/wp-content/mu-plugins/pantheon/pantheon-cache.php

<?php
/*	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
class Pantheon_Cache {

	/**
	 * Define the capability required to see and modify the settings page.
	 *
	 * @var string
	 */
	public $options_capability = 'manage_options';

	/**
	 * Define the default options, which are overridden by what's in wp_options.
	 *
	 * @var array
	 */
	public $default_options = array();

	/**
	 * Stores the options for this plugin (from wp_options).
	 *
	 * @var array
	 */
	public $options = array();

	/**
	 * Store the Paths to be flushed at shutdown.
	 *
	 * @var array
	 */
	public $paths = array();

	/**
	 * The slug for the plugin, used in various places like the options page.
	 */
	const SLUG = 'pantheon-cache';

	/**
	 * Holds the singleton instance.
	 *
	 * @static
	 * @var object
	 */
	protected static $instance;

	/**
	 * Get a reference to the singleton.
	 *
	 * @return object The singleton instance.
	 */
	public static function instance() {
		if ( ! isset( self::$instance ) ) {
			self::$instance = new Pantheon_Cache;
			self::$instance->setup();
		}
		return self::$instance;
	}

	protected function __construct() {
		/** Don't do anything **/
	}


	/**
	 * Setup the actions and filters we need to hook into, and initialize any properties we need.
	 *
	 * @return void
	 */
	protected function setup() {
		$this->options = get_option( self::SLUG, array() );
		$this->default_options = array(
			'default_ttl' => 600
		);
		$this->options = wp_parse_args( $this->options, $this->default_options );

		add_action( 'admin_init', array( $this, 'action_admin_init' ) );
		add_action( 'admin_menu', array( $this, 'action_admin_menu' ) );

		add_action( 'clean_post_cache',                      array( $this, 'clean_post_cache' ) );
		add_action( 'clean_term_cache',                      array( $this, 'clean_term_cache' ), 10, 2 );
		add_action( 'admin_post_pantheon_cache_delete_page', array( $this, 'clean_specific_page' ) );
		add_action( 'admin_post_pantheon_cache_flush_site',  array( $this, 'flush_site' ) );

		if ( ! is_admin() ) {
			add_action( 'send_headers',               array( $this, 'cache_add_headers' ) );
			add_action( 'wp_before_admin_bar_render', array( $this, 'cache_admin_bar_render' ) );
		}

		add_action( 'shutdown', array( $this, 'cache_clean_urls' ), 999 );
	}


	/**
	 * Prep the Settings API.
	 *
	 * @return void
	 */
	public function action_admin_init() {
		register_setting( self::SLUG, self::SLUG, array( self::$instance, 'sanitize_options' ) );
		add_settings_section( 'general', false, '__return_false', self::SLUG );
		add_settings_field( 'default_ttl', __( 'Default Cache Time', 'pantheon-cache' ), array( self::$instance, 'default_ttl_field' ), self::SLUG, 'general' );
	}


	/**
	 * Add the settings page to the menu.
	 *
	 * @return void
	 */
	public function action_admin_menu() {
		add_options_page( __( 'Pantheon Cache', 'pantheon-cache' ), __( 'Pantheon Cache', 'pantheon-cache' ), $this->options_capability, self::SLUG, array( self::$instance, 'view_settings_page' ) );
	}


	/**
	 * Add the HTML for the default TTL field.
	 *
	 * @return void
	 */
	public function default_ttl_field() {
		echo '<input type="text" name="' . self::SLUG . '[default_ttl]" value="' . $this->options['default_ttl'] . '" size="5" /> ' . __( 'seconds', 'pantheon-cache' );
	}


	/**
	 * Sanitize our options.
	 *
	 * @param  array $in The POST values.
	 * @return array     The sanitized POST values.
	 */
	public function sanitize_options( $in ) {
		$out = $this->default_options;

		// Validate default_ttl
		$out['default_ttl'] = absint( $in['default_ttl'] );
		if ( ! $out['default_ttl'] )
			$out['default_ttl'] = 600;

		return $out;
	}


	/**
	 * Output the settings page.
	 *
	 * @return void
	 */
	public function view_settings_page() {
		?>
		<div class="wrap">
			<h2><?php _e( 'Pantheon Cache', 'pantheon-cache' ); ?></h2>

			<?php if ( ! empty( $_GET['cache-cleared'] ) && 'true' == $_GET['cache-cleared'] ) : ?>
				<div class="updated below-h2">
					<p><?php esc_html_e( 'Site cache flushed.', 'pantheon-cache' ); ?></p>
				</div>
			<?php endif ?>

