath -ChildPath $subPath) `
        : $(Join-Path -Path $HomePath -ChildPath $loopzPath -AdditionalChildPath $subPath);
    }

    if (-not(Test-Path -Path $loopzPath -PathType Container)) {
      if (-not($DryRun)) {
        $null = New-Item -Type Directory -Path $loopzPath;
      }
    }

    New-ShellOperant -BaseFilename $Options.BaseFilename `
      -Directory $loopzPath -Operant $($Options.OperantName) -Shell $Options.Shell;
  }
  else {
    $null;
  }

  return $operant;
}

function Move-Match {
  <#
  .NAME
    Move-Match
 
  .SYNOPSIS
    The core move match action function principally used by Rename-Many. Moves a
  match according to the specified anchor(s).
 
  .DESCRIPTION
    Returns a new string that reflects moving the specified $Pattern match to either
  the location designated by $Anchor/$AnchorOccurrence/$Relation or to the Start or
  End of the value indicated by the presence of the $Start/$End switch parameters.
    First Move-Match, removes the Pattern match from the source. This makes the With and
  Anchor match against the remainder ($patternRemoved) of the source. This way, there is
  no overlap between the Pattern match and With/Anchor and it also makes the functionality more
  understandable for the user. NB: $Pattern only tells you what to remove, but it's the
  $With, $Copy and $Paste that defines what to insert, with the $Anchor/$Start/$End
  defining where the replacement text should go. The user should not be using named capture
  groups in $Copy, or $Anchor, rather, they should be defined inside $Paste and referenced
  inside $Paste/$With.
 
  .PARAMETER Anchor
    Anchor is a regular expression string applied to $Value (after the $Pattern match has
  been removed). The $Pattern match that is removed is inserted at the position indicated
  by the anchor match in collaboration with the $Relation parameter.
 
  .PARAMETER AnchorOccurrence
    Can be a number or the letters f, l
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
 
  .PARAMETER Copy
    Regular expression string applied to $Value (after the $Pattern match has been removed),
  indicating a portion which should be copied and re-inserted (via the $Paste parameter;
  see $Paste or $With). Since this is a regular expression to be used in $Paste/$With, there
  is no value in the user specifying a static pattern, because that static string can just be
  defined in $Paste/$With. The value in the $Copy parameter comes when a generic pattern is
  defined eg \d{3} (is non static), specifies any 3 digits as opposed to say '123', which
  could be used directly in the $Paste/$With parameter without the need for $Copy. The match
  defined by $Copy is stored in special variable ${_c} and can be referenced as such from
  $Paste and $With.
 
  .PARAMETER CopyOccurrence
    Can be a number or the letters f, l
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
 
  .PARAMETER Diagnose
    switch parameter that indicates the command should be run in WhatIf mode. When enabled
  it presents additional information that assists the user in correcting the un-expected
  results caused by an incorrect/un-intended regular expression. The current diagnosis
  will show the contents of named capture groups that they may have specified. When an item
  is not renamed (usually because of an incorrect regular expression), the user can use the
  diagnostics along side the 'Not Renamed' reason to track down errors. When $Diagnose has
  been specified, $WhatIf does not need to be specified.
 
  .PARAMETER Drop
    A string parameter (only applicable to move operations, ie any of these Anchor/Star/End
  are present) that defines what text is used to replace the $Pattern match. So in this
  use-case, the user wants to move a particular token/pattern to another part of the name
  and at the same time drop a static string in the place where the $Pattern was removed from.
 
  .PARAMETER End
    Is another type of anchor used instead of $Anchor and specifies that the $Pattern match
  should be moved to the end of the new name.
 
 
  .PARAMETER Marker
    A character used to mark the place where the $Pattern was removed from. It should be a
  special character that is not easily typed on the keyboard by the user so as to not
  interfere wth $Anchor/$Copy matches which occur after $Pattern match is removed.
 
  .PARAMETER Paste
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $With parameter. When $Paste is defined, the $Anchor (if specified) is removed
  from $Value and needs to be be re-inserted using the special variable ${_a}. The
  other special variables that can be used inside a $Paste string is documented under the $With
  parameter.
    The $Paste string can specify a format that defines the replacement and since it removes the
  $Anchor, the $Relation is not applicable ($Relation and $Paste can't be used together).
 
 
  .PARAMETER Pattern
    Regular expression string that indicates which part of the $Value that
  either needs to be moved or replaced as part of overall rename operation. Those characters
  in $Value which match $Pattern, are removed.
 
  .PARAMETER PatternOccurrence
    Can be a number or the letters f, l
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
 
  .PARAMETER Relation
    Used in conjunction with the $Anchor parameter and can be set to either 'before' or
  'after' (the default). Defines the relationship of the $Pattern match with the $Anchor
  match in the new name for $Value.
 
  .PARAMETER Start
    Is another type of anchor used instead of $Anchor and specifies that the $Pattern match
  should be moved to the start of the new name.
 
  .PARAMETER Value
    The source value against which regular expressions are applied.
 
  .PARAMETER With
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $Paste parameter. Defines what text is used as the replacement for the $Pattern
  match. Works in concert with $Relation (whereas $Paste does not). $With can reference special
  variables:
  * $0: the pattern match
  * ${_a}: the anchor match
  * ${_c}: the copy match
  When $Pattern contains named capture groups, these variables can also be referenced. Eg if the
  $Pattern is defined as '(?<day>\d{1,2})-(?<mon>\d{1,2})-(?<year>\d{4})', then the variables
  ${day}, ${mon} and ${year} also become available for use in $With or $Paste.
  Typically, $With is static text which is used to replace the $Pattern match and is inserted
  according to the Anchor match, (or indeed $Start or $End) and $Relation. When using $With,
  whatever is defined in the $Anchor match is not removed from $Value (this is different to how
  $Paste works).
    
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSPossibleIncorrectUsageOfAssignmentOperator', '')]
  [Alias('moma')]
  [OutputType([string])]
  param (
    [Parameter(Mandatory)]
    [string]$Value,

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$Pattern,

    [Parameter()]
    [ValidateScript( { ($_ -ne '*') -and ($_ -ne '0') })]
    [string]$PatternOccurrence = 'f',

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$Anchor,

    [Parameter()]
    [ValidateScript( { ($_ -ne '*') -and ($_ -ne '0') })]
    [string]$AnchorOccurrence = 'f',

    [Parameter()]
    [ValidateSet('before', 'after')]
    [string]$Relation = 'after',

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$Copy,

    [Parameter()]
    [ValidateScript( { ($_ -ne '*') -and ($_ -ne '0') })]
    [string]$CopyOccurrence = 'f',

    [Parameter()]
    [string]$With,

    [Parameter()]
    [string]$Paste,

    [Parameter()]
    [switch]$Start,

    [Parameter()]
    [switch]$End,

    [Parameter()]
    [switch]$Diagnose,

    [Parameter()]
    [string]$Drop,

    [Parameter()]
    [char]$Marker = 0x20DE
  )

  [string]$result = [string]::Empty;
  [string]$failedReason = [string]::Empty;
  [PSCustomObject]$groups = [PSCustomObject]@{
    Named = @{}
  }

  [boolean]$isFormatted = $PSBoundParameters.ContainsKey('Paste') -and -not([string]::IsNullOrEmpty($Paste));
  [boolean]$dropped = $PSBoundParameters.ContainsKey('Drop') -and -not([string]::IsNullOrEmpty($Drop));

  [hashtable]$parameters = @{
    'Source'       = $Value
    'PatternRegEx' = $Pattern
    'Occurrence'   = ($PSBoundParameters.ContainsKey('PatternOccurrence') ? $PatternOccurrence : 'f')
  }

  if ($dropped) {
    $parameters['Marker'] = $Marker;
  }

  [string]$capturedPattern, [string]$patternRemoved, `
    [System.Text.RegularExpressions.Match]$patternMatch = Split-Match @parameters;

  if (-not([string]::IsNullOrEmpty($capturedPattern))) {
    [boolean]$isVanilla = -not($PSBoundParameters.ContainsKey('Copy') -or `
      ($PSBoundParameters.ContainsKey('With') -and -not([string]::IsNullOrEmpty($With))));

    if ($Diagnose.ToBool()) {
      $groups.Named['Pattern'] = get-Captures -MatchObject $patternMatch;
    }

    # Determine the replacement text
    #
    if ($isVanilla) {
      # Insert the original pattern match, because there is no Copy/With.
      #
      [string]$replaceWith = $capturedPattern;
    }
    else {
      [string]$replaceWith = [string]::Empty;
      if ($PSBoundParameters.ContainsKey('Copy')) {
        if ($patternRemoved -match $Copy) {
          [hashtable]$parameters = @{
            'Source'       = $patternRemoved
            'PatternRegEx' = $Copy
            'Occurrence'   = ($PSBoundParameters.ContainsKey('CopyOccurrence') ? $CopyOccurrence : 'f')
          }

          if ($dropped) {
            $parameters['Marker'] = $Marker;
          }

          # With this implementation, it is up to the user to supply a regex proof
          # pattern, so if the Copy contains regex chars which must be treated literally, they
          # must pass in the string pre-escaped: -Copy $(esc('some-pattern') + 'other stuff').
          #
          [string]$replaceWith, $null, `
            [System.Text.RegularExpressions.Match]$copyMatch = Split-Match @parameters;

          if ($Diagnose.ToBool()) {
            $groups.Named['Copy'] = get-Captures -MatchObject $copyMatch;
          }
        }
        else {
          # Copy doesn't match so abort and return unmodified source
          #
          $failedReason = 'Copy Match';
        }
      }
      elseif ($PSBoundParameters.ContainsKey('With')) {
        [string]$replaceWith = $With;
      }
      else {
        [string]$replaceWith = [string]::Empty;
      }
    }

    if (-not($PSBoundParameters.ContainsKey('Anchor')) -and ($isFormatted)) {
      $replaceWith = $Paste.Replace('${_c}', $replaceWith).Replace('$0', $capturedPattern);

      # Now apply the user defined Pattern named group references if they exist
      # to the captured pattern
      #
      $replaceWith = $capturedPattern -replace $pattern, $replaceWith;
    }

    if ($Start.ToBool()) {
      $result = $replaceWith + $patternRemoved;
    }
    elseif ($End.ToBool()) {
      $result = $patternRemoved + $replaceWith;
    }
    elseif ($PSBoundParameters.ContainsKey('Anchor')) {
      [hashtable]$parameters = @{
        'Source'       = $patternRemoved
        'PatternRegEx' = $Anchor
        'Occurrence'   = ($PSBoundParameters.ContainsKey('AnchorOccurrence') ? $AnchorOccurrence : 'f')
      }

      if ($dropped) {
        $parameters['Marker'] = $Marker;
      }

      # As with the Copy parameter, if the user wants to specify an anchor by a pattern
      # which contains regex chars, then can use -Anchor $(esc('anchor-pattern')). If
      # there are no regex chars, then they can use -Anchor 'pattern'. However, if the
      # user needs to do partial escapes, then they will have to do the escaping
      # themselves: -Anchor $(esc('partial-pattern') + 'remaining-pattern').
      #
      [string]$capturedAnchor, $null, `
        [System.Text.RegularExpressions.Match]$anchorMatch = Split-Match @parameters;

      if (-not([string]::IsNullOrEmpty($capturedAnchor))) {
        # Relation and Paste are not compatible, because if the user is defining the
        # replacement format, it is up to them to define the relationship of the anchor
        # with the replacement text. So exotic/vanilla-formatted can't use Relation.
        #

        # How do we handle group references in Pattern? These are done transparently
        # because any group defined in Pattern can be referenced by Paste as long as
        # there is a replace operation of the form regEx.Replace($Pattern, Paste). Of course
        # we can't do the replace in this simplistic way, because that form would replace
        # all matches, when we only want to replace the specified Pattern occurrence.
        #
        if ($isFormatted) {
          # Paste can be something like '___ ${_a}, (${a}, ${b}, [$0], ${_c} ___', where $0
          # represents the pattern capture, the special variable _c represents $Copy,
          # _a represents the anchor and ${a} and ${b} represents user defined capture groups.
          # The Paste replaces the anchor, so to re-insert the anchor _a, it must be referenced
          # in the Paste format. Numeric captures may also be referenced.
          #
          [string]$format = $Paste.Replace('${_c}', $replaceWith).Replace(
            '$0', $capturedPattern).Replace('${_a}', $capturedAnchor);

          # Now apply the user defined Pattern named group references if they exist
          # to the captured pattern
          #
          $format = $capturedPattern -replace $pattern, $format;
        }
        else {
          # If the user has defined a Copy/With without a format(Paste), we define the format
          # in terms of the relationship specified.
          #
          [string]$format = ($Relation -eq 'before') `
            ? $replaceWith + $capturedAnchor : $capturedAnchor + $replaceWith;
        }

        if ($Diagnose.ToBool()) {
          $groups.Named['Anchor'] = get-Captures -MatchObject $anchorMatch;
        }

        $result = $Anchor.Replace($patternRemoved, $format, 1, $anchorMatch.Index);
      }
      else {
        # Anchor doesn't match Pattern
        #
        $failedReason = 'Anchor Match';
      }
    }
    else {
      # This is an error, because there is no place to move the pattern to, as there is no Anchor,
      # Start or End specified. Actually, we're in the twilight zone here as this scenario can't
      # happen and has been engineered out of existence!
      #
      $failedReason = 'Twilight Zone: Missing Anchor';
    }
  }
  else {
    # Source doesn't match Pattern
    #
    $failedReason = 'Pattern Match';
  }

  if ([boolean]$success = $([string]::IsNullOrEmpty($failedReason))) {
    if ($dropped -and $result.Contains([string]$Marker)) {
      $result = $result.Replace([string]$Marker, $Drop);
    }
  }
  else {
    $result = $Value;
  }

  [PSCustomObject]$moveResult = [PSCustomObject]@{
    Payload         = $result;
    Success         = $success;
    CapturedPattern = $capturedPattern;
  }

  if (-not([string]::IsNullOrEmpty($failedReason))) {
    $moveResult | Add-Member -MemberType NoteProperty -Name 'FailedReason' -Value $failedReason;
  }

  if ($Diagnose.ToBool() -and ($groups.Named.Count -gt 0)) {
    $moveResult | Add-Member -MemberType NoteProperty -Name 'Diagnostics' -Value $groups;
  }

  return $moveResult;
} # Move-Match

function New-RegularExpression {
  <#
  .NAME
    New-RegularExpression
 
  .SYNOPSIS
    regex factory function.
 
  .DESCRIPTION
    Creates a regex object from the $Expression specified. Supports inline regex
  flags ('mixsn') which must be specified at the end of the $Expression after a
  '/'.
 
  .PARAMETER Escape
    switch parameter to indicate that the expression should be escaped. (This is an
  alternative to the '~' prefix).
 
  .PARAMETER Expression
    The pattern for the regular expression. If it starts with a tilde ('~'), then
  the whole expression is escaped so any special regex characters are interpreted
  literally.
 
  .PARAMETER Label
    string that gives a name to the regular expression being created and is used for
  logging/error reporting purposes only, so it's not mandatory.
 
  .PARAMETER WholeWord
    switch parameter to indicate the expression should be wrapped with word boundary
  markers \b, so an $Expression defined as 'foo' would be adjusted to '\bfoo\b'.
   
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseShouldProcessForStateChangingFunctions',
    '', Justification = 'Not a state changing function, its a factory')]
  [OutputType([System.Text.RegularExpressions.RegEx])]
  param(
    [Parameter(Position = 0, Mandatory)]
    [string]$Expression,

    [Parameter()]
    [switch]$Escape,

    [Parameter()]
    [switch]$WholeWord,

    [Parameter()]
    [string]$Label
  )

  [System.Text.RegularExpressions.RegEx]$resultRegEx = $null;
  [System.Text.RegularExpressions.RegEx]$extractOptionsRegEx = New-Object `
    -TypeName System.Text.RegularExpressions.RegEx -ArgumentList (
    '[\/\\](?<codes>[mixsn]{1,5})$');

  try {
    [string]$adjustedExpression = $Expression.StartsWith('~') `
      ? [regex]::Escape($Expression.Substring(1)) : $Expression;

    [string[]]$optionsArray = @();

    [string]$options = if ($extractOptionsRegEx.IsMatch($adjustedExpression)) {
      $null, $adjustedExpression, [System.Text.RegularExpressions.Match]$optionsMatch = `
        Split-Match -Source $adjustedExpression -PatternRegEx $extractOptionsRegEx;

      [string]$inlineCodes = $optionsMatch.Groups['codes'];

      # NOTE, beware of [string]::ToCharArray, the returned result MUST be cast to [string[]]
      #
      [string[]]$inlineCodes.ToCharArray() | ForEach-Object {
        $optionsArray += $Loopz.InlineCodeToOption[$_]
      }

      $optionsArray -join ', ';
    } else {
      $null;
    }

    if (-not([string]::IsNullOrEmpty($options))) {
      Write-Debug "New-RegularExpression; created RegEx for pattern: '$adjustedExpression', with options: '$options'";
    }

    if ($Escape.ToBool()) {
      $adjustedExpression = [regex]::Escape($adjustedExpression);
    }
    if ($WholeWord.ToBool()) {
      $adjustedExpression = '\b{0}\b' -f $adjustedExpression;
    }

    $arguments = $options ? @($adjustedExpression, $options) : @(, $adjustedExpression);
    $resultRegEx = New-Object -TypeName System.Text.RegularExpressions.RegEx -ArgumentList (
      $arguments);
  }
  catch [System.Management.Automation.MethodInvocationException] {
    [string]$message = ($PSBoundParameters.ContainsKey('Label')) `
      ? $('Regular expression ({0}) "{1}" is not valid, ... terminating ({2}).' `
        -f $Label, $adjustedExpression, $_.Exception.Message)
    : $('Regular expression "{0}" is not valid, ... terminating ({1}).' `
        -f $adjustedExpression, $_.Exception.Message);
    Write-Error -Message $message -ErrorAction Stop;
  }

  $resultRegEx;
}

function Resolve-PatternOccurrence {
  <#
  .NAME
    Resolve-PatternOccurrence
 
  .SYNOPSIS
    Helper function to assist in processing regular expression parameters that can
  be adorned with an occurrence value.
 
