<?php
/* vim:set tabstop=8 softtabstop=8 shiftwidth=8 noexpandtab: */
/**
 * database_object Class
 *
 * PHP version 5
 *
 * LICENSE: GNU General Public License, version 2 (GPLv2)
 * Copyright (c) 2001 - 2011 Ampache.org All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License v2
 * as published by the Free Software Foundation.
 *
 * 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.
 *
 * @category	database_object
 * @package	Ampache
 * @author	Karl Vollmer <vollmer@ampache.org>
 * @copyright	2001 - 2011 Ampache.org
 * @license	http://opensource.org/licenses/gpl-2.0 GPLv2
 * @version	PHP 5.2
 * @link	http://www.ampache.org/
 * @since	File available since Release 1.0
 */

/**
 * database_object
 *
 * This is a general object that is extended by all of the basic
 * database based objects in ampache. It attempts to do some standard
 * caching for all of the objects to cut down on the database calls
 *
 * @category	database_object
 * @package	Ampache
 * @author	Karl Vollmer <vollmer@ampache.org>
 * @copyright	2001 - 2011 Ampache.org
 * @license	http://opensource.org/licenses/gpl-2.0 GPLv2
 * @version	Release: 3.6
 * @link	http://www.ampache.org/
 * @since	Class available since Release 1.0
 * @abstract
 */
abstract class database_object {

	private static $object_cache = array();

	// Statistics for debugging
	public static $cache_hit = 0;
	private static $_enabled = false;

	/**
	 * get_info
	 * retrieves the info from the database and puts it in the cache
	 */
	public function get_info($id,$table_name='') {

		$table_name = $table_name ? Dba::escape($table_name) : Dba::escape(strtolower(get_class($this)));

		// Make sure we've got a real id
		if (!is_numeric($id)) { return array(); }

		if (self::is_cached($table_name,$id)) {
			return self::get_from_cache($table_name,$id);
		}

		$sql = "SELECT * FROM `$table_name` WHERE `id`='$id'";
		$db_results = Dba::read($sql);

		if (!$db_results) { return array(); }

		$row = Dba::fetch_assoc($db_results);

		self::add_to_cache($table_name,$id,$row);

		return $row;

	} // get_info

	/**
	 * is_cached
	 * this checks the cache to see if the specified object is there
	 */
	public static function is_cached($index,$id) {

		// Make sure we've got some parents here before we dive below
		if (!isset(self::$object_cache[$index])) { return false; }

		return isset(self::$object_cache[$index][$id]);

	} // is_cached

	/**
	 * get_from_cache
	 * This attempts to retrive the specified object from the cache we've got here
	 */
	public static function get_from_cache($index,$id) {

		// Check if the object is set
		if (isset(self::$object_cache[$index])
			&& isset(self::$object_cache[$index][$id])
			) {

			self::$cache_hit++;
			return self::$object_cache[$index][$id];
		}

		return false;

	} // get_from_cache

	/**
	 * add_to_cache
	 * This adds the specified object to the specified index in the cache
	 */
	public static function add_to_cache($index,$id,$data) {

		if (!self::$_enabled) { return false; }

		$value = is_null($data) ? false : $data;
		self::$object_cache[$index][$id] = $value;

	} // add_to_cache

	/**
	 * remove_from_cache
	 * This function clears something from the cache, there are a few places we need to do this
	 * in order to have things display correctly
	 */
	public static function remove_from_cache($index,$id) {

		if (isset(self::$object_cache[$index]) && isset(self::$object_cache[$index][$id])) {
			unset(self::$object_cache[$index][$id]);
		}

	} // remove_from_cache

	/**
	 * _auto_init
	 * Load in the cache settings once so we can avoid function calls
	 */
	public static function _auto_init() {

		self::$_enabled = Config::get('memory_cache');

	} // _auto_init

} // end database_object