<?php
defined( 'ABSPATH' ) || exit;

/**
 * Orchestrator. One output buffer: rewrite, then store in the page cache.
 */
class ZeroConfig_Engine {

	private static $instance = null;

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

	private function __construct() {
		if ( isset( $_GET['zc_verify'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			ZeroConfig_API::serve_verification(); // exits when it answers
		}
		ZeroConfig_API::guard_address(); // cheap string compare; disconnects a copied database on a new address

		// Emergency switch: the first request that reaches WordPress also removes what serves cached
		// pages without WordPress (.htaccess rules, drop-in) and empties the cache. Once an hour at most.
		if ( defined( 'ZEROCONFIG_DISABLE' ) && ZEROCONFIG_DISABLE && ! get_transient( 'zeroconfig_disable_cleaned' ) ) {
			ZeroConfig_Page_Cache::purge_all( 'turn_off' );
			ZeroConfig_Page_Cache::remove_dropin();
			set_transient( 'zeroconfig_disable_cleaned', 1, HOUR_IN_SECONDS );
		}

		if ( ZeroConfig_Options::get( 'engine' ) && ! ( defined( 'ZEROCONFIG_DISABLE' ) && ZEROCONFIG_DISABLE ) ) {
			ZeroConfig_Page_Cache::maybe_refresh_dropin(); // a plugin update reaches the drop-in on the next uncached visit
		}

		ZeroConfig_Cron::init();
		ZeroConfig_Safe_Mode::init();
		ZeroConfig_Page_Cache::hook_purges();
		ZeroConfig_CDN_Purge::init();
		ZeroConfig_Warm::init();

		if ( is_admin() ) {
			ZeroConfig_Admin::init();
			// After a plugin update, bring existing .htaccess rules up to date (no write when unchanged).
			add_action( 'admin_init', function () {
				if ( ZeroConfig_Options::get( 'engine' ) && ZeroConfig_Htaccess::installed() ) {
					ZeroConfig_Htaccess::install();
				}
				if ( ZeroConfig_Options::get( 'engine' ) ) {
					ZeroConfig_Page_Cache::refresh_dropin(); // and the drop-in (rewritten only when it differs)
				}
			} );
		}

		add_action( 'template_redirect', array( $this, 'start_buffer' ), -PHP_INT_MAX );
		add_action( 'wp_enqueue_scripts', array( 'ZeroConfig_Rewriter', 'enqueue' ), 1 );
		add_action( 'init', array( $this, 'register_cli' ) );
		add_action( ZeroConfig_API::EDGE_CHECK, array( 'ZeroConfig_API', 'check_edge' ) );
		add_filter( 'wp_lazy_loading_enabled', array( $this, 'native_lazy' ), 10, 2 );

		// Hide the wp-content marker from other optimisers that look for it.
		add_filter( 'wp_headers', array( $this, 'headers' ) );
	}

	public function start_buffer() {
		// define( 'ZEROCONFIG_DISABLE', true ); in wp-config.php: pages go out untouched, no cache,
		// without having to reach wp-admin. Documented in the readme for emergencies.
		if ( ! ZeroConfig_Options::get( 'engine' ) || ( defined( 'ZEROCONFIG_DISABLE' ) && ZEROCONFIG_DISABLE ) ) {
			return;
		}
		// Safety Check / critical CSS requests: prove the page is this plugin's own render, not a
		// firewall challenge or a host cache that ignored the query string.
		if ( isset( $_GET['zc_off'] ) || isset( $_GET['zc_test'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$mode = isset( $_GET['zc_test'] ) ? sanitize_key( wp_unslash( $_GET['zc_test'] ) ) : 'off'; // phpcs:ignore WordPress.Security.NonceVerification
			if ( ! headers_sent() ) {
				header( 'X-ZC-Check: ' . $mode );
				nocache_headers();
			}
		}
		if ( ZeroConfig_Rewriter::should_skip() && ! ZeroConfig_Page_Cache::storable() ) {
			return;
		}
		ZeroConfig_Page_Cache::mark_render_start();
		// The plugin's own check asks for pages as a visitor; tell it this answer was built by WordPress
		// now (a cache miss). Only for that client: visitors never see this header.
		$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
		if ( false !== strpos( $ua, 'ZeroConfigProbe/' ) && ! headers_sent() ) {
			header( 'X-ZC-Render: 1' );
		}
		// WordPress 6.9+ buffers the template itself when this filter exists (we never open a buffer of our
		// own) and passes only HTML responses. Last in line, so the cache stores what other filters made.
		add_filter( 'wp_template_enhancement_output_buffer', array( $this, 'end_buffer' ), PHP_INT_MAX );
		// Some plugins (Elementor, for one) answer "no buffer" for the whole site, to keep WordPress' on-demand
		// block styles off their pages. Say yes only while WordPress opens the buffer (core does it at 1000):
		// the page can be cached, and the style setting, decided at another moment, keeps their answer.
		add_action( 'wp_before_include_template', array( __CLASS__, 'buffer_wanted' ), 999 );
		add_action( 'wp_before_include_template', array( __CLASS__, 'buffer_wanted_done' ), 1001 );
	}