  .DESCRIPTION
    Since the occurrence part is optional and defaults to mean first occurrence only,
  this function will fill in the default 'f' when occurrence is not specified.
 
  .PARAMETER Value
    The value of a regex parameter, which is an array whose first element is the
  pattern and the second if present is the match occurrence.
   
  #>

  param (
    [Parameter(Position = 0)]
    [array]$Value
  )

  $Value[0], $(($Value.Length -eq 1) ? 'f' : $Value[1]);
} # resolve-PatternOccurrence

function Select-FsItem {
  <#
  .NAME
    Select-FsItem
 
  .SYNOPSIS
    A predicate function that indicates whether an item identified by the Name matches
  the include/exclude filters specified.
 
  .DESCRIPTION
    Use this utility function to help specify a Condition for Invoke-TraverseDirectory.
  This function is partly required because the Include/Exclude parameters on functions
  such as Get-ChildItems/Copy-Item/Get-Item etc only work on files not directories.
 
  .PARAMETER Case
    Switch parameter which controls case sensitivity of inclusion/exclusion. By default
  filtering is case insensitive. When The Case switch is specified, filtering is case
  sensitive.
 
  .PARAMETER Excludes
    An array containing a list of filters, each must contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be ignored. If the Name
  matches any of the filters in the list, will cause the end result to be false.
  Any match in the Excludes overrides a match in Includes, so an item
  that is matched in Include, can be excluded by the Exclude.
 
  .PARAMETER Includes
      An array containing a list of filters, each must contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be ignored. If Name matches
  any of the filters in Includes, and are not Excluded, the result will be true.
 
  .PARAMETER Name
    A string to be matched against the filters.
 
  .EXAMPLE 1
    Define a Condition that allows only directories beginning with A, but also excludes
    any directory containing '_' or '-'.
 
    [scriptblock]$filterDirectories = {
      [OutputType([boolean])]
      param(
        [System.IO.DirectoryInfo]$directoryInfo
      )
      [string[]]$directoryIncludes = @('A*');
      [string[]]$directoryExcludes = @('*_*', '*-*');
 
      $filterDirectories = Select-FsItem -Name $directoryInfo.Name `
        -Includes $directoryIncludes -Excludes $directoryExcludes;
 
      Invoke-TraverseDirectory -Path <path> -Block <block> -Condition $filterDirectories;
    }
  #>


  [OutputType([boolean])]
  param(
    [Parameter(Mandatory)]
    [string]$Name,

    [Parameter()]
    [string[]]$Includes = @(),

    [Parameter()]
    [string[]]$Excludes = @(),

    [Parameter()]
    [switch]$Case
  )

  # Note we wrap the result inside @() array designator just in-case the where-object
  # returns just a single item in which case the array would be flattened out into
  # an individual scalar value which is what we don't want, damn you powershell for
  # doing this and making life just so much more difficult. Actually, on further
  # investigation, we don't need to wrap inside @(), because we've explicitly defined
  # the type of the includes variables to be arrays, which would preserve the type
  # even in the face of powershell annoyingly flattening the single item array. @()
  # being left in for clarity and show of intent.
  #
  [string[]]$validIncludes = @($Includes | Where-Object { $_.Contains('*') })
  [string[]]$validExcludes = @($Excludes | Where-Object { $_.Contains('*') })

  [boolean]$resolvedInclude = $validIncludes `
    ? (select-ResolvedFsItem -FsItem $Name -Filter $Includes -Case:$Case) `
    : $false;

  [boolean]$resolvedExclude = $validExcludes `
    ? (select-ResolvedFsItem -FsItem $Name -Filter $Excludes -Case:$Case) `
    : $false;

  ($resolvedInclude) -and -not($resolvedExclude)
} # Select-FsItem

function Select-SignalContainer {
  <#
  .NAME
    Select-SignalContainer
 
  .SYNOPSIS
    Selects a signal into the container specified (either 'Wide' or 'Props').
  Wide items will appear on their own line, Props are for items which are
  short in length and can be combined into the same line.
 
  .DESCRIPTION
    This is a wrapper around Get-FormattedSignal in addition to selecting the
  signal into a container.
 
  .PARAMETER Containers
    PSCustomObject that contains Wide and Props properties which must be of Krayola's
  type [line].
 
  .PARAMETER CustomLabel
    A custom label applied to the formatted signal.
 
  .PARAMETER Force
    An override (bypassing $Threshold) to push a signal into a specific collection.
 
  .PARAMETER Format
    The format applied to the formatted signal.
 
  .PARAMETER Name
    The signal name.
 
  .PARAMETER Signals
    The signal hashtable collection from which to select the required signal denoted by
  $Name.
 
  .PARAMETER Threshold
    A threshold that defines whether the signal is added to Wide or Props.
 
  .PARAMETER Value
    The value associated wih the signal.
 
  #>

  param(
    [Parameter(Mandatory)]
    [PSCustomObject]$Containers,

    [Parameter(Mandatory)]
    [string]$Name,

    [Parameter(Mandatory)]
    [string]$Value,

    [Parameter()]
    [hashtable]$Signals = $(Get-Signals),

    [Parameter()]
    [string]$Format = '[{1}] {0}', # 0=Label, 1=Emoji,

    [Parameter()]
    [int]$Threshold = 6,

    [Parameter()]
    [string]$CustomLabel,

    [Parameter()]
    [ValidateSet('Wide', 'Props')]
    [string]$Force
  )

  [couplet]$formattedSignal = Get-FormattedSignal -Name $Name -Format $Format -Value $Value `
    -Signals $Signals -CustomLabel $CustomLabel;

  if ($PSBoundParameters.ContainsKey('Force')) {
    if ($Force -eq 'Wide') {
      $null = $Containers.Wide.append($formattedSignal);
    }
    else {
      $null = $Containers.Props.append($formattedSignal);
    }
  }
  else {
    if ($Value.Length -gt $Threshold) {
      $null = $Containers.Wide.append($formattedSignal);
    }
    else {
      $null = $Containers.Props.append($formattedSignal);
    }
  }
}

function Split-Match {
  <#
  .NAME
    Split-Match
 
  .SYNOPSIS
    Splits out a match from the remainder of the $Source text returning the matched
  test, the remainder and the corresponding match object.
 
  .DESCRIPTION
    Helper function to get the pattern match and the remaining text. This helper
  helps us to avoid unnecessary duplicated reg ex matches. It returns
  up to 3 items inside an array, the first is the matched text, the second is
  the source with the matched text removed and the third is the match object
  that represents the matched text.
 
  .PARAMETER CapturedOnly
    switch parameter to indicate what should be returned. When the client does not need
  the match object or the remainder, they can use this switch to ensure only the matched
  text is returned.
   
  .PARAMETER Marker
    A character used to mark the place where the $PatternRegEx's match was removed from.
  It should be a special character that is not easily typed on the keyboard by the user
  so as to not interfere wth $Anchor/$Copy matches which occur after $Pattern match is
  removed.
 
  .PARAMETER Occurrence
    Denotes which match should be used.
 
  .PARAMETER PatternRegEx
    The regex object to apply to the $Source.
 
  .PARAMETER Source
    The source value against which regular expression is applied.
 
 
  #>

  param(
    [Parameter(Mandatory)]
    [string]$Source,

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$PatternRegEx,

    [Parameter()]
    [ValidateScript( { $_ -ne '0' })]
    [string]$Occurrence = 'f',

    [Parameter()]
    [switch]$CapturedOnly,

    [Parameter()]
    [char]$Marker = 0x20DE
  )

  [System.Text.RegularExpressions.MatchCollection]$mc = $PatternRegEx.Matches($Source);

  if ($mc.Count -gt 0) {
    # Get the match instance
    #
    [System.Text.RegularExpressions.Match]$m = if ($Occurrence -eq 'f') {
      $mc[0];
    }
    elseif ($Occurrence -eq 'l') {
      $mc[$mc.Count - 1];
    }
    else {
      try {
        [int]$nth = [int]::Parse($Occurrence);
      }
      catch {
        [int]$nth = 1;
      }

      ($nth -le $mc.Count) ? $mc[$nth - 1] : $null;
    }
  }
  else {
    [System.Text.RegularExpressions.Match]$m = $null;
  }

  $result = $null;
  if ($m) {
    [string]$capturedText = $m.Value;

    $result = if ($CapturedOnly.ToBool()) {
      $capturedText;
    }
    else {
      # Splatting the arguments fails because the parameter validation in Get-InverseSubString
      # fails, due to parameters not having been bound yet.
      # https://github.com/PowerShell/PowerShell/issues/14457
      #
      [string]$remainder = $PSBoundParameters.ContainsKey('Marker') `
        ? $(Get-InverseSubString -Source $Source -StartIndex $m.Index -Length $m.Length -Marker $Marker) `
        : $(Get-InverseSubString -Source $Source -StartIndex $m.Index -Length $m.Length);

      @($capturedText, $remainder, $m);
    }
  }

  return $result;
} # Split-Match

function Update-Match {

  <#
  .NAME
    Update-Match
 
  .SYNOPSIS
    The core update match action function principally used by Rename-Many. Updates
  $Pattern match in it's current location and can update all $Pattern matches if
  '*' is specified as the $PatternOccurrence.
 
  .DESCRIPTION
    Returns a new string that reflects updating the specified $Pattern match.
    First Update-Match, removes the Pattern match from $Value. This makes the With and
  Copy match against the remainder ($patternRemoved) of $Value. This way, there is
  no overlap between the Pattern match and $With and it also makes the functionality more
  understandable for the user. NB: Pattern only tells you what to remove, but it's the
  With, Copy and Paste that defines what to insert. The user should not be using named
  capture groups in Copy rather, they should be defined inside $Paste and referenced
  inside Paste.
   
  .PARAMETER Copy
    Regular expression string applied to $Value (after the $Pattern match has been removed),
  indicating a portion which should be copied and re-inserted (via the $Paste parameter;
  see $Paste or $With). Since this is a regular expression to be used in $Paste/$With, there
  is no value in the user specifying a static pattern, because that static string can just be
  defined in $Paste/$With. The value in the $Copy parameter comes when a generic pattern is
  defined eg \d{3} (is non static), specifies any 3 digits as opposed to say '123', which
  could be used directly in the $Paste/$With parameter without the need for $Copy. The match
  defined by $Copy is stored in special variable ${_p} and can be referenced as such from
  $Paste and $With.
 
  .PARAMETER CopyOccurrence
    Can be a number or the letters f, l
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
 
  .PARAMETER Diagnose
    switch parameter that indicates the command should be run in WhatIf mode. When enabled
  it presents additional information that assists the user in correcting the un-expected
  results caused by an incorrect/un-intended regular expression. The current diagnosis
  will show the contents of named capture groups that they may have specified. When an item
  is not renamed (usually because of an incorrect regular expression), the user can use the
  diagnostics along side the 'Not Renamed' reason to track down errors. When $Diagnose has
  been specified, $WhatIf does not need to be specified.
 
  .PARAMETER Paste
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $With parameter. The other special variables that can be used inside a $Paste
  string is documented under the $With parameter.
 
  .PARAMETER Pattern
    Regular expression string that indicates which part of the $Value that either needs
  to be moved or replaced as part of overall rename operation. Those characters in $Value
  which match $Pattern, are removed.
 
  .PARAMETER PatternOccurrence
    Can be a number or the letters f, l
  * f: first occurrence
  * l: last occurrence
  * <number>: the nth occurrence
 
  .PARAMETER Value
    The source value against which regular expressions are applied.
 
  .PARAMETER With
    This is a NON regular expression string. It would be more accurately described as a formatter,
  similar to the $Paste parameter. Defines what text is used as the replacement for the $Pattern
  match. Works in concert with $Relation (whereas $Paste does not). $With can reference special
  variables:
  * $0: the pattern match
  * ${_c}: the copy match
  When $Pattern contains named capture groups, these variables can also be referenced. Eg if the
  $Pattern is defined as '(?<day>\d{1,2})-(?<mon>\d{1,2})-(?<year>\d{4})', then the variables
  ${day}, ${mon} and ${year} also become available for use in $With or $Paste.
  Typically, $With is static text which is used to replace the $Pattern match.
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseShouldProcessForStateChangingFunctions', '')]
  [OutputType([string])]
  param(
    [Parameter()]
    [string]$Value,

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$Pattern,

    [Parameter()]
    [ValidateScript( { $_ -ne '0' })]
    [string]$PatternOccurrence = 'f',

    [Parameter()]
    [System.Text.RegularExpressions.RegEx]$Copy,

    [Parameter()]
    [ValidateScript( { $_ -ne '0' })]
    [string]$CopyOccurrence = 'f',

    [Parameter()]
    [string]$With,

    [Parameter()]
    [string]$Paste,

    [Parameter()]
    [switch]$Diagnose
  )

  [string]$failedReason = [string]::Empty;
  [PSCustomObject]$groups = [PSCustomObject]@{
    Named = @{}
  }

  [string]$capturedPattern, $patternRemoved, [System.Text.RegularExpressions.Match]$patternMatch = `
    Split-Match -Source $Value -PatternRegEx $Pattern `
    -Occurrence ($PSBoundParameters.ContainsKey('PatternOccurrence') ? $PatternOccurrence : 'f');

  if (-not([string]::IsNullOrEmpty($capturedPattern))) {
    if ($PSBoundParameters.ContainsKey('Copy')) {
      [string]$replaceWith, $null, [System.Text.RegularExpressions.Match]$copyMatch = `
        Split-Match -Source $patternRemoved -PatternRegEx $Copy `
        -Occurrence ($PSBoundParameters.ContainsKey('CopyOccurrence') ? $CopyOccurrence : 'f');

      if ([string]::IsNullOrEmpty($replaceWith)) {
        $failedReason = 'Copy Match';
      }
      elseif ($Diagnose.ToBool()) {
        $groups.Named['Copy'] = get-Captures -MatchObject $copyMatch;
      }
    }
    elseif ($PSBoundParameters.ContainsKey('With')) {
      [string]$replaceWith = $With;
    }
    else {
      [string]$replaceWith = [string]::Empty;
    }

    if ([string]::IsNullOrEmpty($failedReason)) {
      if ($PSBoundParameters.ContainsKey('Paste')) {
        [string]$format = $Paste.Replace('${_c}', $replaceWith).Replace(
          '$0', $capturedPattern);
      }
      else {
        # Just do a straight swap of the pattern match for the replaceWith
        #
        [string]$format = $replaceWith;
      }

      [string]$result = ($PatternOccurrence -eq '*') `
        ? $Pattern.Replace($Value, $format) `
        : $Pattern.Replace($Value, $format, 1, $patternMatch.Index);

      if ($Diagnose.ToBool()) {
        $groups.Named['Pattern'] = get-Captures -MatchObject $patternMatch;
      }
    }
  }
  else {
    $failedReason = 'Pattern Match';
  }

  [boolean]$success = $([string]::IsNullOrEmpty($failedReason));
  if (-not($success)) {
    $result = $Value;
  }

  [PSCustomObject]$updateResult = [PSCustomObject]@{
    Payload         = $result;
    Success         = $success;
    CapturedPattern = $capturedPattern;
  }

  if (-not([string]::IsNullOrEmpty($failedReason))) {
    $updateResult | Add-Member -MemberType NoteProperty -Name 'FailedReason' -Value $failedReason;
  }

  if ($Diagnose.ToBool() -and ($groups.Named.Count -gt 0)) {
    $updateResult | Add-Member -MemberType NoteProperty -Name 'Diagnostics' -Value $groups;
  }

  return $updateResult;
} # Update-Match


function Invoke-ForeachFsItem {
  <#
  .NAME
    Invoke-ForeachFsItem
 
  .SYNOPSIS
    Allows a custom defined script-block or function to be invoked for all file system
  objects delivered through the pipeline.
 
  .DESCRIPTION
    2 parameters sets are defined, one for invoking a named function (InvokeFunction) and
  the other (InvokeScriptBlock, the default) for invoking a script-block. An optional
  Summary script block can be specified which will be invoked at the end of the pipeline
  batch. The user should assemble the candidate items from the file system, be they files or
  directories typically using Get-ChildItem, or can be any other function that delivers
  file systems items via the PowerShell pipeline. For each item in the pipeline,
  Invoke-ForeachFsItem will invoke the script-block/function specified. Invoke-ForeachFsItem
  will deliver what ever is returned from the script-block/function, so the result of
  Invoke-ForeachFsItem can be piped to another command.
 
  .PARAMETER Block
    The script block to be invoked. The script block is invoked for each item in the
  pipeline that satisfy the Condition with the following positional parameters:
    * pipelineItem: the item from the pipeline
    * index: the 0 based index representing current pipeline item
    * Exchange: a hash table containing miscellaneous information gathered internally
  throughout the pipeline batch. This can be of use to the user, because it is the way
  the user can perform bi-directional communication between the invoked custom script block
  and client side logic.
    * trigger: a boolean value, useful for state changing idempotent operations. At the end
  of the batch, the state of the trigger indicates whether any of the items were actioned.
  When the script block is invoked, the trigger should indicate if the trigger was pulled for
  any of the items so far processed in the pipeline. This is the responsibility of the
  client's block implementation. The trigger is only of use for state changing operations
  and can be ignored otherwise.
 
  In addition to these fixed positional parameters, if the invoked script-block is defined
  with additional parameters, then these will also be passed in. In order to achieve this,
  the client has to provide excess parameters in BlockParam and these parameters must be
  defined as the same type and in the same order as the additional parameters in the
  script-block.
 
  .PARAMETER BlockParams
    Optional array containing the excess parameters to pass into the script block.
 
  .PARAMETER Condition
    This is a predicate script-block, which is invoked with either a DirectoryInfo or
  FileInfo object presented as a result of invoking Get-ChildItem. It provides a filtering
  mechanism that is defined by the user to define which file system objects are selected
  for function/script-block invocation.
 
