param(
    [Parameter(Mandatory=$true, HelpMessage="Base URL of the website, e.g., https://example.com/")]
    [ValidatePattern('^https?://.+')]
    [string]$BaseUrl,

    [Parameter(Mandatory=$false, HelpMessage="Root folder to scan. Defaults to current location.")]
    [ValidateScript({ Test-Path $_ -PathType Container })]
    [string]$RootPath = (Get-Location).Path,

    [Parameter(Mandatory=$false, HelpMessage="Output sitemap file path.")]
    [string]$OutputFile = "$RootPath\sitemap.xml",

    [Parameter(Mandatory=$false, HelpMessage="File extensions to include (comma-separated).")]
    [string[]]$IncludeExtensions = @(".html",".htm",".aspx",".php",".asp",".jsp",".js",".css"),

    [Parameter(Mandatory=$false, HelpMessage="Change frequency (always, hourly, daily, weekly, monthly, yearly, never).")]
    [ValidateSet("always","hourly","daily","weekly","monthly","yearly","never")]
    [string]$ChangeFreq = "weekly",

    [Parameter(Mandatory=$false, HelpMessage="Priority (0.0 to 1.0).")]
    [ValidateRange(0.0,1.0)]
    [double]$Priority = 0.5
)

# Ensure BaseUrl ends with a slash
if (-not $BaseUrl.EndsWith('/')) {
    $BaseUrl = "$BaseUrl/"
}

# Resolve root path
$RootPath = (Resolve-Path -Path $RootPath).ProviderPath

# Build a list of files
$filter = $IncludeExtensions | ForEach-Object { "*$_" }
$files = Get-ChildItem -Path $RootPath -Recurse -File -Include $filter -ErrorAction SilentlyContinue

# Prepare XML writer settings
$settings = New-Object System.Xml.XmlWriterSettings
$settings.Indent = $true
$settings.Encoding = [System.Text.Encoding]::UTF8

# Create the XML file
$writer = [System.Xml.XmlWriter]::Create($OutputFile, $settings)

$writer.WriteStartDocument()
$writer.WriteStartElement("urlset")
$writer.WriteAttributeString("xmlns", "http://www.sitemaps.org/schemas/sitemap/0.9")

foreach ($file in $files) {
    # Relative path from root
    $relativePath = $file.FullName.Substring($RootPath.Length).TrimStart('\','/')

    # Convert backslashes to forward slashes for URL
    $urlPath = $relativePath -replace '\\','/'

    # Escape URL characters
    $escapedPath = [System.Web.HttpUtility]::UrlPathEncode($urlPath)

    $loc = $BaseUrl + $escapedPath

    $lastMod = $file.LastWriteTimeUtc.ToString("yyyy-MM-ddTHH:mm:ssZ")

    $writer.WriteStartElement("url")

    $writer.WriteElementString("loc", $loc)
    $writer.WriteElementString("lastmod", $lastMod)
    $writer.WriteElementString("changefreq", $ChangeFreq)
    $writer.WriteElementString("priority", "{0:N1}" -f $Priority)

    $writer.WriteEndElement() # url
}

$writer.WriteEndElement() # urlset
$writer.WriteEndDocument()
$writer.Flush()
$writer.Close()

Write-Host "Sitemap generated at: $OutputFile" -ForegroundColor Green