PowerShell version 2 param block parser

Get-CommandParameter.ps1

function Get-CommandParameter {
    # .SYNOPSIS
    #   A PowerShell version 2 compatible parameter block parser.

    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true, Position = 1, ValueFromPipelineByPropertyName = $true)]
        [String]$Definition
    )

    begin {
        function Get-TokenGroup {
            param (
                [System.Management.Automation.PSToken[]]$tokens
            )

            $i = $j = 0
            do {
                $token = $tokens[$i]
                if ($token.Type -eq 'GroupStart') {
                    $j++
                }
                if ($token.Type -eq 'GroupEnd') {
                    $j--
                }
                if (-not $token.PSObject.Properties.Item('Depth')) {
                    $token | Add-Member Depth -MemberType NoteProperty -Value $j
                }
                $token

                $i++
            } until ($j -eq 0 -or $i -ge $tokens.Count)
        }
    }

    process {
        $errors = $null
        $tokens = [System.Management.Automation.PSParser]::Tokenize($Definition, [Ref]$errors)

        # Find param
        $start = $tokens.IndexOf(($tokens | Where-Object { $_.Content -eq 'param' })[0]) + 1
        $paramBlock = Get-TokenGroup $tokens[$start..($tokens.Count - 1)]

        for ($i = 0; $i -lt $paramBlock.Count; $i++) {
            $token = $paramBlock[$i]

            if ($token.Depth -eq 1 -and $token.Type -eq 'Variable') {
                $paramInfo = New-Object PSObject -Property @{
                    Name = $token.Content
                } | Select-Object Name, Type, DefaultValue, DefaultValueType

                if ($paramBlock[$i + 1].Content -ne ',') {
                    $value = $paramBlock[$i + 2]
                    if ($value.Type -eq 'GroupStart') {
                        $tokenGroup = Get-TokenGroup $paramBlock[($i + 2)..($paramBlock.Count - 1)]
                        $paramInfo.DefaultValue = [String]::Join('', ($tokenGroup | ForEach-Object { $_.Content }))
                        $paramInfo.DefaultValueType = 'Expression'
                    } else {
                        $paramInfo.DefaultValue = $value.Content
                        $paramInfo.DefaultValueType = $value.Type
                    }
                }
                if ($paramBlock[$i - 1].Type -eq 'Type') {
                    $paramInfo.Type = $paramBlock[$i - 1].Content
                }
                $paramInfo
            }
        }
    }
}