<?php defined('SYSPATH') or die('No direct script access.');
/**
 * [Kohana Cache](api/Kohana_Cache) File driver. Provides a file based
 * driver for the Kohana Cache library. This is one of the slowest
 * caching methods.
 * 
 * ### Configuration example
 * 
 * Below is an example of a _file_ server configuration.
 * 
 *     return array(
 *          'file'   => array(                          // File driver group
 *                  'driver'         => 'file',         // using File driver
 *                  'cache_dir'     => APPPATH.'cache/.kohana_cache', // Cache location
 *           ),
 *     )
 * 
 * In cases where only one cache group is required, if the group is named `default` there is
 * no need to pass the group name when instantiating a cache instance.
 * 
 * #### General cache group configuration settings
 * 
 * Below are the settings available to all types of cache driver.
 * 
 * Name           | Required | Description
 * -------------- | -------- | ---------------------------------------------------------------
 * driver         | __YES__  | (_string_) The driver type to use
 * cache_dir      | __NO__   | (_string_) The cache directory to use for this cache instance
 * 
 * ### System requirements
 * 
 * *  Kohana 3.0.x
 * *  PHP 5.2.4 or greater
 * 
 * @package    Kohana/Cache
 * @category   Base
 * @author     Kohana Team
 * @copyright  (c) 2009-2010 Kohana Team
 * @license    http://kohanaphp.com/license
 */
class Kohana_Cache_File extends Cache implements Kohana_Cache_GarbageCollect {

	/**
	 * Creates a hashed filename based on the string. This is used
	 * to create shorter unique IDs for each cache filename.
	 * 
	 *     // Create the cache filename
	 *     $filename = Cache_File::filename($this->_sanitize_id($id));
	 *
	 * @param   string   string to hash into filename
	 * @return  string
	 */
	protected static function filename($string)
	{
		return sha1($string).'.json';
	}

	/**
	 * @var  string   the caching directory
	 */
	protected $_cache_dir;

	/**
	 * Constructs the file cache driver. This method cannot be invoked externally. The file cache driver must
	 * be instantiated using the `Cache::instance()` method.
	 *
	 * @param   array    config 
	 * @throws  Kohana_Cache_Exception
	 */
	protected function __construct(array $config)
	{
		// Setup parent
		parent::__construct($config);

		try
		{
			$directory = Arr::get($this->_config, 'cache_dir', Kohana::$cache_dir);
			$this->_cache_dir = new SplFileInfo($directory);
		}
		// PHP < 5.3 exception handle
		catch (ErrorException $e)
		{
			$this->_cache_dir = $this->_make_directory($directory, 0777, TRUE);
		}
		// PHP >= 5.3 exception handle
		catch (UnexpectedValueException $e)
		{
			$this->_cache_dir = $this->_make_directory($directory, 0777, TRUE);
		}

		// If the defined directory is a file, get outta here
		if ($this->_cache_dir->isFile())
		{
			throw new Kohana_Cache_Exception('Unable to create cache directory as a file already exists : :resource', array(':resource' => $this->_cache_dir->getRealPath()));
		}

		// Check the read status of the directory
		if ( ! $this->_cache_dir->isReadable())
		{
			throw new Kohana_Cache_Exception('Unable to read from the cache directory :resource', array(':resource' => $this->_cache_dir->getRealPath()));
		}

		// Check the write status of the directory
		if ( ! $this->_cache_dir->isWritable())
		{
			throw new Kohana_Cache_Exception('Unable to write to the cache directory :resource', array(':resource' => $this->_cache_dir->getRealPath()));
		}
	}

	/**
	 * Retrieve a cached value entry by id.
	 * 
	 *     // Retrieve cache entry from file group
	 *     $data = Cache::instance('file')->get('foo');
	 * 
	 *     // Retrieve cache entry from file group and return 'bar' if miss
	 *     $data = Cache::instance('file')->get('foo', 'bar');
	 *
	 * @param   string   id of cache to entry
	 * @param   string   default value to return if cache miss
	 * @return  mixed
	 * @throws  Kohana_Cache_Exception
	 */
	public function get($id, $default = NULL)
	{
		$filename = Cache_File::filename($this->_sanitize_id($id));
		$directory = $this->_resolve_directory($filename);

		// Wrap operations in try/catch to handle notices
		try
		{
			// Open file
			$file = new SplFileInfo($directory.$filename);

