DemoHelper.ps1

# Playing around with: https://blogs.msdn.microsoft.com/powershell/2007/03/03/start-demo-help-doing-demos-using-powershell/
# WIP.

function Get-DemoCommand {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory)]
        [String]$Path
    )

    $Path = $pscmdlet.GetUnresolvedProviderPathFromPSPath($Path)

    $tokens = $errors = @()

    $ast = [System.Management.Automation.Language.Parser]::ParseFile(
        $Path,
        [Ref]$tokens,
        [Ref]$errors
    )

    foreach ($statement in $ast.EndBlock.Statements) {
        if ($statement.PipelineElements -and $statement.PipelineElements[0].Expression -is [System.Management.Automation.Language.ScriptBlockExpressionAst]) {
            $statement.PipelineElements[0].Expression.ScriptBlock.GetScriptBlock()
        } else {
            $statement.Extent.Text
        }
    }

    if ($errors.Count -gt 0) {
        $errors | Write-Error
        
        throw 'Demo script has errors!'
    }
}

filter Invoke-DemoCommand {
    param (
        [Parameter(ValueFromPipeline)]
        [Object]$Command
    )

    if ($Command -is [String]) {
        Invoke-Expression $Command | Out-String | Write-Host
    } elseif ($Command -is [ScriptBlock]) {
        & $Command | Out-String | Write-Host
    }

    Write-Host
}

filter Type-DemoCommand {
    param (
        [Parameter(ValueFromPipeline)]
        [Object]$Command
    )
    
    Write-Host 'PS> ' -NoNewLine

    if ($Command -is [ScriptBlock]) {
        Write-Host '& {' -NoNewLine
    }

    foreach ($char in $Command.ToString().ToCharArray()) {
        if ($char -eq "`r") {
            # Discard always
        }
        if ($char -eq "`n") {
            Write-Host
        }

        Write-Host $char -NoNewLine
        Start-Sleep -Milliseconds 60
    }

    if ($Command -is [ScriptBlock]) {
        Write-Host '}' -NoNewLine
    }
    Write-Host

    $Command
}

$commands = Get-DemoCommand C:\temp\demo.ps1
for ($i = 0; $i -lt $commands.Count; $i++) {
    # Input handler goes here
    $commands[$i] | Type-DemoCommand | Invoke-DemoCommand
}