<?php
/**
 * Bootstrap: wires everything together and owns the output buffer.
 */

defined( 'ABSPATH' ) || exit;

class GSSO_Plugin {

	private static $instance = null;

	/** @var bool Whether the optimizer runs on this request. */
	private $optimize = false;

	public static function instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	private function __construct() {
		// Compatibility-mode cache serving (no-op when the drop-in already ran).
		GSSO_Page_Cache::early_serve();

		GSSO_Purge::init();
		GSSO_Bloat::init();
		GSSO_Database::init();
		GSSO_Preload::init();
		GSSO_Metabox::init();
		GSSO_Host_Cache::init();
		GSSO_Assets::init();
		add_action( 'gsso_after_purge_all', array( 'GSSO_Admin', 'forget_stats' ) );
		add_action( 'gsso_after_purge_urls', array( 'GSSO_Admin', 'forget_stats' ) );

		if ( is_admin() ) {
			GSSO_Admin::init();
		}
		add_action( 'admin_bar_menu', array( 'GSSO_Admin', 'admin_bar' ), 100 );
		add_action( 'init', array( 'GSSO_Admin', 'handle_bar_actions' ) );

		add_action( 'template_redirect', array( $this, 'prepare_output' ), 0 );
		add_action( 'gsso_daily', array( __CLASS__, 'daily_maintenance' ) );

		// Upgrade routine: regenerate server files when the plugin version changes.
		if ( get_option( 'gsso_version' ) !== GSSO_VERSION ) {
			add_action( 'admin_init', array( __CLASS__, 'upgrade' ) );
		}
	}

	/* ---------- Page output (WordPress 6.9+ template enhancement output buffer) ---------- */

	/**
	 * Decide what to do with this front-end page and hook into the output
	 * buffer that WordPress core opens and closes around the template
	 * (wp_template_enhancement_output_buffer). The plugin never opens a
	 * buffer of its own.
	 */
	public function prepare_output() {
		if ( is_admin() || wp_doing_ajax() || ( defined( 'REST_REQUEST' ) && REST_REQUEST ) || ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) ) {
			return;
		}
		$method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( sanitize_text_field( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) ) : 'GET';
		if ( 'GET' !== $method && 'HEAD' !== $method ) {
			return;
		}
		if ( ! function_exists( 'wp_start_template_enhancement_output_buffer' ) ) {
			return; // WordPress < 6.9: no core output buffer, so HTML optimization and page storage are skipped.
		}

		GSSO_Page_Cache::evaluate();
		$this->optimize = GSSO_Optimizer::should_run();

		if ( ! headers_sent() && GSSO_Page_Cache::enabled() ) {
			header( 'X-GSSO-Cache: ' . ( GSSO_Page_Cache::is_cacheable() ? 'MISS' : 'BYPASS' ) );
			if ( GSSO_Settings::get( 'host_cache_nocache' ) ) {
				GSSO_Host_Cache::nocache_header();
			}
		}

		if ( ! $this->optimize && ! GSSO_Page_Cache::is_cacheable() ) {
			return;
		}

		if ( GSSO_Request::buffer_level() ) {
			// Our own page buffer is open; process it at shutdown, before WordPress flushes all buffers (priority 1).
			add_action( 'shutdown', array( $this, 'finish_output' ), 0 );
			return;
		}

		// Fallback: WordPress core's template enhancement buffer.
		if ( $this->optimize ) {
			// Late priority: optimize the markup after other enhancement filters have run.
			add_filter( 'wp_template_enhancement_output_buffer', array( $this, 'optimize_html' ), 100 );
		}
		if ( GSSO_Page_Cache::is_cacheable() ) {
			// Fires with the final HTML just before core flushes its buffer.
			add_action( 'wp_finalized_template_enhancement_output_buffer', array( $this, 'store_html' ), 100 );
		}
	}

	/**
	 * Close the page buffer: flush any buffers other plugins opened on top of
	 * it into it, take the finished page, optimize and cache it, and send it.
	 */
	public function finish_output() {
		$level = GSSO_Request::buffer_level();
		if ( ! $level ) {
			return;
		}
		$status = ob_get_status( true );
		if ( ob_get_level() < $level || ! isset( $status[ $level - 1 ]['name'] ) || 'GSSO_Request::buffer_handler' !== $status[ $level - 1 ]['name'] ) {
			GSSO_Request::buffer_closed();
			GSSO_Logger::notice_once( 'buffer-lost', 'Another plugin closed the page output buffer early, so a page could not be optimized or cached.' );
			return;
		}
		while ( ob_get_level() > $level ) {
			$top = ob_get_status();
			if ( empty( $top['flags'] ) || ! ( $top['flags'] & PHP_OUTPUT_HANDLER_REMOVABLE ) || ! ob_end_flush() ) {
				return; // A buffer above ours can't be closed; let WordPress flush everything normally.
			}
		}
		$html = (string) ob_get_contents();
		ob_end_clean();
		GSSO_Request::buffer_closed();

		if ( $this->is_html_response() ) {
			if ( $this->optimize ) {
				$html = $this->optimize_html( $html );
			}
			if ( GSSO_Page_Cache::is_cacheable() ) {
				$this->store_html( $html );
			}
		}
		echo $html; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- The site's own page, already rendered by WordPress.
	}

	private function is_html_response() {
		foreach ( headers_list() as $header ) {
			if ( 0 === stripos( $header, 'content-type:' ) ) {
				return false !== stripos( $header, 'text/html' ) || false !== stripos( $header, 'application/xhtml+xml' );
			}
		}
		return true;
	}

