PipeScript

0.2.6

Transpilers/Core/PipeScript.Aspect.psx.ps1

<#
.SYNOPSIS
    Aspect Transpiler
.DESCRIPTION
    The Aspect Transpiler allows for any Aspect command to be embedded inline anywhere the aspect is found.

    Aspects enable aspect-oriented programming in PipeScript.

    Aspects should be small self-contained functions that solve one "aspect" of a problem.
.EXAMPLE
    Import-PipeScript {
        aspect function SayHi {
            if (-not $args) { "Hello World"}
            else { $args }
        }
        function Greetings {
            SayHi # Aspects can be referred to by their short name
            Aspect.SayHi "hallo Welt" # or their long name
        }
    }

    Greetings
#>
[ValidateScript({
    $validating = $_

    # If we are not validating a command, it cannot be an aspect.
    if ($validating -isnot [Management.Automation.Language.CommandAst]) { return $false }
    
    # Determine the aspect name
    $aspectName = "Aspect?$(@($validating.CommandElements)[0])"
    $aspectName = $aspectName -replace "Aspect\?Aspect", 'Aspect'
    if (-not $script:KnownAspects) {
        $script:KnownAspects = @{}
    }
    if ($script:KnownAspects.Contains($aspectName)) {
        return $script:KnownAspects[$aspectName]
    }
    # and see if we have any matching commands
    $aspectCommand = @($ExecutionContext.SessionState.InvokeCommand.GetCommands($aspectName, 'Function,Alias', $true))
        # If we do, this is a valid aspect.
    $script:KnownAspects[$aspectName] = ($aspectCommand.Length -as [bool])
    return ($aspectCommand.Length -as [bool])
})]
param(
# An Aspect Command. Aspect Commands are embedded inline.
[Parameter(Mandatory,ValueFromPipeline)]
[Management.Automation.Language.CommandAst]
$AspectCommandAst
)

process {
    
    $aspectName = "Aspect?$(@($AspectCommandAst.CommandElements)[0])"
    $aspectName = $aspectName -replace "Aspect\?Aspect", 'Aspect'
    $aspectCommands = @($ExecutionContext.SessionState.InvokeCommand.GetCommands($aspectName, 'Function,Alias', $true))
    
    if (-not $aspectCommands) { return }
    if ($aspectCommands.Length -gt 1) { return }

    $aspectCommand = $aspectCommands[0]

    $aspectScriptBlock = 
        if ($aspectCommand -is [Management.Automation.AliasInfo]) {
            $resolvedCommand = $aspectCommand.ResolvedCommand
            while ($resolvedCommand.ResolvedCommand) {
                $resolvedCommand  = $resolvedCommand.ResolvedCommand
            }
            $resolvedCommand.ScriptBlock
        } else {
            $aspectCommand.ScriptBlock
        }
    
    if (-not $aspectScriptBlock) { return }

    $firstElement, $restOfElements = @($aspectCommandAst.CommandElements)
    
    $InvocationOperator = 
        if ($AspectCommandAst.Parent.InvocationOperator -eq 'Dot') {
            '.'
        } else {
            '&'
        }    

    [ScriptBlock]::Create(
"
# $aspectCommand
$InvocationOperator { $aspectScriptBlock } $restOfElements
".Trim()
    )
}