<?php

/**
 * The plugin cache-control class for X-Litespeed-Cache-Control
 *
 * @since       1.1.3
 * @package     LiteSpeed
 * @subpackage  LiteSpeed/inc
 * @author      LiteSpeed Technologies <info@litespeedtech.com>
 */

namespace LiteSpeed;

defined('WPINC') || exit();

class Control extends Root {

	const LOG_TAG = '💵';

	const BM_CACHEABLE        = 1;
	const BM_PRIVATE          = 2;
	const BM_SHARED           = 4;
	const BM_NO_VARY          = 8;
	const BM_FORCED_CACHEABLE = 32;
	const BM_PUBLIC_FORCED    = 64;
	const BM_STALE            = 128;
	const BM_NOTCACHEABLE     = 256;

	const X_HEADER = 'X-LiteSpeed-Cache-Control';

	protected static $_control    = 0;
	protected static $_custom_ttl = 0;

	private $_response_header_ttls = array();

	/**
	 * Init cache control
	 *
	 * @since  1.6.2
	 */
	public function init() {
		/**
		 * Add vary filter for Role Excludes
		 *
		 * @since  1.6.2
		 */
		add_filter('litespeed_vary', array( $this, 'vary_add_role_exclude' ));

		// 301 redirect hook
		add_filter('wp_redirect', array( $this, 'check_redirect' ), 10, 2);

		// Load response header conf
		$this->_response_header_ttls = $this->conf(Base::O_CACHE_TTL_STATUS);
		foreach ($this->_response_header_ttls as $k => $v) {
			$v = explode(' ', $v);
			if (empty($v[0]) || empty($v[1])) {
				continue;
			}
			$this->_response_header_ttls[$v[0]] = $v[1];
		}

		if ($this->conf(Base::O_PURGE_STALE)) {
			$this->set_stale();
		}
	}

	/**
	 * Exclude role from optimization filter
	 *
	 * @since  1.6.2
	 * @access public
	 */
	public function vary_add_role_exclude( $vary ) {
		if ($this->in_cache_exc_roles()) {
			$vary['role_exclude_cache'] = 1;
		}

		return $vary;
	}

	/**
	 * Check if one user role is in exclude cache group settings
	 *
	 * @since 1.6.2
	 * @since 3.0 Moved here from conf.cls
	 * @access public
	 * @param  string $role The user role
	 * @return int       The set value if already set
	 */
	public function in_cache_exc_roles( $role = null ) {
		// Get user role
		if ($role === null) {
			$role = Router::get_role();
		}

		if (!$role) {
			return false;
		}

		$roles = explode(',', $role);
		$found = array_intersect($roles, $this->conf(Base::O_CACHE_EXC_ROLES));

		return $found ? implode(',', $found) : false;
	}

	/**
	 * 1. Initialize cacheable status for `wp` hook
	 * 2. Hook error page tags for cacheable pages
	 *
	 * @since 1.1.3
	 * @access public
	 */
	public function init_cacheable() {
		// Hook `wp` to mark default cacheable status
		// NOTE: Any process that does NOT run into `wp` hook will not get cacheable by default
		add_action('wp', array( $this, 'set_cacheable' ), 5);

		// Hook WP REST to be cacheable
		if ($this->conf(Base::O_CACHE_REST)) {
			add_action('rest_api_init', array( $this, 'set_cacheable' ), 5);
		}

		// AJAX cache
		$ajax_cache = $this->conf(Base::O_CACHE_AJAX_TTL);
		foreach ($ajax_cache as $v) {
			$v = explode(' ', $v);
			if (empty($v[0]) || empty($v[1])) {
				continue;
			}
			// self::debug("Initializing cacheable status for wp_ajax_nopriv_" . $v[0]);
			add_action(
				'wp_ajax_nopriv_' . $v[0],
				function () use ( $v ) {
					self::set_custom_ttl($v[1]);
					self::force_cacheable('ajax Cache setting for action ' . $v[0]);
				},
				4
			);
		}

		// Check error page
		add_filter('status_header', array( $this, 'check_error_codes' ), 10, 2);
	}

