Adding Core Protocol Transpiler (Fixes #168)

Author: James Brundage

Transpilers/Core/PipeScript.Protocol.psx.ps1

@@ -0,0 +1,91 @@
+<#
+.SYNOPSIS
+    Core Protocol Transpiler
+.DESCRIPTION
+    Enables the transpilation of protocols.
+
+    ```https://api.github.com/repos/StartAutomating/PipeScript/issues``` is a valid command.
+
+    So is ```get https://api.github.com/repos/StartAutomating/PipeScript/issues```.
+    
+    So is ```MyCustomProtocol:// -Parameter value```.
+
+    This transpiler enables commands in protocol format to be transpiled.
+.NOTES
+    This transpiler will match any command whose first or second element contains ```://```
+.EXAMPLE
+    .> -ScriptBlock {
+        https://api.github.com/users/StartAutomating
+    }
+.EXAMPLE
+    .> -ScriptBlock {
+        $userName = 'StartAutomating'
+        https://$GitHubApi/users/$UserName
+    }
+.EXAMPLE
+    .> -ScriptBlock {
+        $env:GitUserName = 'StartAutomating'
+        https://api.github.com/users/$env:GitUserName
+    }
+#>
+[ValidateScript({
+    $commandAst = $_
+    if ($commandAst.CommandElements -and 
+        $commandAst.CommandElements[0] -match '://') {
+        return $true
+    }
+    if ($commandAst.CommandElements.Count -ge 2 -and 
+        $commandAst.CommandElements[1] -match '://') {
+        return $true
+    }
+    return $false
+})]
+param(
+# The Command Abstract Syntax Tree.
+[Parameter(Mandatory,ValueFromPipeline)]
+[Management.Automation.Language.CommandAst]
+$CommandAst
+)
+
+process {    
+    [string]$CommandMethod = ''
+    [string]$commandName   =
+        if ($CommandAst.CommandElements[0].Value -match '://') {
+            $CommandAst.CommandElements[0].Value
+        } 
+        else
+        {
+            $commandMethod =  $CommandAst.CommandElements[0].Value
+            $CommandAst.CommandElements[1].Value
+        }
+    
+    $commandUri  =
+        if ($commandName -as [uri]) {
+            $commandName -as [uri]
+        }
+        else {
+            $commandName -replace '\$(.+)\:','$1__' -replace '\$','__' -as [uri]
+        }
+
+    $commandAstSplat = @{
+        CommandAST = $commandAst        
+    }
+    
+    if ($commandMethod) {
+        $commandAstSplat.Method = $commandMethod
+    }
+
+    $foundTranspiler = 
+        Get-Transpiler -CouldPipe $commandUri -ValidateInput $CommandAst -CouldRun -Parameter $commandAstSplat
+
+    if (-not $foundTranspiler) {
+        Write-Error "Could not find a transpiler for $commandAst"
+        return
+    }
+
+    foreach ($found in $foundTranspiler) {
+        $params = $found.ExtensionParameter
+        $transpilerOutput = & $found.ExtensionCommand @params
+        if ($transpilerOutput) { $transpilerOutput; break }
+    }    
+}