  .PARAMETER Directory
    Switch to indicate that the invoked function/script-block (invokee) is to handle Directory
  objects.
 
  .PARAMETER File
    Switch to indicate that the invoked function/script-block (invokee) is to handle FileInfo
  objects. Is mutually exclusive with the Directory switch. If neither switch is specified, then
  the invokee must be able to handle both therefore the Underscore parameter it defines must
  be declared as FileSystemInfo.
 
  .PARAMETER Functee
    String defining the function to be invoked. Works in a similar way to the Block parameter
  for script-blocks. The Function's base signature is as follows:
    * Underscore: (See pipelineItem described above)
    * Index: (See index described above)
    * Exchange: (See PathThru described above)
    * Trigger: (See trigger described above)
 
  .PARAMETER FuncteeParams
    Optional hash-table containing the named parameters which are splatted into the Functee
  function invoke. As it's a hash table, order is not significant.
 
  .PARAMETER Exchange
    A hash table containing miscellaneous information gathered internally throughout the
  pipeline batch. This can be of use to the user, because it is the way the user can perform
  bi-directional communication between the invoked custom script block and client side logic.
 
  .PARAMETER Header
    A script-block that is invoked at the start of the pipeline batch. The script-block is
  invoked with the following positional parameters:
    * Exchange: (see Exchange previously described)
 
    The Header can be customised with the following Exchange entries:
    * 'LOOPZ.KRAYOLA-THEME': Krayola Theme generally in use
    * 'LOOPZ.HEADER-BLOCK.MESSAGE': message displayed as part of the header
    * 'LOOPZ.HEADER-BLOCK.CRUMB-SIGNAL': Lead text displayed in header, default: '[+] '
    * 'LOOPZ.HEADER.PROPERTIES': An array of Key/Value pairs of items to be displayed
    * 'LOOPZ.HEADER-BLOCK.LINE': A string denoting the line to be displayed. (There are
    predefined lines available to use in $LoopzUI, or a custom one can be used instead)
 
  .PARAMETER Summary
    A script-block that is invoked at the end of the pipeline batch. The script-block is
  invoked with the following positional parameters:
    * count: the number of items processed in the pipeline batch.
    * skipped: the number of items skipped in the pipeline batch. An item is skipped if
    it fails the defined condition or is not of the correct type (eg if its a directory
    but we have specified the -File flag). Also note that, if the script-block/function
    sets the Break flag causing further iteration to stop, then those subsequent items
    in the pipeline which have not been processed are not reflected in the skip count.
    * trigger: Flag set by the script-block/function, but should typically be used to
    indicate whether any of the items processed were actively updated/written in this batch.
    This helps in written idempotent operations that can be re-run without adverse
    consequences.
    * Exchange: (see Exchange previously described)
 
  .PARAMETER Top
    Restricts the number of items processed in the rename batch, the remaining items
  are skipped. User can set this for experimental purposes.
 
  .PARAMETER pipelineItem
    This is the pipeline object, so should not be specified explicitly and can represent
  a file object (System.IO.FileInfo) or a directory object (System.IO.DirectoryInfo).
 
  .EXAMPLE 1
  Invoke a script-block to handle .txt file objects from the same directory (without -Recurse):
  (NB: first parameter is of type FileInfo, -File specified on Get-ChildItem and
  Invoke-ForeachFsItem. If Get-ChildItem is missing -File, then any Directory objects passed in
  are filtered out by Invoke-ForeachFsItem. If -File is missing from Invoke-ForeachFsItem, then
  the script-block's first parameter, must be a FileSystemInfo to handle both types)
 
    [scriptblock]$block = {
      param(
        [System.IO.FileInfo]$FileInfo,
        [int]$Index,
        [hashtable]$Exchange,
        [boolean]$Trigger
      )
      ...
    }
 
    Get-ChildItem './Tests/Data/fefsi' -Recurse -Filter '*.txt' -File | `
      Invoke-ForeachFsItem -File -Block $block;
 
  .EXAMPLE 2
  Invoke a function with additional parameters to handle directory objects from multiple directories
  (with -Recurse):
 
  function invoke-Target {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger,
      [string]$Format
    )
    ...
  }
 
  [hashtable]$parameters = @{
    'Format'
  }
  Get-ChildItem './Tests/Data/fefsi' -Recurse -Directory | `
    Invoke-ForeachFsItem -Directory -Functee 'invoke-Target' -FuncteeParams $parameters
 
  .EXAMPLE 3
  Invoke a script-block to handle empty .txt file objects from the same directory (without -Recurse):
    [scriptblock]$block = {
      param(
        [System.IO.FileInfo]$FileInfo,
        [int]$Index,
        [hashtable]$Exchange,
        [boolean]$Trigger
      )
      ...
    }
 
    [scriptblock]$fileIsEmpty = {
      param(
        [System.IO.FileInfo]$FileInfo
      )
      return (0 -eq $FileInfo.Length)
    }
 
    Get-ChildItem './Tests/Data/fefsi' -Recurse -Filter '*.txt' -File | Invoke-ForeachFsItem `
      -Block $block -File -condition $fileIsEmpty;
 
  .EXAMPLE 4
  Invoke a script-block only for directories whose name starts with "A" from the same
  directory (without -Recurse); Note the use of the LOOPZ function "Select-FsItem" in the
  directory include filter:
 
    [scriptblock]$block = {
      param(
        [System.IO.FileInfo]$FileInfo,
        [int]$Index,
        [hashtable]$Exchange,
        [boolean]$Trigger
      )
      ...
    }
 
  [scriptblock]$filterDirectories = {
    [OutputType([boolean])]
    param(
      [System.IO.DirectoryInfo]$directoryInfo
    )
    Select-FsItem -Name $directoryInfo.Name -Includes 'A*';
  }
 
    Get-ChildItem './Tests/Data/fefsi' -Directory | Invoke-ForeachFsItem `
      -Block $block -Directory -DirectoryIncludes $filterDirectories;
 
  .EXAMPLE 5
  Invoke a script-block to handle .txt file objects from the same directory. This
  example illustrates the use of the Header and Summary blocks. Blocks predefined
  in LoopzHelpers are illustrated but the user can defined their own.
 
    [scriptblock]$block = {
      param(
        [System.IO.FileInfo]$FileInfo,
        [int]$Index,
        [hashtable]$Exchange,
        [boolean]$Trigger
      )
      ...
    }
 
    $exchange = @{
      'LOOPZ.KRAYOLA-THEME' = $(Get-KrayolaTheme);
      'LOOPZ.HEADER-BLOCK.MESSAGE' = 'The owls are not what they seem';
      'LOOPZ.HEADER-BLOCK.PROPERTIES' = @(@('A', 'One'), @('B', 'Two'), @('C', 'Three'));
      'LOOPZ.HEADER-BLOCK.LINE' = $LoopzUI.TildeLine;
      'LOOPZ.SUMMARY-BLOCK.LINE' = $LoopzUI.DashLine;
    }
 
    Get-ChildItem './Tests/Data/fefsi' -Recurse -Filter '*.txt' -File | `
      Invoke-ForeachFsItem -File -Block $block -Exchange $exchange `
        -Header $LoopzHelpers.DefaultHeaderBlock -Summary $LoopzHelpers.SimpleSummaryBlock;
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
  [CmdletBinding(DefaultParameterSetName = 'InvokeScriptBlock')]
  [Alias('ife', 'Foreach-FsItem')]
  param(
    [Parameter(ParameterSetName = 'InvokeScriptBlock', Mandatory, ValueFromPipeline = $true)]
    [Parameter(ParameterSetName = 'InvokeFunction', Mandatory, ValueFromPipeline = $true)]
    [System.IO.FileSystemInfo]$pipelineItem,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Condition = ( { return $true; }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock', Mandatory)]
    [scriptblock]$Block,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [ValidateScript( { $_ -is [Array] })]
    $BlockParams = @(),

    [Parameter(ParameterSetName = 'InvokeFunction', Mandatory)]
    [ValidateScript( { -not([string]::IsNullOrEmpty($_)); })]
    [string]$Functee,

    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$FuncteeParams = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$Exchange = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Header = ( {
        param(
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Summary = ( {
        param(
          [int]$_count,
          [int]$_skipped,
          [int]$_errors,
          [boolean]$_trigger,
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('Directory')) })]
    [switch]$File,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [ValidateScript( { -not($PSBoundParameters.ContainsKey('File')) })]
    [switch]$Directory,

    [Parameter()]
    [ValidateScript( { $_ -gt 0 } )]
    [int]$Top
  ) # param

  begin {
    if (-not($Exchange.ContainsKey('LOOPZ.CONTROLLER'))) {
      $Exchange['LOOPZ.CONTROLLER'] = New-Controller -Type ForeachCtrl -Exchange $Exchange `
        -Header $Header -Summary $Summary;
    }
    $controller = $Exchange['LOOPZ.CONTROLLER'];
    $controller.ForeachBegin();

    [boolean]$topBreached = $false;
  }

  process {
    [boolean]$itemIsDirectory = ($pipelineItem.Attributes -band
      [System.IO.FileAttributes]::Directory) -eq [System.IO.FileAttributes]::Directory;

    [boolean]$acceptAll = -not($File.ToBool()) -and -not($Directory.ToBool());

    if (-not($controller.IsBroken())) {
      if ( $acceptAll -or ($Directory.ToBool() -and $itemIsDirectory) -or
        ($File.ToBool() -and -not($itemIsDirectory)) ) {
        if ($Condition.InvokeReturnAsIs($pipelineItem) -and -not($topBreached)) {
          [PSCustomObject]$result = $null;
          [int]$index = $controller.RequestIndex();
          [boolean]$trigger = $controller.GetTrigger();

          if ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
            $positional = @($pipelineItem, $index, $Exchange, $trigger);

            if ($BlockParams.Length -gt 0) {
              $BlockParams | ForEach-Object {
                $positional += $_;
              }
            }

            $result = Invoke-Command -ScriptBlock $Block -ArgumentList $positional;
          }
          elseif ('InvokeFunction' -eq $PSCmdlet.ParameterSetName) {
            [hashtable]$parameters = $FuncteeParams.Clone();

            $parameters['Underscore'] = $pipelineItem;
            $parameters['Index'] = $index;
            $parameters['Exchange'] = $Exchange;
            $parameters['Trigger'] = $trigger;

            $result = & $Functee @parameters;
          }

          $controller.HandleResult($result);
          if ($result -and $result.psobject.properties.match('Product') -and $result.Product) {
            $result.Product;
          }

          if ($PSBoundParameters.ContainsKey('Top') -and ($index -eq ($Top - 1))) {
            $topBreached = $true;
          }
        }
        else {
          # IDEA! We could allow the user to provide an extra script block which we
          # invoke for skipped items and set a string containing the reason why it was
          # skipped.
          $controller.SkipItem();
        }
      }
      else {
        $controller.SkipItem();
      }
    }
    else {
      $controller.SkipItem();
    }
  }

  end {
    $controller.ForeachEnd();
  }
} # Invoke-ForeachFsItem
function Invoke-MirrorDirectoryTree {
  <#
  .NAME
    Invoke-MirrorDirectoryTree
 
  .SYNOPSIS
    Mirrors a directory tree to a new location, invoking a custom defined scriptblock
  or function as it goes.
 
  .DESCRIPTION
    Copies a source directory tree to a new location applying custom functionality for each
  directory. 2 parameters set are defined, one for invoking a named function (InvokeFunction) and
  the other (InvokeScriptBlock, the default) for invoking a scriptblock. An optional
  Summary script block can be specified which will be invoked at the end of the mirroring
  batch.
 
  .PARAMETER Block
    The script block to be invoked. The script block is invoked for each directory in the
  source directory tree that satisfy the specified Directory Include/Exclude filters with
  the following positional parameters:
    * underscore: the DirectoryInfo object representing the directory in the source tree
    * index: the 0 based index representing current directory in the source tree
    * Exchange object: a hash table containing miscellaneous information gathered internally
    throughout the mirroring batch. This can be of use to the user, because it is the way
    the user can perform bi-directional communication between the invoked custom script block
    and client side logic.
    * trigger: a boolean value, useful for state changing idempotent operations. At the end
    of the batch, the state of the trigger indicates whether any of the items were actioned.
    When the script block is invoked, the trigger should indicate if the trigger was pulled for
    any of the items so far processed in the batch. This is the responsibility of the
    client's script-block/function implementation.
 
  In addition to these fixed positional parameters, if the invoked scriptblock is defined
  with additional parameters, then these will also be passed in. In order to achieve this,
  the client has to provide excess parameters in BlockParams and these parameters must be
  defined as the same type and in the same order as the additional parameters in the
  script-block.
 
  The destination DirectoryInfo object can be accessed via the Exchange denoted by
  the 'LOOPZ.MIRROR.DESTINATION' entry.
 
  .PARAMETER BlockParams
    Optional array containing the excess parameters to pass into the script-block/function.
 
  .PARAMETER CopyFiles
    Switch parameter that indicates that files matching the specified filters should be copied
 
  .PARAMETER CreateDirs
    switch parameter indicates that directories should be created in the destination tree. If
  not set, then Invoke-MirrorDirectoryTree turns into a function that traverses the source
  directory invoking the function/script-block for matching directories.
 
  .PARAMETER DestinationPath
    The destination Path denoting the root of the directory tree where the source tree
  will be mirrored to.
 
  .PARAMETER DirectoryIncludes
    An array containing a list of filters, each must contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be ignored. If the directory
  matches any of the filters in the list, it will be mirrored in the destination tree.
  If DirectoryIncludes contains just a single element which is the empty string, this means
  that nothing is included (rather than everything being included).
 
  .PARAMETER DirectoryExcludes
    An array containing a list of filters, each must contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be ignored. If the directory
  matches any of the filters in the list, it will NOT be mirrored in the destination tree.
  Any match in the DirectoryExcludes overrides a match in DirectoryIncludes, so a directory
  that is matched in Include, can be excluded by the Exclude.
 
  .PARAMETER Exchange
    A hash table containing miscellaneous information gathered internally
  throughout the pipeline batch. This can be of use to the user, because it is the way
  the user can perform bi-directional communication between the invoked custom script block
  and client side logic.
 
  .PARAMETER FileExcludes
    An array containing a list of filters, each may contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be treated as a file suffix.
  If the file in the source tree matches any of the filters in the list, it will NOT be
  mirrored in the destination tree. Any match in the FileExcludes overrides a match in
  FileIncludes, so a file that is matched in Include, can be excluded by the Exclude.
 
  .PARAMETER FileIncludes
    An array containing a list of filters, each may contain a wild-card ('*'). If a
  particular filter does not contain a wild-card, then it will be treated as a file suffix.
  If the file in the source tree matches any of the filters in the list, it will be mirrored
  in the destination tree. If FileIncludes contains just a single element which is the empty
  string, this means that nothing is included (rather than everything being included).
 
 
  .PARAMETER Functee
    String defining the function to be invoked. Works in a similar way to the Block parameter
  for script-blocks. The Function's base signature is as follows:
  * "Underscore": (See underscore described above)
  * "Index": (See index described above)
  * "Exchange": (See PathThru described above)
  * "Trigger": (See trigger described above)
 
  The destination DirectoryInfo object can be accessed via the Exchange denoted by
  the 'LOOPZ.MIRROR.DESTINATION' entry.
 
  .PARAMETER FuncteeParams
    Optional hash-table containing the named parameters which are splatted into the Functee
  function invoke. As it's a hash table, order is not significant.
 
  .PARAMETER Header
    A script-block that is invoked for each directory that also contains child directories.
  The script-block is invoked with the following positional parameters:
    * Exchange: (see Exchange previously described)
 
    The Header can be customised with the following Exchange entries:
    * 'LOOPZ.KRAYOLA-THEME': Krayola Theme generally in use
    * 'LOOPZ.HEADER-BLOCK.MESSAGE': message displayed as part of the header
    * 'LOOPZ.HEADER-BLOCK.CRUMB-SIGNAL': Lead text displayed in header, default: '[+] '
    * 'LOOPZ.HEADER.PROPERTIES': An array of Key/Value pairs of items to be displayed
    * 'LOOPZ.HEADER-BLOCK.LINE': A string denoting the line to be displayed. (There are
    predefined lines available to use in $LoopzUI, or a custom one can be used instead)
 
  .PARAMETER Hoist
    switch parameter. Without Hoist being specified, the filters can prove to be too restrictive
  on matching against directories. If a directory does not match the filters then none of its
  descendants will be considered to be mirrored in the destination tree. When Hoist is specified
  then a descendant directory that does match the filters will be mirrored even though any of
  its ancestors may not match the filters.
 
  .PARAMETER Path
    The source Path denoting the root of the directory tree to be mirrored.
 
  .PARAMETER SessionHeader
    A script-block that is invoked at the start of the mirroring batch. The script-block has
  the same signature as the Header script block.
 
  .PARAMETER SessionSummary
    A script-block that is invoked at the end of the mirroring batch. The script-block has
  the same signature as the Summary script block.
 
