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

    [Parameter(Mandatory=$false,HelpMessage="Root directory to scan (defaults to current location)")]
    [string]$RootPath = (Get-Location).Path,

    [Parameter(Mandatory=$false,HelpMessage="File extensions to include (comma‑separated, without the dot)")]
    [string[]]$IncludeExtensions = @('html','htm','php','aspx','jsp','asp','txt','xml'),

    [Parameter(Mandatory=$false,HelpMessage="Change frequency for all URLs (default: weekly)")]
    [ValidateSet('always','hourly','daily','weekly','monthly','yearly','never')]
    [string]$ChangeFreq = 'weekly',

    [Parameter(Mandatory=$false,HelpMessage="Default priority for all URLs (0.0‑1.0)")]
    [ValidateRange(0.0,1.0)]
    [double]$Priority = 0.5,

    [Parameter(Mandatory=$false,HelpMessage="Path to output sitemap.xml (defaults to RootPath)")]
    [string]$OutputPath = "$RootPath\sitemap.xml"
)

function Convert-ToUrlPath {
    param(
        [string]$Path,
        [string]$Root
    )
    $relative = Resolve-Path -LiteralPath $Path -Relative -BasePath $Root
    $urlPath = $relative -replace '\\','/'
    # URL‑encode reserved characters
    $urlPath = [System.Web.HttpUtility]::UrlPathEncode($urlPath)
    return $urlPath
}

function Get-FileLastModUtc {
    param([string]$Path)
    $dt = (Get-Item -LiteralPath $Path).LastWriteTimeUtc
    return $dt.ToString("yyyy-MM-ddTHH:mm:ss'Z'")
}

# Ensure BaseUrl ends without trailing slash
if ($BaseUrl.EndsWith('/')) {
    $BaseUrl = $BaseUrl.TrimEnd('/')
}

# Prepare XmlWriter settings
$settings = New-Object System.Xml.XmlWriterSettings
$settings.Indent = $true
$settings.Encoding = [System.Text.UTF8Encoding]::new($false) # omit BOM

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

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

# Enumerate files
$filter = '*.*'
$files = Get-ChildItem -Path $RootPath -Recurse -File -Include $IncludeExtensions | Where-Object {
    $ext = $_.Extension.TrimStart('.').ToLower()
    $IncludeExtensions -contains $ext
}

foreach ($file in $files) {
    $urlPath = Convert-ToUrlPath -Path $file.FullName -Root $RootPath
    $loc = "$BaseUrl/$urlPath"

    $writer.WriteStartElement('url')
    $writer.WriteElementString('loc', $loc)
    $writer.WriteElementString('lastmod', (Get-FileLastModUtc -Path $file.FullName))
    $writer.WriteElementString('changefreq', $ChangeFreq)
    $writer.WriteElementString('priority', $Priority.ToString('0.0'))
    $writer.WriteEndElement() # url
}

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

Write-Host "Sitemap generated at:" $OutputPath