<?php
namespace W3TC;

// To support legacy updates with old add-ins
if ( class_exists( 'PgCache_ContentGrabber' ) )
	return;

/**
 * W3 PgCache
 */

/**
 * class PgCache
 */
class PgCache_ContentGrabber {
	/**
	 * Advanced cache config
	 */
	var $_config = null;

	/**
	 * Caching flag
	 *
	 * @var boolean
	 */
	var $_caching = false;

	/**
	 * Time start
	 *
	 * @var double
	 */
	var $_time_start = 0;

	/**
	 * Lifetime
	 *
	 * @var integer
	 */
	var $_lifetime = 0;

	/**
	 * Enhanced mode flag
	 *
	 * @var boolean
	 */
	var $_enhanced_mode = false;

	/**
	 * Debug flag
	 *
	 * @var boolean
	 */
	var $_debug = false;

	/**
	 * Request URI
	 *
	 * @var string
	 */
	private $_request_uri;

	// filled by _preprocess_request_uri
	// - ['host' => 'path' => , 'querystring' => ]
	private $_request_url_fragments;

	/**
	 * Page key
	 *
	 * @var string
	 */
	var $_page_key = '';
	private $_page_key_extension;

	/**
	 * Shutdown buffer
	 *
	 * @var string
	 */
	var $_shutdown_buffer = '';

	/**
	 * Mobile object
	 *
	 * @var W3_Mobile
	 */
	var $_mobile = null;

	/**
	 * Referrer object
	 *
	 * @var W3_Referrer
	 */
	var $_referrer = null;

	/**
	 * Cache reject reason
	 *
	 * @var string
	 */
	var $cache_reject_reason = '';

	private $process_status = '';
	private $output_size = 0;

	/**
	 * @var bool If cached page should be displayed after init
	 */
	var $_late_init = false;

	/**
	 * @var bool late caching
	 */
	var $_late_caching = false;

	var $_cached_data = null;

	var $_old_exists = false;

	/**
	 * @var bool Nginx memcached flag
	 */
	var $_nginx_memcached = false;

	/**
	 * @var string
	 */
	var $_page_group;

	/**
	 * PHP5 Constructor
	 */
	function __construct() {
		$this->_config = Dispatcher::config();
		$this->_debug = $this->_config->get_boolean( 'pgcache.debug' );

		$this->_request_url_fragments = array(
			'host' => Util_Environment::host_port()
		);

		$this->_request_uri = isset( $_SERVER['REQUEST_URI'] ) ?
			filter_var( $_SERVER['REQUEST_URI'], FILTER_SANITIZE_URL ) : ''; // phpcs:ignore
		$this->_lifetime = $this->_config->get_integer( 'pgcache.lifetime' );
		$this->_late_init = $this->_config->get_boolean( 'pgcache.late_init' );
		$this->_late_caching = $this->_config->get_boolean( 'pgcache.late_caching' );

		$engine = $this->_config->get_string( 'pgcache.engine' );
		$this->_enhanced_mode = ( $engine == 'file_generic' );
		$this->_nginx_memcached = ( $engine == 'nginx_memcached' );

		if ( $this->_config->get_boolean( 'mobile.enabled' ) ) {
			$this->_mobile = Dispatcher::component( 'Mobile_UserAgent' );
		}

		if ( $this->_config->get_boolean( 'referrer.enabled' ) ) {
			$this->_referrer = Dispatcher::component( 'Mobile_Referrer' );
		}
	}

	/**
	 * Do cache logic
	 */
	function process() {
		$this->run_extensions_dropin();

		/**
		 * Skip caching for some pages
		 */
		switch ( true ) {
		case defined( 'DONOTCACHEPAGE' ):
			$this->process_status = 'miss_third_party';
			$this->cache_reject_reason = 'DONOTCACHEPAGE defined';
			if ( $this->_debug ) {
				self::log( 'skip processing because of DONOTCACHEPAGE constant' );
			}
			return;
		case defined( 'DOING_AJAX' ):
			$this->process_status = 'miss_ajax';
			$this->cache_reject_reason = 'AJAX request';
			if ( $this->_debug ) {
				self::log( 'skip processing because of AJAX constant' );
			}
			return;

		case defined( 'APP_REQUEST' ):
		case defined( 'XMLRPC_REQUEST' ):
			$this->cache_reject_reason = 'API call constant defined';
			$this->process_status = 'miss_api_call';
			if ( $this->_debug ) {
				self::log( 'skip processing because of API call constant' );
			}
			return;

		case defined( 'DOING_CRON' ):
		case defined( 'WP_ADMIN' ):
		case ( defined( 'SHORTINIT' ) && SHORTINIT ):
			$this->cache_reject_reason = 'WP_ADMIN defined';
			$this->process_status = 'miss_wp_admin';
			if ( $this->_debug ) {
				self::log( 'skip processing because of generic constant' );
			}
			return;
		}

		/**
		 * Do page cache logic
		 */
		if ( $this->_debug ) {
			$this->_time_start = Util_Debug::microtime();
		}

		// TODO: call modifies object state, rename method at least
		$this->_caching = $this->_can_read_cache();
		global $w3_late_init;

		if ( $this->_debug ) {
			self::log( 'start, can_cache: ' .
				( $this->_caching ? 'true' : 'false' ) .
				 ', reject reason: ' . $this->cache_reject_reason );
		}

		$this->_page_key_extension = $this->_get_key_extension();

		if ( !$this->_page_key_extension['cache'] ) {
			$this->_caching = false;
			$this->cache_reject_reason =
				$this->_page_key_extension['cache_reject_reason'];
		}

		if ( ! empty( $_SERVER['HTTP_W3TCALWAYSCACHED'] ) ) {
			$this->_page_key_extension['alwayscached'] = true;
		}

		if ( $this->_caching && !$this->_late_caching ) {
			$this->_cached_data = $this->_extract_cached_page( false );
			if ( $this->_cached_data ) {
				if ( $this->_late_init ) {
					$w3_late_init = true;
					return;
				} else {
					$this->process_status = 'hit';
					$this->process_cached_page_and_exit( $this->_cached_data );
					// if is passes here - exit is not possible now and
					// will happen on init
					return;
				}
			} else
				$this->_late_init = false;
		} else {
			$this->_late_init = false;
		}
		$w3_late_init = $this->_late_init;
		/**
		 * Start output buffering
		 */

		Util_Bus::add_ob_callback( 'pagecache', array( $this, 'ob_callback' ) );
	}



	private function run_extensions_dropin() {
		$c = $this->_config;
		$extensions = $c->get_array( 'extensions.active' );

		$dropin = $c->get_array( 'extensions.active_dropin' );
		foreach ( $dropin as $extension => $nothing ) {
			if ( isset( $extensions[$extension] ) ) {
				$path = $extensions[$extension];
				$filename = W3TC_EXTENSION_DIR . '/' .
					str_replace( '..', '', trim( $path, '/' ) );

				if ( file_exists( $filename ) ) {
					include_once( $filename );
				}
			}
		}
	}



	/**
	 * Extracts page from cache
	 *
	 * @return boolean
	 */
	function _extract_cached_page( $with_filter ) {
		if ( ! empty( $this->_page_key_extension['alwayscached'] ) ) {
			return null;
		}

		$cache = $this->_get_cache( $this->_page_key_extension['group'] );

		$mobile_group = $this->_page_key_extension['useragent'];
		$referrer_group = $this->_page_key_extension['referrer'];
		$encryption = $this->_page_key_extension['encryption'];
		$compression = $this->_page_key_extension['compression'];

		/**
		 * Check if page is cached
		 */
		if ( !$this->_set_extract_page_key( $this->_page_key_extension, $with_filter ) ) {
			$data = null;
		} else {
			$data = $cache->get_with_old( $this->_page_key, $this->_page_group );
			list( $data, $this->_old_exists ) = $data;
		}

		/**
		 * Try to get uncompressed version of cache
		 */
		if ( $compression && !$data ) {
			if ( !$this->_set_extract_page_key(
					array_merge( $this->_page_key_extension,
						array( 'compression' => '') ), $with_filter ) ) {
				$data = null;
			} else {
				$data = $cache->get_with_old( $this->_page_key, $this->_page_group );
				list( $data, $this->_old_exists ) = $data;
				$compression = false;
			}
		}

		if ( !$data ) {
			if ( $this->_debug ) {
				self::log( 'no cache entry for ' .
					$this->_request_url_fragments['host'] . $this->_request_uri . ' ' .
					$this->_page_key );
			}

			return null;
		}

		$data['compression'] = $compression;

		return $data;
	}



	private function _set_extract_page_key( $page_key_extension, $with_filter ) {
		// set page group
		$this->_page_group = $page_key_extension['group'];
		if ( $with_filter ) {
			// return empty value if caching should not happen
			$this->_page_group = apply_filters( 'w3tc_page_extract_group',
				$page_key_extension['group'],
				$this->_request_url_fragments['host'] . $this->_request_uri,
				$page_key_extension );
			$page_key_extension['group'] = $this->_page_group;
		}