  .PARAMETER Summary
    A script-block that is invoked foreach directory that also contains child directories,
  after all its descendants have been processed and serves as a sub-total for the current
  directory. The script-block is invoked with the following positional parameters:
    * count: the number of items processed in the mirroring batch.
    * skipped: the number of items skipped in the mirroring batch. An item is skipped if
    it fails the defined condition or is not of the correct type (eg if its a directory
    but we have specified the -File flag).
    * errors: the number of items which resulted in error. An error occurs when the function
    or the script-block has set the Error property on the invoke result.
    * trigger: Flag set by the script-block/function, but should typically be used to
    indicate whether any of the items processed were actively updated/written in this batch.
    This helps in written idempotent operations that can be re-run without adverse
    consequences.
    * Exchange: (see Exchange previously described)
 
  .EXAMPLE 1
    Invoke a named function for every directory in the source tree and mirror every
  directory in the destination tree. The invoked function has an extra parameter in it's
  signature, so the extra parameters must be passed in via FuncteeParams (the standard
  signature being the first 4 parameters shown.)
 
  function Test-Mirror {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger,
      [string]$Format
    )
    ...
  }
 
  [hashtable]$parameters = @{
    'Format' = '---- {0} ----';
  }
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' `
    -DestinationPath './Tests/Data/mirror' -CreateDirs `
    -Functee 'Test-Mirror' -FuncteeParams $parameters;
 
  .EXAMPLE 2
  Invoke a script-block for every directory in the source tree and copy all files
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' `
    -DestinationPath './Tests/Data/mirror' -CreateDirs -CopyFiles -block {
      param(
        [System.IO.DirectoryInfo]$Underscore,
        [int]$Index,
        [hashtable]$Exchange,
        [boolean]$Trigger
      )
      ...
    };
 
  .EXAMPLE 3
  Mirror a directory tree, including only directories beginning with A (filter A*)
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' -DestinationPath './Tests/Data/mirror' `
    -DirectoryIncludes @('A*')
 
  Note the possible issue with this example is that any descendants named A... which are located
  under an ancestor which is not named A..., will not be mirrored;
 
  eg './Tests/Data/fefsi/Audio/mp3/A/Amorphous Androgynous', even though "Audio", "A" and
  "Amorphous Androgynous" clearly match the A* filter, they will not be mirrored because
  the "mp3" directory, would be filtered out.
  See the following example for a resolution.
 
  .EXAMPLE 4
  Mirror a directory tree, including only directories beginning with A (filter A*) regardless of
  the matching of intermediate ancestors (specifying -Hoist flag resolves the possible
  issue in the previous example)
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' -DestinationPath './Tests/Data/mirror' `
    -DirectoryIncludes @('A*') -CreateDirs -CopyFiles -Hoist
 
  Note that the directory filter must include a wild-card, otherwise it will be ignored. So a
  directory include of @('A'), is problematic, because A is not a valid directory filter so its
  ignored and there are no remaining filters that are able to include any directory, so no
  directory passes the filter.
 
  .EXAMPLE 5
  Mirror a directory tree, including files with either .flac or .wav suffix
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' -DestinationPath './Tests/Data/mirror' `
    -FileIncludes @('flac', '*.wav') -CreateDirs -CopyFiles -Hoist
 
  Note that for files, a filter may or may not contain a wild-card. If the wild-card is missing
  then it is automatically treated as a file suffix; so 'flac' means '*.flac'.
 
  .EXAMPLE 6
  Mirror a directory tree copying over just flac files
 
  [scriptblock]$summary = {
    param(
      [int]$_count,
      [int]$_skipped,
      [boolean]$_triggered,
      [hashtable]$_exchange
    )
    ...
  }
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' -DestinationPath './Tests/Data/mirror' `
    -FileIncludes @('flac') -CopyFiles -Hoist -Summary $summary
 
  Note that -CreateDirs is missing which means directories will not be mirrored by default. They
  are only mirrored as part of the process of copying over flac files, so in the end the
  resultant mirror directory tree will contain directories that include flac files.
 
  .EXAMPLE 7
  Same as EXAMPLE 6, but using predefined Header and Summary script-blocks for Session header/summary
  and per directory header/summary.
 
  Invoke-MirrorDirectoryTree -Path './Tests/Data/fefsi' -DestinationPath './Tests/Data/mirror' `
  -FileIncludes @('flac') -CopyFiles -Hoist `
  -Header $LoopzHelpers.DefaultHeaderBlock -Summary $DefaultHeaderBlock.SimpleSummaryBlock `
  -SessionHeader $LoopzHelpers.DefaultHeaderBlock -SessionSummary $DefaultHeaderBlock.SimpleSummaryBlock;
  #>


  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
  [CmdletBinding(SupportsShouldProcess, DefaultParameterSetName = 'InvokeScriptBlock')]
  [Alias('imdt', 'Mirror-Directory')]
  param
  (
    [Parameter(Mandatory, ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(Mandatory, ParameterSetName = 'InvokeFunction')]
    [ValidateScript( { Test-path -Path $_; })]
    [String]$Path,

    [Parameter(Mandatory, ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(Mandatory, ParameterSetName = 'InvokeFunction')]
    [String]$DestinationPath,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [String[]]$DirectoryIncludes = @('*'),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [String[]]$DirectoryExcludes = @(),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [String[]]$FileIncludes = @('*'),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [String[]]$FileExcludes = @(),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$Exchange = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [scriptblock]$Block = ( {
        [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
        param(
          [System.IO.DirectoryInfo]$underscore,
          [int]$index,
          [hashtable]$exchange,
          [boolean]$trigger
        )
      } ),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [ValidateScript( { $_ -is [Array] })]
    $BlockParams = @(),

    [Parameter(ParameterSetName = 'InvokeFunction', Mandatory)]
    [ValidateScript( { -not([string]::IsNullOrEmpty($_)); })]
    [string]$Functee,

    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$FuncteeParams = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [switch]$CreateDirs,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [switch]$CopyFiles,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [switch]$Hoist,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Header = ( {
        param(
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Summary = ( {
        [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
        param(
          [int]$_index,
          [int]$_skipped,
          [int]$_errors,
          [boolean]$_trigger,
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$SessionHeader = ( {
        param(
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$SessionSummary = ( {
        param(
          [int]$_count,
          [int]$_skipped,
          [int]$_errors,
          [boolean]$_trigger,
          [hashtable]$_exchange
        )
      })
  ) # param

  # ================================================================== [doMirrorBlock] ===
  #
  [scriptblock]$doMirrorBlock = {
    param(
      [Parameter(Mandatory)]
      [System.IO.DirectoryInfo]$_underscore,

      [Parameter(Mandatory)]
      [int]$_index,

      [Parameter(Mandatory)]
      [hashtable]$_exchange,

      [Parameter(Mandatory)]
      [boolean]$_trigger
    )

    # Write-Host "[+] >>> doMirrorBlock: $($_underscore.Name)";

    [string]$rootSource = $_exchange['LOOPZ.MIRROR.ROOT-SOURCE'];
    [string]$rootDestination = $_exchange['LOOPZ.MIRROR.ROOT-DESTINATION'];

    $sourceDirectoryFullName = $_underscore.FullName;

    # sourceDirectoryFullName must end with directory separator
    #
    if (-not($sourceDirectoryFullName.EndsWith([System.IO.Path]::DirectorySeparatorChar))) {
      $sourceDirectoryFullName += [System.IO.Path]::DirectorySeparatorChar;
    }

    $destinationBranch = edit-RemoveSingleSubString -Target $sourceDirectoryFullName -Subtract $rootSource;

    $destinationDirectory = Join-Path -Path $rootDestination -ChildPath $destinationBranch;
    $_exchange['LOOPZ.MIRROR.BRANCH-DESTINATION'] = $destinationBranch;

    [boolean]$whatIf = $_exchange.ContainsKey('WHAT-IF') -and ($_exchange['WHAT-IF']);
    Write-Debug "[+] >>> doMirrorBlock: destinationDirectory: '$destinationDirectory'";

    if ($whatIf) {
      if (Test-Path -Path $destinationDirectory) {
        Write-Debug " [-] (WhatIf) Get existing destination branch directory: '$destinationBranch'";
        $destinationInfo = (Get-Item -Path $destinationDirectory);
      }
      else {
        Write-Debug " [-] (WhatIf) Creating synthetic destination branch directory: '$destinationBranch'";
        $destinationInfo = ([System.IO.DirectoryInfo]::new($destinationDirectory));
      }
    }
    else {
      if ($CreateDirs.ToBool()) {
        Write-Debug " [-] Creating destination branch directory: '$destinationBranch'";

        $destinationInfo = (Test-Path -Path $destinationDirectory) `
          ? (Get-Item -Path $destinationDirectory) `
          : (New-Item -ItemType 'Directory' -Path $destinationDirectory);
      }
      else {
        Write-Debug " [-] Creating destination branch directory INFO obj: '$destinationBranch'";
        $destinationInfo = New-Object -TypeName System.IO.DirectoryInfo ($destinationDirectory);
      }
    }

    if ($CopyFiles.ToBool()) {
      Write-Debug " [-] Creating files for branch directory: '$destinationBranch'";

      # To use the include/exclude parameters on Copy-Item, the Path specified
      # must end in /*. We only need to add the star though because we added the /
      # previously.
      #
      [string]$sourceDirectoryWithWildCard = $sourceDirectoryFullName + '*';

      [string[]]$adjustedFileIncludes = $FileIncludes | ForEach-Object {
        $_.Contains('*') ? $_ : "*.$_".Replace('..', '.');
      }

      [string[]]$adjustedFileExcludes = $FileExcludes | ForEach-Object {
        $_.Contains('*') ? $_ : "*.$_".Replace('..', '.');
      }

      # Ensure that the destination directory exists, but only if there are
      # files to copy over which pass the include/exclude filters. This is
      # required in the case where CreateDirs has not been specified.
      #
      [array]$filesToCopy = Get-ChildItem $sourceDirectoryWithWildCard `
        -Include $adjustedFileIncludes -Exclude $adjustedFileExcludes -File;

      if ($filesToCopy) {
        if (-not($whatIf)) {
          if (-not(Test-Path -Path $destinationDirectory)) {
            New-Item -ItemType 'Directory' -Path $destinationDirectory;
          }

          Copy-Item -Path $sourceDirectoryWithWildCard `
            -Include $adjustedFileIncludes -Exclude $adjustedFileExcludes `
            -Destination $destinationDirectory;
        }
        $_exchange['LOOPZ.MIRROR.COPIED-FILES.COUNT'] = $filesToCopy.Count;

        Write-Debug " [-] No of files copied: '$($filesToCopy.Count)'";
      }
      else {
        $_exchange.Remove('LOOPZ.MIRROR.COPIED-FILES.COUNT');
        $_exchange.Remove('LOOPZ.MIRROR.COPIED-FILES.INCLUDES');
      }
    }

    # To be consistent with Invoke-ForeachFsItem, the user function/block is invoked
    # with the source directory info. The destination for this mirror operation is
    # returned via 'LOOPZ.MIRROR.DESTINATION' within the Exchange.
    #
    $_exchange['LOOPZ.MIRROR.DESTINATION'] = $destinationInfo;

    $invokee = $_exchange['LOOPZ.MIRROR.INVOKEE'];

    if ($invokee -is [scriptblock]) {
      $positional = @($_underscore, $_index, $_exchange, $_trigger);

      if ($_exchange.ContainsKey('LOOPZ.MIRROR.INVOKEE.PARAMS')) {
        $_exchange['LOOPZ.MIRROR.INVOKEE.PARAMS'] | ForEach-Object {
          $positional += $_;
        }
      }

      $invokee.InvokeReturnAsIs($positional);
    }
    elseif ($invokee -is [string]) {
      [hashtable]$parameters = $_exchange.ContainsKey('LOOPZ.MIRROR.INVOKEE.PARAMS') `
        ? $_exchange['LOOPZ.MIRROR.INVOKEE.PARAMS'] : @{};
      $parameters['Underscore'] = $_underscore;
      $parameters['Index'] = $_index;
      $parameters['Exchange'] = $_exchange;
      $parameters['Trigger'] = $_trigger;

      & $invokee @parameters;
    }
    else {
      Write-Warning "User defined function/block not valid, not invoking.";
    }

    @{ Product = $destinationInfo }
  } #doMirrorBlock

  # ===================================================== [Invoke-MirrorDirectoryTree] ===

  [string]$resolvedSourcePath = Convert-Path $Path;
  [string]$resolvedDestinationPath = Convert-Path $DestinationPath;

  $Exchange['LOOPZ.MIRROR.ROOT-SOURCE'] = $resolvedSourcePath;
  $Exchange['LOOPZ.MIRROR.ROOT-DESTINATION'] = $resolvedDestinationPath;

  if ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
    $Exchange['LOOPZ.MIRROR.INVOKEE'] = $Block;

    if ($BlockParams.Count -gt 0) {
      $Exchange['LOOPZ.MIRROR.INVOKEE.PARAMS'] = $BlockParams;
    }
  }
  else {
    $Exchange['LOOPZ.MIRROR.INVOKEE'] = $Functee;

    if ($FuncteeParams.Count -gt 0) {
      $Exchange['LOOPZ.MIRROR.INVOKEE.PARAMS'] = $FuncteeParams.Clone();
    }
  }

  if ($PSBoundParameters.ContainsKey('WhatIf') -and ($true -eq $PSBoundParameters['WhatIf'])) {
    $Exchange['WHAT-IF'] = $true;
  }

  if ($CopyFiles.ToBool()) {
    $Exchange['LOOPZ.MIRROR.COPIED-FILES.INCLUDES'] = $FileIncludes -join ', ';
  }

  [scriptblock]$filterDirectories = {
    [OutputType([boolean])]
    param(
      [System.IO.DirectoryInfo]$directoryInfo
    )
    Select-FsItem -Name $directoryInfo.Name `
      -Includes $DirectoryIncludes -Excludes $DirectoryExcludes;
  }

  $null = Invoke-TraverseDirectory -Path $resolvedSourcePath `
    -Block $doMirrorBlock -Exchange $Exchange -Header $Header -Summary $Summary `
    -SessionHeader $SessionHeader -SessionSummary $SessionSummary -Condition $filterDirectories -Hoist:$Hoist;
} # Invoke-MirrorDirectoryTree

function Invoke-TraverseDirectory {
  <#
  .NAME
    Invoke-TraverseDirectory
 
  .SYNOPSIS
    Traverses a directory tree invoking a custom defined script-block or named function
  as it goes.
 
  .DESCRIPTION
    Navigates a directory tree applying custom functionality for each directory. A Condition
  script-block can be applied for conditional functionality. 2 parameters set are defined, one
  for invoking a named function (InvokeFunction) and the other (InvokeScriptBlock, the default)
  for invoking a scriptblock. An optional Summary script block can be specified which will be
  invoked at the end of the traversal batch.
 
  .PARAMETER Block
    The script block to be invoked. The script block is invoked for each directory in the
  source directory tree that satisfy the specified Condition predicate with
  the following positional parameters:
    * underscore: the DirectoryInfo object representing the directory in the source tree
    * index: the 0 based index representing current directory in the source tree
    * Exchange object: a hash table containing miscellaneous information gathered internally
    throughout the mirroring batch. This can be of use to the user, because it is the way
    the user can perform bi-directional communication between the invoked custom script block
    and client side logic.
    * trigger: a boolean value, useful for state changing idempotent operations. At the end
    of the batch, the state of the trigger indicates whether any of the items were actioned.
    When the script block is invoked, the trigger should indicate if the trigger was pulled for
    any of the items so far processed in the batch. This is the responsibility of the
    client's script-block/function implementation.
 
  In addition to these fixed positional parameters, if the invoked scriptblock is defined
  with additional parameters, then these will also be passed in. In order to achieve this,
  the client has to provide excess parameters in BlockParams and these parameters must be
  defined as the same type and in the same order as the additional parameters in the
  script-block.
 
  .PARAMETER BlockParams
    Optional array containing the excess parameters to pass into the script-block.
 
  .PARAMETER Condition
    This is a predicate script-block, which is invoked with a DirectoryInfo object presented
  as a result of invoking Get-ChildItem. It provides a filtering mechanism that is defined
  by the user to define which directories are selected for function/script-block invocation.
 
  .PARAMETER Exchange
    A hash table containing miscellaneous information gathered internally throughout the
  traversal batch. This can be of use to the user, because it is the way the user can perform
  bi-directional communication between the invoked custom script block and client side logic.
 
  .PARAMETER Functee
    String defining the function to be invoked. Works in a similar way to the Block parameter
  for script-blocks. The Function's base signature is as follows:
  * "Underscore": (See underscore described above)
  * "Index": (See index described above)
  * "Exchange": (See PathThru described above)
  * "Trigger": (See trigger described above)
 
  The destination DirectoryInfo object can be accessed via the Exchange denoted by
  the 'LOOPZ.MIRROR.DESTINATION' entry.
 
  .PARAMETER FuncteeParams
    Optional hash-table containing the named parameters which are splatted into the Functee
  function invoke. As it's a hash table, order is not significant.
 
  .PARAMETER Header
    A script-block that is invoked for each directory that also contains child directories.
  The script-block is invoked with the following positional parameters:
    * Exchange: (see Exchange previously described)
 
    The Header can be customised with the following Exchange entries:
    * 'LOOPZ.KRAYOLA-THEME': Krayola Theme generally in use
    * 'LOOPZ.HEADER-BLOCK.MESSAGE': message displayed as part of the header
    * 'LOOPZ.HEADER-BLOCK.CRUMB-SIGNAL': Lead text displayed in header, default: '[+] '
    * 'LOOPZ.HEADER.PROPERTIES': An array of Key/Value pairs of items to be displayed
    * 'LOOPZ.HEADER-BLOCK.LINE': A string denoting the line to be displayed. (There are
    predefined lines available to use in $LoopzUI, or a custom one can be used instead)
 
  .PARAMETER Hoist
    Switch parameter. Without Hoist being specified, the Condition can prove to be too restrictive
  on matching against directories. If a directory does not match the Condition then none of its
  descendants will be considered to be traversed. When Hoist is specified then a descendant directory
  that does match the Condition will be traversed even though any of its ancestors may not match the
  same Condition.
 
  .PARAMETER Path
    The source Path denoting the root of the directory tree to be traversed.
 
  .PARAMETER SessionHeader
    A script-block that is invoked at the start of the traversal batch. The script-block has
  the same signature as the Header script block.
 
  .PARAMETER SessionSummary
    A script-block that is invoked at the end of the traversal batch. The script-block has
  the same signature as the Summary script block.
 