			// If file does not exist
			if ( ! $file->isFile())
			{
				// Return default value
				return $default;
			}
			else
			{
				// Open the file and extract the json
				$json = $file->openFile()->current();

				// Decode the json into PHP object
				$data = json_decode($json);

				// Test the expiry
				if ($data->expiry < time())
				{
					// Delete the file
					$this->_delete_file($file, NULL, TRUE);

					// Return default value
					return $default;
				}
				else
				{
					return ($data->type === 'string') ? $data->payload : unserialize($data->payload);
				}
			}
			
		}
		catch (ErrorException $e)
		{
			// Handle ErrorException caused by failed unserialization
			if ($e->getCode() === E_NOTICE)
			{
				throw new Kohana_Cache_Exception(__METHOD__.' failed to unserialize cached object with message : '.$e->getMessage());
			}

			// Otherwise throw the exception
			throw $e;
		}
	}

	/**
	 * Set a value to cache with id and lifetime
	 * 
	 *     $data = 'bar';
	 * 
	 *     // Set 'bar' to 'foo' in file group, using default expiry
	 *     Cache::instance('file')->set('foo', $data);
	 * 
	 *     // Set 'bar' to 'foo' in file group for 30 seconds
	 *     Cache::instance('file')->set('foo', $data, 30);
	 *
	 * @param   string   id of cache entry
	 * @param   string   data to set to cache
	 * @param   integer  lifetime in seconds
	 * @return  boolean
	 */
	public function set($id, $data, $lifetime = NULL)
	{
		$filename = Cache_File::filename($this->_sanitize_id($id));
		$directory = $this->_resolve_directory($filename);

		// If lifetime is NULL
		if ($lifetime === NULL)
		{
			// Set to the default expiry
			$lifetime = Arr::get($this->_config, 'default_expire', Cache::DEFAULT_EXPIRE);
		}

		// Open directory
		$dir = new SplFileInfo($directory);

		// If the directory path is not a directory
		if ( ! $dir->isDir())
		{
			// Create the directory 
			if ( ! mkdir($directory, 0777, TRUE))
			{
				throw new Kohana_Cache_Exception(__METHOD__.' unable to create directory : :directory', array(':directory' => $directory));
			}

			// chmod to solve potential umask issues
			chmod($directory, 0777);
		}

		// Open file to inspect
		$resouce = new SplFileInfo($directory.$filename);
		$file = $resouce->openFile('w');

		try
		{
			$type = gettype($data);

			// Serialize the data
			$data = json_encode( (object) array(
				'payload'  => ($type === 'string') ? $data : serialize($data),
				'expiry'   => time() + $lifetime,
				'type'     => $type
			));

			$size = strlen($data);
		}
		catch (ErrorException $e)
		{
			// If serialize through an error exception
			if ($e->getCode() === E_NOTICE)
			{
				// Throw a caching error
				throw new Kohana_Cache_Exception(__METHOD__.' failed to serialize data for caching with message : '.$e->getMessage());
			}

			// Else rethrow the error exception
			throw $e;
		}

		try
		{
			$file->fwrite($data, $size);
			return (bool) $file->fflush();
		}
		catch (Exception $e)
		{
			throw $e;
		}
	}

	/**
	 * Delete a cache entry based on id
	 * 
	 *     // Delete 'foo' entry from the file group
	 *     Cache::instance('file')->delete('foo');
	 *
	 * @param   string   id to remove from cache
	 * @return  boolean
	 */
	public function delete($id)
	{
		$filename = Cache_File::filename($this->_sanitize_id($id));
		$directory = $this->_resolve_directory($filename);

		return $this->_delete_file(new SplFileInfo($directory.$filename), NULL, TRUE);
	}

	/**
	 * Delete all cache entries.
	 * 
	 * Beware of using this method when
	 * using shared memory cache systems, as it will wipe every
	 * entry within the system for all clients.
	 * 
	 *     // Delete all cache entries in the file group
	 *     Cache::instance('file')->delete_all();
	 *
	 * @return  boolean
	 */
	public function delete_all()
	{
		return $this->_delete_file($this->_cache_dir, TRUE);
	}

	/**
	 * Garbage collection method that cleans any expired
	 * cache entries from the cache.
	 *
	 * @return  void
	 */
	public function garbage_collect()
	{
		$this->_delete_file($this->_cache_dir, TRUE, FALSE, TRUE);
		return;
	}