	/**
	 * Check if the page returns any error code.
	 *
	 * @since 1.0.13.1
	 * @access public
	 * @param $status_header
	 * @param $code
	 * @return $error_status
	 */
	public function check_error_codes( $status_header, $code ) {
		if (array_key_exists($code, $this->_response_header_ttls)) {
			if (self::is_cacheable() && !$this->_response_header_ttls[$code]) {
				self::set_nocache('[Ctrl] TTL is set to no cache [status_header] ' . $code);
			}

			// Set TTL
			self::set_custom_ttl($this->_response_header_ttls[$code]);
		} elseif (self::is_cacheable()) {
			if (substr($code, 0, 1) == 4 || substr($code, 0, 1) == 5) {
				self::set_nocache('[Ctrl] 4xx/5xx default to no cache [status_header] ' . $code);
			}
		}

		// Set cache tag
		if (in_array($code, Tag::$error_code_tags)) {
			Tag::add(Tag::TYPE_HTTP . $code);
		}

		// Give the default status_header back
		return $status_header;
	}

	/**
	 * Set no vary setting
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public static function set_no_vary() {
		if (self::is_no_vary()) {
			return;
		}
		self::$_control |= self::BM_NO_VARY;
		self::debug('X Cache_control -> no-vary', 3);
	}

	/**
	 * Get no vary setting
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public static function is_no_vary() {
		return self::$_control & self::BM_NO_VARY;
	}

	/**
	 * Set stale
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public function set_stale() {
		if (self::is_stale()) {
			return;
		}
		self::$_control |= self::BM_STALE;
		self::debug('X Cache_control -> stale');
	}

	/**
	 * Get stale
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public static function is_stale() {
		return self::$_control & self::BM_STALE;
	}

	/**
	 * Set cache control to shared private
	 *
	 * @access public
	 * @since 1.1.3
	 * @param string $reason The reason to no cache
	 */
	public static function set_shared( $reason = false ) {
		if (self::is_shared()) {
			return;
		}
		self::$_control |= self::BM_SHARED;
		self::set_private();

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = "( $reason )";
		}
		self::debug('X Cache_control -> shared ' . $reason);
	}

	/**
	 * Check if is shared private
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public static function is_shared() {
		return self::$_control & self::BM_SHARED && self::is_private();
	}

	/**
	 * Set cache control to forced public
	 *
	 * @access public
	 * @since 1.7.1
	 */
	public static function set_public_forced( $reason = false ) {
		if (self::is_public_forced()) {
			return;
		}
		self::$_control |= self::BM_PUBLIC_FORCED;

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = "( $reason )";
		}
		self::debug('X Cache_control -> public forced ' . $reason);
	}

	/**
	 * Check if is public forced
	 *
	 * @access public
	 * @since 1.7.1
	 */
	public static function is_public_forced() {
		return self::$_control & self::BM_PUBLIC_FORCED;
	}

	/**
	 * Set cache control to private
	 *
	 * @access public
	 * @since 1.1.3
	 * @param string $reason The reason to no cache
	 */
	public static function set_private( $reason = false ) {
		if (self::is_private()) {
			return;
		}
		self::$_control |= self::BM_PRIVATE;

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = "( $reason )";
		}
		self::debug('X Cache_control -> private ' . $reason);
	}

	/**
	 * Check if is private
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public static function is_private() {
		if (defined('LITESPEED_GUEST') && LITESPEED_GUEST) {
			// return false;
		}

		return self::$_control & self::BM_PRIVATE && !self::is_public_forced();
	}

	/**
	 * Initialize cacheable status in `wp` hook, if not call this, by default it will be non-cacheable
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public function set_cacheable( $reason = false ) {
		self::$_control |= self::BM_CACHEABLE;

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = ' [reason] ' . $reason;
		}
		self::debug('Cache_control init on' . $reason);
	}

	/**
	 * This will disable non-cacheable BM
	 *
	 * @access public
	 * @since 2.2
	 */
	public static function force_cacheable( $reason = false ) {
		self::$_control |= self::BM_FORCED_CACHEABLE;

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = ' [reason] ' . $reason;
		}
		self::debug('Forced cacheable' . $reason);
	}