  .PARAMETER Summary
    A script-block that is invoked foreach directory that also contains child directories,
  after all its descendants have been processed and serves as a sub-total for the current
  directory. The script-block is invoked with the following positional parameters:
    * count: the number of items processed in the mirroring batch.
    * skipped: the number of items skipped in the mirroring batch. An item is skipped if
    it fails the defined condition or is not of the correct type (eg if its a directory
    but we have specified the -File flag).
    * errors: the number of items which resulted in error. An error occurs when the function
    or the script-block has set the Error property on the invoke result.
    * trigger: Flag set by the script-block/function, but should typically be used to
    indicate whether any of the items processed were actively updated/written in this batch.
    This helps in written idempotent operations that can be re-run without adverse
    consequences.
    * Exchange: (see Exchange previously described)
 
  .EXAMPLE 1
    Invoke a script-block for every directory in the source tree.
 
    [scriptblock]$block = {
      param(
        $underscore,
        [int]$index,
        [hashtable]$exchange,
        [boolean]$trigger
      )
      ...
    }
 
  Invoke-TraverseDirectory -Path './Tests/Data/fefsi' -Block $block
 
  .EXAMPLE 2
    Invoke a named function with extra parameters for every directory in the source tree.
 
  function Test-Traverse {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger,
      [string]$Format
    )
    ...
  }
  [hashtable]$parameters = @{
    'Format' = "=== {0} ===";
  }
 
  Invoke-TraverseDirectory -Path './Tests/Data/fefsi' `
    -Functee 'Test-Traverse' -FuncteeParams $parameters;
 
  .EXAMPLE 3
  Invoke a named function, including only directories beginning with A (filter A*)
 
  function Test-Traverse {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger
    )
    ...
  }
 
  [scriptblock]$filterDirectories = {
    [OutputType([boolean])]
    param(
      [System.IO.DirectoryInfo]$directoryInfo
    )
 
    Select-FsItem -Name $directoryInfo.Name -Includes @('A*');
  }
 
  Invoke-TraverseDirectory -Path './Tests/Data/fefsi' -Functee 'Test-Traverse' `
    -Condition $filterDirectories;
 
  Note the possible issue with this example is that any descendants named A... which are located
  under an ancestor which is not named A..., will not be processed by the provided function
 
  .EXAMPLE 4
  Mirror a directory tree, including only directories beginning with A (filter A*) regardless of
  the matching of intermediate ancestors (specifying -Hoist flag resolves the possible
  issue in the previous example)
 
  function Test-Traverse {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger
    )
    ...
  }
 
  [scriptblock]$filterDirectories = {
    [OutputType([boolean])]
    param(
      [System.IO.DirectoryInfo]$directoryInfo
    )
 
    Select-FsItem -Name $directoryInfo.Name -Includes @('A*');
  }
 
  Invoke-TraverseDirectory -Path './Tests/Data/fefsi' -Functee 'Test-Traverse' `
    -Condition $filterDirectories -Hoist;
 
  Note that the directory filter must include a wild-card, otherwise it will be ignored. So a
  directory include of @('A'), is problematic, because A is not a valid directory filter so its
  ignored and there are no remaining filters that are able to include any directory, so no
  directory passes the filter.
 
  .EXAMPLE 5
  Same as EXAMPLE 4, but using predefined Header and Summary script-blocks for Session header/summary
  and per directory header/summary. (Test-Traverse and filterDirectories as per EXAMPLE 4)
 
  Invoke-TraverseDirectory -Path './Tests/Data/fefsi' -Functee 'Test-Traverse' `
    -Condition $filterDirectories -Hoist `
    -Header $LoopzHelpers.DefaultHeaderBlock -Summary $DefaultHeaderBlock.SimpleSummaryBlock `
    -SessionHeader $LoopzHelpers.DefaultHeaderBlock -SessionSummary $DefaultHeaderBlock.SimpleSummaryBlock;
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
  [CmdletBinding(DefaultParameterSetName = 'InvokeScriptBlock')]
  [Alias('itd', 'Traverse-Directory')]
  param
  (
    [Parameter(ParameterSetName = 'InvokeScriptBlock', Mandatory)]
    [Parameter(ParameterSetName = 'InvokeFunction', Mandatory)]
    [ValidateScript( { Test-path -Path $_ })]
    [String]$Path,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [ValidateScript( { -not($_ -eq $null) })]
    [scriptblock]$Condition = (
      {
        [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
        param([System.IO.DirectoryInfo]$directoryInfo)
        return $true;
      }
    ),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$Exchange = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [ValidateScript( { -not($_ -eq $null) })]
    [scriptblock]$Block,

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [ValidateScript( { $_ -is [Array] })]
    $BlockParams = @(),

    [Parameter(ParameterSetName = 'InvokeFunction', Mandatory)]
    [ValidateScript( { -not([string]::IsNullOrEmpty($_)); })]
    [string]$Functee,

    [Parameter(ParameterSetName = 'InvokeFunction')]
    [hashtable]$FuncteeParams = @{},

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Header = ( {
        param(
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$Summary = ( {
        [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
        param(
          [int]$_count,
          [int]$_skipped,
          [int]$_errors,
          [boolean]$_triggered,
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$SessionHeader = ( {
        param(
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [scriptblock]$SessionSummary = ( {
        param(
          [int]$_count,
          [int]$_skipped,
          [int]$_errors,
          [boolean]$_trigger,
          [hashtable]$_exchange
        )
      }),

    [Parameter(ParameterSetName = 'InvokeScriptBlock')]
    [Parameter(ParameterSetName = 'InvokeFunction')]
    [switch]$Hoist
  ) # param

  # ======================================================= [recurseTraverseDirectory] ===
  #
  [scriptblock]$recurseTraverseDirectory = { # Invoked by adapter
    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
    param(
      [Parameter(Position = 0, Mandatory)]
      [System.IO.DirectoryInfo]$directoryInfo,

      [Parameter(Position = 1)]
      [ValidateScript( { -not($_ -eq $null) })]
      [scriptblock]$condition,

      [Parameter(Position = 2, Mandatory)]
      [ValidateScript( { -not($_ -eq $null) })]
      [hashtable]$exchange,

      [Parameter(Position = 3)]
      [ValidateScript( { ($_ -is [scriptblock]) -or ($_ -is [string]) })]
      $invokee, # (scriptblock or function name; hence un-typed parameter)

      [Parameter(Position = 4)]
      [boolean]$trigger
    )

    $result = $null;
    $index = $exchange['LOOPZ.FOREACH.INDEX'];

    # This is the invoke, for the current directory
    #
    if ($invokee -is [scriptblock]) {
      $positional = @($directoryInfo, $index, $exchange, $trigger);

      if ($exchange.ContainsKey('LOOPZ.TRAVERSE.INVOKEE.PARAMS') -and
        ($exchange['LOOPZ.TRAVERSE.INVOKEE.PARAMS'].Count -gt 0)) {
        $exchange['LOOPZ.TRAVERSE.INVOKEE.PARAMS'] | ForEach-Object {
          $positional += $_;
        }
      }
      $result = $invokee.InvokeReturnAsIs($positional);
    }
    else {
      [hashtable]$parameters = $exchange.ContainsKey('LOOPZ.TRAVERSE.INVOKEE.PARAMS') `
        ? $exchange['LOOPZ.TRAVERSE.INVOKEE.PARAMS'] : @{};

      # These are directory specific overwrites. The custom parameters
      # will still be present
      #
      $parameters['Underscore'] = $directoryInfo;
      $parameters['Index'] = $index;
      $parameters['Exchange'] = $exchange;
      $parameters['Trigger'] = $trigger;

      $result = & $invokee @parameters;
    }

    [string]$fullName = $directoryInfo.FullName;
    [System.IO.DirectoryInfo[]]$directoryInfos = Get-ChildItem -Path $fullName `
      -Directory | Where-Object { $condition.InvokeReturnAsIs($_) };

    [scriptblock]$adapter = $Exchange['LOOPZ.TRAVERSE.ADAPTOR'];

    if ($directoryInfos) {
      # adapter is always a script block, this has nothing to do with the invokee,
      # which may be a script block or a named function(functee)
      #
      $directoryInfos | Invoke-ForeachFsItem -Directory -Block $adapter `
        -Exchange $Exchange -Condition $condition -Summary $Summary;
    }

    return $result;
  } # recurseTraverseDirectory

  # ======================================================================== [adapter] ===
  #
  [scriptblock]$adapter = {
    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
    param(
      [Parameter(Mandatory)]
      [System.IO.DirectoryInfo]$_underscore,

      [Parameter(Mandatory)]
      [int]$_index,

      [Parameter(Mandatory)]
      [hashtable]$_exchange,

      [Parameter(Mandatory)]
      [boolean]$_trigger
    )

    [scriptblock]$adapted = $_exchange['LOOPZ.TRAVERSE.ADAPTED'];
    $controller = $_exchange['LOOPZ.CONTROLLER'];

    try {
      $adapted.InvokeReturnAsIs(
        $_underscore,
        $_exchange['LOOPZ.TRAVERSE.CONDITION'],
        $_exchange,
        $Exchange['LOOPZ.TRAVERSE.INVOKEE'],
        $_trigger
      );
    }
    catch [System.Management.Automation.MethodInvocationException] {
      $controller.ErrorItem();
      # This is a mystery exception, that has no effect on processing the batch:
      #
      # Exception calling ".ctor" with "2" argument(s): "Count cannot be less than zero.
      #
      # Resolve-Error
      # Write-Error "Problem with: '$_underscore'" -ErrorAction Stop;
    }
    catch {
      $controller.ErrorItem();
      Write-Error "[!] Error: $($_.Exception.Message)" -ErrorAction Continue;

      throw;
    }
  } # adapter

  # ======================================================= [Invoke-TraverseDirectory] ===

  $controller = New-Controller -Type TraverseCtrl -Exchange $Exchange `
    -Header $Header -Summary $Summary -SessionHeader $SessionHeader -SessionSummary $SessionSummary;
  $Exchange['LOOPZ.CONTROLLER'] = $controller;

  $controller.BeginSession();

  # Handle top level directory, before recursing through child directories
  #
  [System.IO.DirectoryInfo]$directory = Get-Item -Path $Path;

  [boolean]$itemIsDirectory = ($directory.Attributes -band
    [System.IO.FileAttributes]::Directory) -eq [System.IO.FileAttributes]::Directory;

  if ($itemIsDirectory) {
    if ($Condition.InvokeReturnAsIs($directory)) {
      [boolean]$trigger = $controller.GetTrigger();

      # The index of the top level directory is always 0
      #
      [int]$index = $controller.RequestIndex();

      if ('InvokeFunction' -eq $PSCmdlet.ParameterSetName) {
        # set-up custom parameters
        #
        [hashtable]$parameters = $FuncteeParams.Clone();
        $parameters['Underscore'] = $directory;
        $parameters['Index'] = $index;
        $parameters['Exchange'] = $Exchange;
        $parameters['Trigger'] = $trigger;
        $Exchange['LOOPZ.TRAVERSE.INVOKEE.PARAMS'] = $parameters;
      }
      elseif ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
        $positional = @($directory, $index, $Exchange, $trigger);

        if ($BlockParams.Count -gt 0) {
          $BlockParams | Foreach-Object {
            $positional += $_;
          }
        }

        # Note, for the positional parameters, we can only pass in the additional
        # custom parameters provided by the client here via the Exchange otherwise
        # we could accidentally build up the array of positional parameters with
        # duplicated entries. This is in contrast to splatted arguments for function
        # invokes where parameter names are paired with parameter values in a
        # hashtable and naturally prevent duplicated entries. This is why we set
        # 'LOOPZ.TRAVERSE.INVOKEE.PARAMS' to $BlockParams and not $positional.
        #
        $Exchange['LOOPZ.TRAVERSE.INVOKEE.PARAMS'] = $BlockParams;
      }

      $result = $null;

      # This is the top level invoke
      #
      try {
        if ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
          $result = $Block.InvokeReturnAsIs($positional);
        }
        elseif ('InvokeFunction' -eq $PSCmdlet.ParameterSetName) {
          $result = & $Functee @parameters;
        }
      }
      catch {
        $controller.IncrementError();
      }
      finally {
        $controller.HandleResult($result);
      }
    }
    else {
      $controller.SkipItem();
    }

    # --- end of top level invoke ----------------------------------------------------------

    if ($Hoist.ToBool()) {
      # Perform non-recursive retrieval of descendant directories
      #
      [System.IO.DirectoryInfo[]]$directoryInfos = Get-ChildItem -Path $Path `
        -Directory -Recurse | Where-Object { $Condition.InvokeReturnAsIs($_) }

      Write-Debug " [o] Invoke-TraverseDirectory (Hoist); Count: $($directoryInfos.Count)";

      if ($directoryInfos) {
        # No need to manage the index, let Invoke-ForeachFsItem do this for us,
        # except we do need to inform Invoke-ForeachFsItem to start the index at
        # +1, because 0 is for the top level directory which has already been
        # handled.
        #
        [hashtable]$parametersFeFsItem = @{
          'Directory' = $true;
          'Exchange'  = $Exchange;
          'Summary'   = $Summary;
        }

        if ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
          $parametersFeFsItem['Block'] = $Block;
          $parametersFeFsItem['BlockParams'] = $BlockParams;
        }
        else {
          $parametersFeFsItem['Functee'] = $Functee;
          $parametersFeFsItem['FuncteeParams'] = $FuncteeParams;
        }

        $directoryInfos | & 'Invoke-ForeachFsItem' @parametersFeFsItem;
      }
    }
    else {
      # Top level descendants
      #
      # Set up the adapter. (NB, can't use splatting because we're invoking a script block
      # as opposed to a named function.)
      #
      $Exchange['LOOPZ.TRAVERSE.CONDITION'] = $Condition;
      $Exchange['LOOPZ.TRAVERSE.ADAPTED'] = $recurseTraverseDirectory;
      $Exchange['LOOPZ.TRAVERSE.ADAPTOR'] = $adapter;

      if ('InvokeScriptBlock' -eq $PSCmdlet.ParameterSetName) {
        $Exchange['LOOPZ.TRAVERSE.INVOKEE'] = $Block;
      }
      elseif ('InvokeFunction' -eq $PSCmdlet.ParameterSetName) {
        $Exchange['LOOPZ.TRAVERSE.INVOKEE'] = $Functee;
      }

      # Now perform start of recursive traversal
      #
      [System.IO.DirectoryInfo[]]$directoryInfos = Get-ChildItem -Path $Path `
        -Directory | Where-Object { $Condition.InvokeReturnAsIs($_) }

      if ($directoryInfos) {
        $directoryInfos | Invoke-ForeachFsItem -Directory -Block $adapter `
          -Exchange $Exchange -Condition $Condition -Summary $Summary;
      }
    }
  }
  else {
    $controller.SkipItem();
    Write-Error "Path specified '$($Path)' is not a directory";
  }

  $controller.EndSession();
} # Invoke-TraverseDirectory

function Format-StructuredLine {
  <#
  .NAME
    Format-StructuredLine
 
  .SYNOPSIS
    Helper function to make it easy to generate a line to be displayed.
 
  .DESCRIPTION
    A structured line is some text that includes embedded colour instructions that
  will be interpreted by the Krayola krayon writer. This function behaves like a
  layout manager for a single line.
 
  .PARAMETER CrumbKey
    The key used to index into the $Exchange hashtable to denote which crumb is used.
 
  .PARAMETER Exchange
    The exchange hashtable object.
 
  .PARAMETER Krayon
    The writer object which contains the Krayola theme.
 
  .PARAMETER LineKey
    The key used to index into the $Exchange hashtable to denote the core line.
 
  .PARAMETER MessageKey
    The key used to index into the $Exchange hashtable to denote what message to display.
 
  .PARAMETER Options
 
   + this is the crumb
   |
   V <-- message ->|
  [@@] --------------------------------------------------- [ Rename (WhatIf) ] ---
                                                                                |<-- This is a trailing wing
                                                                                whose length is WingLength
       |<--- flex part (which must be at least -------->|
                        MinimumFlexSize in length, it shrinks to accommodate the message)
 
    A PSCustomObject that allows further customisation of the structured line. Can contain the following
  fields:
  - WingLength: The size of the lead and tail portions of the line ('---')
  - MinimumFlexSize: The smallest size that the flex part can shrink to, to accommodate
  the message. If the message is so large that is pushes up against the minimal flex size
  it will be truncated according to the presence of Truncate switch
  - Ellipses: When message truncation occurs, the ellipses string is used to indicate that
  the message has been truncated.
  - WithLead: boolean flag to indicate whether a leading wing is displayed which would precede
  the crumb. In the above example and by default, there is no leading wing.
 
  .PARAMETER Truncate
    switch parameter to indicate whether the message is truncated to fit the line length.
 
