<?php


/**
 * Advanced_Sidebar_Menu_Cache
 *
 * @author Mat Lipe
 * @since  12/19/2015
 *
 */
class Advanced_Sidebar_Menu_Cache {
	const CACHE_GROUP = 'advanced-sidebar-menu';
	const CHILD_PAGES_KEY = 'child-pages';


	protected function hook() {
		add_action( 'save_post', array( $this, 'clear_cache_group' ) );
	}


	/**
	 * Clear all of items in this cache group
	 *
	 * @return void
	 */
	public function clear_cache_group() {
		if( function_exists( 'wp_cache_get_last_changed' ) ){
			wp_cache_set( 'last_changed', microtime(), self::CACHE_GROUP . ':' . ADVANCED_SIDEBAR_BASIC_VERSION );
		} else {
			wp_cache_delete( self::CHILD_PAGES_KEY, $this->get_cache_group() );
		}
	}


	/**
	 * Get unique key for this group
	 * Use wp_cache_get_last_changed() if on WP 4.7+
	 *
	 * @return string
	 */
	public function get_cache_group() {
		$key = '';
		if( function_exists( 'wp_cache_get_last_changed' ) ){
			$key = wp_cache_get_last_changed( self::CACHE_GROUP . ':' . ADVANCED_SIDEBAR_BASIC_VERSION );
		}

		return self::CACHE_GROUP . ':' . ADVANCED_SIDEBAR_BASIC_VERSION . ':' . $key;
	}


	/**
	 * Retrieve a posts child pages from the cache
	 * If no exist in the cache will return false
	 *
	 * @param Advanced_Sidebar_Menu_Menu|Advanced_Sidebar_Menu_List_Pages $class
	 *
	 * @return array|false
	 */
	public function get_child_pages( $class ) {
		$key = $this->get_key_from_asm( $class );
		$all_child_pages = (array) wp_cache_get( self::CHILD_PAGES_KEY, $this->get_cache_group() );
		if( isset( $all_child_pages[ $key ] ) ){
			return $all_child_pages[ $key ];
		}
		return false;
	}


	/**
	 * Add a post and its children to the cache
	 * Uses a global key for all posts so this appends to an array
	 *
	 * @param Advanced_Sidebar_Menu_Menu|Advanced_Sidebar_Menu_List_Pages $class
	 * @param array                                                       $child_pages
	 *
	 * @return void
	 */
	public function add_child_pages( $class, $child_pages ) {
		$key = $this->get_key_from_asm( $class );
		$all_child_pages = (array) wp_cache_get( self::CHILD_PAGES_KEY, $this->get_cache_group() );
		$all_child_pages[ $key ] = $child_pages;
		wp_cache_set( self::CHILD_PAGES_KEY, $all_child_pages, $this->get_cache_group() );
	}


	/**
	 * There are many possibilities for properties
	 * set to the object used for generations.
	 * To guarantee we have a unique id for the cache
	 * we serialize the whole object and hash it
	 *
	 *
	 * @param Advanced_Sidebar_Menu_Menu|Advanced_Sidebar_Menu_List_Pages $class
	 *
	 * @return string
	 */
	private function get_key_from_asm( $class ) {
		$string = serialize( $class );
		return md5( $string );
	}


	//********** SINGLETON FUNCTIONS **********/


	/**
	 * Instance of this class for use as singleton
	 */
	private static $instance;


	/**
	 * Create the instance of the class
	 *
	 * @static
	 * @return void
	 */
	public static function init() {
		self::instance()->hook();
	}


	/**
	 * Get (and instantiate, if necessary) the instance of the
	 * class
	 *
	 * @static
	 * @return self
	 */
	public static function instance() {
		if( !is_a( self::$instance, __CLASS__ ) ){
			self::$instance = new self();
		}

		return self::$instance;
	}
}