param(
    [Parameter(Mandatory=$true, Position=0)]
    [string]$RootPath,

    [Parameter(Mandatory=$true, Position=1)]
    [ValidatePattern('^https?://')]
    [string]$BaseUrl,

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

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

Set-StrictMode -Version Latest

function Get-RelativeUrl {
    param(
        [string]$FullPath,
        [string]$RootPath
    )
    $relative = $FullPath.Substring($RootPath.Length)
    $relative = $relative.TrimStart('\','/')
    $relative = $relative -replace '\\','/'
    return $relative
}

function Escape-Xml {
    param([string]$Text)
    $xmlSettings = New-Object System.Xml.XmlWriterSettings
    $xmlSettings.OmitXmlDeclaration = $true
    $stringWriter = New-Object System.IO.StringWriter
    $writer = [System.Xml.XmlWriter]::Create($stringWriter, $xmlSettings)
    $writer.WriteString($Text)
    $writer.Flush()
    $writer.Close()
    return $stringWriter.ToString()
}

# Resolve full path and ensure it ends with a directory separator
$rootFullPath = (Resolve-Path -Path $RootPath).ProviderPath
if (-not $rootFullPath.EndsWith([System.IO.Path]::DirectorySeparatorChar)) {
    $rootFullPath += [System.IO.Path]::DirectorySeparatorChar
}

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

$writer = [System.Xml.XmlWriter]::Create($OutputFile, $settings)
$writer.WriteStartDocument()
$writer.WriteStartElement('urlset')
$writer.WriteAttributeString('xmlns', 'http://www.sitemaps.org/schemas/sitemap/0.9')

# Retrieve files
$files = Get-ChildItem -Path $rootFullPath -Recurse -File -Include $IncludeExtensions -ErrorAction SilentlyContinue

foreach ($file in $files) {
    $relativeUrl = Get-RelativeUrl -FullPath $file.FullName -RootPath $rootFullPath
    $escapedRelative = [System.Web.HttpUtility]::UrlPathEncode($relativeUrl)
    $loc = "$BaseUrl/$escapedRelative".TrimEnd('/')

    $lastMod = $file.LastWriteTimeUtc.ToString('yyyy-MM-ddTHH:mm:sszzz')

    $writer.WriteStartElement('url')
    $writer.WriteElementString('loc', $loc)
    $writer.WriteElementString('lastmod', $lastMod)
    # Optional: changefreq and priority can be added here if desired
    $writer.WriteEndElement() # </url>
}

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

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