<?php
/*
 *  $Id$
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the MIT license. For more information, see
 * <http://www.doctrine-project.org>.
 */

namespace Doctrine\Common\Cache;

/**
 * Interface for cache drivers.
 *
 * @license http://www.opensource.org/licenses/lgpl-license.php LGPL
 * @link    www.doctrine-project.org
 * @since   2.0
 * @author  Benjamin Eberlei <kontakt@beberlei.de>
 * @author  Guilherme Blanco <guilhermeblanco@hotmail.com>
 * @author  Jonathan Wage <jonwage@gmail.com>
 * @author  Roman Borschel <roman@code-factory.org>
 * @author  Fabio B. Silva <fabio.bat.silva@gmail.com>
 */
interface Cache
{
    const STATS_HITS    = 'hits';
    const STATS_MISSES  = 'misses';
    const STATS_UPTIME  = 'uptime';
    const STATS_MEMORY_USAGE        = 'memory_usage';
    const STATS_MEMORY_AVAILIABLE   = 'memory_available';

    /**
     * Fetches an entry from the cache.
     *
     * @param string $id cache id The id of the cache entry to fetch.
     * @return mixed The cached data or FALSE, if no cache entry exists for the given id.
     */
    function fetch($id);

    /**
     * Test if an entry exists in the cache.
     *
     * @param string $id cache id The cache id of the entry to check for.
     * @return boolean TRUE if a cache entry exists for the given cache id, FALSE otherwise.
     */
    function contains($id);

    /**
     * Puts data into the cache.
     *
     * @param string $id The cache id.
     * @param mixed $data The cache entry/data.
     * @param int $lifeTime The lifetime. If != 0, sets a specific lifetime for this cache entry (0 => infinite lifeTime).
     * @return boolean TRUE if the entry was successfully stored in the cache, FALSE otherwise.
     */
    function save($id, $data, $lifeTime = 0);

    /**
     * Deletes a cache entry.
     *
     * @param string $id cache id
     * @return boolean TRUE if the cache entry was successfully deleted, FALSE otherwise.
     */
    function delete($id);

    /**
     * Retrieves cached information from data store
     *
     * The server's statistics array has the following values:
     *
     * - <b>hits</b>
     * Number of keys that have been requested and found present.
     *
     * - <b>misses</b>
     * Number of items that have been requested and not found.
     *
     * - <b>uptime</b>
     * Time that the server is running.
     *
     * - <b>memory_usage</b>
     * Memory used by this server to store items.
     *
     * - <b>memory_available</b>
     * Memory allowed to use for storage.
     *
     * @since   2.2
     * @return  array Associative array with server's statistics if available, NULL otherwise.
     */
    function getStats();
}