		// set page key
		$this->_page_key = $this->_get_page_key( $page_key_extension );

		if ( $with_filter ) {
			// return empty value if caching should not happen
			$this->_page_key = apply_filters( 'w3tc_page_extract_key',
				$this->_page_key,
				$page_key_extension['useragent'],
				$page_key_extension['referrer'],
				$page_key_extension['encryption'],
				$page_key_extension['compression'],
				$page_key_extension['content_type'],
				$this->_request_url_fragments['host'] . $this->_request_uri,
				$page_key_extension );
		}

		if ( !empty( $this->_page_key ) )
			return true;

		$this->caching = false;
		$this->cache_reject_reason =
			'w3tc_page_extract_key filter result forced not to cache';

		return false;
	}



	/**
	 * Process extracted cached pages
	 *
	 * @param unknown $data
	 */
	private function process_cached_page_and_exit( $data ) {
		/**
		 * Do Bad Behavior check
		 */
		$this->_bad_behavior();

		$is_404 = isset( $data['404'] ) ? $data['404'] : false;
		$headers = isset( $data['headers'] ) ? $data['headers'] : array();
		$content = $data['content'];
		$has_dynamic = isset( $data['has_dynamic'] ) && $data['has_dynamic'];
		$etag = md5( $content );

		if ( $has_dynamic ) {
			// its last modification date is now, and any compression
			// browser wants cant be used, since its compressed now
			$time = time();
			$compression = $this->_page_key_extension['compression'];
		} else {
			$time = isset( $data['time'] ) ? $data['time'] : time();
			$compression = $data['compression'];
		}

		/**
		 * Send headers
		 */
		$this->_send_headers( $is_404, $time, $etag, $compression, $headers );
		if ( isset( $_SERVER['REQUEST_METHOD'] ) && $_SERVER['REQUEST_METHOD'] == 'HEAD' )
			return;

		// parse dynamic content and compress if it's dynamic page with mfuncs
		if ( $has_dynamic ) {
			$content = $this->_parse_dynamic( $content );
			$content = $this->_compress( $content, $compression );
		}

		echo $content; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped

		Dispatcher::usage_statistics_apply_before_init_and_exit( array( $this,
				'w3tc_usage_statistics_of_request' ) );
	}

	/**
	 * Output buffering callback
	 *
	 * @param string  $buffer
	 * @return string
	 */
	function ob_callback( $buffer ) {
		$this->output_size = strlen( $buffer );

		if ( !$this->_is_cacheable_content_type() ) {
			if ( $this->_debug )
				self::log( 'storing cached page - not a cached content' );

			return $buffer;
		}

		$compression = false;
		$has_dynamic = $this->_has_dynamic( $buffer );
		$response_headers = $this->_get_response_headers();

		// TODO: call modifies object state, rename method at least
		$original_can_cache = $this->_can_write_cache( $buffer, $response_headers );
		$can_cache = apply_filters( 'w3tc_can_cache', $original_can_cache, $this, $buffer );
		if ( $can_cache != $original_can_cache ) {
			$this->cache_reject_reason = 'Third-party plugin has modified caching activity';
		}

		if ( $this->_debug ) {
			self::log( 'storing cached page: ' .
				( $can_cache ? 'true' : 'false' ) .
				' original ' . ( $this->_caching ? ' true' : 'false' ) .
				' reason ' . $this->cache_reject_reason );
		}

		$buffer = str_replace('{w3tc_pagecache_reject_reason}',
			( $this->cache_reject_reason != '' ? sprintf( ' (%s)', $this->cache_reject_reason )
				: '' ),
			$buffer );

		if ( $can_cache ) {
			$buffer = $this->_maybe_save_cached_result( $buffer, $response_headers, $has_dynamic );
		} else {
			if ( $has_dynamic ) {
				// send common headers since output will be compressed
				$compression_header = $this->_page_key_extension['compression'];
				if ( defined( 'W3TC_PAGECACHE_OUTPUT_COMPRESSION_OFF' ) )
					$compression_header = false;
				$headers = $this->_get_common_headers( $compression_header );
				$this->_headers( $headers );
			}

			// remove cached entries if its not cached anymore
			if ( $this->cache_reject_reason ) {
				if ( $this->_old_exists ) {
					$cache = $this->_get_cache( $this->_page_key_extension['group'] );

					$compressions_to_store = $this->_get_compressions();

					foreach ( $compressions_to_store as $_compression ) {
						$_page_key = $this->_get_page_key(
							array_merge( $this->_page_key_extension,
								array( 'compression' => $_compression ) ) );
						$cache->hard_delete( $_page_key );
					}
				}
			}
		}

		/**
		 * We can't capture output in ob_callback
		 * so we use shutdown function
		 */
		if ( $has_dynamic ) {
			$this->_shutdown_buffer = $buffer;

			$buffer = '';

			register_shutdown_function( array(
					$this,
					'shutdown'
				) );
		}

		return $buffer;
	}

	/**
	 * Shutdown callback
	 *
	 * @return void
	 */
	public function shutdown() {
		$compression = $this->_page_key_extension['compression'];

		// Parse dynamic content.
		$buffer = $this->_parse_dynamic( $this->_shutdown_buffer );

		// Compress page according to headers already set.
		$compressed_buffer = $this->_compress( $buffer, $compression );

		echo $compressed_buffer; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
	}

	/**
	 * Checks if can we do cache logic
	 *
	 * @return boolean
	 */
	private function _can_read_cache() {
		/**
		 * Don't cache in console mode
		 */
		if ( PHP_SAPI === 'cli' ) {
			$this->cache_reject_reason = 'Console mode';

			return false;
		}

		/**
		 * Skip if session defined
		 */
		if ( defined( 'SID' ) && SID != '' ) {
			$this->cache_reject_reason = 'Session started';

			return false;
		}

		if ( !$this->_config->get_boolean('pgcache.cache.ssl') && Util_Environment::is_https() ) {
			$this->cache_reject_reason = 'SSL caching disabled';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Skip if posting
		 */
		$request_method = isset( $_SERVER['REQUEST_METHOD'] ) ?
			htmlspecialchars( stripslashes( $_SERVER['REQUEST_METHOD'] ) ) : ''; // phpcs:ignore

		if ( in_array( strtoupper( $request_method ), array( 'DELETE', 'PUT', 'OPTIONS', 'TRACE', 'CONNECT', 'POST' ), true ) ) {
			$this->cache_reject_reason = sprintf( 'Requested method is %s', $request_method );

			return false;
		}

		/**
		 * Skip if HEAD request.
		 */
		if ( isset( $_SERVER['REQUEST_METHOD'] ) &&
			strtoupper( $_SERVER['REQUEST_METHOD'] ) === 'HEAD' && // phpcs:ignore
			( $this->_enhanced_mode || $this->_config->get_boolean( 'pgcache.reject.request_head' ) ) ) {
			$this->cache_reject_reason = 'Requested method is HEAD';

			return false;
		}

		/**
		 * Skip if there is query in the request uri
		 */
		$this->_preprocess_request_uri();

		if ( !empty( $this->_request_url_fragments['querystring'] ) ) {
			$should_reject_qs =
				( !$this->_config->get_boolean( 'pgcache.cache.query' ) ||
				$this->_config->get_string( 'pgcache.engine' ) == 'file_generic' );

			if ( $should_reject_qs &&
				$this->_config->get_string( 'pgcache.rest' ) == 'cache' &&
				Util_Environment::is_rest_request( $this->_request_uri ) ) {
				$should_reject_qs = false;
			}

			if ( $should_reject_qs ) {
				$this->cache_reject_reason = 'Requested URI contains query';
				$this->process_status = 'miss_query_string';

				return false;
			}
		}

		/**
		 * Check request URI
		 */
		if ( !$this->_passed_accept_files() && !$this->_passed_reject_uri() ) {
			$this->cache_reject_reason = 'Requested URI is rejected';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Check User Agent
		 */
		if ( ! $this->_check_ua() ) {
			$this->cache_reject_reason = 'User agent is rejected';
			if ( ! empty( Util_Request::get_string( 'w3tc_rewrite_test' ) ) ) {
				// special common case - w3tc_rewrite_test check request.
				$this->process_status = 'miss_wp_admin';
			} else {
				$this->process_status = 'miss_configuration';
			}

			return false;
		}

		/**
		 * Check WordPress cookies
		 */
		if ( !$this->_check_cookies() ) {
			$this->cache_reject_reason = 'Cookie is rejected';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Skip if user is logged in or user role is logged in
		 */
		if ( $this->_config->get_boolean( 'pgcache.reject.logged' ) ) {
			if ( !$this->_check_logged_in() ) {
				$this->cache_reject_reason = 'User is logged in';
				$this->process_status = 'miss_logged_in';

				return false;
			}
		} else {
			if ( !$this->_check_logged_in_role_allowed() ) {
				$this->cache_reject_reason = 'Rejected user role is logged in';
				$this->process_status = 'miss_logged_in';
				return false;
			}
		}

		return true;
	}

	/**
	 * Checks if can we do cache logic
	 *
	 * @param string  $buffer
	 * @return boolean
	 */
	private function _can_write_cache( $buffer, $response_headers ) {
		/**
		 * Skip if caching is disabled
		 */
		if ( !$this->_caching ) {
			return false;
		}