	public static function buffer_wanted() {
		add_filter( 'wp_should_output_buffer_template_for_enhancement', '__return_true', PHP_INT_MAX );
	}

	public static function buffer_wanted_done() {
		remove_filter( 'wp_should_output_buffer_template_for_enhancement', '__return_true', PHP_INT_MAX );
	}

	public function end_buffer( $html ) {
		if ( ! ZeroConfig_Rewriter::should_skip() ) {
			$rewriter = new ZeroConfig_Rewriter();
			$html     = $rewriter->process( $html );
		}
		if ( ZeroConfig_Page_Cache::storable() ) {
			ZeroConfig_Page_Cache::store( $html );
		}
		return $html;
	}

	/** We decide lazy loading ourselves (LCP-aware); let core stay out of it. */
	public function native_lazy( $enabled, $tag ) {
		return ZeroConfig_Options::feature_on( 'images' ) && 'img' === $tag ? false : $enabled;
	}

	public function headers( $headers ) {
		if ( ZeroConfig_Options::get( 'engine' ) && ! ZeroConfig_Options::is_white_label() ) {
			$headers['X-ZeroConfig-Engine'] = 'ZeroConfig/' . ZEROCONFIG_VERSION;
		}
		return $headers;
	}

	public function register_cli() {
		if ( defined( 'WP_CLI' ) && WP_CLI ) {
			WP_CLI::add_command(
				'zeroconfig',
				function ( $args ) {
					$cmd = isset( $args[0] ) ? $args[0] : 'status';
					switch ( $cmd ) {
						case 'on':
							self::turn_on();
							WP_CLI::success( 'Engine on.' );
							break;
						case 'off':
							self::turn_off();
							WP_CLI::success( 'Engine off.' );
							break;
						case 'purge':
							if ( ! empty( $args[1] ) ) {
								ZeroConfig_Page_Cache::purge_url( $args[1] );
								ZeroConfig_CDN_Purge::run_queue();
								WP_CLI::success( 'Purged ' . $args[1] );
								break;
							}
							ZeroConfig_Page_Cache::purge_all( 'cli' );
							ZeroConfig_CDN_Purge::run_queue(); // an explicit purge is believed at once
							WP_CLI::success( 'Cache purged (local, upstream, edge).' );
							break;
						case 'check':
							ZeroConfig_Safe_Mode::schedule( 1 );
							WP_CLI::success( 'Safety Check scheduled.' );
							break;
						case 'doctor': // the five rows and their reason codes, for pasting into a support ticket
							$d = ZeroConfig_Doctor::run();
							if ( ! empty( $d['off'] ) ) {
								WP_CLI::log( 'Engine is off.' );
								break;
							}
							foreach ( ZeroConfig_Doctor::ROWS as $row ) {
								$r = $d['rows'][ $row ];
								WP_CLI::log( sprintf( '%-5s %s', strtoupper( $r['status'] ), ZeroConfig_Doctor::row_label( $row ) ) );
								foreach ( $r['items'] as $item ) {
									list( $owner, $text, $fix ) = ZeroConfig_Doctor::reason( $item['code'], $item['args'] );
									WP_CLI::log( "      [{$item['code']}] $text" . ( '' !== $fix ? "\n      → $fix" : '' ) );
								}
							}
							WP_CLI::log( 'probe: ' . wp_json_encode( $d['probe'] ) );
							break;
						case 'warm':
							$w = ZeroConfig_Warm::run();
							WP_CLI::log( wp_json_encode( array_diff_key( $w, array( 'items' => 1 ) ) ) );
							break;
						default:
							// Secrets stay out of terminals and support tickets.
							$all = ZeroConfig_Options::all();
							foreach ( array( 'site_token', 'cloudflare_token', 'purge_token', 'license_key' ) as $secret ) {
								$all[ $secret ] = '' === (string) $all[ $secret ] ? '' : '(set)';
							}
							WP_CLI::log( wp_json_encode( $all, JSON_PRETTY_PRINT ) );
					}
				}
			);
		}
	}

