Cache-powered ORM model extension (Kohana 3.3) - [!!] Not tested

Cached.php

<?php defined('SYSPATH') or die('No direct script access.');
/**
 * Extend this class if you want your model cached. Example usage:
 * 
 * 1. Model
 *    class Model_User extends ORM_Cached {}
 * 
 * 2. Usage
 * 
 *    // This will either retrieve the user with specified ID from cache
 *    // or get him from the database and cache him anyways
 *    $user = Model_User::cache($this->request->param('id'));
 * 
 *    // This will get the user with username "Jason" and email "jason@nosaj.com"
 *    // and also save him by these params (not the PK)
 *    $user = Model_User::cache(array('username' => 'Jason','email' => 'jason@nosaj.com'));
 *
 *    // Now if we update this user, related cache will also be updated
 *    $user->set('password' => 'test')->update();
 *
 *    // And if we delete this user, related cache will also be deleted
 *    $user->delete();
 * 
 * @package ORM
 * @author  Kemal Delalic <kemal.delalic@gmail.com>
 */
class ORM_Cached extends ORM {
	
	/**
	 * @var string Default cache group, e.g. 'file' or 'memcached'
	 */
	protected static $_cacher_driver = 'apc';
	
	/**
	 * @var int For how long should the cache for current model last?
	 */
	protected static $_cacher_lifetime = 60;
	
	/**
	 * List of columns to be serialized when going to 'sleep'
	 * 
	 * @var array
	 * @see http://php.net/serializable
	 */
	protected static $_serialized_columns = array(
		'_cache_loader_key',
		'_primary_key_value',
		'_object', 
		'_changed', 
		'_loaded', 
		'_saved', 
		'_sorting', 
		'_original_values',
	);

	/**
	 * Cached "factory" method
	 *
	 *   $post = Model_User::cache($request->param('id'));
	 *
	 * @param  mixed  $id primary key or array of values to be matched
	 * @return ORM_Cached
	 */
	public static function cache($id)
	{
		$model     = get_called_class();
		$cache_key = static::cache_key($model, $id);
		
		if ( ! $object = static::cacher()->get($cache_key))
		{
			$object = new $model($id);
			
			// Only save the object cache if its' loaded
			if ($object->loaded())
			{
				// Save the loader key into the object (to use when deleting the cache)
				$object->cache_loader_key($cache_key);
				
				// Save this objects' cache
				static::save_cache($object);
			}
		}
		
		return $object;
	}

	/**
	 * Retrieves the cache driver for current model
	 *
	 * @return Cache
	 */
	public static function cacher()
	{
		return Cache::instance(static::$_cacher_driver);
	}

	/**
	 * Returns the cache key for ORM_Cached::cache()
	 *
	 * @param  string $model
	 * @param  mixed  $id
	 * @return string
	 */
	public static function cache_key($model, $id)
	{
		if (is_array($id))
		{
			// Sort the passed array keys for consistency
			ksort($id);
			
			$id = http_build_query($id, '', '::');
		}
		elseif (Valid::digit($id))
		{
			// Make sure the key is a string to have consistent cache keys
			$id = (string) $id;
		}
		elseif ( ! is_string($id))
		{
			throw new Kohana_Exception('Unsupported $id type: :type', 
				array(':type' => gettype($id)));
		}
		
		return $model.':::'.$id;
	}
	
	/**
	 * Deletes the cache for passed ORM_Cached object
	 *
	 * @param ORM_Cached $object
	 * @return void
	 */
	public static function delete_cache(ORM_Cached $object)
	{
		if ($key = $object->cache_loader_key())
		{
			static::cacher()->delete($key);
		}
	}
	
	/**
	 * Saves the cache for passed ORM object
	 *
	 * @param ORM $object
	 * @return void
	 */
	public static function save_cache(ORM_Cached $object)
	{
		if ($key = $object->cache_loader_key())
		{
			static::cacher()->set($key, $object, static::$_cacher_lifetime);
		}
	}
	
	/**
	 * @var string  The key current object was loaded with, if any
	 */
	protected $_cache_loader_key;

	/**
	 * @var boolean Should table columns be reloaded on wakeup?
	 */
	protected $_reload_on_wakeup = FALSE;
	
	/**
	 * ORM contructor overloaded to auto-assign a cache key if none provided
	 * 
	 * @param mixed $id
	 */
	public function __construct($id = NULL)
	{
		parent::__construct($id);
		
		// If the current record has been loaded and no cache key is set,
		// use the primary key for creating a cache key
		if ($this->_loaded AND ! $this->cache_loader_key())
		{
			$this->cache_loader_key(static::cache_key(get_class($this), $this->pk()));
		}
	}
	
	/**
	 * Cache loader key setter / getter
	 * 
	 * @param  mixed $key to set
	 * @return string|self 
	 * @chainable (on set)
	 */
	public function cache_loader_key($key = NULL)
	{
		if ($key === NULL)
			return $this->_cache_loader_key;
			
		$this->_cache_loader_key = $key;
		
		return $this;
	}
	
	/**
	 * Overloaded create method
	 * Once the object is created, cache will be saved
	 *
	 * @param  Validation $validation
	 * @return $this (chainable)
	 */
	public function create(Validation $validation = NULL)
	{
		$result = parent::create($validation);
		
		// Assign the cache loader key now that we have the primary key
		$this->cache_loader_key(static::cache_key(get_called_class(), $this->pk()));
		
		// Save the cache for this object
		static::save_cache($this);
		
		return $result;
	}
	
	/**
	 * Delete override with cache support
	 *
	 * @chainable
	 * @return $this
	 */
	public function delete()
	{
		static::delete_cache($this);
		
		return parent::delete();
	}

	/**
	 * Proxy method to Database list_columns.
	 *
	 * @cached
	 * @return array
	 */
	public function list_columns()
	{
		$cache_key = "{$this->_table_name}::list_columns()";
		
		if ( ! $columns = ORM_Cached::cacher()->get($cache_key))
		{
			$columns = $this->_db->list_columns($this->_table_name);
			
			ORM_Cached::cacher()->set($cache_key, $columns, Date::MINUTE);
		}
		
		return $columns;
	}

	/**
	 * Allows serialization of only the object data and state, to prevent
	 * "stale" objects being unserialized, which also requires less memory.
	 *
	 * @return array
	 */
	public function serialize()
	{
		$data = array();
		
		// Store only information about the object
		foreach (static::$_serialized_columns as $var)
		{
			$data[$var] = $this->{$var};
		}

		return serialize($data);
	}
	
	/**
	 * Update override with cache support
	 *
	 * @param  Validation $validation
	 * @return $this
	 * @throws ORM_Validation_Exception
	 */
	public function update(Validation $validation = NULL)
	{
		$result = parent::update($validation);
		
		static::save_cache($this);
		
		return $result;
	}
	
}