  #>

  [OutputType([string])]
  param(
    [Parameter(Mandatory)]
    [hashtable]$Exchange,

    # We need to replace the exchange key parameters with direct parameters
    [Parameter(Mandatory)]
    [string]$LineKey,

    [Parameter()]
    [string]$CrumbKey,

    [Parameter()]
    [string]$MessageKey,

    [Parameter()]
    [switch]$Truncate,

    [Parameter()]
    [Krayon]$Krayon,

    [Parameter()]
    [PSCustomObject]$Options = (@{
        WingLength      = 3;
        MinimumFlexSize = 6;
        Ellipses        = ' ...';
        WithLead        = $false;
      })
  )
  [int]$wingLength = Get-PsObjectField $Options 'WingLength' 3;
  [int]$minimumFlexSize = Get-PsObjectField $Options 'MinimumFlexSize' 6;
  [string]$ellipses = Get-PsObjectField $Options 'Ellipses' ' ...';
  [boolean]$withLead = Get-PsObjectField $Options 'WithLead' $false;
  [string]$formatWithArg = $Krayon.ApiFormatWithArg;

  [hashtable]$theme = $Krayon.Theme;

  [string]$line = $Exchange.ContainsKey($LineKey) `
    ? $Exchange[$LineKey] : ([string]::new("_", 81));
  [string]$char = ($line -match '[^\s]') ? $matches[0] : ' ';
  [string]$wing = [string]::new($char, $wingLength);

  [string]$message = -not([string]::IsNullOrEmpty($MessageKey)) -and ($Exchange.ContainsKey($MessageKey)) `
    ? $Exchange[$MessageKey] : $null;

  [string]$crumb = if (-not([string]::IsNullOrEmpty($CrumbKey)) -and ($Exchange.ContainsKey($CrumbKey))) {
    if ($Exchange.ContainsKey('LOOPZ.SIGNALS')) {
      [hashtable]$signals = $Exchange['LOOPZ.SIGNALS'];
      [string]$crumbName = $Exchange[$CrumbKey];
      $signals[$crumbName].Value;
    }
    else {
      '+';
    }
  }
  else {
    $null;
  }

  [string]$structuredLine = if ([string]::IsNullOrEmpty($message) -and [string]::IsNullOrEmpty($crumb)) {
    $($formatWithArg -f "ThemeColour", "meta") + $line;
  }
  else {
    [string]$open = $theme['OPEN'];
    [string]$close = $theme['CLOSE'];

    # TODO: The deductions need to be calculated in a dynamic form, to cater
    # for optional fields.
    #

    if (-not([string]::IsNullOrEmpty($message)) -and -not([string]::IsNullOrEmpty($crumb))) {
      # 'lead' + 'open' + 'crumb' + 'close' + 'mid' + 'open' + 'message' + 'close' + 'tail'
      #
      # '*{lead} *{open}*{crumb}*{close} *{mid} *{open} *{message} *{close} *{tail}' => Format
      # +-----------------------------------------------|--------|-----------------+
      # | Start | | End | => Snippet
      #
      [string]$startFormat = '*{open}*{crumb}*{close} *{mid} *{open} ';
      if ($withLead) {
        $startFormat = '*{lead} ' + $startFormat;
      }
      [string]$endFormat = ' *{close} *{tail}';

      [string]$startSnippet = $startFormat.Replace('*{lead}', $wing). `
        Replace('*{open}', $open). `
        Replace('*{crumb}', $crumb). `
        Replace('*{close}', $close);

      [string]$endSnippet = $endFormat.Replace('*{close}', $close). `
        Replace('*{tail}', $wing);

      [string]$withoutMid = $startSnippet.Replace('*{mid}', '') + $endSnippet;
      [int]$deductions = $withoutMid.Length + $minimumFlexSize;
      [int]$messageSpace = $line.Length - $deductions;
      [boolean]$overflow = $message.Length -gt $messageSpace;

      [int]$midSize = if ($overflow) {
        # message size is the unknown variable and $midSize is a known
        # quantity: minimumFlexSize.
        #
        if ($Truncate.ToBool()) {
          [int]$messageKeepAmount = $messageSpace - $ellipses.Length;
          $message = $message.Substring(0, $messageKeepAmount) + $ellipses;
        }
        $minimumFlexSize;
      }
      else {
        # midSize is the unknown variable and the message size is a known
        # quantity: $message.Length
        #
        [int]$deductions = $withoutMid.Length + $message.Length;
        $line.Length - $deductions;
      }

      [string]$mid = [string]::new($char, $midSize);
      $startSnippet = $startSnippet.Replace('*{mid}', $mid);

      $($formatWithArg -f "ThemeColour", "meta") + $startSnippet + `
      $($formatWithArg -f "ThemeColour", "message") + $message + `
      $($formatWithArg -f "ThemeColour", "meta") + $endSnippet;
    }
    elseif (-not([string]::IsNullOrEmpty($message))) {
      # 'lead' + 'open' + 'message' + 'close' + 'tail'
      #
      # '*{lead} *{open} *{message} *{close} *{tail}'
      # +----------------|--------|-----------------+
      # | Start | | End | => Snippet
      #
      # The lead is mandatory in this case so ignore withLead
      #
      [string]$startFormat = '*{lead} *{open} ';
      [string]$endFormat = ' *{close} *{tail}';
      [string]$endSnippet = $endFormat.Replace('*{close}', $close). `
        Replace('*{tail}', $wing);

      [string]$withoutLead = $startFormat.Replace('*{lead}', ''). `
        Replace('*{open}', $open);

      [int]$deductions = $minimumFlexSize + $withoutLead.Length + $endSnippet.Length;
      [int]$messageSpace = $line.Length - $deductions;
      [boolean]$overflow = $message.Length -gt $messageSpace;
      [int]$leadSize = if ($overflow) {
        if ($Truncate.ToBool()) {
          # Truncate the message
          #
          [int]$messageKeepAmount = $messageSpace - $Ellipses.Length;
          $message = $message.Substring(0, $messageKeepAmount) + $Ellipses;
        }
        $minimumFlexSize;
      }
      else {
        $line.Length - $withoutLead.Length - $message.Length - $endSnippet.Length;
      }

      # The lead is now the variable part so should be calculated last
      #
      [string]$lead = [string]::new($char, $leadSize);
      [string]$startSnippet = $startFormat.Replace('*{lead}', $lead). `
        Replace('*{open}', $open);

      $($formatWithArg -f "ThemeColour", "meta") + $startSnippet + `
      $($formatWithArg -f "ThemeColour", "message") + $message + `
      $($formatWithArg -f "ThemeColour", "meta") + $endSnippet;
    }
    elseif (-not([string]::IsNullOrEmpty($crumb))) {
      # 'lead' + 'open' + 'crumb' + 'close' + 'tail'
      #
      # '*{lead} *{open}*{crumb}*{close} *{tail}'
      # +--------------------------------+------+
      # |Start |End | => 2 Snippets can be combined into lineSnippet
      # because they use the same colours.
      #
      [string]$startFormat = '*{open}*{crumb}*{close} ';
      if ($withLead) {
        $startFormat = '*{lead} ' + $startFormat;
      }

      [string]$startFormat = '*{open}*{crumb}*{close} ';
      [string]$startSnippet = $startFormat.Replace('*{lead}', $wing). `
        Replace('*{open}', $open). `
        Replace('*{crumb}', $crumb). `
        Replace('*{close}', $close);

      [string]$withTailFormat = $startSnippet + '*{tail}';
      [int]$deductions = $startSnippet.Length;
      [int]$tailSize = $line.Length - $deductions;
      [string]$tail = [string]::new($char, $tailSize);
      [string]$lineSnippet = $withTailFormat.Replace('*{tail}', $tail);

      $($formatWithArg -f "ThemeColour", "meta") + $lineSnippet;
    }
  }

  return $structuredLine;
}

function Show-Header {
  <#
  .NAME
    Show-Header
 
  .SYNOPSIS
    Function to display header as part of an iteration batch.
 
  .DESCRIPTION
    Behaviour can be customised by the following entries in the Exchange:
  * 'LOOPZ.KRAYON' (mandatory): the Krayola Krayon writer object.
  * 'LOOPZ.HEADER-BLOCK.MESSAGE': The custom message to be displayed as
  part of the header.
  * 'LOOPZ.HEADER.PROPERTIES': A Krayon [line] instance contain a collection
  of Krayola [couplet]s. When present, the header displayed will be a static
  line, the collection of these properties then another static line.
  * 'LOOPZ.HEADER-BLOCK.LINE': The static line text. The length of this line controls
  how everything else is aligned (ie the flex part and the message if present).
 
  .PARAMETER Exchange
    The exchange hashtable object.
 
  #>

  param(
    [Parameter()]
    [hashtable]$Exchange
  )

  [Krayon]$krayon = $Exchange['LOOPZ.KRAYON'];

  if (-not($krayon)) {
    throw "Writer missing from Exchange under key 'LOOPZ.KRAYON'"
  }
  $null = $krayon.Reset();
  [string]$writerFormatWithArg = $krayon.ApiFormatWithArg;
  [string]$message = $Exchange.ContainsKey(
    'LOOPZ.HEADER-BLOCK.MESSAGE') ? $Exchange['LOOPZ.HEADER-BLOCK.MESSAGE'] : [string]::Empty;

  # get the properties from Exchange ('LOOPZ.HEADER.PROPERTIES')
  # properties should not be a line, because line implies all these properties are
  # written on the same line. Rather it is better described as array of Krayola pairs,
  # which is does not share the same semantics as line. However, since line is just a
  # collection of pairs, the client can use the line abstraction, but not the line
  # method on the writer, unless they want it to actually represent a line.
  #
  [line]$properties = $Exchange.ContainsKey(
    'LOOPZ.HEADER.PROPERTIES') ? $Exchange['LOOPZ.HEADER.PROPERTIES'] : [line]::new();

  if ($properties.Line.Length -gt 0) {
    # First line
    #
    [string]$line = $Exchange.ContainsKey('LOOPZ.HEADER-BLOCK.LINE') `
      ? $Exchange['LOOPZ.HEADER-BLOCK.LINE'] : ([string]::new('_', $_LineLength)); # $_LineLength ??? (oops my bad)

    [string]$structuredLine = $($writerFormatWithArg -f 'ThemeColour', 'meta') + $line;

    $null = $krayon.ScribbleLn($structuredLine);

    # Inner detail
    #
    if (-not([string]::IsNullOrEmpty($message))) {
      $null = $krayon.Message($message);
    }
    $null = $krayon.Line($properties);

    # Second line
    #
    [string]$structuredLine = $($writerFormatWithArg -f 'ThemeColour', 'meta') + $line;
    $null = $krayon.ScribbleLn($structuredLine);
  }
  else {
    # Alternative line
    #
    [string]$lineKey = 'LOOPZ.HEADER-BLOCK.LINE';
    [string]$crumbKey = 'LOOPZ.HEADER-BLOCK.CRUMB-SIGNAL';
    [string]$messageKey = 'LOOPZ.HEADER-BLOCK.MESSAGE';

    [string]$structuredLine = Format-StructuredLine -Exchange $exchange `
      -LineKey $LineKey -CrumbKey $CrumbKey -MessageKey $messageKey -Krayon $krayon -Truncate;
    $null = $krayon.ScribbleLn($structuredLine);
  }
}

function Show-Summary {
  <#
  .NAME
    Show-Header
 
  .SYNOPSIS
    Function to display summary as part of an iteration batch.
 
  .DESCRIPTION
    Behaviour can be customised by the following entries in the Exchange:
  * 'LOOPZ.KRAYON' (mandatory): the Krayola Krayon writer object.
  * 'LOOPZ.SUMMARY-BLOCK.MESSAGE': The custom message to be displayed as
  part of the summary.
  * 'LOOPZ.SUMMARY.PROPERTIES': A Krayon [line] instance contain a collection
  of Krayola [couplet]s. The first line of summary properties shows the values of
  $Count, $Skipped and $Triggered. The properties, if present are appended to this line.
  * 'LOOPZ.SUMMARY-BLOCK.LINE': The static line text. The length of this line controls
  how everything else is aligned (ie the flex part and the message if present).
  * 'LOOPZ.SUMMARY-BLOCK.WIDE-ITEMS': The collection (an array of Krayola [lines]s)
  containing 'wide' items and therefore should be on their own separate line.
  * 'LOOPZ.SUMMARY-BLOCK.GROUP-WIDE-ITEMS': Perhaps the wide items are not so wide after
  all, so if this entry is set (a boolean value), the all wide items appear on their
  own line.
 
  .PARAMETER CapturedOnly
 
  .PARAMETER Count
    The number items processed, this is the number of items in the pipeline which match
  the $Pattern specified and therefore are allocated an index.
 
  .PARAMETER Errors
    The number of errors that occurred during the batch.
 
  .PARAMETER Exchange
    The exchange hashtable object.
 
  .PARAMETER Skipped
    The number of pipeline items skipped. An item is skipped for the following reasons:
  * Item name does not match the $Include expression
  * Item name satisfies the $Exclude expression. ($Exclude overrides $Include)
  * Iteration is terminated early by the invoked function/script-block returning a
  PSCustomObject with a Break property set to $true.
  * FileSystem item is not of the request type. Eg, if File is specified, then all
  directory items will be skipped.
  * An item fails to satisfy the $Condition predicate.
  * Number of items processed breaches Top.
 
  .PARAMETER Triggered
    Indicates whether any of the processed pipeline items were actioned in a modifying
  batch; ie if no items were mutated, then Triggered would be $false.
 
  #>

  param(
    [Parameter()]
    [int]$Count,

    [Parameter()]
    [int]$Skipped,

    [Parameter()]
    [int]$Errors,

    [Parameter()]
    [boolean]$Triggered,

    [Parameter()]
    [hashtable]$Exchange = @{}
  )

  [Krayon]$krayon = $Exchange['LOOPZ.KRAYON'];
  if (-not($krayon)) {
    throw "Writer missing from Exchange under key 'LOOPZ.KRAYON'"
  }

  [string]$writerFormatWithArg = $krayon.ApiFormatWithArg;

  # First line
  #
  if ($Exchange.ContainsKey('LOOPZ.SUMMARY-BLOCK.LINE')) {
    [string]$line = $Exchange['LOOPZ.SUMMARY-BLOCK.LINE'];

    # Assuming writerFormatWithArg is &[{0},{1}]
    # => generates &[ThemeColour,meta] which is an instruction to set the
    # colours to the krayola theme's 'META-COLOURS'
    #
    [string]$structuredBorderLine = $($writerFormatWithArg -f 'ThemeColour', 'meta') + $line;
    $null = $krayon.ScribbleLn($structuredBorderLine);
  }
  else {
    $structuredBorderLine = [string]::Empty;
  }

  # Inner detail
  #
  [line]$properties = New-Line(@(
      $(New-Pair('Count', $Count)),
      $(New-Pair('Skipped', $Skipped)),
      $(New-Pair('Errors', $Errors)),
      $(New-Pair('Triggered', $Triggered))
    ));

  [string]$message = $Exchange.ContainsKey('LOOPZ.SUMMARY-BLOCK.MESSAGE') `
    ? $Exchange['LOOPZ.SUMMARY-BLOCK.MESSAGE'] : 'Summary';

  $null = $krayon.Line($message, $properties);
  [string]$blank = [string]::new(' ', $message.Length);

  # Custom properties
  #
  [line]$summaryProperties = $Exchange.ContainsKey(
    'LOOPZ.SUMMARY.PROPERTIES') ? $Exchange['LOOPZ.SUMMARY.PROPERTIES'] : [line]::new(@());

  if ($summaryProperties.Line.Length -gt 0) {
    $null = $krayon.Line($blank, $summaryProperties);
  }

  # Wide items
  #
  if ($Exchange.ContainsKey('LOOPZ.SUMMARY-BLOCK.WIDE-ITEMS')) {
    [line]$wideItems = $Exchange['LOOPZ.SUMMARY-BLOCK.WIDE-ITEMS'];

    [boolean]$group = ($Exchange.ContainsKey('LOOPZ.SUMMARY-BLOCK.GROUP-WIDE-ITEMS') -and
      $Exchange['LOOPZ.SUMMARY-BLOCK.GROUP-WIDE-ITEMS']);

    if ($group) {
      $null = $krayon.Line($blank, $wideItems);
    }
    else {
      foreach ($couplet in $wideItems.Line) {
        [line]$syntheticLine = New-Line($couplet);
        $null = $krayon.Line($blank, $syntheticLine);
      }
    }
  }

  # Second line
  #
  if (-not([string]::IsNullOrEmpty($structuredBorderLine))) {
    $null = $krayon.ScribbleLn($structuredBorderLine);
  }
}
function Write-HostFeItemDecorator {
  <#
  .NAME
    Write-HostFeItemDecorator
 
  .SYNOPSIS
    Wraps a function or script-block as a decorator writing appropriate user interface
    info to the host for each entry in the pipeline.
 
  .DESCRIPTION
      The script-block/function (invokee) being decorated may or may not Support ShouldProcess. If it does,
    then the client should add 'WHAT-IF' to the pass through, set to the current
    value of WhatIf; or more accurately the existence of 'WhatIf' in PSBoundParameters. Or another
    way of putting it is, the presence of WHAT-IF indicates SupportsShouldProcess, and the value of
    'WHAT-IF' dictates the value of WhatIf. This way, we only need a single
    value in the Exchange, rather than having to represent SupportShouldProcess explicitly with
    another value.
      The Exchange must contain either a 'LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME' entry meaning
    a named function is being decorated or 'LOOPZ.WH-FOREACH-DECORATOR.BLOCK' meaning a script
    block is being decorated, but not both.
      By default, Write-HostFeItemDecorator will display an item no for each object in the pipeline
    and a property representing the Product. The Product is a property that the invokee can set on the
    PSCustomObject it returns. However, additional properties can be displayed. This can be achieved by
    the invokee populating another property Pairs, which is an array of string based key/value pairs. All
    properties found in Pairs will be written out by Write-HostFeItemDecorator.
      By default, to render the value displayed (ie the 'Product' property item on the PSCustomObject
    returned by the invokee), ToString() is called. However, the 'Product' property may not have a
    ToString() method, in this case (you will see an error indicating ToString method not being
    available), the user should provide a custom script-block to determine how the value is
    constructed. This can be done by assigning a custom script-block to the
    'LOOPZ.WH-FOREACH-DECORATOR.GET-RESULT' entry in Exchange. eg:
 
      [scriptblock]$customGetResult = {
        param($result)
        $result.SomeCustomPropertyOfRelevanceThatIsAString;
      }
      $Exchange['LOOPZ.WH-FOREACH-DECORATOR.GET-RESULT'] = $customGetResult;
      ...
 
      Note also, the user can provide a custom 'GET-RESULT' in order to control what is displayed
    by Write-HostFeItemDecorator.
 
      This function is designed to be used with Invoke-ForeachFsItem and as such, it's signature
    needs to match that required by Invoke-ForeachFsItem. Any additional parameters can be
    passed in via the Exchange.
      The rationale behind Write-HostFeItemDecorator is to maintain separation of concerns
    that allows development of functions that could be used with Invoke-ForeachFsItem which do
    not contain any UI related code. This strategy also helps for the development of different
    commands that produce output to the terminal in a consistent manner.
 