	/**
	 * Switch to nocacheable status
	 *
	 * @access public
	 * @since 1.1.3
	 * @param string $reason The reason to no cache
	 */
	public static function set_nocache( $reason = false ) {
		self::$_control |= self::BM_NOTCACHEABLE;

		if (!is_string($reason)) {
			$reason = false;
		}

		if ($reason) {
			$reason = "( $reason )";
		}
		self::debug('X Cache_control -> no Cache ' . $reason, 5);
	}

	/**
	 * Check current notcacheable bit set
	 *
	 * @access public
	 * @since 1.1.3
	 * @return bool True if notcacheable bit is set, otherwise false.
	 */
	public static function isset_notcacheable() {
		return self::$_control & self::BM_NOTCACHEABLE;
	}

	/**
	 * Check current force cacheable bit set
	 *
	 * @access public
	 * @since   2.2
	 */
	public static function is_forced_cacheable() {
		return self::$_control & self::BM_FORCED_CACHEABLE;
	}

	/**
	 * Check current cacheable status
	 *
	 * @access public
	 * @since 1.1.3
	 * @return bool True if is still cacheable, otherwise false.
	 */
	public static function is_cacheable() {
		if (defined('LSCACHE_NO_CACHE') && LSCACHE_NO_CACHE) {
			self::debug('LSCACHE_NO_CACHE constant defined');
			return false;
		}

		// Guest mode always cacheable
		if (defined('LITESPEED_GUEST') && LITESPEED_GUEST) {
			// return true;
		}

		// If its forced public cacheable
		if (self::is_public_forced()) {
			return true;
		}

		// If its forced cacheable
		if (self::is_forced_cacheable()) {
			return true;
		}

		return !self::isset_notcacheable() && self::$_control & self::BM_CACHEABLE;
	}

	/**
	 * Set a custom TTL to use with the request if needed.
	 *
	 * @access public
	 * @since 1.1.3
	 * @param mixed $ttl An integer or string to use as the TTL. Must be numeric.
	 */
	public static function set_custom_ttl( $ttl, $reason = false ) {
		if (is_numeric($ttl)) {
			self::$_custom_ttl = $ttl;
			self::debug('X Cache_control TTL -> ' . $ttl . ($reason ? ' [reason] ' . $ttl : ''));
		}
	}

	/**
	 * Generate final TTL.
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public function get_ttl() {
		if (self::$_custom_ttl != 0) {
			return self::$_custom_ttl;
		}

		// Check if is in timed url list or not
		$timed_urls      = Utility::wildcard2regex($this->conf(Base::O_PURGE_TIMED_URLS));
		$timed_urls_time = $this->conf(Base::O_PURGE_TIMED_URLS_TIME);
		if ($timed_urls && $timed_urls_time) {
			$current_url = Tag::build_uri_tag(true);
			// Use time limit ttl
			$scheduled_time = strtotime($timed_urls_time);
			$ttl            = $scheduled_time - time();
			if ($ttl < 0) {
				$ttl += 86400; // add one day
			}
			foreach ($timed_urls as $v) {
				if (strpos($v, '*') !== false) {
					if (preg_match('#' . $v . '#iU', $current_url)) {
						self::debug('X Cache_control TTL is limited to ' . $ttl . ' due to scheduled purge regex ' . $v);
						return $ttl;
					}
				} elseif ($v == $current_url) {
					self::debug('X Cache_control TTL is limited to ' . $ttl . ' due to scheduled purge rule ' . $v);
					return $ttl;
				}
			}
		}

		// Private cache uses private ttl setting
		if (self::is_private()) {
			return $this->conf(Base::O_CACHE_TTL_PRIV);
		}

		if (is_front_page()) {
			return $this->conf(Base::O_CACHE_TTL_FRONTPAGE);
		}

		$feed_ttl = $this->conf(Base::O_CACHE_TTL_FEED);
		if (is_feed() && $feed_ttl > 0) {
			return $feed_ttl;
		}

		if ($this->cls('REST')->is_rest() || $this->cls('REST')->is_internal_rest()) {
			return $this->conf(Base::O_CACHE_TTL_REST);
		}

		return $this->conf(Base::O_CACHE_TTL_PUB);
	}

	/**
	 * Check if need to set no cache status for redirection or not
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public function check_redirect( $location, $status ) {
		// TODO: some env don't have SCRIPT_URI but only REQUEST_URI, need to be compatible
		if (!empty($_SERVER['SCRIPT_URI'])) {
			// dont check $status == '301' anymore
			self::debug('301 from ' . $_SERVER['SCRIPT_URI']);
			self::debug("301 to $location");

