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

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

    [string]$OutputPath = "$RootPath\sitemap.xml",

    [switch]$IncludeLastMod,
    [switch]$IncludeChangeFreq,
    [switch]$IncludePriority
)

# Normalize inputs
$BaseUrl = $BaseUrl.TrimEnd('/')
$RootPath = (Resolve-Path -Path $RootPath).ProviderPath.TrimEnd('\')
if (-not (Test-Path -Path $RootPath -PathType Container)) {
    Write-Error "RootPath '$RootPath' does not exist or is not a directory."
    exit 1
}

# Gather all .html/.htm files recursively
$files = Get-ChildItem -Path $RootPath -Recurse -File -Include *.html, *.htm

if ($files.Count -eq 0) {
    Write-Warning "No .html or .htm files found under '$RootPath'."
    exit 0
}

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

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

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

foreach ($file in $files) {
    # Build relative URL path
    $relativePath = $file.FullName.Substring($RootPath.Length).TrimStart('\','/')
    $relativeUrl = $relativePath -replace '\\','/'

    # Special handling for default documents (e.g., index.html)
    if ($relativeUrl -match '^(.*?)(index\.html?|default\.aspx?)$') {
        $relativeUrl = $Matches[1]
    }

    $loc = "$BaseUrl/$relativeUrl".TrimEnd('/')

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

    if ($IncludeLastMod) {
        $lastmod = $file.LastWriteTimeUtc.ToString('yyyy-MM-ddTHH:mm:ssZ')
        $writer.WriteElementString('lastmod', $lastmod)
    }

    if ($IncludeChangeFreq) {
        # You could make this configurable; defaulting to 'weekly'
        $writer.WriteElementString('changefreq', 'weekly')
    }

    if ($IncludePriority) {
        # Simple heuristic: depth determines priority
        $depth = ($relativeUrl -split '/').Count
        $priority = [Math]::Round(1.0 / $depth, 2)
        if ($priority -lt 0.1) { $priority = 0.1 }
        $writer.WriteElementString('priority', $priority.ToString('0.0'))
    }

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

$writer.WriteEndElement() # </urlset>
$writer.WriteEndDocument()
$writer.Flush()
$writer.Close()

Write-Host "Sitemap generated successfully at: $OutputPath"