		/**
		 * Check for DONOTCACHEPAGE constant
		 */
		if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
			$this->cache_reject_reason = 'DONOTCACHEPAGE constant is defined';
			$this->process_status = 'miss_third_party';
			return false;
		}

		if ( $this->_config->get_string( 'pgcache.rest' ) != 'cache' ) {
			if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
				$this->cache_reject_reason = 'REST request';
				$this->process_status = 'miss_api_call';

				return false;
			}
		}

		/**
		 * Don't cache 404 pages
		 */
		if ( !$this->_config->get_boolean( 'pgcache.cache.404' ) && function_exists( 'is_404' ) && is_404() ) {
			$this->cache_reject_reason = 'Page is 404';
			$this->process_status = 'miss_404';

			return false;
		}

		/**
		 * Don't cache homepage
		 */
		if ( !$this->_config->get_boolean( 'pgcache.cache.home' ) && function_exists( 'is_home' ) && is_home() ) {
			$this->cache_reject_reason = is_front_page() && is_home() ? 'Page is front page' : 'Page is posts page';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Don't cache front page
		 */
		if ( $this->_config->get_boolean( 'pgcache.reject.front_page' ) && function_exists( 'is_front_page' ) && is_front_page() && !is_home() ) {
			$this->cache_reject_reason = 'Page is front page';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Don't cache feed
		 */
		if ( !$this->_config->get_boolean( 'pgcache.cache.feed' ) && function_exists( 'is_feed' ) && is_feed() ) {
			$this->cache_reject_reason = 'Page is feed';
			$this->process_status = 'miss_configuration';

			return false;
		}

		/**
		 * Check if page contains dynamic tags
		 */
		if ( $this->_enhanced_mode && $this->_has_dynamic( $buffer ) ) {
			$this->cache_reject_reason = 'Page contains dynamic tags (mfunc or mclude) can not be cached in enhanced mode';
			$this->process_status = 'miss_mfunc';

			return false;
		}

		if ( !$this->_passed_accept_files() ) {
			if ( is_single() ) {
				/**
				 * Don't cache pages associated with categories
				 */
				if ( $this->_passed_reject_categories() ) {
					$this->cache_reject_reason = 'Page associated with a rejected category';
					$this->process_status = 'miss_configuration';
					return false;
				}
				/**
				 * Don't cache pages that use tags
				 */
				if ( $this->_passed_reject_tags() ) {
					$this->cache_reject_reason = 'Page using a rejected tag';
					$this->process_status = 'miss_configuration';
					return false;
				}
			}
			/**
			 * Don't cache pages by these authors
			 */
			if ( $this->_passed_reject_authors() ) {
				$this->cache_reject_reason = 'Page written by a rejected author';
				$this->process_status = 'miss_configuration';
				return false;
			}
			/**
			 * Don't cache pages using custom fields
			 */
			if ( $this->_passed_reject_custom_fields() ) {
				$this->cache_reject_reason = 'Page using a rejected custom field';
				$this->process_status = 'miss_configuration';
				return false;
			}
		}

		if ( !empty( $response_headers['kv']['content-encoding'] ) ) {
			$this->cache_reject_reason = 'Response is compressed';
			$this->process_status = 'miss_compressed';
			return false;
		}

		if ( empty( $buffer ) && empty( $response_headers['kv']['location'] ) ) {
			$this->cache_reject_reason = 'Empty response';
			$this->process_status = 'miss_empty_response';
			return false;
		}

		if ( isset( $response_headers['kv']['location'] ) ) {
			// dont cache query-string normalization redirects
			// (e.g. from wp core)
			// when cache key is normalized, since that cause redirect loop

			if ( $this->_get_page_key( $this->_page_key_extension ) ==
					$this->_get_page_key( $this->_page_key_extension, $response_headers['kv']['location'] ) ) {
				$this->cache_reject_reason = 'Normalization redirect';
				$this->process_status = 'miss_normalization_redirect';
				return false;
			}
		}

		if ( isset( $_SERVER['REQUEST_METHOD'] ) && $_SERVER['REQUEST_METHOD'] == 'HEAD' ) {
			$this->cache_reject_reason = 'HEAD request';
			$this->process_status = 'miss_request_method';
			return;
		}

		return true;
	}

	public function get_cache_stats_size( $timeout_time ) {
		$cache = $this->_get_cache();
		if ( method_exists( $cache, 'get_stats_size' ) )
			return $cache->get_stats_size( $timeout_time );

		return null;
	}

	public function get_usage_statistics_cache_config() {
		$engine = $this->_config->get_string( 'pgcache.engine' );

		switch ( $engine ) {
		case 'memcached':
		case 'nginx_memcached':
			$engineConfig = array(
				'servers' => $this->_config->get_array( 'pgcache.memcached.servers' ),
				'persistent' => $this->_config->get_boolean( 'pgcache.memcached.persistent' ),
				'aws_autodiscovery' => $this->_config->get_boolean( 'pgcache.memcached.aws_autodiscovery' ),
				'username' => $this->_config->get_string( 'pgcache.memcached.username' ),
				'password' => $this->_config->get_string( 'pgcache.memcached.password' ),
				'binary_protocol' => $this->_config->get_boolean( 'pgcache.memcached.binary_protocol' )
			);
			break;

		case 'redis':
			$engineConfig = array(
				'servers' => $this->_config->get_array( 'pgcache.redis.servers' ),
				'verify_tls_certificates' => $this->_config->get_boolean( 'pgcache.redis.verify_tls_certificates' ),
				'persistent' => $this->_config->get_boolean( 'pgcache.redis.persistent' ),
				'timeout' => $this->_config->get_integer( 'pgcache.redis.timeout' ),
				'retry_interval' => $this->_config->get_integer( 'pgcache.redis.retry_interval' ),
				'read_timeout' => $this->_config->get_integer( 'pgcache.redis.read_timeout' ),
				'dbid' => $this->_config->get_integer( 'pgcache.redis.dbid' ),
				'password' => $this->_config->get_string( 'pgcache.redis.password' )
			);
			break;

		case 'file_generic':
			$engine = 'file';
			break;

		default:
			$engineConfig = array();
		}

		$engineConfig['engine'] = $engine;
		return $engineConfig;
	}

	/**
	 * Returns cache object
	 *
	 * @return W3_Cache_Base
	 */
	function _get_cache( $group = '*' ) {
		static $caches = array();

		if ( empty( $group ) ) {
			$group = '*';
		}

		if ( empty( $caches[$group] ) ) {
			$engine = $this->_config->get_string( 'pgcache.engine' );

			switch ( $engine ) {
			case 'memcached':
			case 'nginx_memcached':
				$engineConfig = array(
					'servers' => $this->_config->get_array( 'pgcache.memcached.servers' ),
					'persistent' => $this->_config->get_boolean( 'pgcache.memcached.persistent' ),
					'aws_autodiscovery' => $this->_config->get_boolean( 'pgcache.memcached.aws_autodiscovery' ),
					'username' => $this->_config->get_string( 'pgcache.memcached.username' ),
					'password' => $this->_config->get_string( 'pgcache.memcached.password' ),
					'binary_protocol' => $this->_config->get_boolean( 'pgcache.memcached.binary_protocol' ),
					'host' => Util_Environment::host(),
				);
				break;

			case 'redis':
				$engineConfig = array(
					'servers' => $this->_config->get_array( 'pgcache.redis.servers' ),
					'verify_tls_certificates' => $this->_config->get_boolean( 'pgcache.redis.verify_tls_certificates' ),
					'persistent' => $this->_config->get_boolean( 'pgcache.redis.persistent' ),
					'timeout' => $this->_config->get_integer( 'pgcache.redis.timeout' ),
					'retry_interval' => $this->_config->get_integer( 'pgcache.redis.retry_interval' ),
					'read_timeout' => $this->_config->get_integer( 'pgcache.redis.read_timeout' ),
					'dbid' => $this->_config->get_integer( 'pgcache.redis.dbid' ),
					'password' => $this->_config->get_string( 'pgcache.redis.password' )
				);
				break;

			case 'file':
				$engineConfig = array(
					'section' => 'page',
					'flush_parent' => ( Util_Environment::blog_id() == 0 ),
					'locking' => $this->_config->get_boolean( 'pgcache.file.locking' ),
					'flush_timelimit' => $this->_config->get_integer( 'timelimit.cache_flush' )
				);
				break;

			case 'file_generic':
				if ( $group != '*' ) {
					$engine = 'file';

