GC_Sitemaps

class GC_Sitemaps {
	/**
	 * The main index of supported sitemaps.
	 *
	 * @since 5.5.0
	 *
	 * @var GC_Sitemaps_Index
	 */
	public $index;

	/**
	 * The main registry of supported sitemaps.
	 *
	 * @since 5.5.0
	 *
	 * @var GC_Sitemaps_Registry
	 */
	public $registry;

	/**
	 * An instance of the renderer class.
	 *
	 * @since 5.5.0
	 *
	 * @var GC_Sitemaps_Renderer
	 */
	public $renderer;

	/**
	 * GC_Sitemaps constructor.
	 *
	 * @since 5.5.0
	 */
	public function __construct() {
		$this->registry = new GC_Sitemaps_Registry();
		$this->renderer = new GC_Sitemaps_Renderer();
		$this->index    = new GC_Sitemaps_Index( $this->registry );
	}

	/**
	 * Initiates all sitemap functionality.
	 *
	 * If sitemaps are disabled, only the rewrite rules will be registered
	 * by this method, in order to properly send 404s.
	 *
	 * @since 5.5.0
	 */
	public function init() {
		// These will all fire on the init hook.
		$this->register_rewrites();

		add_action( 'template_redirect', array( $this, 'render_sitemaps' ) );

		if ( ! $this->sitemaps_enabled() ) {
			return;
		}

		$this->register_sitemaps();

		// Add additional action callbacks.
		add_filter( 'pre_handle_404', array( $this, 'redirect_sitemapxml' ), 10, 2 );
		add_filter( 'robots_txt', array( $this, 'add_robots' ), 0, 2 );
	}

	/**
	 * Determines whether sitemaps are enabled or not.
	 *
	 * @since 5.5.0
	 *
	 * @return bool Whether sitemaps are enabled.
	 */
	public function sitemaps_enabled() {
		$is_enabled = (bool) get_option( 'blog_public' );

		/**
		 * Filters whether XML Sitemaps are enabled or not.
		 *
		 * When XML Sitemaps are disabled via this filter, rewrite rules are still
		 * in place to ensure a 404 is returned.
		 *
		 * @see GC_Sitemaps::register_rewrites()
		 *
		 * @since 5.5.0
		 *
		 * @param bool $is_enabled Whether XML Sitemaps are enabled or not. Defaults
		 * to true for public sites.
		 */
		return (bool) apply_filters( 'gc_sitemaps_enabled', $is_enabled );
	}

	/**
	 * Registers and sets up the functionality for all supported sitemaps.
	 *
	 * @since 5.5.0
	 */
	public function register_sitemaps() {
		$providers = array(
			'posts'      => new GC_Sitemaps_Posts(),
			'taxonomies' => new GC_Sitemaps_Taxonomies(),
			'users'      => new GC_Sitemaps_Users(),
		);

		/* @var GC_Sitemaps_Provider $provider */
		foreach ( $providers as $name => $provider ) {
			$this->registry->add_provider( $name, $provider );
		}
	}

	/**
	 * Registers sitemap rewrite tags and routing rules.
	 *
	 * @since 5.5.0
	 */
	public function register_rewrites() {
		// Add rewrite tags.
		add_rewrite_tag( '%sitemap%', '([^?]+)' );
		add_rewrite_tag( '%sitemap-subtype%', '([^?]+)' );

		// Register index route.
		add_rewrite_rule( '^gc-sitemap.xml$', 'index.php?sitemap=index', 'top' );

		// Register rewrites for the XSL stylesheet.
		add_rewrite_tag( '%sitemap-stylesheet%', '([^?]+)' );
		add_rewrite_rule( '^gc-sitemap.xsl$', 'index.php?sitemap-stylesheet=sitemap', 'top' );
		add_rewrite_rule( '^gc-sitemap-index.xsl$', 'index.php?sitemap-stylesheet=index', 'top' );

		// Register routes for providers.
		add_rewrite_rule(
			'^gc-sitemap-([a-z]+?)-([a-zd_-]+?)-(d+?).xml$',
			'index.php?sitemap=$matches[1]&sitemap-subtype=$matches[2]&paged=$matches[3]',
			'top'
		);
		add_rewrite_rule(
			'^gc-sitemap-([a-z]+?)-(d+?).xml$',
			'index.php?sitemap=$matches[1]&paged=$matches[2]',
			'top'
		);
	}

	/**
	 * Renders sitemap templates based on rewrite rules.
	 *
	 * @since 5.5.0
	 *
	 * @global GC_Query $gc_query GeChiUI Query object.
	 */
	public function render_sitemaps() {
		global $gc_query;

		$sitemap         = sanitize_text_field( get_query_var( 'sitemap' ) );
		$object_subtype  = sanitize_text_field( get_query_var( 'sitemap-subtype' ) );
		$stylesheet_type = sanitize_text_field( get_query_var( 'sitemap-stylesheet' ) );
		$paged           = absint( get_query_var( 'paged' ) );

		// Bail early if this isn't a sitemap or stylesheet route.
		if ( ! ( $sitemap || $stylesheet_type ) ) {
			return;
		}

		if ( ! $this->sitemaps_enabled() ) {
			$gc_query->set_404();
			status_header( 404 );
			return;
		}

		// Render stylesheet if this is stylesheet route.
		if ( $stylesheet_type ) {
			$stylesheet = new GC_Sitemaps_Stylesheet();

			$stylesheet->render_stylesheet( $stylesheet_type );
			exit;
		}

		// Render the index.
		if ( 'index' === $sitemap ) {
			$sitemap_list = $this->index->get_sitemap_list();

			$this->renderer->render_index( $sitemap_list );
			exit;
		}

		$provider = $this->registry->get_provider( $sitemap );

		if ( ! $provider ) {
			return;
		}

		if ( empty( $paged ) ) {
			$paged = 1;
		}

		$url_list = $provider->get_url_list( $paged, $object_subtype );

		// Force a 404 and bail early if no URLs are present.
		if ( empty( $url_list ) ) {
			$gc_query->set_404();
			status_header( 404 );
			return;
		}

		$this->renderer->render_sitemap( $url_list );
		exit;
	}

	/**
	 * Redirects a URL to the gc-sitemap.xml
	 *
	 * @since 5.5.0
	 *
	 * @param bool     $bypass Pass-through of the pre_handle_404 filter value.
	 * @param GC_Query $query  The GC_Query object.
	 * @return bool Bypass value.
	 */
	public function redirect_sitemapxml( $bypass, $query ) {
		// If a plugin has already utilized the pre_handle_404 function, return without action to avoid conflicts.
		if ( $bypass ) {
			return $bypass;
		}

		// 'pagename' is for most permalink types, name is for when the %postname% is used as a top-level field.
		if ( 'sitemap-xml' === $query->get( 'pagename' )
			|| 'sitemap-xml' === $query->get( 'name' )
		) {
			gc_safe_redirect( $this->index->get_index_url() );
			exit();
		}

		return $bypass;
	}

	/**
	 * Adds the sitemap index to robots.txt.
	 *
	 * @since 5.5.0
	 *
	 * @param string $output robots.txt output.
	 * @param bool   $public Whether the site is public.
	 * @return string The robots.txt output.
	 */
	public function add_robots( $output, $public ) {
		if ( $public ) {
			$output .= "nSitemap: " . esc_url( $this->index->get_index_url() ) . "n";
		}

		return $output;
	}
}