			<h3><?php _e( 'General Settings', 'pantheon-cache' ); ?></h3>
			<form action="options.php" method="POST">
				<?php settings_fields( self::SLUG ); ?>
				<?php do_settings_sections( self::SLUG ); ?>
				<?php submit_button(); ?>
			</form>

			<?php if ( apply_filters( 'pantheon_cache_allow_clear_all', true ) ) : ?>

				<hr />

				<form action="admin-post.php" method="POST">
					<input type="hidden" name="action" value="pantheon_cache_flush_site" />
					<?php wp_nonce_field( 'pantheon-cache-clear-all', 'pantheon-cache-nonce' ); ?>
					<h3><?php _e( 'Clear Site Cache', 'pantheon-cache' ); ?></h3>
					<p><?php _e( "Clear the cache for the entire site. Use with care, as it will negatively impact your site's performance for a short period of time.", 'pantheon-cache' ); ?></p>
					<?php submit_button( __( 'Clear Cache', 'pantheon-cache' ), 'secondary' ); ?>
				</form>

			<?php endif ?>
		</div>
		<?php
	}


	/**
	 * Add the cache-control header.
	 *
	 * @return void
	 */
	public function cache_add_headers() {
		$ttl = absint( $this->options['default_ttl'] );
		if ( $ttl < 60 )
			$ttl = 600;

		header( 'cache-control: public, max-age=' . $ttl );
	}


	/**
	 * Add the "Delete Cache" button to the admin bar.
	 *
	 * @return void
	 */
	public function cache_admin_bar_render() {
		global $wp_admin_bar;

		if ( ! is_user_logged_in() )
			return false;

		if ( function_exists( 'current_user_can' ) && false == current_user_can( 'delete_others_posts' ) )
			return false;

		$wp_admin_bar->add_menu( array(
			'parent' => '',
			'id' => 'delete-cache',
			'title' => __( 'Delete Cache', 'pantheon-cache' ),
			'meta' => array( 'title' => __( 'Delete cache of the current page', 'pantheon-cache' ) ),
			'href' => wp_nonce_url( admin_url( 'admin-post.php?action=pantheon_cache_delete_page&path=' . urlencode( preg_replace( '/[ <>\'\"\r\n\t\(\)]/', '', $_SERVER[ 'REQUEST_URI' ] ) ) ), 'delete-cache' )
		) );
	}


	/**
	 * Clear a specific path from cache. This handles the action from the admin bar button.
	 *
	 * @return void
	 */
	public function clean_specific_page() {
		if ( ! function_exists( 'current_user_can' ) || false == current_user_can( 'delete_others_posts' ) )
			return false;

		if ( ! empty( $_REQUEST[ '_wpnonce' ] ) && wp_verify_nonce( $_REQUEST[ '_wpnonce' ], 'delete-cache' ) ) {
			$this->enqueue_urls( $_REQUEST['path'] );
			wp_redirect( preg_replace( '/[ <>\'\"\r\n\t\(\)]/', '', $_REQUEST['path'] ) );
			exit();
		}
	}


	/**
	 * Clear the cache for the entire site.
	 *
	 * @return void
	 */
	public function flush_site() {
		if ( ! function_exists( 'current_user_can' ) || false == current_user_can( 'manage_options' ) )
			return false;

		if ( ! empty( $_POST['pantheon-cache-nonce'] ) && wp_verify_nonce( $_POST['pantheon-cache-nonce'], 'pantheon-cache-clear-all' ) ) {
			$this->enqueue_regex( '/.*' );
			wp_redirect( admin_url( 'options-general.php?page=pantheon-cache&cache-cleared=true' ) );
			exit();
		}
	}


	/**
	 * Clear the cache for a post.
	 *
	 * @param  int $post_id A post ID to clean.
	 * @return void
	 */
	public function clean_post_cache( $post_id, $include_homepage = true ) {
		if ( get_post_type( $post_id ) == 'revision' || get_post_status( $post_id ) != 'publish' )
			return;

		$urls = array();
		$post_link = get_permalink( $post_id );
		if ( $post_link ) {
			$urls[] = $post_link;
		}

		if ( $include_homepage ) {
			$urls[] = get_option( 'home' );
			$urls[] = trailingslashit( get_option( 'home' ) );
		}

		$urls = apply_filters( 'pantheon_clean_post_cache', $urls, $post_id, $include_homepage );
		$this->enqueue_urls( $urls );
	}


