param(
    [Parameter(Mandatory=$true, HelpMessage="Root folder containing the website files.")]
    [ValidateNotNullOrEmpty()]
    [string]$RootPath,

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

    [Parameter(Mandatory=$false, HelpMessage="Output sitemap file path.")]
    [string]$OutputFile = (Join-Path -Path $RootPath -ChildPath "sitemap.xml"),

    [Parameter(Mandatory=$false, HelpMessage="File extensions to include (comma‑separated).")]
    [string[]]$IncludeExtensions = @("html","htm","aspx","php","jsp","jspx"),

    [Parameter(Mandatory=$false, HelpMessage="Exclude paths (regex).")]
    [string]$ExcludePattern = $null,

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

    [Parameter(Mandatory=$false, HelpMessage="Priority for all URLs (0.0‑1.0).")]
    [ValidateRange(0.0,1.0)]
    [float]$Priority = $null
)

function Convert-PathToUrl {
    param(
        [Parameter(Mandatory=$true)][string]$FilePath,
        [Parameter(Mandatory=$true)][string]$RootPath,
        [Parameter(Mandatory=$true)][string]$BaseUrl
    )
    # Normalise separators
    $relative = Resolve-Path -Path $FilePath -Relative -BasePath $RootPath
    $relative = $relative -replace '[\\]+','/'
    # Ensure leading slash
    if (-not $relative.StartsWith('/')) { $relative = '/' + $relative }
    return ($BaseUrl.TrimEnd('/') + $relative)
}

# Ensure root exists
if (-not (Test-Path -Path $RootPath -PathType Container)) {
    Write-Error "RootPath '$RootPath' does not exist or is not a folder."
    exit 1
}

# Prepare XML writer settings
$settings = New-Object System.Xml.XmlWriterSettings
$settings.Indent = $true
$settings.Encoding = [System.Text.UTF8Encoding]::new($false)  # no BOM

$writer = [System.Xml.XmlWriter]::Create($OutputFile, $settings)
try {
    $writer.WriteStartDocument()
    $writer.WriteStartElement("urlset", "http://www.sitemaps.org/schemas/sitemap/0.9")
    
    # Build a filter for file extensions
    $extFilter = $IncludeExtensions | ForEach-Object { "*.$_" } 

    Get-ChildItem -Path $RootPath -Recurse -File -Include $extFilter |
        Where-Object {
            $include = $true
            if ($ExcludePattern) {
                $include = -not ($_ .FullName -match $ExcludePattern)
            }
            $include
        } |
        Sort-Object FullName |
        ForEach-Object {
            $url = Convert-PathToUrl -FilePath $_.FullName -RootPath (Resolve-Path $RootPath) -BaseUrl $BaseUrl

            $writer.WriteStartElement("url")

            $writer.WriteElementString("loc", $url)

            $lastMod = $_.LastWriteTimeUtc.ToString("yyyy-MM-ddTHH:mm:ssZ")
            $writer.WriteElementString("lastmod", $lastMod)

            if ($ChangeFreq) {
                $writer.WriteElementString("changefreq", $ChangeFreq)
            }

            if ($null -ne $Priority) {
                $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: $OutputFile" -ForegroundColor Green