	/**
	 * @param string $html Full HTML document from the core output buffer.
	 * @return string
	 */
	public function optimize_html( $html ) {
		try {
			$optimizer = new GSSO_Optimizer();
			return $optimizer->process( (string) $html );
		} catch ( \Throwable $e ) {
			GSSO_Logger::error( 'Optimization failed, page served unmodified: ' . $e->getMessage() );
			return (string) $html;
		}
	}

	/** @param string $html Final HTML sent to the visitor. */
	public function store_html( $html ) {
		try {
			GSSO_Page_Cache::maybe_store( (string) $html );
		} catch ( \Throwable $e ) {
			GSSO_Logger::error( 'Could not store page in cache: ' . $e->getMessage() );
		}
	}

	/* ---------- Lifecycle ---------- */

	public static function activate() {
		GSSO_Filesystem::mkdir( GSSO_CACHE_DIR );
		if ( false === get_option( GSSO_Settings::OPTION ) ) {
			add_option( GSSO_Settings::OPTION, GSSO_Settings::defaults() );
		}
		update_option( 'gsso_version', GSSO_VERSION );
		self::migrate_legacy();
		if ( ! wp_next_scheduled( 'gsso_daily' ) ) {
			wp_schedule_event( time() + DAY_IN_SECONDS, 'daily', 'gsso_daily' );
		}
		// Server files are written on the first admin page load after activation,
		// so a problem can be reported in the UI instead of failing silently.
		set_transient( 'gsso_apply_pending', 1, HOUR_IN_SECONDS );
	}

	/**
	 * Clean up what older versions left behind. Runs on upgrade and on activation
	 * (a renamed plugin folder is "activated", not "upgraded").
	 */
	public static function migrate_legacy() {
		GSSO_Settings::migrate();
		// 1.0-1.2 kept wp-config.php/.htaccess backups and a PHP config here. Remove them.
		GSSO_Filesystem::rrmdir( GSSO_LEGACY_CONFIG_DIR );
		delete_transient( 'gsso_packages_feed' );
		wp_clear_scheduled_hook( 'gsso_refresh_packages' );
	}

	public static function deactivate() {
		// Stop the purge/preload hooks that fire on 'deactivated_plugin' from
		// recreating anything after cleanup.
		if ( ! defined( 'GSSO_DEACTIVATING' ) ) {
			define( 'GSSO_DEACTIVATING', true );
		}
		GSSO_Dropin::uninstall();
		GSSO_Htaccess::remove();
		GSSO_Config_File::delete();
		GSSO_Filesystem::rrmdir( GSSO_CACHE_DIR . '/pages', true );
		GSSO_Preload::stop();
		wp_clear_scheduled_hook( 'gsso_daily' );
		wp_clear_scheduled_hook( GSSO_Database::HOOK );
		wp_clear_scheduled_hook( 'gsso_refresh_packages' ); // Removed in 1.3.0.
	}

	public static function upgrade() {
		update_option( 'gsso_version', GSSO_VERSION );
		self::migrate_legacy();
		self::apply_settings();
	}

	/**
	 * Push the current settings out to every place they live: the drop-in
	 * config, advanced-cache.php / WP_CACHE, .htaccess, and cron.
	 *
	 * @return string[] Problems worth showing to the admin.
	 */
	public static function apply_settings() {
		GSSO_Settings::flush_cache();
		$messages = array();

		if ( ! GSSO_Config_File::write() ) {
			$messages[] = 'The cache configuration could not be written. Make sure wp-content/cache is writable.';
		}

		if ( GSSO_Page_Cache::enabled() ) {
			$result = GSSO_Dropin::install();
			if ( ! $result['ok'] && $result['message'] ) {
				$messages[] = $result['message'];
			}
		} else {
			GSSO_Dropin::uninstall();
			GSSO_Filesystem::rrmdir( GSSO_CACHE_DIR . '/pages', true );
		}

		$result = GSSO_Htaccess::apply();
		if ( ! $result['ok'] && $result['message'] ) {
			$messages[] = $result['message'];
		}

		GSSO_Database::reschedule();
		if ( ! wp_next_scheduled( 'gsso_daily' ) ) {
			wp_schedule_event( time() + DAY_IN_SECONDS, 'daily', 'gsso_daily' );
		}

		return $messages;
	}

	/** Prune minified files that no cached page can still reference. */
	public static function daily_maintenance() {
		$lifespan = (int) GSSO_Settings::get( 'cache_lifespan' ) * HOUR_IN_SECONDS;
		if ( $lifespan <= 0 ) {
			return; // Pages never expire, so their assets must not either.
		}
		$max_age = max( 30 * DAY_IN_SECONDS, $lifespan * 3 );
		foreach ( array( 'css', 'js' ) as $type ) {
			foreach ( (array) glob( GSSO_CACHE_DIR . '/assets/' . $type . '/*.' . $type ) as $file ) {
				if ( $file && ( time() - (int) @filemtime( $file ) ) > $max_age ) {
					wp_delete_file( $file );
				}
			}
		}
	}
}