	/**
	 * Deletes files recursively and returns FALSE on any errors
	 * 
	 *     // Delete a file or folder whilst retaining parent directory and ignore all errors
	 *     $this->_delete_file($folder, TRUE, TRUE);
	 *
	 * @param   SplFileInfo  file
	 * @param   boolean  retain the parent directory
	 * @param   boolean  ignore_errors to prevent all exceptions interrupting exec
	 * @param   boolean  only expired files
	 * @return  boolean
	 * @throws  Kohana_Cache_Exception
	 */
	protected function _delete_file(SplFileInfo $file, $retain_parent_directory = FALSE, $ignore_errors = FALSE, $only_expired = FALSE)
	{
		// Allow graceful error handling
		try
		{
			// If is file
			if ($file->isFile())
			{
				try
				{
					// If only expired is not set
					if ($only_expired === FALSE)
					{
						// We want to delete the file
						$delete = TRUE;
					}
					// Otherwise...
					else
					{
						// Assess the file expiry to flag it for deletion
						$json = $file->openFile('r')->current();
						$data = json_decode($json);
						$delete = $data->expiry < time();
					}

					// If the delete flag is set
					if ($delete === TRUE)
					{
						// Try to delete
						unlink($file->getRealPath());
					}
				}
				catch (ErrorException $e)
				{
					// Catch any delete file warnings
					if ($e->getCode() === E_WARNING)
					{
						throw new Kohana_Cache_Exception(__METHOD__.' failed to delete file : :file', array(':file' => $file->getRealPath()));
					}
				}
			}
			// Else, is directory
			elseif ($file->isDir())
			{
				// Create new DirectoryIterator
				$files = new DirectoryIterator($file->getPathname());

				// Iterate over each entry
				while ($files->valid())
				{
					// Extract the entry name
					$name = $files->getFilename();

					// If the name is not a dot
					if ($name != '.' and $name != '..')
					{
						// Create new file resource
						$fp = new SplFileInfo($files->getRealPath());
						// Delete the file
						$this->_delete_file($fp);
					}

					// Move the file pointer on
					$files->next();
				}

				// If set to retain parent directory, return now
				if ($retain_parent_directory)
				{
					return TRUE;
				}

				try
				{
					// Remove the files iterator
					// (fixes Windows PHP which has permission issues with open iterators)
					unset($files);

					// Try to remove the parent directory
					return rmdir($file->getRealPath());
				}
				catch (ErrorException $e)
				{
					// Catch any delete directory warnings
					if ($e->getCode() === E_WARNING)
					{
						throw new Kohana_Cache_Exception(__METHOD__.' failed to delete directory : :directory', array(':directory' => $file->getRealPath()));
					}
				}
			}
		}
		// Catch all exceptions
		catch (Exception $e)
		{
			// If ignore_errors is on
			if ($ignore_errors === TRUE)
			{
				// Return
				return FALSE;
			}
			// Throw exception
			throw $e;
		}
	}

	/**
	 * Resolves the cache directory real path from the filename
	 * 
	 *      // Get the realpath of the cache folder
	 *      $realpath = $this->_resolve_directory($filename);
	 *
	 * @param   string   filename to resolve
	 * @return  string
	 */
	protected function _resolve_directory($filename)
	{
		return $this->_cache_dir->getRealPath().DIRECTORY_SEPARATOR.$filename[0].$filename[1].DIRECTORY_SEPARATOR;
	}

	/**
	 * Makes the cache directory if it doesn't exist. Simply a wrapper for
	 * `mkdir` to ensure DRY principles
	 *
	 * @see     http://php.net/manual/en/function.mkdir.php
	 * @param   string   directory 
	 * @param   string   mode 
	 * @param   string   recursive 
	 * @param   string   context 
	 * @return  SplFileInfo
	 * @throws  Kohana_Cache_Exception
	 */
	protected function _make_directory($directory, $mode = 0777, $recursive = FALSE, $context = NULL)
	{
		if ( ! mkdir($directory, $mode, $recursive, $context))
		{
			throw new Kohana_Cache_Exception('Failed to create the defined cache directory : :directory', array(':directory' => $directory));
		}
		chmod($directory, $mode);

		return new SplFileInfo($directory);;
	}
}