  .PARAMETER Exchange
    A hash table containing miscellaneous information gathered internally
    throughout the iteration batch. This can be of use to the user, because it is the way
    the user can perform bi-directional communication between the invoked custom script block
    and client side logic.
 
  .PARAMETER Index
    The 0 based index representing current item in the pipeline.
 
  .PARAMETER Trigger
      A boolean value, useful for state changing idempotent operations. At the end
    of the batch, the state of the trigger indicates whether any of the items were actioned.
    When the script block is invoked, the trigger should indicate if the trigger was pulled for
    any of the items so far processed in the batch. This is the responsibility of the
    client's block implementation.
 
  .PARAMETER Underscore
    The current pipeline object.
 
  .RETURNS
    The result of invoking the decorated script-block.
 
  .EXAMPLE 1
 
  function Test-FN {
    param(
      [System.IO.DirectoryInfo]$Underscore,
      [int]$Index,
      [hashtable]$Exchange,
      [boolean]$Trigger,
    )
 
    $format = $Exchange['CLIENT.FORMAT'];
    @{ Product = $format -f $Underscore.Name, $Underscore.Exists }
    ...
  }
 
  [Systems.Collection.Hashtable]$exchange = @{
    'LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME' = 'Test-FN';
    'CLIENT.FORMAT' = '=== [{0}] -- [{1}] ==='
  }
 
  Get-ChildItem ... | Invoke-ForeachFsItem -Path <path> -Exchange $exchange
    -Functee 'Write-HostFeItemDecorator'
 
    So, Test-FN is not concerned about writing any output to the console, it simply does
  what it does silently and Write-HostFeItemDecorator handles generation of output. It
  invokes the function defined in 'LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME' and generates
  corresponding output. It happens to use the console colouring facility provided by a
  a dependency Elizium.Krayola to create colourful output in a predefined format via the
  Krayola Theme.
 
  Note, Write-HostFeItemDecorator does not forward additional parameters to the decorated
  function (Test-FN), but this can be circumvented via the Exchange as illustrated by
  the 'CLIENT.FORMAT' parameter in this example.
 
  #>


  [OutputType([PSCustomObject])]
  [CmdletBinding()]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute("PSAvoidUsingWriteHost", "")]
  [Alias('wife', 'Decorate-Foreach')]
  param (
    [Parameter(
      Mandatory = $true
    )]
    $Underscore,

    [Parameter(
      Mandatory = $true
    )]
    [int]$Index,

    [Parameter(
      Mandatory = $true
    )]
    [ValidateScript( {
        return ($_.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME') -xor
          $_.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.BLOCK'))
      })]
    [hashtable]
    $Exchange,

    [Parameter()]
    [boolean]$Trigger
  )

  [scriptblock]$defaultGetResult = {
    param($result)
    $result.ToString();
  }

  [Krayon]$krayon = $_exchange['LOOPZ.KRAYON'];

  [scriptblock]$decorator = {
    param ($_underscore, $_index, $_exchange, $_trigger)

    if ($_exchange.Contains('LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME')) {
      [string]$functee = $_exchange['LOOPZ.WH-FOREACH-DECORATOR.FUNCTION-NAME'];

      [hashtable]$parameters = @{
        'Underscore' = $_underscore;
        'Index'      = $_index;
        'Exchange'   = $_exchange;
        'Trigger'    = $_trigger;
      }
      if ($_exchange.Contains('WHAT-IF')) {
        $parameters['WhatIf'] = $_exchange['WHAT-IF'];
      }

      return & $functee @parameters;
    }
    elseif ($_exchange.Contains('LOOPZ.WH-FOREACH-DECORATOR.BLOCK')) {
      [scriptblock]$block = $_exchange['LOOPZ.WH-FOREACH-DECORATOR.BLOCK'];

      return $block.InvokeReturnAsIs($_underscore, $_index, $_exchange, $_trigger);
    }
  }

  $invokeResult = $decorator.InvokeReturnAsIs($Underscore, $Index, $Exchange, $Trigger);

  [string]$message = $Exchange['LOOPZ.WH-FOREACH-DECORATOR.MESSAGE'];
  [string]$productValue = [string]::Empty;
  [boolean]$ifTriggered = $Exchange.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.IF-TRIGGERED');
  [boolean]$resultIsTriggered = $invokeResult.psobject.properties.match('Trigger') -and $invokeResult.Trigger;

  # Suppress the write if client has set IF-TRIGGERED and the result is not triggered.
  # This makes re-runs of a state changing operation less verbose if that's required.
  #
  if (-not($ifTriggered) -or ($resultIsTriggered)) {
    $getResult = $Exchange.Contains('LOOPZ.WH-FOREACH-DECORATOR.GET-RESULT') `
      ? $Exchange['LOOPZ.WH-FOREACH-DECORATOR.GET-RESULT'] : $defaultGetResult;

    [line]$themedPairs = $( New-Line( $(New-Pair('No', $("{0,3}" -f ($Index + 1)))) ) );

    # Get Product if it exists
    #
    [string]$productLabel = [string]::Empty;
    if ($invokeResult -and $invokeResult.psobject.properties.match('Product') -and $invokeResult.Product) {
      [boolean]$affirm = $invokeResult.psobject.properties.match('Affirm') -and $invokeResult.Affirm;
      $productValue = $getResult.InvokeReturnAsIs($invokeResult.Product);
      $productLabel = $Exchange.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.PRODUCT-LABEL') `
        ? $Exchange['LOOPZ.WH-FOREACH-DECORATOR.PRODUCT-LABEL'] : 'Product';

      if (-not([string]::IsNullOrWhiteSpace($productLabel))) {
        $themedPairs.append($(New-Pair(@($productLabel, $productValue, $affirm))));
      }
    }

    # Get Key/Value Pairs
    #
    if ($invokeResult -and $invokeResult.psobject.properties.match('Pairs') -and
      $invokeResult.Pairs -and ($invokeResult.Pairs -is [line]) -and ($invokeResult.Pairs.Line.Count -gt 0)) {
      $themedPairs.append($invokeResult.Pairs);
    }

    [hashtable]$krayolaTheme = $krayon.Theme;

    # Write the primary line
    #
    if (-not([string]::IsNullOrEmpty($message))) {
      $null = $krayon.Message($message);
    }
    $null = $krayon.Line($themedPairs);

    # Write additional lines
    #
    if ($invokeResult -and $invokeResult.psobject.properties.match('Lines') -and $invokeResult.Lines) {
      [int]$indent = $Exchange.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.INDENT') `
        ? $Exchange['LOOPZ.WH-FOREACH-DECORATOR.INDENT'] : 3;
      [string]$blank = [string]::new(' ', $indent);

      [Krayon]$adjustedWriter = if ($Exchange.ContainsKey('LOOPZ.WH-FOREACH-DECORATOR.WRITER')) {
        $Exchange['LOOPZ.WH-FOREACH-DECORATOR.WRITER'];
      }
      else {
        [hashtable]$adjustedTheme = $krayolaTheme.Clone();
        $adjustedTheme['MESSAGE-SUFFIX'] = [string]::Empty;
        $adjustedTheme['OPEN'] = [string]::Empty;
        $adjustedTheme['CLOSE'] = [string]::Empty;
        $Exchange['LOOPZ.WH-FOREACH-DECORATOR.WRITER'] = New-Krayon -Theme $adjustedTheme;

        $Exchange['LOOPZ.WH-FOREACH-DECORATOR.WRITER'];
      }

      [line[]]$additionalLines = if ([string]::IsNullOrEmpty($invokeResult.ErrorReason)) {
        $invokeResult.Lines;
      } else {
        $( New-Line( $(New-Pair('Error', $invokeResult.ErrorReason)) ) ) + $invokeResult.Lines;
      }

      foreach ($line in $additionalLines) {
        $null = $adjustedWriter.Message($blank).Line($line);
      }
    }
  }

  return $invokeResult;
} # Write-HostFeItemDecorator

function Edit-RemoveSingleSubString {
  <#
.NAME
  edit-RemoveSingleSubString
 
.SYNOPSIS
  Removes a sub-string from the target string provided.
 
.DESCRIPTION
  Either the first or the last occurrence of a single substring can be removed
  depending on whether the Last flag has been set.
 
.PARAMETER Last
  Flag to indicate whether the last occurrence of a sub string is to be removed from the
  Target.
 
.PARAMETER Subtract
  The sub string to subtract from the Target.
 
.PARAMETER Target
  The string from which the subtraction is to occur.
 
.PARAMETER Insensitive
  Flag to indicate if the search is case sensitive or not. By default, search is case
  sensitive.
 
 
#>

  [CmdletBinding(DefaultParameterSetName = 'Single')]
  [OutputType([string])]
  param
  (
    [Parameter(ParameterSetName = 'Single')]
    [String]$Target,

    [Parameter(ParameterSetName = 'Single')]
    [String]$Subtract,

    [Parameter(ParameterSetName = 'Single')]
    [switch]$Insensitive,

    [Parameter(ParameterSetName = 'Single')]
    [Parameter(ParameterSetName = 'LastOnly')]
    [switch]$Last
  )

  [StringComparison]$comparison = $Insensitive.ToBool() ? `
    [StringComparison]::OrdinalIgnoreCase : [StringComparison]::Ordinal;

  $result = $Target;

  # https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings
  #
  if (($Subtract.Length -gt 0) -and ($Target.Contains($Subtract, $comparison))) {
    $slen = $Subtract.Length;

    $foundAt = $Last.ToBool() ? $Target.LastIndexOf($Subtract, $comparison) : `
      $Target.IndexOf($Subtract, $comparison);

    if ($foundAt -eq 0) {
      $result = $Target.Substring($slen);
    }
    elseif ($foundAt -gt 0) {
      $result = $Target.Substring(0, $foundAt);
      $result += $Target.Substring($foundAt + $slen);
    }
  }

  $result;
}

function Get-InverseSubString {
  <#
  .NAME
    Get-InverseSubString
 
  .SYNOPSIS
    Performs the opposite of [string]::Substring.
 
  .DESCRIPTION
    Returns the remainder of that part of the substring denoted by the $StartIndex
  $Length.
 
  .PARAMETER Length
    The number of characters in the sub-string.
 
  .PARAMETER Marker
    A character used to mark the position of the sub-string. If the client specifies
  a marker, then this marker is inserted between the head and the tail.
 
  .PARAMETER Source
    The source string
 
  .PARAMETER Split
    When getting the inverse sub-string there are two elements that are returned,
  the head (prior to sub-string) and the tail, what comes after the sub-string.
    This switch indicates whether the function returns the head and tail as separate
  entities in an array, or should simply return the tail appended to the head.
 
  .PARAMETER StartIndex
    The index of sub-string.
 
  #>

  param(
    [Parameter(Position = 0, Mandatory)]
    [string]$Source,

    [Parameter()]
    [ValidateScript( { $_ -lt $Source.Length })]
    [int]$StartIndex = 0,

    [Parameter()]
    [ValidateScript( { $_ -le ($Source.Length - $StartIndex ) })]
    [int]$Length = 0,

    [Parameter()]
    [switch]$Split,

    [Parameter()]
    [char]$Marker
  )

  $result = if ($StartIndex -eq 0) {
    $PSBoundParameters.ContainsKey('Marker') `
      ? $($Marker + $Source.SubString($Length)) : $Source.SubString($Length);
  }
  else {
    [string]$head = $Source.SubString(0, $StartIndex);

    if ($PSBoundParameters.ContainsKey('Marker')) {
      $head += $Marker;
    }

    [string]$tail = $Source.SubString($StartIndex + $Length);
    ($Split.ToBool()) ? ($head, $tail) : ($head + $tail);
  }
  $result;
}

function Get-IsLocked {
  <#
  .NAME
    Get-IsLocked
 
  .SYNOPSIS
    Utility function to determine whether the environment variable specified
  denotes that it is set to $true to indicate the associated function is in a locked
  state.
 
  .DESCRIPTION
    Returns a boolean indicating the 'locked' status of the associated functionality.
  Eg, for the Rename-Many command, a user can only use it for real when it has been
  unlocked by setting it's associated environment variable 'LOOPZ_REMY_LOCKED' to $false.
 
  .PARAMETER Variable
    The environment variable to check.
 
  #>

  [OutputType([boolean])]
  param(
   [Parameter(Mandatory)]
   [string]$Variable
  )

  [string]$lockedEnv = Get-EnvironmentVariable $Variable;
  [boolean]$locked = ([string]::IsNullOrEmpty($lockedEnv) -or
    (-not([string]::IsNullOrEmpty($lockedEnv)) -and
      ($lockedEnv -eq [boolean]::TrueString)));

  return $locked;
}

function Get-PlatformName {
  <#
  .NAME
    Get-PlatformName
 
  .SYNOPSIS
    Get the name of the operating system.
 
  .DESCRIPTION
    There are multiple ways to get the OS type in PowerShell but they are convoluted
  and can return an unfriendly name such as 'Win32NT'. This command simply returns
  'windows', 'linux' or 'mac', simples! This function is typically used alongside
  Invoke-ByPlatform and Resolve-ByPlatform.
 
  #>

  $result = if ($IsWindows) {
    'windows';
  } elseif ($IsLinux) {
    'linux';
  } elseif ($IsMacOS) {
    'mac';
  } else {
    [string]::Empty;
  }

  $result;
}

function Get-PsObjectField {
  <#
  .NAME
    Get-PsObjectField
 
  .SYNOPSIS
    Simplifies getting the value of a field from a PSCustomObject.
 
  .DESCRIPTION
    Returns the value of the specified field. If the field is missing, then
  the default is returned.
 
  .PARAMETER Default
    Default value to return if the $Field doesn't exist on the $Object.
 
  .PARAMETER Field
    The field to get value of.
 
  .PARAMETER Object
    The object to get the field value from.
 
  #>

  param(
    [Parameter(Position = 0, Mandatory)]
    [PSCustomObject]$Object,

    [Parameter(Position = 1, Mandatory)]
    [string]$Field,

    [Parameter(Position = 2)]
    $Default = $null
  )

  ($Object.psobject.properties.match($Field) -and $Object.$Field) ? ($Object.$Field) : $Default;
}

function Invoke-ByPlatform {
  <#
  .NAME
    Invoke-ByPlatform
 
  .SYNOPSIS
    Given a hashtable, invokes the function/script-block whose corresponding key matches
  the operating system name as returned by Get-PlatformName.
 
  .DESCRIPTION
    Provides a way to provide OS specific functionality. Returns $null if the $Hash does
  not contain an entry corresponding to the current platform.
    (Doesn't support invoking a function with named parameters; PowerShell doesn't currently
  support this, not even via splatting, if this changes, this will be implemented.)
 
  .PARAMETER Hash
    A hashtable object whose keys are values that can be returned by Get-PlatformName. The
  values are of type PSCustomObject and can contain the following properties:
  + FnInfo: A FunctionInfo instance. This can be obtained from an existing function by
  invoking Get-Command -Name <function-name>
  + Positional: an array of positional parameter values
 
  #>

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute("PSAvoidUsingWriteHost", "")]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute("PSPossibleIncorrectUsageOfAssignmentOperator", "")]
  param(
    [Parameter()]
    [hashtable]$Hash
  )

  $result = $null;
  [string]$platform = Get-PlatformName;

  [PSCustomObject]$invokeInfo = if ($Hash.ContainsKey($platform)) {
    $Hash[$platform];
  }
  elseif ($Hash.ContainsKey('default')) {
    $Hash['default'];
  }
  else {
    Write-Error "!!!!!! Missing platform: '$platform' (and no default available)" -ErrorAction Continue;
    $null;
  }

  if ($invokeInfo -and $invokeInfo.FnInfo) {
    if ($invokeInfo.psobject.properties.match('Positional') -and $invokeInfo.Positional) {
      [array]$positional = $invokeInfo.Positional;

      if ([scriptblock]$block = $invokeInfo.FnInfo.ScriptBlock) {
        $result = $block.InvokeReturnAsIs($positional);
      }
      else {
        Write-Error $("ScriptBlock for function: '$($invokeInfo.FnInfo.Name)', ('$platform': platform) is missing") `
          -ErrorAction Continue;
      }
    }
    elseif ($invokeInfo.psobject.properties.match('Named') -and $invokeInfo.Named) {
      [hashtable]$named = $invokeInfo.Named;

      $result = & $invokeInfo.FnInfo.Name @named;
    }
    else {
      Write-Error $("Missing Positional/Named: '$($invokeInfo.FnInfo.Name)', ('$platform': platform)") `
        -ErrorAction Continue;
    }
  }

  return $result;
}

function Resolve-ByPlatform {
  <#
  .NAME
    Resolve-ByPlatform
 
  .SYNOPSIS
    Given a hashtable, resolves to the value whose corresponding key matches
  the operating system name as returned by Get-PlatformName.
 
  .DESCRIPTION
    Provides a way to select data depending on the current OS as determined by
  Get-PlatformName.
 
  .PARAMETER Hash
    A hashtable object whose keys are values that can be returned by Get-PlatformName. The
  values can be anything.
 
  #>

  param(
    [Parameter()]
    [hashtable]$Hash
  )

  $result = $null;
  [string]$platform = Get-PlatformName;

  if ($Hash.ContainsKey($platform)) {
    $result = $Hash[$platform];
  }
  elseif ($Hash.ContainsKey('default')) {
    $result = $Hash['default'];
  }

  return $result;
}

function Test-IsFileSystemSafe {
  <#
  .NAME
    Test-IsFileSystemSafe
 
  .SYNOPSIS
    Checks the $Value to see if it contains any file-system un-safe characters.
 
  .DESCRIPTION
    Warning, this function is not comprehensive nor platform specific, but it does not
  intend to be. There are some characters eg /, that are are allowable under mac/linux
  as part of the filename but are not under windows; in this case they are considered
  unsafe for all platforms. This approach is taken because of the likely possibility
  that a file may be copied over from differing file system types.
 
  .PARAMETER Value
    The string value to check.
 
