<?php
  /**
   * Container for all PDO-based cache methods. Inherits additional methods from <CacheCore>. Adheres
   * to the ICacheCore interface.
   *
   * @version 2012.04.17
   * @copyright 2006-2012 Ryan Parman
   * @copyright 2006-2010 Foleeo, Inc.
   * @copyright 2012 Amazon.com, Inc. or its affiliates.
   * @copyright 2008-2010 Contributors
   * @license http://opensource.org/licenses/bsd-license.php Simplified BSD License
   * @link http://github.com/skyzyx/cachecore CacheCore
   * @link http://getcloudfusion.com CloudFusion
   * @link http://php.net/pdo PDO
   */
  class CachePDO extends CacheCore implements ICacheCore
  {
  	/**
  	 * Reference to the PDO connection object.
  	 */
  	var $pdo = null;
  
  	/**
  	 * Holds the parsed URL components.
  	 */
  	var $dsn = null;
  
  	/**
  	 * Holds the PDO-friendly version of the connection string.
  	 */
  	var $dsn_string = null;
  
  	/**
  	 * Holds the prepared statement for creating an entry.
  	 */
  	var $create = null;
  
  	/**
  	 * Holds the prepared statement for reading an entry.
  	 */
  	var $read = null;
  
  	/**
  	 * Holds the prepared statement for updating an entry.
  	 */
  	var $update = null;
  
  	/**
  	 * Holds the prepared statement for resetting the expiry of an entry.
  	 */
  	var $reset = null;
  
  	/**
  	 * Holds the prepared statement for deleting an entry.
  	 */
  	var $delete = null;
  
  	/**
  	 * Holds the response of the read so we only need to fetch it once instead of doing
  	 * multiple queries.
  	 */
  	var $store_read = null;
  
  
  	/*%******************************************************************************************%*/
  	// CONSTRUCTOR
  
  	/**
  	 * Constructs a new instance of this class.
  	 *
  	 * Tested with [MySQL 5.0.x](http://mysql.com), [PostgreSQL](http://postgresql.com), and
  	 * [SQLite 3.x](http://sqlite.org). SQLite 2.x is assumed to work. No other PDO-supported databases have
  	 * been tested (e.g. Oracle, Microsoft SQL Server, IBM DB2, ODBC, Sybase, Firebird). Feel free to send
  	 * patches for additional database support.
  	 *
  	 * See <http://php.net/pdo> for more information.
  	 *
  	 * @param string $name (Required) A name to uniquely identify the cache object.
  	 * @param string $location (Optional) The location to store the cache object in. This may vary by cache method. The default value is NULL.
  	 * @param integer $expires (Optional) The number of seconds until a cache object is considered stale. The default value is 0.
  	 * @param boolean $gzip (Optional) Whether data should be gzipped before being stored. The default value is true.
  	 * @return object Reference to the cache object.
  	 */
  	public function __construct($name, $location = null, $expires = 0, $gzip = true)
  	{
  		// Make sure the name is no longer than 40 characters.
  		$name = sha1($name);
  
  		// Call parent constructor and set id.
  		parent::__construct($name, $location, $expires, $gzip);
  		$this->id = $this->name;
  		$options = array();
  
  		// Check if the location contains :// (e.g. mysql://user:pass@hostname:port/table)
  		if (stripos($location, '://') === false)
  		{
  			// No? Just pass it through.
  			$this->dsn = parse_url($location);
  			$this->dsn_string = $location;
  		}
  		else
  		{
  			// Yes? Parse and set the DSN
  			$this->dsn = parse_url($location);
  			$this->dsn_string = $this->dsn['scheme'] . ':host=' . $this->dsn['host'] . ((isset($this->dsn['port'])) ? ';port=' . $this->dsn['port'] : '') . ';dbname=' . substr($this->dsn['path'], 1);
  		}
  
  		// Make sure that user/pass are defined.
  		$user = isset($this->dsn['user']) ? $this->dsn['user'] : null;
  		$pass = isset($this->dsn['pass']) ? $this->dsn['pass'] : null;
  
  		// Set persistence for databases that support it.
  		switch ($this->dsn['scheme'])
  		{
  			case 'mysql': // MySQL
  			case 'pgsql': // PostgreSQL
  				$options[PDO::ATTR_PERSISTENT] = true;
  				break;
  		}
  
  		// Instantiate a new PDO object with a persistent connection.
  		$this->pdo = new PDO($this->dsn_string, $user, $pass, $options);
  
