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<?php defined('SYSPATH') or die('No direct script access.');
/**
* SQLite-based Cache driver.
*
* @package Cache
* @author Kohana Team
* @copyright (c) 2007 Kohana Team
* @license http://kohanaphp.com/license.html
*/
class Cache_Sqlite_Driver implements Cache_Driver {

// SQLite database instance
protected $db;

// Database error messages
protected $error;

/**
* Logs an SQLite error.
*/
protected static function log_error($code)
{
// Log an error
Log::add('error', 'Cache: SQLite error: '.sqlite_error_string($error));
}

/**
* Tests that the storage location is a directory and is writable.
*/
public function __construct($filename)
{
// Find the real path to the directory
$filename = str_replace('\\', '/', realpath($filename));

// Get the filename from the directory
$directory = substr($filename, 0, strrpos($filename, '/') + 1);

// Make sure the cache directory is writable
if ( ! is_dir($directory) OR ! is_writable($directory))
throw new Kohana_Exception('cache.unwritable', $directory);

// Make sure the cache database is writable
if (file_exists($filename) AND ! is_writable($filename))
throw new Kohana_Exception('cache.unwritable', $filename);

// Open up an instance of the database
$this->db = new SQLiteDatabase($filename, '0666', $error);

// Throw an exception if there's an error
if ( ! empty($error))
throw new Kohana_Exception('cache.driver_error', sqlite_error_string($error));

$query = "SELECT name FROM sqlite_master WHERE type = 'table' AND name = 'caches'";
$tables = $this->db->query($query, SQLITE_BOTH, $error);

// Throw an exception if there's an error
if ( ! empty($error))
throw new Kohana_Exception('cache.driver_error', sqlite_error_string($error));

if ($tables->numRows() == 0)
{
Log::add('error', 'Cache: Initializing new SQLite cache database');

// Issue a CREATE TABLE command
$this->db->unbufferedQuery(Config::item('cache_sqlite.schema'));
}
}

/**
* Checks if a cache id is already set.
*
* @param string cache id
* @return boolean
*/
public function exists($id)
{
// Find the id that matches
$query = "SELECT id FROM caches WHERE id = '$id'";

return ($this->db->query($query)->numRows() > 0);
}

/**
* Sets a cache item to the given data, tags, and expiration.
*
* @param string cache id to set
* @param string data in the cache
* @param array cache tags
* @param integer timestamp
* @return bool
*/
public function set($id, $data, $tags, $expiration)
{
// Find the data hash
$hash = sha1($data);

// Escape the data
$data = sqlite_escape_string($data);

// Escape the tags
$tags = sqlite_escape_string(implode(',', $tags));

$query = $this->exists($id)
? "UPDATE caches SET hash = '$hash', tags = '$tags', expiration = '$expiration', cache = '$data' WHERE id = '$id'"
: "INSERT INTO caches VALUES('$id', '$hash', '$tags', '$expiration', '$data')";

// Run the query
$this->db->unbufferedQuery($query, SQLITE_BOTH, $error);

empty($error) or self::log_error($error);

return empty($error);
}

/**
* Finds an array of ids for a given tag.
*
* @param string tag name
* @return array of ids that match the tag
*/
public function find($tag)
{
$query = "SELECT id FROM caches WHERE tags LIKE '%{$tag}%'";
$query = $this->db->query($query, SQLITE_BOTH, $error);

empty($error) or self::log_error($error);

if (empty($error) AND $query->numRows() > 0)
{
$array = array();
while($row = $query->fetchObject())
{
// Add each id to the array
$array[] = $row->id;
}
return $array;
}

return FALSE;
}

/**
* Fetches a cache item. This will delete the item if it is expired or if
* the hash does not match the stored hash.
*
* @param string cache id
* @return mixed|NULL
*/
public function get($id)
{
$query = "SELECT id, hash, expiration, cache FROM caches WHERE id = '{$id}' LIMIT 0, 1";
$query = $this->db->query($query, SQLITE_BOTH, $error);

empty($error) or self::log_error($error);

if (empty($error) AND $cache = $query->fetchObject())
{
// Make sure the expiration is valid and that the hash matches
if (($cache->expiration != 0 AND $cache->expiration <= time()) OR $cache->hash !== sha1($cache->cache))
{
// Cache is not valid, delete it now
$this->delete($cache->id);
}
else
{
// Return the valid cache data
return $cache->cache;
}
}

// No valid cache foud
return NULL;
}

/**
* Deletes a cache item by id or tag
*
* @param string cache id or tag, or TRUE for "all items"
* @param bool use tags
* @return bool
*/
public function delete($id, $tag = FALSE)
{
if ($id === TRUE)
{
// Delete all caches
$where = '1';
}
elseif ($tag == FALSE)
{
// Delete by id
$where = "id = '{$id}'";
}
else
{
// Delete by tag
$where = "tags LIKE '%{$tag}%'";
}

$this->db->unbufferedQuery('DELETE FROM caches WHERE '.$where, SQLITE_BOTH, $error);

empty($error) or self::log_error($error);

return empty($error);
}

/**
* Deletes all cache files that are older than the current time.
*/
public function delete_expired()
{
// Delete all expired caches
$query = 'DELETE FROM caches WHERE expiration != 0 AND expiration <= '.time();

$this->db->unbufferedQuery($query);

return TRUE;
}

} // End Cache SQLite Driver