			$to_check = array( PHP_URL_SCHEME, PHP_URL_HOST, PHP_URL_PATH, PHP_URL_QUERY );

			$is_same_redirect = true;

			foreach ($to_check as $v) {
				$url_parsed = $v == PHP_URL_QUERY ? $_SERVER['QUERY_STRING'] : parse_url($_SERVER['SCRIPT_URI'], $v);
				$target     = parse_url($location, $v);

				self::debug("Compare [from] $url_parsed [to] $target");

				if ($v == PHP_URL_QUERY) {
					$url_parsed = $url_parsed ? urldecode($url_parsed) : '';
					$target     = $target ? urldecode($target) : '';
					if (substr($url_parsed, -1) == '&') {
						$url_parsed = substr($url_parsed, 0, -1);
					}
				}

				if ($url_parsed != $target) {
					$is_same_redirect = false;
					self::debug('301 different redirection');
					break;
				}
			}

			if ($is_same_redirect) {
				self::set_nocache('301 to same url');
			}
		}

		return $location;
	}

	/**
	 * Sets up the Cache Control header.
	 *
	 * @since 1.1.3
	 * @access public
	 * @return string empty string if empty, otherwise the cache control header.
	 */
	public function output() {
		$esi_hdr = '';
		if (ESI::has_esi()) {
			$esi_hdr = ',esi=on';
		}

		$hdr = self::X_HEADER . ': ';

		if (defined('DONOTCACHEPAGE') && apply_filters('litespeed_const_DONOTCACHEPAGE', DONOTCACHEPAGE)) {
			self::debug('❌ forced no cache [reason] DONOTCACHEPAGE const');
			$hdr .= 'no-cache' . $esi_hdr;
			return $hdr;
		}

		// Guest mode directly return cacheable result
		// if ( defined( 'LITESPEED_GUEST' ) && LITESPEED_GUEST ) {
		// If is POST, no cache
		// if ( defined( 'LSCACHE_NO_CACHE' ) && LSCACHE_NO_CACHE ) {
		// self::debug( "[Ctrl] ❌ forced no cache [reason] LSCACHE_NO_CACHE const" );
		// $hdr .= 'no-cache';
		// }
		// else if( $_SERVER[ 'REQUEST_METHOD' ] !== 'GET' ) {
		// self::debug( "[Ctrl] ❌ forced no cache [reason] req not GET" );
		// $hdr .= 'no-cache';
		// }
		// else {
		// $hdr .= 'public';
		// $hdr .= ',max-age=' . $this->get_ttl();
		// }

		// $hdr .= $esi_hdr;

		// return $hdr;
		// }

		// Fix cli `uninstall --deactivate` fatal err

		if (!self::is_cacheable()) {
			$hdr .= 'no-cache' . $esi_hdr;
			return $hdr;
		}

		if (self::is_shared()) {
			$hdr .= 'shared,private';
		} elseif (self::is_private()) {
			$hdr .= 'private';
		} else {
			$hdr .= 'public';
		}

		if (self::is_no_vary()) {
			$hdr .= ',no-vary';
		}

		$hdr .= ',max-age=' . $this->get_ttl() . $esi_hdr;
		return $hdr;
	}

	/**
	 * Generate all `control` tags before output
	 *
	 * @access public
	 * @since 1.1.3
	 */
	public function finalize() {
		if (defined('LITESPEED_GUEST') && LITESPEED_GUEST) {
			// return;
		}

		if (is_preview()) {
			self::set_nocache('preview page');
			return;
		}

		// Check if has metabox non-cacheable setting or not
		if (file_exists(LSCWP_DIR . 'src/metabox.cls.php') && $this->cls('Metabox')->setting('litespeed_no_cache')) {
			self::set_nocache('per post metabox setting');
			return;
		}

