Param(
    [Parameter(Mandatory=$true, HelpMessage="Root folder containing the website files.")]
    [ValidateScript({Test-Path $_ -PathType Container})]
    [string]$RootPath,

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

    [Parameter(HelpMessage="Full path where sitemap.xml will be saved. Defaults to <RootPath>\sitemap.xml")]
    [string]$OutputFile = (Join-Path -Path $RootPath -ChildPath "sitemap.xml")
)

# Ensure BaseUrl does not end with a slash
if ($BaseUrl.EndsWith('/')) {
    $BaseUrl = $BaseUrl.TrimEnd('/')
}

# Define file extensions to include in the sitemap
$extensions = '.html', '.htm', '.php', '.asp', '.aspx', '.jsp', '.txt', '.md'

# Gather files recursively, excluding the output sitemap itself
$files = Get-ChildItem -Path $RootPath -Recurse -File |
    Where-Object {
        $extensions -contains $_.Extension.ToLower() -and
        $_.FullName -ne (Resolve-Path -Path $OutputFile -ErrorAction SilentlyContinue).Path
    }

# Create XmlWriter settings for pretty output
$settings = New-Object System.Xml.XmlWriterSettings
$settings.Indent = $true
$settings.IndentChars = "    "
$settings.NewLineOnAttributes = $false
$settings.Encoding = [System.Text.Encoding]::UTF8

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

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

    foreach ($file in $files) {
        # Compute relative URL path
        $relativePath = $file.FullName.Substring($RootPath.Length).TrimStart('\','/')
        $urlPath = $relativePath -replace '\\','/'
        # Encode spaces and other URI characters
        $escapedPath = [System.Web.HttpUtility]::UrlPathEncode($urlPath)

        $loc = "$BaseUrl/$escapedPath".Replace(':/','://') # ensure proper scheme separator

        $writer.WriteStartElement("url")

        $writer.WriteElementString("loc", $loc)

        # Last modification date in ISO 8601 (UTC)
        $lastMod = $file.LastWriteTimeUtc.ToString("yyyy-MM-ddTHH:mm:ssZ")
        $writer.WriteElementString("lastmod", $lastMod)

        # Optional tags – you can adjust as needed
        $writer.WriteElementString("changefreq", "weekly")
        $writer.WriteElementString("priority", "0.5")

        $writer.WriteEndElement() # </url>
    }

    $writer.WriteEndElement() # </urlset>
    $writer.WriteEndDocument()
}
finally {
    $writer.Flush()
    $writer.Close()
    $writer.Dispose()
}

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