	/* ---------- switch ---------- */

	/**
	 * The only place the site connects to the ZeroConfig service. It runs when an
	 * admin presses "Turn on" under a disclosure of exactly what is sent.
	 */
	public static function turn_on() {
		// One network shares wp-config.php, .htaccess and advanced-cache.php: a single site's admin must
		// not change them for every site. Multisite is not supported yet.
		if ( is_multisite() ) {
			return new WP_Error( 'zc_multisite', __( 'ZeroConfig does not support WordPress multisite networks yet.', 'zeroconfig' ) );
		}
		ZeroConfig_Options::update( array( 'engine' => true, 'activated_at' => time(), 'disabled' => array(), 'disabled_pages' => array() ) );
		ZeroConfig_Cron::ensure();
		// The page cache works locally right away; edge features follow once the site is verified.
		$dropin = ZeroConfig_Page_Cache::install_dropin();
		ZeroConfig_CDN_Purge::purge_token();
		// One purge per click: on_connected() purges once the edge URLs are known; otherwise purge here.
		$purged = false;
		if ( ZeroConfig_Options::is_connected() ) {
			$hb = ZeroConfig_API::heartbeat();
			if ( ZeroConfig_Options::is_connected() && ! is_wp_error( $hb ) ) {
				self::on_connected( 'turn_on' );
				$purged = true;
			}
		} else {
			ZeroConfig_API::register_site(); // ownership check runs in the background; see claim_pending()
		}
		if ( ! $purged ) {
			ZeroConfig_Page_Cache::purge_all( 'turn_on' );
		}
		return $dropin;
	}

	/** Edge features that need a verified connection. */
	public static function on_connected( $source = 'connected' ) {
		if ( ! ZeroConfig_Options::get( 'engine' ) ) {
			return;
		}
		if ( ! ZeroConfig_Options::get( 'rules' ) ) {
			ZeroConfig_API::fetch_rules();
		}
		// Reconnected after a reinstall or move: put the saved licence back on (fails harmlessly if its seats are used).
		$key = (string) ZeroConfig_Options::get( 'license_key' );
		if ( '' !== $key && 'free' === ZeroConfig_Options::get( 'plan' ) ) {
			ZeroConfig_API::activate_license( $key );
		}
		ZeroConfig_Page_Cache::purge_all( $source ); // cached HTML must pick up edge URLs
		ZeroConfig_Cron::request_critical();
		ZeroConfig_Safe_Mode::schedule( 90 );
	}

	public static function turn_off() {
		$was_on = (bool) ZeroConfig_Options::get( 'engine' );
		ZeroConfig_Options::update( array( 'engine' => false ) );
		if ( $was_on ) {
			ZeroConfig_API::heartbeat_off(); // the service stops its visits; nothing else is sent after this
		}
		ZeroConfig_Page_Cache::purge_all( 'turn_off' );
		ZeroConfig_CDN_Purge::run_queue(); // background events are cleared below: Cloudflare must hear it now
		ZeroConfig_Page_Cache::remove_dropin();
		ZeroConfig_Cron::clear(); // engine off = no background calls to the service at all
	}

	/* ---------- lifecycle ---------- */

	public static function activate( $network_wide = false ) {
		// Activation is local only. Nothing is sent anywhere until an admin presses "Turn on".
		wp_mkdir_p( ZEROCONFIG_CACHE_DIR );
		ZeroConfig_Page_Cache::write_config();
		// Open the settings page once, for the admin who activated it in the browser.
		if ( ! $network_wide && ! ( defined( 'WP_CLI' ) && WP_CLI ) && get_current_user_id() ) {
			set_transient( 'zeroconfig_activation_redirect', get_current_user_id(), 60 );
		}
	}

	public static function deactivate() {
		self::turn_off();
		ZeroConfig_Cron::clear();
	}
}