		// Check if URI is forced public cache
		$excludes = $this->conf(Base::O_CACHE_FORCE_PUB_URI);
		$hit      = Utility::str_hit_array($_SERVER['REQUEST_URI'], $excludes, true);
		if ($hit) {
			list($result, $this_ttl) = $hit;
			self::set_public_forced('Setting: ' . $result);
			self::debug('Forced public cacheable due to setting: ' . $result);
			if ($this_ttl) {
				self::set_custom_ttl($this_ttl);
			}
		}

		if (self::is_public_forced()) {
			return;
		}

		// Check if URI is forced cache
		$excludes = $this->conf(Base::O_CACHE_FORCE_URI);
		$hit      = Utility::str_hit_array($_SERVER['REQUEST_URI'], $excludes, true);
		if ($hit) {
			list($result, $this_ttl) = $hit;
			self::force_cacheable();
			self::debug('Forced cacheable due to setting: ' . $result);
			if ($this_ttl) {
				self::set_custom_ttl($this_ttl);
			}
		}

		// if is not cacheable, terminate check
		// Even no need to run 3rd party hook
		if (!self::is_cacheable()) {
			self::debug('not cacheable before ctrl finalize');
			return;
		}

		// Apply 3rd party filter
		// NOTE: Hook always needs to run asap because some 3rd party set is_mobile in this hook
		do_action('litespeed_control_finalize', defined('LSCACHE_IS_ESI') ? LSCACHE_IS_ESI : false); // Pass ESI block id

		// if is not cacheable, terminate check
		if (!self::is_cacheable()) {
			self::debug('not cacheable after api_control');
			return;
		}

		// Check litespeed setting to set cacheable status
		if (!$this->_setting_cacheable()) {
			self::set_nocache();
			return;
		}

		// If user has password cookie, do not cache (moved from vary)
		global $post;
		if (!empty($post->post_password) && isset($_COOKIE['wp-postpass_' . COOKIEHASH])) {
			// If user has password cookie, do not cache
			self::set_nocache('pswd cookie');
			return;
		}

		// The following check to the end is ONLY for mobile
		$is_mobile = apply_filters('litespeed_is_mobile', false);
		if (!$this->conf(Base::O_CACHE_MOBILE)) {
			if ($is_mobile) {
				self::set_nocache('mobile');
			}
			return;
		}

		$env_vary = isset($_SERVER['LSCACHE_VARY_VALUE']) ? $_SERVER['LSCACHE_VARY_VALUE'] : false;
		if (!$env_vary) {
			$env_vary = isset($_SERVER['HTTP_X_LSCACHE_VARY_VALUE']) ? $_SERVER['HTTP_X_LSCACHE_VARY_VALUE'] : false;
		}
		if ($env_vary && strpos($env_vary, 'ismobile') !== false) {
			if (!wp_is_mobile() && !$is_mobile) {
				self::set_nocache('is not mobile'); // todo: no need to uncache, it will correct vary value in vary finalize anyways
				return;
			}
		} elseif (wp_is_mobile() || $is_mobile) {
			self::set_nocache('is mobile');
			return;
		}
	}

	/**
	 * Check if is mobile for filter `litespeed_is_mobile` in API
	 *
	 * @since 3.0
	 * @access public
	 */
	public static function is_mobile() {
		return wp_is_mobile();
	}

	/**
	 * Get request method w/ compatibility to X-Http-Method-Override
	 *
	 * @since 6.2
	 */
	private function _get_req_method() {
		if (isset($_SERVER['HTTP_X_HTTP_METHOD_OVERRIDE'])) {
			self::debug('X-Http-Method-Override -> ' . $_SERVER['HTTP_X_HTTP_METHOD_OVERRIDE']);
			defined('LITESPEED_X_HTTP_METHOD_OVERRIDE') || define('LITESPEED_X_HTTP_METHOD_OVERRIDE', true);
			return $_SERVER['HTTP_X_HTTP_METHOD_OVERRIDE'];
		}
		if (isset($_SERVER['REQUEST_METHOD'])) {
			return $_SERVER['REQUEST_METHOD'];
		}
		return 'unknown';
	}

	/**
	 * Check if a page is cacheable based on litespeed setting.
	 *
	 * @since 1.0.0
	 * @access private
	 * @return boolean True if cacheable, false otherwise.
	 */
	private function _setting_cacheable() {
		// logged_in users already excluded, no hook added

		if (!empty($_REQUEST[Router::ACTION])) {
			return $this->_no_cache_for('Query String Action');
		}