  .PARAMETER Value
     
 
  #>

  [OutputType([boolean])]
  param(
    [Parameter()]
    [string]$Value,

    [Parameter()]
    [char[]]$InvalidSet = $Loopz.InvalidCharacterSet
  )
  return ($Value.IndexOfAny($InvalidSet) -eq -1);
}

function Resolve-Error ($ErrorRecord = $Error[0]) {
  $ErrorRecord | Format-List * -Force
  $ErrorRecord.InvocationInfo | Format-List *
  $Exception = $ErrorRecord.Exception
  for ($i = 0; $Exception; $i++, ($Exception = $Exception.InnerException)) {
    "$i" * 80
    $Exception | Format-List * -Force
  }
}
function get-Captures {
  [OutputType([hashtable])]
  param(
    [Parameter(Mandatory)]
    [System.Text.RegularExpressions.Match]$MatchObject
  )

  [hashtable]$captures = @{}
  [System.Text.RegularExpressions.GroupCollection]$groups = $MatchObject.Groups;

  foreach ($key in $groups.Keys) {
    $captures[$key] = $groups[$key];
  }

  return $captures;
}

function initialize-Signals {
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSAvoidGlobalVars', '')]
  [OutputType([hashtable])]
  param(
    [Parameter()]
    [hashtable]$Signals = $global:Loopz.DefaultSignals,

    [Parameter()]
    [hashtable]$Overrides = $global:Loopz.OverrideSignals
  )

  [hashtable]$result = $Signals.Clone();
  [hashtable]$withOverrides = Resolve-ByPlatform -Hash $Overrides;

  $withOverrides.GetEnumerator() | ForEach-Object {
    try {
      $result[$_.Key] = $_.Value;
    }
    catch {
      Write-Error "Skipping override signal: '$($_.Key)'";
    }
  }

  return $result;
}


function invoke-PostProcessing {
  param(
    [Parameter()]
    [string]$InputSource,

    [Parameter()]
    [PSCustomObject]$Rules,

    [Parameter()]
    [hashtable]$signals
  )
  [string]$transformResult = $InputSource;
  [string[]]$appliedSignals = @();
  [array]$iterationRules = $Rules.psobject.Members | where-Object MemberType -like 'NoteProperty';

  foreach ($_r in $iterationRules) {
    $rule = $_r.Value;

    if ($rule['IsApplicable'].InvokeReturnAsIs($transformResult)) {
      $transformResult = $rule['Transform'].InvokeReturnAsIs($transformResult);
      $appliedSignals += $rule['Signal'];
    }
  }

  [PSCustomObject]$result = if ($appliedSignals.Count -gt 0) {
    [string]$indication = [string]::Empty;
    [string[]]$labels = @();

    foreach ($name in $appliedSignals) {
      $indication += $signals[$name].Value;
      $labels += $signals[$name].Key;
    }
    $indication = "[{0}]" -f $indication;

    [PSCustomObject]@{
      TransformResult = $transformResult
      Indication      = $indication;
      Signals         = $appliedSignals;
      Label           = 'Post ({0})' -f $($labels -join ', ');
      Modified        = $true;
    }
  }
  else {
    [PSCustomObject]@{
      TransformResult = $InputSource;
      Modified        = $false;
    }
  }

  $result;
}

function rename-FsItem {
  [CmdletBinding(SupportsShouldProcess)]
  param(
    [Parameter()]
    [System.IO.FileSystemInfo]$From,

    [Parameter()]
    [string]$To,

    [Parameter()]
    [AllowNull()]
    [UndoRename]$UndoOperant
  )
  [boolean]$itemIsDirectory = ($From.Attributes -band
    [System.IO.FileAttributes]::Directory) -eq [System.IO.FileAttributes]::Directory;

  [string]$parentPath = $itemIsDirectory ? $From.Parent.FullName : $From.Directory.FullName;
  [string]$destinationPath = Join-Path -Path $parentPath -ChildPath $To;

  if (-not($PSBoundParameters.ContainsKey('WhatIf') -and $PSBoundParameters['WhatIf'])) {
    try {
      [boolean]$differByCaseOnly = $From.Name.ToLower() -eq $To.ToLower();

      if ($differByCaseOnly) {
        # Just doing a double rename to get around the problem of not being able to rename
        # an item unless the case is different
        #
        [string]$tempName = $From.Name + "_";

        Rename-Item -LiteralPath $From.FullName -NewName $tempName -PassThru | `
          Rename-Item -NewName $To;
      }
      else {
        Rename-Item -LiteralPath $From.FullName -NewName $To;
      }

      if ($UndoOperant) {
        [PSCustomObject]$operation = [PSCustomObject]@{
          Directory = $parentPath;
          From      = $From.Name;
          To        = $To;
        }
        Write-Debug "rename-FsItem (Undo Rename) => alert: From: '$($operation.From.Name)', To: '$($operation.To)'";
        $UndoOperant.alert($operation);
      }

      $result = Get-Item -LiteralPath $destinationPath;
    }
    catch [System.IO.IOException] {
      $result = $null;
    }
  }
  else {
    $result = $To;
  }

  return $result;
} # rename-FsItem
  function select-ResolvedFsItem {
    [OutputType([boolean])]
    param(
      [Parameter(Mandatory)]
      [string]$FsItem,

      [Parameter(Mandatory)]
      [AllowEmptyCollection()]
      [string[]]$Filter,

      [Parameter()]
      [switch]$Case
    )

    [boolean]$liked = $false;
    [int]$counter = 0;

    do {
      $liked = $Case.ToBool() `
        ? $FsItem -CLike $Filter[$counter] `
        : $FsItem -Like $Filter[$counter];
      $counter++;
    } while (-not($liked) -and ($counter -lt $Filter.Count));

    $liked;
  }

function test-ValidPatternArrayParam {
  [OutputType([boolean])]
  param(
    [Parameter(Mandatory)]
    [array]$Arg,

    [Parameter()]
    [switch]$AllowWildCard
  )

  [boolean]$result = $Arg -and ($Arg.Count -gt 0) -and ($Arg.Count -lt 2) -and `
    -not([string]::IsNullOrEmpty($Arg[0])) -and (($Arg.Length -eq 1) -or $Arg[1] -ne '*');

  if ($result -and $Arg.Count -gt 1 -and $Arg[1] -eq '*') {
    $result = $AllowWildCard.ToBool();
  }

  $result;
}

# The only reason why all the controller classes are implemented in the same file is because
# there is a deficiency in PSScriptAnalyzer (in VSCode) which reports class references as errors
# if they are not defined in the same file from where they are referenced. The only way to circumvent
# this problem is to place all class related code into the same file.
#
enum ControllerType {
  ForeachCtrl = 0
  TraverseCtrl = 1
}

class Counter {
  [int]hidden $_errors = 0;
  [int]hidden $_value = 0;
  [int]hidden $_skipped = 0;

  [int] Increment() {
    return ++$this._value;
  }

  [int] Value() {
    return $this._value;
  }

  [int] IncrementError() {
    return ++$this._errors;
  }

  [int] Errors() {
    return $this._errors;
  }

  [int] IncrementSkipped() {
    return ++$this._skipped;
  }

  [int] Skipped() {
    return $this._skipped;
  }
}

class BaseController {
  [scriptblock]$_header;
  [scriptblock]$_summary;
  [hashtable]hidden $_exchange;
  [int]hidden $_index = 0;
  [boolean]$_trigger = $false;
  [boolean]hidden $_broken = $false;

  BaseController([hashtable]$exchange,
    [scriptblock]$header,
    [scriptblock]$summary) {
    $this._exchange = $exchange;
    $this._header = $header;
    $this._summary = $summary;
  }

  [int] RequestIndex() {
    if ($this._exchange.ContainsKey('LOOPZ.CONTROLLER.STACK')) {
      $this._exchange['LOOPZ.CONTROLLER.STACK'].Peek().Increment();
    }
    return $this._exchange['LOOPZ.FOREACH.INDEX'] = $this._index++;
  }

  [boolean] IsBroken () {
    return $this._broken;
  }

  [boolean] GetTrigger() {
    return $this._trigger;
  }

  # I don't know how to define abstract methods in PowerShell classes, so
  # throwing an exception is the best thing we can do for now.
  #
  [void] SkipItem() {
    throw [System.Management.Automation.MethodInvocationException]::new(
      'Abstract method not implemented (BaseController.SkipItem)');
  }

  [int] Skipped() {
    throw [System.Management.Automation.MethodInvocationException]::new(
      'Abstract method not implemented (BaseController.Skipped)');
  }

  [void] ErrorItem() {
    throw [System.Management.Automation.MethodInvocationException]::new(
      'Abstract method not implemented (BaseController.ErrorItem)');
  }

  [int] Errors() {
    throw [System.Management.Automation.MethodInvocationException]::new(
      'Abstract method not implemented (BaseController.Errors)');
  }

  [void] ForeachBegin () {
    [System.Collections.Stack]$stack = $this._exchange.ContainsKey('LOOPZ.CONTROLLER.STACK') `
      ? ($this._exchange['LOOPZ.CONTROLLER.STACK']) : ([System.Collections.Stack]::new());

    $stack.Push([Counter]::new());
    $this._exchange['LOOPZ.CONTROLLER.DEPTH'] = $stack.Count;
    $this._header.InvokeReturnAsIs($this._exchange);
  }

  [void] ForeachEnd () {
    throw [System.Management.Automation.MethodInvocationException]::new(
      'Abstract method not implemented (BaseController.ForeachEnd)');
  }

  [void] BeginSession () {}
  [void] EndSession () {}

  [void] HandleResult([PSCustomObject]$invokeResult) {
    # Note, the _index at this point has already been incremented and refers to the
    # next allocated item.
    #
    if ($invokeResult) {
      if ($invokeResult.psobject.properties.match('Trigger') -and $invokeResult.Trigger) {
        $this._exchange['LOOPZ.FOREACH.TRIGGER'] = $true;
        $this._trigger = $true;
      }

      if ($invokeResult.psobject.properties.match('Break') -and $invokeResult.Break) {
        $this._broken = $true;
      }

      if ($invokeResult.psobject.properties.match('Skipped') -and $invokeResult.Skipped) {
        $this.SkipItem();
      }

      if ($invokeResult.psobject.properties.match('ErrorReason') -and
        ($invokeResult.ErrorReason -is [string])) {
        $this.ErrorItem();
      }
    }
  }
}

class ForeachController : BaseController {
  [int]hidden $_skipped = 0;
  [int]hidden $_errors = 0;

  ForeachController([hashtable]$exchange,
    [scriptblock]$header,
    [scriptblock]$summary
  ): base($exchange, $header, $summary) {

  }

  [void] SkipItem() {
    $this._skipped++;
  }

  [int] Skipped() {
    return $this._skipped;
  }

  [void] ErrorItem() {
    $this._errors++;
  }

  [int] Errors() {
    return $this._errors;
  }

  [void] ForeachEnd () {
    $this._exchange['LOOPZ.FOREACH.TRIGGER'] = $this._trigger;
    $this._exchange['LOOPZ.FOREACH.COUNT'] = $this._index;

    $this._summary.InvokeReturnAsIs($this._index, $this._skipped, $this._errors,
      $this._trigger, $this._exchange);
  }
}

class TraverseController : BaseController {

  [PSCustomObject]$_session = @{
    Count   = 0;
    Errors  = 0;
    Skipped = 0;
    Trigger = $false;
    Header  = $null;
    Summary = $null;
  }

  TraverseController([hashtable]$exchange,
    [scriptblock]$header,
    [scriptblock]$summary,
    [scriptblock]$sessionHeader,
    [scriptblock]$sessionSummary
  ): base($exchange, $header, $summary) {
    $this._session.Header = $sessionHeader;
    $this._session.Summary = $sessionSummary;
  }

  [void] SkipItem() {
    $this._exchange['LOOPZ.CONTROLLER.STACK'].Peek().IncrementSkipped();
  }

  [int] Skipped() {
    return $this._session.Skipped;
  }

  [void] ErrorItem() {
    $this._exchange['LOOPZ.CONTROLLER.STACK'].Peek().IncrementError();
  }

  [int] Errors() {
    return $this._session.Errors;
  }

  [void] ForeachEnd () {
    $this._exchange['LOOPZ.FOREACH.TRIGGER'] = $this._trigger;
    $this._exchange['LOOPZ.FOREACH.COUNT'] = $this._index;

    [System.Collections.Stack]$stack = $this._exchange['LOOPZ.CONTROLLER.STACK'];
    [Counter]$counter = $stack.Pop();
    $this._exchange['LOOPZ.CONTROLLER.DEPTH'] = $stack.Count;
    $this._session.Count += $counter.Value();
    $this._session.Errors += $counter.Errors();
    $this._session.Skipped += $counter.Skipped();
    if ($this._trigger) {
      $this._session.Trigger = $true;
    }

    $this._summary.InvokeReturnAsIs($counter.Value(), $counter.Skipped(),
      $counter.Errors(), $this._trigger, $this._exchange);
  }

  [void] BeginSession () {
    [System.Collections.Stack]$stack = [System.Collections.Stack]::new();

    # The Counter for the session represents the top-level invoke
    #
    $stack.Push([Counter]::new());
    $this._exchange['LOOPZ.CONTROLLER.STACK'] = $stack;
    $this._exchange['LOOPZ.CONTROLLER.DEPTH'] = $stack.Count;
    $this._session.Header.InvokeReturnAsIs($this._exchange);
  }

  [void] EndSession () {
    [System.Collections.Stack]$stack = $this._exchange['LOOPZ.CONTROLLER.STACK'];

    # This counter value represents the top-level invoke which is not included in
    # a foreach sequence.
    #
    [Counter]$counter = $stack.Pop();
    $this._exchange['LOOPZ.CONTROLLER.DEPTH'] = $stack.Count;

    if ($stack.Count -eq 0) {
      $this._exchange.Remove('LOOPZ.CONTROLLER.STACK');
    }
    else {
      Write-Warning "!!!!!! END-SESSION; stack contains $($stack.Count) excess items";
    }

    $this._session.Count += $counter.Value();
    $this._session.Summary.InvokeReturnAsIs($this._session.Count,
      $this._session.Skipped,
      $this._session.Errors,
      $this._session.Trigger,
      $this._exchange
    );
  }
}

function New-Controller {
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseShouldProcessForStateChangingFunctions',
    '', Justification = 'Not a state changing function, its a factory')]
  [CmdletBinding(DefaultParameterSetName = 'Iterating')]
  [OutputType([BaseController])]
  param (
    [Parameter(ParameterSetName = 'Iterating')]
    [Parameter(ParameterSetName = 'Traversing')]
    [ControllerType]$Type,

    [Parameter(ParameterSetName = 'Iterating')]
    [Parameter(ParameterSetName = 'Traversing')]
    [hashtable]$Exchange,

    [Parameter(ParameterSetName = 'Iterating')]
    [Parameter(ParameterSetName = 'Traversing')]
    [scriptblock]$Header,

    [Parameter(ParameterSetName = 'Iterating')]
    [Parameter(ParameterSetName = 'Traversing')]
    [scriptblock]$Summary,

    [Parameter(ParameterSetName = 'Traversing')]
    [scriptblock]$SessionHeader,

    [Parameter(ParameterSetName = 'Traversing')]
    [scriptblock]$SessionSummary
  )

  $instance = $null;

  switch ($Type) {
    ForeachCtrl {
      $instance = [ForeachController]::new($Exchange, $Header, $Summary);
      break;
    }

    TraverseCtrl {
      $instance = [TraverseController]::new($Exchange, $Header, $Summary,
        $SessionHeader, $SessionSummary);
      break;
    }
  }

  $instance;
}

class EndAdapter {
  [System.IO.FileSystemInfo]$_fsInfo;
  [boolean]$_isDirectory;
  [string]$_adjustedName;

  EndAdapter([System.IO.FileSystemInfo]$fsInfo) {
    $this._fsInfo = $fsInfo;
    $this._isDirectory = ($fsInfo.Attributes -band
      [System.IO.FileAttributes]::Directory) -eq [System.IO.FileAttributes]::Directory;

    $this._adjustedName = $this._isDirectory ? $fsInfo.Name `
      : [System.IO.Path]::GetFileNameWithoutExtension($this._fsInfo.Name);
  }

  [string] GetAdjustedName() {
    return $this._adjustedName;
  }

  [string] GetNameWithExtension([string]$newName) {
    [string]$result = ($this._isDirectory) ? $newName `
      : ($newName + [System.IO.Path]::GetExtension($this._fsInfo.Name));

    return $result;
  }

  [string] GetNameWithExtension([string]$newName, [string]$extension) {
    [string]$result = ($this._isDirectory) ? $newName `
      : ($newName + $extension);

    return $result;
  }
}

function New-EndAdapter {
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseShouldProcessForStateChangingFunctions',
    '', Justification = 'Not a state changing function, its a factory')]
  param(
    [System.IO.FileSystemInfo]$fsInfo
  )
  return [EndAdapter]::new($fsInfo);
}
Export-ModuleMember -Variable LoopzHelpers, LoopzUI, Loopz

Export-ModuleMember -Alias remy, greps, esc, moma, ife, Foreach-FsItem, imdt, Mirror-Directory, itd, Traverse-Directory, wife, Decorate-Foreach

Export-ModuleMember -Function Rename-Many, Select-Patterns, Show-Signals, Update-CustomSignals, Format-Escape, Get-FormattedSignal, Get-PaddedLabel, Get-Signals, Initialize-ShellOperant, Move-Match, new-RegularExpression, resolve-PatternOccurrence, Select-FsItem, Select-SignalContainer, Split-Match, Update-Match, Invoke-ForeachFsItem, Invoke-MirrorDirectoryTree, Invoke-TraverseDirectory, Format-StructuredLine, Show-Header, Show-Summary, Write-HostFeItemDecorator, edit-RemoveSingleSubString, Get-InverseSubString, Get-IsLocked, get-PlatformName, Get-PsObjectField, invoke-ByPlatform, resolve-ByPlatform, Test-IsFileSystemSafe

# Custom Module Initialisation
#
$Loopz.Signals = $(Initialize-Signals)