Invoke-ConditionalAction.fs

namespace PSFSharp
open System.Management.Automation
open System.Management.Automation.Internal

[<Cmdlet(VerbsLifecycle.Invoke, "ConditionalAction",
    ConfirmImpact = ConfirmImpact.Medium, SupportsShouldProcess = true)>]
[<Alias("?!")>]
type InvokeConditionalActionCommand() =
    inherit PSCmdlet()

    let mutable inputCount = 0
    let mutable firstObject = AutomationNull.Value

    [<Parameter(Mandatory = true, ValueFromPipeline = true)>]
    [<Alias("InputObject")>]
    member val If : PSObject = null
        with get, set

    [<Parameter(Mandatory = true, Position = 0)>]
    member val Then : ScriptBlock = null
        with get, set

    [<Parameter(Position = 1)>]
    member val Else : ScriptBlock = null
        with get, set

    override self.ProcessRecord() =
        if firstObject <> AutomationNull.Value then
            firstObject <- self.If

        inputCount <- inputCount + 1

    override self.EndProcessing() =
        let isTrue = inputCount > 1 || (inputCount = 1 && LanguagePrimitives.ConvertTo<bool>(firstObject))

        if isTrue then
            self.WriteObject(self.Then.Invoke(), true)
        else
            self.WriteObject(self.Else.Invoke(), true)