  		// Define prepared statements for improved performance.
  		$this->create = $this->pdo->prepare("INSERT INTO cache (id, expires, data) VALUES (:id, :expires, :data)");
  		$this->read = $this->pdo->prepare("SELECT id, expires, data FROM cache WHERE id = :id");
  		$this->reset = $this->pdo->prepare("UPDATE cache SET expires = :expires WHERE id = :id");
  		$this->delete = $this->pdo->prepare("DELETE FROM cache WHERE id = :id");
  	}
  
  	/**
  	 * Creates a new cache.
  	 *
  	 * @param mixed $data (Required) The data to cache.
  	 * @return boolean Whether the operation was successful.
  	 */
  	public function create($data)
  	{
  		$data = serialize($data);
  		$data = $this->gzip ? gzcompress($data) : $data;
  
  		$this->create->bindParam(':id', $this->id);
  		$this->create->bindParam(':data', $data);
  		$this->create->bindParam(':expires', $this->generate_timestamp());
  
  		return (bool) $this->create->execute();
  	}
  
  	/**
  	 * Reads a cache.
  	 *
  	 * @return mixed Either the content of the cache object, or boolean `false`.
  	 */
  	public function read()
  	{
  		if (!$this->store_read)
  		{
  			$this->read->bindParam(':id', $this->id);
  			$this->read->execute();
  			$this->store_read = $this->read->fetch(PDO::FETCH_ASSOC);
  		}
  
  		if ($this->store_read)
  		{
  			$data = $this->store_read['data'];
  			$data = $this->gzip ? gzuncompress($data) : $data;
  
  			return unserialize($data);
  		}
  
  		return false;
  	}
  
  	/**
  	 * Updates an existing cache.
  	 *
  	 * @param mixed $data (Required) The data to cache.
  	 * @return boolean Whether the operation was successful.
  	 */
  	public function update($data)
  	{
  		$this->delete();
  		return $this->create($data);
  	}
  
  	/**
  	 * Deletes a cache.
  	 *
  	 * @return boolean Whether the operation was successful.
  	 */
  	public function delete()
  	{
  		$this->delete->bindParam(':id', $this->id);
  		return $this->delete->execute();
  	}
  
  	/**
  	 * Checks whether the cache object is expired or not.
  	 *
  	 * @return boolean Whether the cache is expired or not.
  	 */
  	public function is_expired()
  	{
  		if ($this->timestamp() + $this->expires < time())
  		{
  			return true;
  		}
  
  		return false;
  	}
  
  	/**
  	 * Retrieves the timestamp of the cache.
  	 *
  	 * @return mixed Either the Unix time stamp of the cache creation, or boolean `false`.
  	 */
  	public function timestamp()
  	{
  		if (!$this->store_read)
  		{
  			$this->read->bindParam(':id', $this->id);
  			$this->read->execute();
  			$this->store_read = $this->read->fetch(PDO::FETCH_ASSOC);
  		}
  
  		if ($this->store_read)
  		{
  			$value = $this->store_read['expires'];
  
  			// If 'expires' isn't yet an integer, convert it into one.
  			if (!is_numeric($value))
  			{
  				$value = strtotime($value);
  			}
  
  			$this->timestamp = date('U', $value);
  			return $this->timestamp;
  		}
  
  		return false;
  	}
  
  	/**
  	 * Resets the freshness of the cache.
  	 *
  	 * @return boolean Whether the operation was successful.
  	 */
  	public function reset()
  	{
  		$this->reset->bindParam(':id', $this->id);
  		$this->reset->bindParam(':expires', $this->generate_timestamp());
  		return (bool) $this->reset->execute();
  	}
  
  	/**
  	 * Returns a list of supported PDO database drivers. Identical to <PDO::getAvailableDrivers()>.
  	 *
  	 * @return array The list of supported database drivers.
  	 * @link http://php.net/pdo.getavailabledrivers PHP Method
  	 */
  	public function get_drivers()
  	{
  		return PDO::getAvailableDrivers();
  	}
  
  	/**
  	 * Returns a timestamp value apropriate to the current database type.
  	 *
  	 * @return mixed Timestamp for MySQL and PostgreSQL, integer value for SQLite.
  	 */
  	protected function generate_timestamp()
  	{
  		// Define 'expires' settings differently.
  		switch ($this->dsn['scheme'])
  		{
  			// These support timestamps.
  			case 'mysql': // MySQL
  			case 'pgsql': // PostgreSQL
  				$expires = date(DATE_FORMAT_MYSQL, time());
  				break;
  
  			// These support integers.
  			case 'sqlite': // SQLite 3
  			case 'sqlite2': // SQLite 2
  				$expires = time();
  				break;
  		}
  
  		return $expires;
  	}
  }
  
  
  /*%******************************************************************************************%*/
  // EXCEPTIONS
  
  class CachePDO_Exception extends CacheCore_Exception {}