pwsh-handy-helpers

1.0.7.5

src/data.ps1

function Invoke-PropertyTransform {
  <#
  .SYNOPSIS
  Helper function that can be used to rename object keys and transform values.
  .PARAMETER Transform
  The Transform function that can be a simple identity function or complex reducer (as used by Redux.js and React.js)
  The Transform function can use pipeline values or the automatice variables, $Name and $Value which represent the associated old key name and original value, respectively.

  A reducer that would transform the values with the keys, 'foo' or 'bar', migh look something like this:

  $Reducer = {
    Param($Name, $Value)
    switch ($Name) {
      'foo' { ... }
      'bar' { ... }
      Default { $Value }
    }
  }
  .PARAMETER Lookup
  Dictionary lookup object that will map old key names to new key names.

  Example:

  $Lookup = @{
    foobar = 'foo_bar'
    Name = 'first_name'
  }
  .EXAMPLE
  $Data = @{}
  $Data | Add-member -NotePropertyName 'fighter_power_level' -NotePropertyValue 90
  $Lookup = @{
    level = 'fighter_power_level'
  }
  $Reducer = {
    Param($Value)
    ($Value * 100) + 1
  }
  $Data | Invoke-PropertyTransform -Lookup $Lookup -Transform $Reducer
  .EXAMPLE
  $Data = @{
    fighter_power_level = 90
  }
  $Lookup = @{
    level = 'fighter_power_level'
  }
  $Reducer = {
    Param($Value)
    ($Value * 100) + 1
  }
  $Data | transform $Lookup $Reducer
  .EXAMPLE
  $Lookup = @{
    PIID = 'award_id_piid'
    Name = 'recipient_name'
    Program = 'major_program'
    Cost = 'total_dollars_obligated'
    Url = 'usaspending_permalink'
  }
  $Reducer = {
    Param($Name, $Value)
    switch ($Name) {
      'total_dollars_obligated' { ConvertTo-MoneyString $Value }
      Default { $Value }
    }
  }
  (Import-Csv -Path '.\contracts.csv') | Invoke-PropertyTransform -Lookup $Lookup -Transform $Reducer | Format-Table
  #>
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '', Scope='Function')]
  [CmdletBinding()]
  [Alias('transform')]
  Param(
    [Parameter(Mandatory=$true, ValueFromPipeline=$true)]
    $InputObject,
    [Parameter(Mandatory=$true, Position=0)]
    [PSObject] $Lookup,
    [Parameter(Position=1)]
    [ScriptBlock] $Transform = { Param($Value) $Value }
  )
  Begin {
    function New-PropertyExpression {
      [CmdletBinding()]
      Param(
        [Parameter(Mandatory=$true)]
        [String] $Name,
        [Parameter(Mandatory=$true)]
        [ScriptBlock] $Transform
      )
      {
        & $Transform -Name $Name -Value ($_.$Name)
      }.GetNewClosure()
    }
    $Property = $Lookup.GetEnumerator() | ForEach-Object {
      $OldName = $_.Value
      $NewName = $_.Name
      @{
        Name = $NewName
        Expression = (New-PropertyExpression -Name $OldName -Transform $Transform)
      }
    }
  }
  Process {
    $InputObject | Select-Object -Property $Property
  }
}