					$engineConfig = array(
						'section' => 'page',
						'cache_dir' =>
							W3TC_CACHE_PAGE_ENHANCED_DIR .
							DIRECTORY_SEPARATOR .
							Util_Environment::host_port(),
						'flush_parent' => ( Util_Environment::blog_id() == 0 ),
						'locking' => $this->_config->get_boolean( 'pgcache.file.locking' ),
						'flush_timelimit' => $this->_config->get_integer( 'timelimit.cache_flush' )
					);
					break;
				}

				if ( Util_Environment::blog_id() == 0 ) {
					$flush_dir = W3TC_CACHE_PAGE_ENHANCED_DIR;
				} else {
					$flush_dir = W3TC_CACHE_PAGE_ENHANCED_DIR .
						DIRECTORY_SEPARATOR .
						Util_Environment::host();
				}

				$engineConfig = array(
					'exclude' => array(
						'.htaccess'
					),
					'expire' => $this->_lifetime,
					'cache_dir' => W3TC_CACHE_PAGE_ENHANCED_DIR,
					'locking' => $this->_config->get_boolean( 'pgcache.file.locking' ),
					'flush_timelimit' => $this->_config->get_integer( 'timelimit.cache_flush' ),
					'flush_dir' => $flush_dir,
				);
				break;

			default:
				$engineConfig = array();
			}

			$engineConfig['use_expired_data'] = true;
			$engineConfig['module']           = 'pgcache';
			$engineConfig['host']             = '';
			$engineConfig['instance_id']      = Util_Environment::instance_id();

			$caches[$group] = Cache::instance( $engine, $engineConfig );
		}

		return $caches[$group];
	}

	/**
	 * Checks request URI
	 *
	 * @return boolean
	 */
	function _passed_reject_uri() {
		$auto_reject_uri = array(
			'wp-login',
			'wp-register'
		);

		foreach ( $auto_reject_uri as $uri ) {
			if ( strstr( $this->_request_uri, $uri ) !== false ) {
				return false;
			}
		}

		$reject_uri = $this->_config->get_array( 'pgcache.reject.uri' );
		$reject_uri = array_map( array( '\W3TC\Util_Environment', 'parse_path' ), $reject_uri );

		foreach ( $reject_uri as $expr ) {
			$expr = trim( $expr );
			if ( $expr != '' && preg_match( '~' . $expr . '~i', $this->_request_uri ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Check if in the cache exception list
	 *
	 * @return boolean
	 */
	function _passed_accept_files() {
		$accept_uri = $this->_config->get_array( 'pgcache.accept.files' );
		$accept_uri = array_map( array( '\W3TC\Util_Environment', 'parse_path' ), $accept_uri );
		foreach ( $accept_uri as &$val ) $val = trim( str_replace( "~", "\~", $val ) );
		$accept_uri = array_filter( $accept_uri, function( $val ){ return $val != ""; } );
		if ( !empty( $accept_uri ) && @preg_match( '~' . implode( "|", $accept_uri ) . '~i', $this->_request_uri ) ) {
			return true;
		}
		return false;
	}
	/**
	 * Checks page against rejected categories
	 *
	 * @return boolean
	 */
	function _passed_reject_categories() {
		$reject_categories = $this->_config->get_array( 'pgcache.reject.categories' );
		if ( !empty( $reject_categories ) ) {
			if ( $cats = get_the_category() ) {
			   foreach( $cats as $cat ) {
				  if ( in_array( $cat->slug, $reject_categories ) ) {
						return true;
				  }
			   }
			}
		}
		return false;
	}
	/**
	 * Checks page against rejected tags
	 *
	 * @return boolean
	 */
	function _passed_reject_tags() {
		$reject_tags = $this->_config->get_array( 'pgcache.reject.tags' );
		if ( !empty( $reject_tags ) ) {
			if ( $tags = get_the_tags() ) {
			   foreach( $tags as $tag ) {
				  if ( in_array( $tag->slug,$reject_tags ) ) {
						return true;
				  }
			   }
			}
		}
		return false;
	}
	/**
	 * Checks page against rejected authors
	 *
	 * @return boolean
	 */
	function _passed_reject_authors() {
		$reject_authors = $this->_config->get_array( 'pgcache.reject.authors' );
		if ( !empty( $reject_authors ) ) {
			if ( $author = get_the_author_meta( 'user_login' ) ) {
				if ( in_array( $author, $reject_authors ) ) {
					return true;
				}
			}
		}
		return false;
	}
	/**
	 * Checks page against rejected custom fields
	 *
	 * @return boolean
	 */
	function _passed_reject_custom_fields() {
		$reject_custom = $this->_config->get_array( 'pgcache.reject.custom' );
		if ( empty( $reject_custom ) )
			return false;

		foreach ( $reject_custom as &$val ) {
			$val = preg_quote( trim( $val ), '~' );
		}
		$reject_custom = implode( '|', array_filter( $reject_custom ) );
		if ( !empty( $reject_custom ) ) {
			if ( $customs = get_post_custom() ) {
				foreach ( $customs as $key => $value ) {
					if ( @preg_match( '~' . $reject_custom . '~i', $key . ( isset( $value[0] ) ? "={$value[0]}" : "" ) ) ) {
						return true;
					}
				}
			}
		}

		return false;
	}

	/**
	 * Checks User Agent
	 *
	 * @return boolean
	 */
	function _check_ua() {
		$uas = $this->_config->get_array( 'pgcache.reject.ua' );

		$uas = array_merge( $uas, array( W3TC_POWERED_BY ) );

		foreach ( $uas as $ua ) {
			if ( !empty( $ua ) ) {
				if ( isset( $_SERVER['HTTP_USER_AGENT'] ) &&
					stristr( htmlspecialchars( stripslashes( $_SERVER['HTTP_USER_AGENT'] ) ), $ua ) !== false ) // phpcs:ignore
					return false;
			}
		}

		return true;
	}

	/**
	 * Checks WordPress cookies
	 *
	 * @return boolean
	 */
	function _check_cookies() {
		foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
			if ( $cookie_name == 'wordpress_test_cookie' ) {
				continue;
			}
			if ( preg_match( '/^(wp-postpass|comment_author)/', $cookie_name ) ) {
				return false;
			}
		}

		foreach ( $this->_config->get_array( 'pgcache.reject.cookie' ) as $reject_cookie ) {
			if ( !empty( $reject_cookie ) ) {
				foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
					if ( strstr( $cookie_name, $reject_cookie ) !== false ) {
						return false;
					}
				}
			}
		}

		return true;
	}

	/**
	 * Check if user is logged in
	 *
	 * @return boolean
	 */
	function _check_logged_in() {
		foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
			if ( strpos( $cookie_name, 'wordpress_logged_in' ) === 0 )
				return false;
		}

		return true;
	}

	/**
	 * Check if logged in user role is allwed to be cached
	 *
	 * @return boolean
	 */
	function _check_logged_in_role_allowed() {
		if ( !$this->_config->get_boolean( 'pgcache.reject.logged_roles' ) )
			return true;
		$roles = $this->_config->get_array( 'pgcache.reject.roles' );

		if ( empty( $roles ) )
			return true;

		foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
			if ( strpos( $cookie_name, 'w3tc_logged_' ) === 0 ) {
				foreach ( $roles as $role ) {
					if ( strstr( $cookie_name, md5( NONCE_KEY . $role ) ) )
						return false;
				}
			}
		}

		return true;
	}

	/**
	 * Checks if rules file present and creates it if not
	 */
	function _check_rules_present() {
		if ( Util_Environment::is_nginx() )
			return;   // nginx store it in a single file

