param(
    [Parameter(Mandatory=$true)]
    [ValidateNotNullOrEmpty()]
    [string]$RootPath,

    [Parameter(Mandatory=$true)]
    [ValidatePattern('^https?://')]
    [string]$BaseUrl,

    [string]$OutputFile = "sitemap.xml",

    [ValidateSet('always','hourly','daily','weekly','monthly','yearly','never')]
    [string]$ChangeFreq = 'weekly',

    [ValidateRange(0,1)]
    [double]$Priority = 0.5
)

function Write-ErrorAndExit {
    param([string]$Message)
    Write-Error $Message
    exit 1
}

if (-not (Test-Path -LiteralPath $RootPath -PathType Container)) {
    Write-ErrorAndExit "RootPath '$RootPath' does not exist or is not a directory."
}

# Ensure BaseUrl ends with a slash
if ($BaseUrl[-1] -ne '/') {
    $BaseUrl = "$BaseUrl/"
}

# Resolve full paths
$rootFullPath = (Resolve-Path -LiteralPath $RootPath).Path

# Gather files to include in sitemap
$extensions = @('*.html','*.htm','*.php','*.asp','*.aspx')
$files = Get-ChildItem -Path $rootFullPath -Recurse -File -Include $extensions -ErrorAction Stop

# Create XML document
$xmlDoc = New-Object System.Xml.XmlDocument
$xmlDeclaration = $xmlDoc.CreateXmlDeclaration('1.0','UTF-8',$null)
$xmlDoc.AppendChild($xmlDeclaration) | Out-Null

$urlset = $xmlDoc.CreateElement('urlset')
$xmlnsAttr = $xmlDoc.CreateAttribute('xmlns')
$xmlnsAttr.Value = 'http://www.sitemaps.org/schemas/sitemap/0.9'
$urlset.Attributes.Append($xmlnsAttr) | Out-Null
$xmlDoc.AppendChild($urlset) | Out-Null

foreach ($file in $files) {
    $relativePath = $file.FullName.Substring($rootFullPath.Length).TrimStart('\','/')
    $urlPath = $relativePath -replace '\\','/'
    $loc = $BaseUrl + $urlPath

    $urlNode = $xmlDoc.CreateElement('url')
    
    $locNode = $xmlDoc.CreateElement('loc')
    $locNode.InnerText = $loc
    $urlNode.AppendChild($locNode) | Out-Null

    $lastModNode = $xmlDoc.CreateElement('lastmod')
    $lastModNode.InnerText = $file.LastWriteTime.ToString('yyyy-MM-dd')
    $urlNode.AppendChild($lastModNode) | Out-Null

    $changeFreqNode = $xmlDoc.CreateElement('changefreq')
    $changeFreqNode.InnerText = $ChangeFreq
    $urlNode.AppendChild($changeFreqNode) | Out-Null

    $priorityNode = $xmlDoc.CreateElement('priority')
    $priorityNode.InnerText = $Priority.ToString('0.##')
    $urlNode.AppendChild($priorityNode) | Out-Null

    $urlset.AppendChild($urlNode) | Out-Null
}

# Save to file
try {
    $outputPath = Join-Path -Path (Get-Location) -ChildPath $OutputFile
    $xmlDoc.Save($outputPath)
    Write-Host "Sitemap generated successfully at: $outputPath"
}
catch {
    Write-Error "Failed to save sitemap: $_"
    exit 1
}