	/**
	 * Clear the cache for a given term or terms and taxonomy.
	 *
	 * @param int|array $ids Single or list of Term IDs.
	 * @param string $taxonomy Can be empty and will assume tt_ids, else will use for context.
	 * @return void
	 */
	public function clean_term_cache( $term_ids, $taxonomy ) {
		$urls = array();

		foreach ( (array) $term_ids as $term_id ) {
			$term_link = get_term_link( intval( $term_id ), $taxonomy );
			if ( ! is_wp_error( $term_link ) ) {
				$urls[] = $term_link;
			}
		}

		$urls = apply_filters( 'pantheon_clean_term_cache', $urls, $term_ids, $taxonomy );
		$this->enqueue_urls( $urls );
	}


	/**
	 * Clear the cache for a given term or terms and taxonomy.
	 *
	 * This is a placeholder and is not currently active.
	 *
	 * @param int|array $object_ids Single or list of term object ID(s).
	 * @param array|string $object_type The taxonomy object type.
	 * @return void
	 */
	public function clean_object_term_cache( $object_ids, $object_type ) {
		$urls = array();
		if ( post_type_exists( $object_type ) ) {
			foreach ( (array) $object_ids as $post_id ) {
				$urls[] = get_permalink( $post_id );
			}
		}

		global $wp_rewrite;
		$taxonomies = get_object_taxonomies( $object_type );
		foreach ( $taxonomies as $taxonomy ) {
			$termlink = $wp_rewrite->get_extra_permastruct( $taxonomy );
			# Let's make sure that the taxonomy doesn't have a root-level permalink,
			# which is unlikely, but possible. If it did, this would clear the whole site.
			if ( preg_match( "#^.+/%$taxonomy%#i", $termlink ) ) {
				$urls[] = str_replace( "%$taxonomy%", '.*', $termlink );
			}
		}

		$urls = apply_filters( 'pantheon_clean_object_term_cache', $urls, $object_ids, $object_type );
		$this->enqueue_urls( $urls );
	}

	/**
	 * Enqueue Fully-qualified urls to be cleared on shutdown.
	 *
	 * @param array|string $urls List of full urls to clear.
	 * @return void
	 */
	public function enqueue_urls( $urls ) {
	  $paths = array();
		$urls = array_filter( (array) $urls, 'is_string' );
		foreach ( $urls as $full_url ) {
			# Parse down to the path+query, escape regex.
			$parsed = parse_url( $full_url );
			$path = $parsed['path'] . $parsed['query'];
			if ( '' == $path ) {
				continue;
			}
			$path = '^' . preg_quote( $path ) . '$';
			$paths[] = $path;
		}

		$this->paths = array_merge( $this->paths, $paths );
	}

	/**
	 * Enqueue a regex to be cleared.
	 *
	 * You must understand regular expressions to use this, and be careful.
	 *
	 * @param string $regex path regex to clear.
	 * @return void
	 */
	public function enqueue_regex( $regex ) {
		$this->paths[] = $regex;
	}


	public function cache_clean_urls() {
		if ( empty( $this->paths ) )
			return;

		$this->paths = apply_filters( 'pantheon_clean_urls', array_unique( $this->paths ) );

		# Call the big daddy here
		$url = home_url();
		$host = parse_url( $url, PHP_URL_HOST );
		$this->paths = apply_filters( 'pantheon_final_clean_urls', $this->paths );
		if ( function_exists( 'pantheon_clear_edge' ) ) {
			pantheon_clear_edge( $host, $this->paths );
		}
	}
}



/**
 * Get a reference to the singleton.
 *
 * This can be used to reference public methods, e.g. `Pantheon_Cache()->clean_post_cache( 123 )`
 *
 * @return void
 */
function Pantheon_Cache() {
	return Pantheon_Cache::instance();
}
add_action( 'plugins_loaded', 'Pantheon_Cache' );


/**
 * @see Pantheon_Cache::clean_post_cache
 */
function pantheon_clean_post_cache( $post_id, $include_homepage = true ) {
	Pantheon_Cache()->clean_post_cache( $post_id, $include_homepage );
}


/**
 * @see Pantheon_Cache::clean_term_cache
 */
function pantheon_clean_term_cache( $term_ids, $taxonomy ) {
	Pantheon_Cache()->clean_term_cache( $term_ids, $taxonomy );
}


/**
 * @see Pantheon_Cache::enqueue_urls
 */
function pantheon_enqueue_urls( $urls ) {
	Pantheon_Cache()->enqueue_urls( $urls );
}