		$filename = Util_Rule::get_pgcache_rules_cache_path();
		if ( file_exists( $filename ) )
			return;

		// we call it as little times as possible
		// its expensive, but have to restore lost .htaccess file
		$e = Dispatcher::component( 'PgCache_Environment' );
		try {
			$e->fix_on_wpadmin_request( $this->_config, true );
		} catch ( \Exception $ex ) {
		}
	}

	/**
	 * Compress data
	 *
	 * @param string  $data
	 * @param string  $compression
	 * @return string
	 */
	function _compress( $data, $compression ) {
		switch ( $compression ) {
		case 'gzip':
			$data = gzencode( $data );
			break;

		case 'deflate':
			$data = gzdeflate( $data );
			break;

		case 'br':
			$data = brotli_compress( $data );
			break;
		}

		return $data;
	}

	/**
	 * Returns page key extension for current request
	 *
	 * @return string
	 */
	private function _get_key_extension() {
		$extension = array(
			'useragent' => '',
			'referrer' => '',
			'cookie' => '',
			'encryption' => '',
			'compression' => $this->_get_compression(),
			'content_type' => '',
			'cache' => true,
			'cache_reject_reason' => '',
			'group' => ''
		);

		if ( $this->_mobile )
			$extension['useragent'] = $this->_mobile->get_group();
		if ( $this->_referrer )
			$extension['referrer'] = $this->_referrer->get_group();
		if ( Util_Environment::is_https() )
			$extension['encryption'] = 'ssl';

		$this->_fill_key_extension_cookie( $extension );

		// fill group
		$extension['group'] = $this->get_cache_group_by_uri( $this->_request_uri );
		$extension = w3tc_apply_filters( 'pagecache_key_extension', $extension,
			$this->_request_url_fragments['host'], $this->_request_uri );

		return $extension;
	}

	private function _fill_key_extension_cookie( &$extension ) {
		if ( !$this->_config->get_boolean( 'pgcache.cookiegroups.enabled' ) )
			return;

		$groups = $this->_config->get_array( 'pgcache.cookiegroups.groups' );
		foreach ( $groups as $group_name => $g ) {
			if ( isset( $g['enabled'] ) && $g['enabled'] ) {

				$cookies = array();
				foreach ($g['cookies'] as $cookie ) {
					$cookie = trim( $cookie );
					if ( !empty( $cookie ) ) {
						$cookie = str_replace( '+', ' ', $cookie );
						$cookie = Util_Environment::preg_quote( $cookie );
						if ( strpos( $cookie, '=') === false )
							$cookie .= '=.*';
						$cookies[] = $cookie;
					}
				}

				if ( count( $cookies ) > 0 ) {
					$cookies_regexp = '~^(' . implode( '|', $cookies ) . ')$~i';

					foreach ( $_COOKIE as $key => $value ) {
						if ( @preg_match( $cookies_regexp, $key . '=' . $value ) ) {
							$extension['cookie'] = $group_name;
							if ( !$g['cache'] ) {
								$extension['cache'] = false;
								$extension['cache_reject_reason'] = 'cookiegroup ' . $group_name;
							}
							return;
						}
					}
				}
			}
		}
	}

	protected function get_cache_group_by_uri( $uri ) {
		// "!$this->_enhanced_mode" in condition above
		// prevents usage of separate group under disk-enhanced
		// so that rewrite rules still work.
		// flushing is handled by workaround in this case
		if ( !$this->_enhanced_mode ) {
			$sitemap_regex = $this->_config->get_string(
				'pgcache.purge.sitemap_regex' );

			if ( $sitemap_regex && preg_match( '~' . $sitemap_regex . '~',
					basename( $uri ) ) ) {
				return 'sitemaps';
			}
		}

		if ( $this->_config->get_string( 'pgcache.rest' ) == 'cache' &&
				Util_Environment::is_rest_request( $uri ) &&
				Util_Environment::is_w3tc_pro( $this->_config ) ) {
			return 'rest';
		}

		return '';
	}

	/**
	 * Returns current compression
	 *
	 * @return boolean
	 */
	function _get_compression() {
		if ( $this->_debug )   // cannt generate/use compressed files during debug mode
			return '';

		if ( !Util_Environment::is_zlib_enabled() && !$this->_is_buggy_ie() ) {
			$compressions = $this->_get_compressions();

			foreach ( $compressions as $compression ) {
				if ( is_string( $compression ) &&
					isset( $_SERVER['HTTP_ACCEPT_ENCODING'] ) &&
					stristr( htmlspecialchars( stripslashes( $_SERVER['HTTP_ACCEPT_ENCODING'] ) ), $compression ) !== false ) { // phpcs:ignore
					return $compression;
				}
			}
		}

		return '';
	}

	/**
	 * Returns array of compressions
	 *
	 * @return array
	 */
	function _get_compressions() {
		$compressions = array(
			false
		);

		if ( defined( 'W3TC_PAGECACHE_STORE_COMPRESSION_OFF' ) ) {
			return $compressions;
		}

		if ( $this->_config->get_boolean( 'browsercache.enabled' ) &&
			$this->_config->get_boolean( 'browsercache.html.compression' ) &&
			function_exists( 'gzencode' ) ) {
			$compressions[] = 'gzip';
		}

		if ( $this->_config->get_boolean( 'browsercache.enabled' ) &&
			$this->_config->get_boolean( 'browsercache.html.brotli' ) &&
			function_exists( 'brotli_compress' ) ) {
			$compressions[] = 'br';
		}

		return $compressions;
	}

	/**
	 * Returns array of response headers
	 *
	 * @return array
	 */
	function _get_response_headers() {
		$headers_kv = array();
		$headers_plain = array();

		if ( function_exists( 'headers_list' ) ) {
			$headers_list = headers_list();
			if ( $headers_list ) {
				foreach ( $headers_list as $header ) {
					$pos = strpos( $header, ':' );
					if ( $pos ) {
						$header_name = trim( substr( $header, 0, $pos ) );
						$header_value = trim( substr( $header, $pos + 1 ) );
					} else {
						$header_name = $header;
						$header_value = '';
					}
					$headers_kv[strtolower($header_name)] = $header_value;
					$headers_plain[] = array(
						'name' => $header_name,
						'value' => $header_value
					);
				}
			}
		}

		return array(
			'kv' => $headers_kv,
			'plain' => $headers_plain
		);
	}

	/**
	 * Checks for buggy IE6 that doesn't support compression
	 *
	 * @return boolean
	 */
	function _is_buggy_ie() {
		if ( isset( $_SERVER['HTTP_USER_AGENT'] ) ) {
			$ua = htmlspecialchars( stripslashes( $_SERVER['HTTP_USER_AGENT'] ) ); // phpcs:ignore

			if ( strpos( $ua, 'Mozilla/4.0 (compatible; MSIE ' ) === 0 && strpos( $ua, 'Opera' ) === false ) {
				$version = (float) substr( $ua, 30 );

				return $version < 6 || ( $version == 6 && strpos( $ua, 'SV1' ) === false );
			}
		}

		return false;
	}

	/**
	 * Returns array of data headers
	 *
	 * @return array
	 */
	function _get_cached_headers( $response_headers ) {
		$data_headers = array();
		$cache_headers = array_merge(
			array( 'Location', 'X-WP-Total', 'X-WP-TotalPages' ),
			$this->_config->get_array( 'pgcache.cache.headers' )
		);

		if ( function_exists( 'http_response_code' ) ) {   // php5.3 compatibility
			$data_headers['Status-Code'] = http_response_code();
		}

		$repeating_headers = array(
			'link',
			'cookie',
			'set-cookie'
		);
		$repeating_headers = apply_filters( 'w3tc_repeating_headers',
			$repeating_headers );

		foreach ( $response_headers as $i ) {
			$header_name = $i['name'];
			$header_value = $i['value'];

			foreach ( $cache_headers as $cache_header_name ) {
				if ( strcasecmp( $header_name, $cache_header_name ) == 0 ) {
					$header_name_lo = strtolower( $header_name );
					if ( in_array($header_name_lo, $repeating_headers) ) {
						// headers may repeat
						$data_headers[] = array(
							'n' => $header_name,
							'v' => $header_value
						);
					} else {
						$data_headers[$header_name] = $header_value;
					}
				}
			}
		}

		return $data_headers;
	}

	/**
	 * Returns page key
	 *
	 * @return string
	 */
	function _get_page_key( $page_key_extension, $request_url = '' ) {
		// key url part
		if ( empty( $request_url ) ) {
			$request_url_fragments = $this->_request_url_fragments;
		} else {
			$request_url_fragments = array();

