Public/Add-JiraIssueAttachment.ps1

function Add-JiraIssueAttachment {
    [CmdletBinding( SupportsShouldProcess )]
    param(
        [Parameter( Mandatory )]
        [ValidateNotNullOrEmpty()]
        [ValidateScript(
            {
                if (("JiraPS.Issue" -notin $_.PSObject.TypeNames) -and (($_ -isnot [String]))) {
                    $errorItem = [System.Management.Automation.ErrorRecord]::new(
                        ([System.ArgumentException]"Invalid Type for Parameter"),
                        'ParameterType.NotJiraIssue',
                        [System.Management.Automation.ErrorCategory]::InvalidArgument,
                        $_
                    )
                    $errorItem.ErrorDetails = "Wrong object type provided for Issue. Expected [JiraPS.Issue] or [String], but was $($_.GetType().Name)"
                    $PSCmdlet.ThrowTerminatingError($errorItem)
                    <#
                      #ToDo:CustomClass
                      Once we have custom classes, this check can be done with Type declaration
                    #>

                }
                else {
                    return $true
                }
            }
        )]
        [Alias('Key')]
        [Object]
        $Issue,
        <#
          #ToDo:CustomClass
          Once we have custom classes, this can also accept ValueFromPipeline
        #>


        [Parameter( Mandatory, ValueFromPipeline, ValueFromPipelineByPropertyName )]
        [ValidateScript(
            {
                if (-not (Test-Path $_ -PathType Leaf)) {
                    $errorItem = [System.Management.Automation.ErrorRecord]::new(
                        ([System.ArgumentException]"File not found"),
                        'ParameterValue.FileNotFound',
                        [System.Management.Automation.ErrorCategory]::ObjectNotFound,
                        $_
                    )
                    $errorItem.ErrorDetails = "No file could be found with the provided path '$_'."
                    $PSCmdlet.ThrowTerminatingError($errorItem)
                }
                else {
                    return $true
                }
            }
        )]
        [Alias('InFile', 'FullName', 'Path')]
        [String[]]
        $FilePath,

        [PSCredential]
        $Credential,

        [Switch]
        $PassThru
    )

    begin {
        Write-Verbose "[$($MyInvocation.MyCommand.Name)] Function started"

        $resourceURi = "{0}/attachments"
    }

    process {
        Write-DebugMessage "[$($MyInvocation.MyCommand.Name)] ParameterSetName: $($PsCmdlet.ParameterSetName)"
        Write-DebugMessage "[$($MyInvocation.MyCommand.Name)] PSBoundParameters: $($PSBoundParameters | Out-String)"

        if (@($Issue).Count -ne 1) {
            $errorItem = [System.Management.Automation.ErrorRecord]::new(
                ([System.ArgumentException]"invalid Issue provided"),
                'ParameterValue.JiraIssue',
                [System.Management.Automation.ErrorCategory]::InvalidArgument,
                $_
            )
            $errorItem.ErrorDetails = "Only one Issue can be provided at a time."
            $PSCmdlet.ThrowTerminatingError($errorItem)
        }

        # Find the proper object for the Issue
        $issueObj = Resolve-JiraIssueObject -InputObject $Issue -Credential $Credential

        $parameter = @{
            URI        = $resourceURi -f $issueObj.RestURL
            Method     = "POST"
            Credential = $Credential
        }

        foreach ($file in $FilePath) {
            $parameter["InFile"] = $file

            Write-Debug "[$($MyInvocation.MyCommand.Name)] Invoking JiraMethod with `$parameter"
            if ($PSCmdlet.ShouldProcess($IssueObj.Key, "Adding attachment '$($fileName)'.")) {
                $rawResult = Invoke-JiraMethod @parameter

                if ($PassThru) {
                    Write-Output (ConvertTo-JiraAttachment -InputObject $rawResult)
                }
            }
        }
    }

    end {
        Write-Verbose "[$($MyInvocation.MyCommand.Name)] Complete"
    }
}