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

    [Parameter(Mandatory=$false, HelpMessage="Root folder to scan for web files")]
    [string]$Path = (Get-Location).Path,

    [Parameter(Mandatory=$false, HelpMessage="Output sitemap file name (full path or relative to -Path)")]
    [string]$Output = "sitemap.xml",

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

    [Parameter(Mandatory=$false, HelpMessage="Default <changefreq> value (always, hourly, daily, weekly, monthly, yearly, never)")]
    [ValidateSet('always','hourly','daily','weekly','monthly','yearly','never')]
    [string]$ChangeFreq = 'weekly',

    [Parameter(Mandatory=$false, HelpMessage="Default <priority> value (0.0 – 1.0)")]
    [ValidateRange(0.0,1.0)]
    [double]$Priority = 0.5
)

function ConvertTo-UrlPath {
    param(
        [string]$FullPath,
        [string]$RootPath,
        [string]$BaseUrl
    )
    $relative = Resolve-Path -Path $FullPath -Relative -RelativeBasePath $RootPath
    $relative = $relative -replace '\\','/'
    $url = $BaseUrl.TrimEnd('/') + '/' + $relative.TrimStart('/')
    return $url
}

# Ensure the root path ends without a trailing slash for proper relative calculations
$rootPath = (Get-Item -LiteralPath $Path).FullName.TrimEnd('\')

# Build a list of pattern strings like *.html, *.htm …
$patterns = $IncludeExtensions | ForEach-Object { "*.$_" }

# Gather files
$files = Get-ChildItem -Path $rootPath -Recurse -File -Include $patterns -ErrorAction SilentlyContinue

if (-not $files) {
    Write-Warning "No files matching the specified extensions were found under '$rootPath'."
    exit 1
}

# Resolve output path
if ([System.IO.Path]::IsPathRooted($Output)) {
    $outputPath = $Output
} else {
    $outputPath = Join-Path -Path $rootPath -ChildPath $Output
}

# Create XML writer settings
$settings = New-Object System.Xml.XmlWriterSettings
$settings.Indent = $true
$settings.IndentChars = "`t"
$settings.NewLineOnAttributes = $false
$settings.Encoding = [System.Text.Encoding]::UTF8

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

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

    foreach ($file in $files) {
        $loc = ConvertTo-UrlPath -FullPath $file.FullName -RootPath $rootPath -BaseUrl $BaseUrl
        $lastMod = $file.LastWriteTimeUtc.ToString('yyyy-MM-ddTHH:mm:ssZ')

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

        if ($ChangeFreq) {
            $writer.WriteElementString('changefreq', $ChangeFreq)
        }
        if ($Priority -ge 0 -and $Priority -le 1) {
            $writer.WriteElementString('priority', $Priority.ToString('0.0'))
        }
        $writer.WriteEndElement() # url
    }

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

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