			$parts = parse_url( $request_url );

			if ( isset( $parts['host'] ) ) {
				$request_url_fragments['host'] = $parts['host'] .
					( isset( $parts['port'] ) ? ':' . $parts['port'] : '' );
			} else {
				$request_url_fragments['host'] = $this->_request_url_fragments['host'];
			}

			$request_url_fragments['path'] =
				( isset( $parts['path'] ) ? $parts['path'] : '' );
			$request_url_fragments['querystring'] =
				( isset( $parts['query'] ) ? '?' . $parts['query'] : '' );
			$request_url_fragments = $this->_normalize_url_fragments(
				$request_url_fragments );
		}

		$key_urlpart =
			$request_url_fragments['host'] .
			( $request_url_fragments['path'] ?? '' ) .
			( $request_url_fragments['querystring'] ?? '' );

		$key_urlpart = $this->_get_page_key_urlpart( $key_urlpart, $page_key_extension );

		// key extension
		$key_extension = '';
		$extensions = array( 'useragent', 'referrer', 'cookie', 'encryption' );
		foreach ( $extensions as $e ) {
			if ( !empty( $page_key_extension[$e] ) ) {
				$key_extension .= '_' . $page_key_extension[$e];
			}
		}
		if ( Util_Environment::is_preview_mode() ) {
			$key_extension .= '_preview';
		}

		// key postfix
		$key_postfix = '';
		if ( $this->_enhanced_mode && empty( $page_key_extension['group'] ) ) {
			$key_postfix = '.html';
			if ( $this->_config->get_boolean( 'pgcache.cache.nginx_handle_xml' ) ) {
				$content_type = isset( $page_key_extension['content_type'] ) ?
					$page_key_extension['content_type'] : '';

				if ( @preg_match( "~(text/xml|text/xsl|application/xhtml\+xml|application/rdf\+xml|application/rss\+xml|application/atom\+xml|application/xml)~i", $content_type ) ||
				preg_match( W3TC_FEED_REGEXP, $request_url_fragments['path'] ) ||
					strpos( $request_url_fragments['path'], ".xsl" ) !== false ) {
					$key_postfix = '.xml';
				}
			}
		}

		// key compression
		$key_compression = '';
		if ( $page_key_extension['compression'] ) {
			$key_compression = '_' . $page_key_extension['compression'];
		}

		$key = w3tc_apply_filters( 'pagecache_page_key', array(
				'key' => array(
					$key_urlpart,
					$key_extension,
					$key_postfix,
					$key_compression
				),
				'page_key_extension' => $page_key_extension,
				'url_fragments' => $this->_request_url_fragments
			) );

		return implode( '', $key['key'] );
	}

	private function _get_page_key_urlpart( $key, $page_key_extension ) {
		// remove fragments
		$key = preg_replace( '~#.*$~', '', $key );

		// host/uri in different cases means the same page in wp
		$key = strtolower( $key );

		if ( empty( $page_key_extension['group'] ) ) {
			if ( $this->_enhanced_mode || $this->_nginx_memcached ) {
				$extra = '';

				// URL decode
				$key = urldecode( $key );

				// replace double slashes
				$key = preg_replace( '~[/\\\]+~', '/', $key );

				// replace index.php
				$key = str_replace( '/index.php', '/', $key );

				// remove querystring
				$key = preg_replace( '~\?.*$~', '', $key );

				// make sure one slash is at the end
				if (substr($key, strlen($key) - 1, 1) == '/') {
					$extra = '_slash';
				}
				$key = trim( $key, '/' ) . '/';

				if ( $this->_nginx_memcached ) {
					return $key;
				}

				return $key . '_index' . $extra;
			}
		}

		return md5( $key );
	}

	/**
	 * Returns debug info
	 *
	 * @param boolean $cache
	 * @param string  $reason
	 * @param boolean $status
	 * @param double  $time
	 * @return string
	 */
	public function w3tc_footer_comment( $strings ) {
		$strings[] = sprintf(
			// translators: 1: Engine name, 2: Reject reason placeholder, 3: Page key extension.
			__( 'Page Caching using %1$s%2$s%3$s', 'w3-total-cache' ),
			Cache::engine_name( $this->_config->get_string( 'pgcache.engine' ) ),
			'{w3tc_pagecache_reject_reason}',
			isset( $this->_page_key_extension['cookie'] ) ? ' ' . $this->_page_key_extension['cookie'] : ''
		);


		if ( $this->_debug ) {
			$time_total = Util_Debug::microtime() - $this->_time_start;
			$engine = $this->_config->get_string( 'pgcache.engine' );
			$strings[] = '';
			$strings[] = 'Page cache debug info:';
			$strings[] = sprintf( "%s%s", str_pad( 'Engine: ', 20 ), Cache::engine_name( $engine ) );
			$strings[] = sprintf( "%s%s", str_pad( 'Cache key: ', 20 ), $this->_page_key );

			$strings[] = sprintf( "%s%.3fs", str_pad( 'Creation Time: ', 20 ), time() );

			$headers = $this->_get_response_headers();

			if ( count( $headers['plain'] ) ) {
				$strings[] = "Header info:";

				foreach ( $headers['plain'] as $i ) {
					$strings[] = sprintf( "%s%s",
						str_pad( $i['name'] . ': ', 20 ),
						Util_Content::escape_comment( $i['value'] ) );
				}
			}

			$strings[] = '';
		}

		return $strings;
	}

	/**
	 * Sends headers
	 *
	 * @param array   $headers
	 * @return boolean
	 */
	function _headers( $headers ) {
		if ( headers_sent() )
			return false;

		$repeating = array();
		// headers are sent as name->value and array(n=>, v=>)
		// to support repeating headers
		foreach ( $headers as $name0 => $value0 ) {
			if ( is_array( $value0 ) && isset( $value0['n'] ) ) {
				$name = $value0['n'];
				$value = $value0['v'];
			} else {
				$name = $name0;
				$value = $value0;
			}

			if ( $name == 'Status' ) {
				@header( $headers['Status'] );
			} elseif ( $name == 'Status-Code' ) {
				if ( function_exists( 'http_response_code' ) )   // php5.3 compatibility)
					@http_response_code( $headers['Status-Code'] );
			} elseif ( !empty( $name ) && !empty( $value ) ) {
				@header( $name . ': ' . $value, !isset( $repeating[$name] ) );
				$repeating[$name] = true;
			}
		}

		return true;
	}

	/**
	 * Sends headers
	 *
	 * @param boolean $is_404
	 * @param string  $etag
	 * @param integer $time
	 * @param string  $compression
	 * @param array   $custom_headers
	 * @return boolean
	 */
	function _send_headers( $is_404, $time, $etag, $compression, $custom_headers = array() ) {
		$exit = false;
		$headers = ( is_array( $custom_headers ) ? $custom_headers : array() );
		$curr_time = time();

		$bc_lifetime = $this->_config->get_integer(
			'browsercache.html.lifetime' );

		$expires = ( is_null( $time ) ? $curr_time : $time ) + $bc_lifetime;
		$max_age = ( $expires > $curr_time ? $expires - $curr_time : 0 );

		if ( $is_404 ) {
			/**
			 * Add 404 header
			 */
			$headers['Status'] = 'HTTP/1.1 404 Not Found';
		} elseif ( ( !is_null( $time ) && $this->_check_modified_since( $time ) ) || $this->_check_match( $etag ) ) {
			/**
			 * Add 304 header
			 */
			$headers['Status'] = 'HTTP/1.1 304 Not Modified';

			/**
			 * Don't send content if it isn't modified
			 */
			$exit = true;
		}

		if ( $this->_config->get_boolean( 'browsercache.enabled' ) ) {

			if ( $this->_config->get_boolean( 'browsercache.html.last_modified' ) ) {
				$headers['Last-Modified'] = Util_Content::http_date( $time );
			}

			if ( $this->_config->get_boolean( 'browsercache.html.expires' ) ) {
				$headers['Expires'] = Util_Content::http_date( $expires );
			}

			if ( $this->_config->get_boolean( 'browsercache.html.cache.control' ) ) {
				switch ( $this->_config->get_string( 'browsercache.html.cache.policy' ) ) {
				case 'cache':
					$headers['Pragma'] = 'public';
					$headers['Cache-Control'] = 'public';
					break;

				case 'cache_public_maxage':
					$headers['Pragma'] = 'public';
					$headers['Cache-Control'] = sprintf( 'max-age=%d, public', $max_age );
					break;

				case 'cache_validation':
					$headers['Pragma'] = 'public';
					$headers['Cache-Control'] = 'public, must-revalidate, proxy-revalidate';
					break;

				case 'cache_noproxy':
					$headers['Pragma'] = 'public';
					$headers['Cache-Control'] = 'private, must-revalidate';
					break;

				case 'cache_maxage':
					$headers['Pragma'] = 'public';
					$headers['Cache-Control'] = sprintf( 'max-age=%d, public, must-revalidate, proxy-revalidate', $max_age );
					break;

				case 'no_cache':
					$headers['Pragma'] = 'no-cache';
					$headers['Cache-Control'] = 'private, no-cache';
					break;

				case 'no_store':
					$headers['Pragma'] = 'no-store';
					$headers['Cache-Control'] = 'no-store';
					break;
				}
			}

			if ( $this->_config->get_boolean( 'browsercache.html.etag' ) ) {
				$headers['ETag'] = '"' . $etag . '"';
			}
		}


