<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Service_WindowsAzure

 * @subpackage Session

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

/**

 * @category   Zend

 * @package    Zend_Service_WindowsAzure

 * @subpackage Session

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

class Zend_Service_WindowsAzure_SessionHandler

{

	/**

	 * Maximal property size in table storage.

	 * 

	 * @var int

	 * @see http://msdn.microsoft.com/en-us/library/dd179338.aspx

	 */

	const MAX_TS_PROPERTY_SIZE = 65536;

	/** Storage backend type */

	const STORAGE_TYPE_TABLE = 'table';

	const STORAGE_TYPE_BLOB = 'blob';

    /**

     * Storage back-end

     * 

     * @var Zend_Service_WindowsAzure_Storage_Table|Zend_Service_WindowsAzure_Storage_Blob

     */

    protected $_storage;

    /**

     * Storage backend type

     * 

     * @var string

     */

    protected $_storageType;

    /**

     * Session container name

     * 

     * @var string

     */

    protected $_sessionContainer;

    /**

     * Session container partition

     * 

     * @var string

     */

    protected $_sessionContainerPartition;

    /**

     * Creates a new Zend_Service_WindowsAzure_SessionHandler instance

     * 

     * @param Zend_Service_WindowsAzure_Storage_Table|Zend_Service_WindowsAzure_Storage_Blob $storage Storage back-end, can be table storage and blob storage

     * @param string $sessionContainer Session container name

     * @param string $sessionContainerPartition Session container partition

     */

    public function __construct(Zend_Service_WindowsAzure_Storage $storage, $sessionContainer = 'phpsessions', $sessionContainerPartition = 'sessions')

	{

		// Validate $storage

		if (!($storage instanceof Zend_Service_WindowsAzure_Storage_Table || $storage instanceof Zend_Service_WindowsAzure_Storage_Blob)) {

			require_once 'Zend/Service/WindowsAzure/Exception.php';

			throw new Zend_Service_WindowsAzure_Exception('Invalid storage back-end given. Storage back-end should be of type Zend_Service_WindowsAzure_Storage_Table or Zend_Service_WindowsAzure_Storage_Blob.');

		}

		// Validate other parameters

		if ($sessionContainer == '' || $sessionContainerPartition == '') {

			require_once 'Zend/Service/WindowsAzure/Exception.php';

			throw new Zend_Service_WindowsAzure_Exception('Session container and session partition should be specified.');

		}

		// Determine storage type

		$storageType = self::STORAGE_TYPE_TABLE;

		if ($storage instanceof Zend_Service_WindowsAzure_Storage_Blob) {

			$storageType = self::STORAGE_TYPE_BLOB;

		}

	    // Set properties

		$this->_storage = $storage;

		$this->_storageType = $storageType;

		$this->_sessionContainer = $sessionContainer;

		$this->_sessionContainerPartition = $sessionContainerPartition;

	}

	/**

	 * Registers the current session handler as PHP's session handler

	 * 

	 * @return boolean

	 */

	public function register()

	{

        return session_set_save_handler(array($this, 'open'),

                                        array($this, 'close'),

                                        array($this, 'read'),

                                        array($this, 'write'),

                                        array($this, 'destroy'),

                                        array($this, 'gc')

        );

	}

    /**

     * Open the session store

     * 

     * @return bool

     */

    public function open()

    {

    	// Make sure storage container exists

    	if ($this->_storageType == self::STORAGE_TYPE_TABLE) {

    		$this->_storage->createTableIfNotExists($this->_sessionContainer);

    	} else if ($this->_storageType == self::STORAGE_TYPE_BLOB) {

    		$this->_storage->createContainerIfNotExists($this->_sessionContainer);

    	}

		// Ok!

		return true;

    }

    /**

     * Close the session store

     * 

     * @return bool

     */

    public function close()

    {

        return true;

    }

    /**

     * Read a specific session

     * 

     * @param int $id Session Id

     * @return string

     */

    public function read($id)

    {

    	// Read data

       	if ($this->_storageType == self::STORAGE_TYPE_TABLE) {

    		// In table storage

	        try

	        {

	            $sessionRecord = $this->_storage->retrieveEntityById(

	                $this->_sessionContainer,

	                $this->_sessionContainerPartition,

	                $id

	            );

	            return unserialize(base64_decode($sessionRecord->serializedData));

	        }

	        catch (Zend_Service_WindowsAzure_Exception $ex)

	        {

	            return '';

	        }

       	} else if ($this->_storageType == self::STORAGE_TYPE_BLOB) {

    		// In blob storage

    	    try

	        {

    			$data = $this->_storage->getBlobData(

    				$this->_sessionContainer,

    				$this->_sessionContainerPartition . '/' . $id

    			);

	            return unserialize(base64_decode($data));

