param(
    [Parameter(Mandatory=$true, Position=0)]
    [string]$SiteRoot,          # Base URL, e.g. https://www.example.com

    [Parameter(Mandatory=$true, Position=1)]
    [ValidateScript({Test-Path $_ -PathType Container})]
    [string]$Path,              # Physical path to the web root

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

    [ValidateRange(0.0,1.0)]
    [double]$Priority = 0.5,

    [string[]]$IncludeExtensions = @('.html','.htm','.php','.aspx','.asp','.jsp'),
    
    [switch]$Recursive
)

# Normalize inputs
$SiteRoot = $SiteRoot.TrimEnd('/')
$Path = (Resolve-Path -Path $Path).Path

# Gather files
$searchOption = if ($Recursive) { [System.IO.SearchOption]::AllDirectories } else { [System.IO.SearchOption]::TopDirectoryOnly }
$files = Get-ChildItem -Path $Path -File -Include $IncludeExtensions -Recurse:$Recursive

if (-not $files) {
    Write-Warning "No files matching extensions $($IncludeExtensions -join ', ') were found in $Path."
    exit 0
}

# Create XML writer settings
$xmlSettings = New-Object System.Xml.XmlWriterSettings
$xmlSettings.Indent = $true
$xmlSettings.Encoding = [System.Text.UTF8Encoding]::new($false)

$sitemapPath = Join-Path -Path $Path -ChildPath 'sitemap.xml'
$writer = [System.Xml.XmlWriter]::Create($sitemapPath, $xmlSettings)

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

    foreach ($file in $files) {
        $relativePath = $file.FullName.Substring($Path.Length).TrimStart('\','/')
        $urlPath = $relativePath -replace '\\','/'
        $loc = "$SiteRoot/$urlPath"

        $writer.WriteStartElement('url')

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

        $lastMod = $file.LastWriteTimeUtc.ToString('yyyy-MM-dd')
        $writer.WriteElementString('lastmod', $lastMod)

        $writer.WriteElementString('changefreq', $ChangeFreq)

        $writer.WriteElementString('priority', $Priority.ToString('0.0', [cultureinfo]::InvariantCulture))

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

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

Write-Output "Sitemap generated at: $sitemapPath"