		$headers = array_merge( $headers,
			$this->_get_common_headers( $compression ) );

		/**
		 * Send headers to client
		 */
		$result = $this->_headers( $headers );

		if ( $exit )
			exit();

		return $result;
	}

	/**
	 * Returns headers to send regardless is page caching is active
	 */
	function _get_common_headers( $compression ) {
		$headers = array();

		if ( $this->_config->get_boolean( 'browsercache.enabled' ) ) {
			if ( $this->_config->get_boolean( 'browsercache.html.w3tc' ) ) {
				$headers['X-Powered-By'] = Util_Environment::w3tc_header();
			}
		}

		$vary = '';
		//compressed && UAG
		if ( $compression && $this->_page_key_extension['useragent'] ) {
			$vary = 'Accept-Encoding,User-Agent,Cookie';
			$headers['Content-Encoding'] = $compression;
			//compressed
		} elseif ( $compression ) {
			$vary = 'Accept-Encoding';
			$headers['Content-Encoding'] = $compression;
			//uncompressed && UAG
		} elseif ( $this->_page_key_extension['useragent'] ) {
			$vary = 'User-Agent,Cookie';
		}

		//Add Cookie to vary if user logged in and not previously set
		if ( !$this->_check_logged_in() && strpos( $vary, 'Cookie' ) === false ) {
			if ( $vary )
				$vary .= ',Cookie';
			else
				$vary = 'Cookie';
		}

		/**
		 * Add vary header
		 */
		if ( $vary )
			$headers['Vary'] = $vary;

		/**
		 * Disable caching for preview mode
		 */
		if ( Util_Environment::is_preview_mode() ) {
			$headers['Pragma'] = 'private';
			$headers['Cache-Control'] = 'private';
		}

		return $headers;
	}

	/**
	 * Check if content was modified by time
	 *
	 * @param integer $time
	 * @return boolean
	 */
	function _check_modified_since( $time ) {
		if ( !empty( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) {
			$if_modified_since = htmlspecialchars( stripslashes( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ); // phpcs:ignore

			// IE has tacked on extra data to this header, strip it
			if ( ( $semicolon = strrpos( $if_modified_since, ';' ) ) !== false ) {
				$if_modified_since = substr( $if_modified_since, 0, $semicolon );
			}

			return $time == strtotime( $if_modified_since );
		}

		return false;
	}

	/**
	 * Check if content was modified by etag
	 *
	 * @param string  $etag
	 * @return boolean
	 */
	function _check_match( $etag ) {
		if ( !empty( $_SERVER['HTTP_IF_NONE_MATCH'] ) ) {
			$if_none_match = htmlspecialchars( stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) ); // phpcs:ignore
			$client_etags  = explode( ',', $if_none_match );

			foreach ( $client_etags as $client_etag ) {
				$client_etag = trim( $client_etag );

				if ( $etag == $client_etag ) {
					return true;
				}
			}
		}

		return false;
	}

	/**
	 * Bad Behavior support
	 *
	 * @return void
	 */
	function _bad_behavior() {
		$bb_file = $this->_config->get_string( 'pgcache.bad_behavior_path' );
		if ( $bb_file != '' )
			require_once $bb_file;
	}

	/**
	 * Parses dynamic tags
	 */
	function _parse_dynamic( $buffer ) {
		if ( !defined( 'W3TC_DYNAMIC_SECURITY' ) )
			return $buffer;

		$buffer = preg_replace_callback( '~<!--\s*mfunc\s*' . W3TC_DYNAMIC_SECURITY . '(.*)-->(.*)<!--\s*/mfunc\s*' . W3TC_DYNAMIC_SECURITY . '\s*-->~Uis', array(
				$this,
				'_parse_dynamic_mfunc'
			), $buffer );

		$buffer = preg_replace_callback( '~<!--\s*mclude\s*' . W3TC_DYNAMIC_SECURITY . '(.*)-->(.*)<!--\s*/mclude\s*' . W3TC_DYNAMIC_SECURITY . '\s*-->~Uis', array(
				$this,
				'_parse_dynamic_mclude'
			), $buffer );

		return $buffer;
	}

	/**
	 * Parse dynamic mfunc callback
	 *
	 * @param array   $matches
	 * @return string
	 */
	function _parse_dynamic_mfunc( $matches ) {
		$code1 = trim( $matches[1] );
		$code2 = trim( $matches[2] );
		$code = ( $code1 ? $code1 : $code2 );

		if ( $code ) {
			$code = trim( $code, ';' ) . ';';

			try {
				ob_start();
				$result = eval( $code );
				$output = ob_get_contents();
				ob_end_clean();
			} catch ( \Exception $ex ) {
				$result = false;
			}

			if ( $result === false ) {
				$output = sprintf( 'Unable to execute code: %s', htmlspecialchars( $code ) );
			}
		} else {
			$output = htmlspecialchars( 'Invalid mfunc tag syntax. The correct format is: <!-- W3TC_DYNAMIC_SECURITY mfunc PHP code --><!-- /mfunc W3TC_DYNAMIC_SECURITY --> or <!-- W3TC_DYNAMIC_SECURITY mfunc -->PHP code<!-- /mfunc W3TC_DYNAMIC_SECURITY -->.' );
		}

		return $output;
	}

	/**
	 * Parse dynamic mclude callback
	 *
	 * @param array   $matches
	 * @return string
	 */
	function _parse_dynamic_mclude( $matches ) {
		$file1 = trim( $matches[1] );
		$file2 = trim( $matches[2] );

		$file = ( $file1 ? $file1 : $file2 );

		if ( $file ) {
			$file = ABSPATH . $file;

			if ( file_exists( $file ) && is_readable( $file ) ) {
				ob_start();
				include $file;
				$output = ob_get_contents();
				ob_end_clean();
			} else {
				$output = sprintf( 'Unable to open file: %s', htmlspecialchars( $file ) );
			}
		} else {
			$output = htmlspecialchars( 'Incorrect mclude tag syntax. The correct format is: <!-- mclude W3TC_DYNAMIC_SECURITY path/to/file.php --><!-- /mclude W3TC_DYNAMIC_SECURITY --> or <!-- mclude W3TC_DYNAMIC_SECURITY -->path/to/file.php<!-- /mclude W3TC_DYNAMIC_SECURITY -->.' );
		}

		return $output;
	}

	/**
	 * Checks if buffer has dynamic tags
	 *
	 * @param string  $buffer
	 * @return boolean
	 */
	function _has_dynamic( $buffer ) {
		if ( !defined( 'W3TC_DYNAMIC_SECURITY' ) )
			return false;

		return preg_match( '~<!--\s*m(func|clude)\s*' . W3TC_DYNAMIC_SECURITY . '(.*)-->(.*)<!--\s*/m(func|clude)\s*' . W3TC_DYNAMIC_SECURITY . '\s*-->~Uis', $buffer );
	}

	/**
	 * Check whether requested page has content type that can be cached
	 *
	 * @return bool
	 */
	private function _is_cacheable_content_type() {
		$content_type = '';
		$headers = headers_list();
		foreach ( $headers as $header ) {
			$header = strtolower( $header );
			$m = null;
			if ( preg_match( '~\s*content-type\s*:([^;]+)~', $header, $m ) ) {
				$content_type = trim( $m[1] );
			}
		}

		$cache_headers = apply_filters( 'w3tc_is_cacheable_content_type',
			array(
				'' /* redirects, they have only Location header set */,
				'application/json', 'text/html', 'text/xml', 'text/xsl',
				'application/xhtml+xml', 'application/rss+xml',
				'application/atom+xml', 'application/rdf+xml',
				'application/xml'
			)
		);
		return in_array( $content_type, $cache_headers );
	}