	        }

	        catch (Zend_Service_WindowsAzure_Exception $ex)

	        {

	            return false;

	        }

    	}

    }

    /**

     * Write a specific session

     * 

     * @param int $id Session Id

     * @param string $serializedData Serialized PHP object

     * @throws Exception

     */

    public function write($id, $serializedData)

    {

    	// Encode data

    	$serializedData = base64_encode(serialize($serializedData));

    	if (strlen($serializedData) >= self::MAX_TS_PROPERTY_SIZE && $this->_storageType == self::STORAGE_TYPE_TABLE) {

    		throw new Zend_Service_WindowsAzure_Exception('Session data exceeds the maximum allowed size of ' . self::MAX_TS_PROPERTY_SIZE . ' bytes that can be stored using table storage. Consider switching to a blob storage back-end or try reducing session data size.');

    	}

    	// Store data

       	if ($this->_storageType == self::STORAGE_TYPE_TABLE) {

    		// In table storage

       	    $sessionRecord = new Zend_Service_WindowsAzure_Storage_DynamicTableEntity($this->_sessionContainerPartition, $id);

	        $sessionRecord->sessionExpires = time();

	        $sessionRecord->serializedData = $serializedData;

	        $sessionRecord->setAzurePropertyType('sessionExpires', 'Edm.Int32');

	        try

	        {

	            $this->_storage->updateEntity($this->_sessionContainer, $sessionRecord);

	        }

	        catch (Zend_Service_WindowsAzure_Exception $unknownRecord)

	        {

	            $this->_storage->insertEntity($this->_sessionContainer, $sessionRecord);

	        }

    	} else if ($this->_storageType == self::STORAGE_TYPE_BLOB) {

    		// In blob storage

    		$this->_storage->putBlobData(

    			$this->_sessionContainer,

    			$this->_sessionContainerPartition . '/' . $id,

    			$serializedData,

    			array('sessionexpires' => time())

    		);

    	}

    }

    /**

     * Destroy a specific session

     * 

     * @param int $id Session Id

     * @return boolean

     */

    public function destroy($id)

    {

		// Destroy data

       	if ($this->_storageType == self::STORAGE_TYPE_TABLE) {

    		// In table storage

       	    try

	        {

	            $sessionRecord = $this->_storage->retrieveEntityById(

	                $this->_sessionContainer,

	                $this->_sessionContainerPartition,

	                $id

	            );

	            $this->_storage->deleteEntity($this->_sessionContainer, $sessionRecord);

	            return true;

	        }

	        catch (Zend_Service_WindowsAzure_Exception $ex)

	        {

	            return false;

	        }

    	} else if ($this->_storageType == self::STORAGE_TYPE_BLOB) {

    		// In blob storage

    	    try

	        {

    			$this->_storage->deleteBlob(

    				$this->_sessionContainer,

    				$this->_sessionContainerPartition . '/' . $id

    			);

	            return true;

	        }

	        catch (Zend_Service_WindowsAzure_Exception $ex)

	        {

	            return false;

	        }

    	}

    }

    /**

     * Garbage collector

     * 

     * @param int $lifeTime Session maximal lifetime

     * @see session.gc_divisor  100

     * @see session.gc_maxlifetime 1440

     * @see session.gc_probability 1

     * @usage Execution rate 1/100 (session.gc_probability/session.gc_divisor)

     * @return boolean

     */

    public function gc($lifeTime)

    {

       	if ($this->_storageType == self::STORAGE_TYPE_TABLE) {

    		// In table storage

       	    try

	        {

	            $result = $this->_storage->retrieveEntities($this->_sessionContainer, 'PartitionKey eq \'' . $this->_sessionContainerPartition . '\' and sessionExpires lt ' . (time() - $lifeTime));

	            foreach ($result as $sessionRecord)

	            {

	                $this->_storage->deleteEntity($this->_sessionContainer, $sessionRecord);

	            }

	            return true;

	        }

	        catch (Zend_Service_WindowsAzure_exception $ex)

	        {

	            return false;

	        }

    	} else if ($this->_storageType == self::STORAGE_TYPE_BLOB) {

    		// In blob storage

    	    try

	        {

	            $result = $this->_storage->listBlobs($this->_sessionContainer, $this->_sessionContainerPartition, '', null, null, 'metadata');

	            foreach ($result as $sessionRecord)

	            {

	            	if ($sessionRecord->Metadata['sessionexpires'] < (time() - $lifeTime)) {

	                	$this->_storage->deleteBlob($this->_sessionContainer, $sessionRecord->Name);

	            	}

	            }

	            return true;

	        }

	        catch (Zend_Service_WindowsAzure_exception $ex)

	        {

	            return false;

	        }

    	}

    }

}