Highlight-Syntax.ps1

[CmdletBinding()]
param($Code)

# Load required assemblies
[void] [System.Reflection.Assembly]::Load("System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")

# Generate an HTML span and append it to HTML string builder

Function Append-HtmlSpan ($block, $TokenClass)
{
    If ( ( $TokenClass -eq 'NewLine' ) -or ( $TokenClass -eq 'LineContinuation' ) )
    {
        If ( $TokenClass -eq 'LineContinuation' )
        {
            $null = $CodeBuilder.Append("`")
        }

        $null = $CodeBuilder.Append("`n")
    }
    Else
    {
        $Block = [System.Web.HttpUtility]::HtmlEncode($Block)

        If ( -not $Block.Trim() )
        {
            $Block = $Block.Replace(' ', ' ')
        }

        If ( $TokenColor -eq 'String' )
        {
            $Lines = $block -split "`n"
            $Block = ""

            $MultipleLines = $False

            ForEach ( $Line in $Lines )
            {
                If ( $MultipleLines )
                {
                    $Block += "`n"
                }

                $NewText = $line.TrimStart()
                $NewText = " " * ($Line.Length - $NewText.Length) + $NewText
                $Block += $NewText
                $MultipleLines = $True
            }
        }

        $null = $CodeBuilder.Append("<span class='ps-$TokenClass'>$block</span>")
    }
}

Function Main
{
    # Do syntax parsing.
    $Errors = $null
    $Tokens = [System.Management.Automation.PsParser]::Tokenize( $Code, [ref]$Errors )

    # Initialize HTML builder.
    $CodeBuilder = New-Object System.Text.StringBuilder

    # Iterate over the tokens and set the colors appropriately.
    $position = 0

    ForEach ( $Token in $Tokens)
    {
        If ( $Position -lt $Token.Start )
        {
            $Block = $Code.Substring( $Position, ($Token.Start-$Position) )
            $TokenColor = 'Unknown'
            Append-HtmlSpan $block $TokenColor
        }

        $Block = $Code.Substring( $Token.Start, $Token.Length )

        $TokenColor = $Token.Type.ToString()
        Append-HtmlSpan $Block $TokenColor

        $Position = $Token.Start + $Token.Length
    }

    # Build the entire syntax-highlighted script
    $Code = $CodeBuilder.ToString()

    # Replace some problematic characters
    $Code = $Code -replace '\t', '&#9;' -replace '\$', "&#36;" -replace '\{', '&#123;' -replace '\}', '&#125;'

    # Output HTML
    $Code
}