	/**
	 * Fills $_request_url_fragments['path'], $_request_url_fragments['querystring']
	 * with cache-related normalized values
	 */
	private function _preprocess_request_uri() {
		$p = explode( '?', $this->_request_uri, 2 );

		$this->_request_url_fragments['path'] = $p[0];
		$this->_request_url_fragments['querystring'] =
			( empty( $p[1] ) ? '' : '?' . $p[1] );

		$this->_request_url_fragments = $this->_normalize_url_fragments(
			$this->_request_url_fragments );
	}



	private function _normalize_url_fragments( $fragments ) {
		$fragments = w3tc_apply_filters( 'pagecache_normalize_url_fragments',
			$fragments );
		$fragments['querystring'] = $this->_normalize_querystring(
			$fragments['querystring'] );

		return $fragments;
	}



	private function _normalize_querystring( $querystring ) {
		$ignore_qs = $this->_config->get_array( 'pgcache.accept.qs' );
		$ignore_qs = w3tc_apply_filters( 'pagecache_extract_accept_qs', $ignore_qs );
		Util_Rule::array_trim( $ignore_qs );

		if ( empty( $ignore_qs ) || empty( $querystring ) ) {
			return $querystring;
		}

		$querystring_naked = substr( $querystring, 1 );

		foreach ( $ignore_qs as $qs ) {
			$m = null;
			if ( strpos( $qs, '=' ) === false ) {
				$regexp = Util_Environment::preg_quote( str_replace( '+', ' ', $qs ) );
				if ( @preg_match( "~^(.*?&|)$regexp(=[^&]*)?(&.*|)$~i", $querystring_naked, $m ) ) {
					$querystring_naked = $m[1] . $m[3];
				}
			} else {
				$regexp = Util_Environment::preg_quote( str_replace( '+', ' ', $qs ) );

				if ( @preg_match( "~^(.*?&|)$regexp(&.*|)$~i", $querystring_naked, $m ) ) {
					$querystring_naked = $m[1] . $m[2];
				}
			}
		}

		$querystring_naked = preg_replace( '~[&]+~', '&', $querystring_naked );
		$querystring_naked = trim( $querystring_naked, '&' );

		return empty( $querystring_naked ) ? '' : '?' . $querystring_naked;
	}

	/**
	 *
	 */
	public function delayed_cache_print() {
		if ( $this->_late_caching && $this->_caching ) {
			$this->_cached_data = $this->_extract_cached_page( true );
			if ( $this->_cached_data ) {
				global $w3_late_caching_succeeded;
				$w3_late_caching_succeeded  = true;

				$this->process_status = 'hit';
				$this->process_cached_page_and_exit( $this->_cached_data );
				// if is passes here - exit is not possible now and
				// will happen on init
				return;
			}
		}

		if ( $this->_late_init && $this->_caching ) {
			$this->process_status = 'hit';
			$this->process_cached_page_and_exit( $this->_cached_data );
			// if is passes here - exit is not possible now and
			// will happen on init
			return;
		}
	}

	private function _maybe_save_cached_result( $buffer, $response_headers, $has_dynamic ) {
		$mobile_group = $this->_page_key_extension['useragent'];
		$referrer_group = $this->_page_key_extension['referrer'];
		$encryption = $this->_page_key_extension['encryption'];
		$compression_header = $this->_page_key_extension['compression'];
		$compressions_to_store = $this->_get_compressions();

		/**
		 * Don't compress here for debug mode or dynamic tags
		 * because we need to modify buffer before send it to client
		 */
		if ( $this->_debug || $has_dynamic ) {
			$compressions_to_store = array( false );
		}

		// right now dont return compressed buffer if we are dynamic,
		// that will happen on shutdown after processing dynamic stuff
		$compression_of_returned_content =
			( $has_dynamic ? false : $compression_header );

		$headers = $this->_get_cached_headers( $response_headers['plain'] );
		if ( !empty( $headers['Status-Code'] ) ) {
			$is_404 = ( $headers['Status-Code'] == 404 );
		} elseif ( function_exists( 'is_404' ) ) {
			$is_404 = is_404();
		} else {
			$is_404 = false;
		}

		if ( $this->_enhanced_mode ) {
			// redirect issued, if we have some old cache entries
			// they will be turned into fresh files and catch further requests
			if ( isset( $response_headers['kv']['location'] ) ) {
				$cache = $this->_get_cache( $this->_page_key_extension['group'] );

				foreach ( $compressions_to_store as $_compression ) {
					$_page_key = $this->_get_page_key(
						array_merge( $this->_page_key_extension,
							array( 'compression' => $_compression ) ) );
					$cache->hard_delete( $_page_key );
				}

				return $buffer;
			}
		}

		$content_type = '';
		if ( $this->_enhanced_mode && !$this->_late_init ) {
			register_shutdown_function( array(
					$this,
					'_check_rules_present'
				) );

			if ( isset( $response_headers['kv']['content-type'] ) ) {
				$content_type = $response_headers['kv']['content-type'];
			}
		}

		$time = time();
		$cache = $this->_get_cache( $this->_page_key_extension['group'] );

		/**
		 * Store different versions of cache
		 */
		$buffers = array();
		$something_was_set = false;

		do_action( 'w3tc_pagecache_before_set', array(
				'request_url_fragments' => $this->_request_url_fragments,
				'page_key_extension' => $this->_page_key_extension
			) );

		foreach ( $compressions_to_store as $_compression ) {
			$this->_set_extract_page_key(
				array_merge( $this->_page_key_extension, [
						'compression' => $_compression,
						'content_type' => $content_type
					] ),
				true );
			if ( empty( $this->_page_key ) ) {
				continue;
			}

			// Compress content
			$buffers[$_compression] = $this->_compress( $buffer, $_compression );

			// Store cache data
			$_data = array(
				'404' => $is_404,
				'headers' => $headers,
				'time' => $time,
				'content' => $buffers[$_compression]
			);
			if ( !empty( $_compression ) ) {
				$_data['c'] = $_compression;
			}
			if ( $has_dynamic )
				$_data['has_dynamic'] = true;

			$_data = apply_filters( 'w3tc_pagecache_set', $_data, $this->_page_key,
				$this->_page_group );

			if ( !empty( $_data ) ) {
				$cache->set( $this->_page_key, $_data, $this->_lifetime, $this->_page_group );
				$something_was_set = true;
			}
		}

		if ( $something_was_set ) {
			$this->process_status = 'miss_fill';
		} else {
			$this->process_status = 'miss_third_party';
		}

		// Change buffer if using compression
		if ( defined( 'W3TC_PAGECACHE_OUTPUT_COMPRESSION_OFF' ) ) {
			$compression_header = false;
		} elseif ( $compression_of_returned_content &&
			isset( $buffers[$compression_of_returned_content] ) ) {
			$buffer = $buffers[$compression_of_returned_content];
		}

		// Calculate content etag
		$etag = md5( $buffer );

		// Send headers
		$this->_send_headers( $is_404, $time, $etag, $compression_header,
			$headers );
		return $buffer;
	}

	public function w3tc_usage_statistics_of_request( $storage ) {
		global $w3tc_start_microtime;
		$time_ms = 0;
		if ( !empty( $w3tc_start_microtime ) ) {
			$time_ms = (int)( ( microtime( true ) - $w3tc_start_microtime ) * 1000 );
			$storage->counter_add( 'pagecache_requests_time_10ms', (int)( $time_ms / 10 ) );
		}

		if ( !empty( $this->process_status ) ) {
			// see registered keys in PgCache_Plugin.w3tc_usage_statistics_metrics
			$storage->counter_add( 'php_requests_pagecache_' . $this->process_status, 1 );

			if ( $this->_debug ) {
				self::log( 'finished in ' . $time_ms .
					' size ' . $this->output_size .
					' with process status ' .
					$this->process_status .
					' reason ' . $this->cache_reject_reason);
			}
		}
	}

	/**
	 * Log.
	 */
	static protected function log( $msg ) {
		$data = sprintf(
			'[%1$s] [%2$s] [%3$s] %4$s ' . "\n",
			date( 'r' ),
			isset( $_SERVER['REQUEST_URI'] ) ? filter_var( stripslashes( $_SERVER['REQUEST_URI'] ), FILTER_SANITIZE_URL ) : '',
			! empty( $_SERVER['HTTP_REFERER'] ) ? htmlspecialchars( $_SERVER['HTTP_REFERER'] ) : '-',
			$msg
		);
		$data = strtr( $data, '<>', '..' );
		$date = Util_Debug::redact_wpnonce( $data );

		$filename = Util_Debug::log_filename( 'pagecache' );

		return @file_put_contents( $filename, $data, FILE_APPEND );
	}
}