		$method = $this->_get_req_method();
		if (defined('LITESPEED_X_HTTP_METHOD_OVERRIDE') && LITESPEED_X_HTTP_METHOD_OVERRIDE && $method == 'HEAD') {
			return $this->_no_cache_for('HEAD method from override');
		}
		if ('GET' !== $method && 'HEAD' !== $method) {
			return $this->_no_cache_for('Not GET method: ' . $method);
		}

		if (is_feed() && $this->conf(Base::O_CACHE_TTL_FEED) == 0) {
			return $this->_no_cache_for('feed');
		}

		if (is_trackback()) {
			return $this->_no_cache_for('trackback');
		}

		if (is_search()) {
			return $this->_no_cache_for('search');
		}

		// if ( !defined('WP_USE_THEMES') || !WP_USE_THEMES ) {
		// return $this->_no_cache_for('no theme used');
		// }

		// Check private cache URI setting
		$excludes = $this->conf(Base::O_CACHE_PRIV_URI);
		$result   = Utility::str_hit_array($_SERVER['REQUEST_URI'], $excludes);
		if ($result) {
			self::set_private('Admin cfg Private Cached URI: ' . $result);
		}

		if (!self::is_forced_cacheable()) {
			// Check if URI is excluded from cache
			$excludes = $this->cls('Data')->load_cache_nocacheable($this->conf(Base::O_CACHE_EXC));
			$result   = Utility::str_hit_array($_SERVER['REQUEST_URI'], $excludes);
			if ($result) {
				return $this->_no_cache_for('Admin configured URI Do not cache: ' . $result);
			}

			// Check QS excluded setting
			$excludes = $this->conf(Base::O_CACHE_EXC_QS);
			if (!empty($excludes) && ($qs = $this->_is_qs_excluded($excludes))) {
				return $this->_no_cache_for('Admin configured QS Do not cache: ' . $qs);
			}

			$excludes = $this->conf(Base::O_CACHE_EXC_CAT);
			if (!empty($excludes) && has_category($excludes)) {
				return $this->_no_cache_for('Admin configured Category Do not cache.');
			}

			$excludes = $this->conf(Base::O_CACHE_EXC_TAG);
			if (!empty($excludes) && has_tag($excludes)) {
				return $this->_no_cache_for('Admin configured Tag Do not cache.');
			}

			$excludes = $this->conf(Base::O_CACHE_EXC_COOKIES);
			if (!empty($excludes) && !empty($_COOKIE)) {
				$cookie_hit = array_intersect(array_keys($_COOKIE), $excludes);
				if ($cookie_hit) {
					return $this->_no_cache_for('Admin configured Cookie Do not cache.');
				}
			}

			$excludes = $this->conf(Base::O_CACHE_EXC_USERAGENTS);
			if (!empty($excludes) && isset($_SERVER['HTTP_USER_AGENT'])) {
				$nummatches = preg_match(Utility::arr2regex($excludes), $_SERVER['HTTP_USER_AGENT']);
				if ($nummatches) {
					return $this->_no_cache_for('Admin configured User Agent Do not cache.');
				}
			}

			// Check if is exclude roles ( Need to set Vary too )
			if ($result = $this->in_cache_exc_roles()) {
				return $this->_no_cache_for('Role Excludes setting ' . $result);
			}
		}

		return true;
	}

	/**
	 * Write a debug message for if a page is not cacheable.
	 *
	 * @since 1.0.0
	 * @access private
	 * @param string $reason An explanation for why the page is not cacheable.
	 * @return boolean Return false.
	 */
	private function _no_cache_for( $reason ) {
		self::debug('X Cache_control off - ' . $reason);
		return false;
	}

	/**
	 * Check if current request has qs excluded setting
	 *
	 * @since  1.3
	 * @access private
	 * @param  array $excludes QS excludes setting
	 * @return boolean|string False if not excluded, otherwise the hit qs list
	 */
	private function _is_qs_excluded( $excludes ) {
		if (!empty($_GET) && ($intersect = array_intersect(array_keys($_GET), $excludes))) {
			return implode(',', $intersect);
		}
		return false;
	}
}
