<?php
/*
 * 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;

use MongoBinData;
use MongoCollection;
use MongoDate;

/**
 * MongoDB cache provider.
 *
 * @since  1.1
 * @author Jeremy Mikola <jmikola@gmail.com>
 */
class MongoDBCache extends CacheProvider
{
    /**
     * The data field will store the serialized PHP value.
     */
    const DATA_FIELD = 'd';

    /**
     * The expiration field will store a MongoDate value indicating when the
     * cache entry should expire.
     *
     * With MongoDB 2.2+, entries can be automatically deleted by MongoDB by
     * indexing this field with the "expireAfterSeconds" option equal to zero.
     * This will direct MongoDB to regularly query for and delete any entries
     * whose date is older than the current time. Entries without a date value
     * in this field will be ignored.
     *
     * The cache provider will also check dates on its own, in case expired
     * entries are fetched before MongoDB's TTLMonitor pass can expire them.
     *
     * @see http://docs.mongodb.org/manual/tutorial/expire-data/
     */
    const EXPIRATION_FIELD = 'e';

    /**
     * @var MongoCollection
     */
    private $collection;

    /**
     * Constructor.
     *
     * This provider will default to the write concern and read preference
     * options set on the MongoCollection instance (or inherited from MongoDB or
     * MongoClient). Using an unacknowledged write concern (< 1) may make the
     * return values of delete() and save() unreliable. Reading from secondaries
     * may make contain() and fetch() unreliable.
     *
     * @see http://www.php.net/manual/en/mongo.readpreferences.php
     * @see http://www.php.net/manual/en/mongo.writeconcerns.php
     * @param MongoCollection $collection
     */
    public function __construct(MongoCollection $collection)
    {
        $this->collection = $collection;
    }

    /**
     * {@inheritdoc}
     */
    protected function doFetch($id)
    {
        $document = $this->collection->findOne(array('_id' => $id), array(self::DATA_FIELD, self::EXPIRATION_FIELD));

        if ($document === null) {
            return false;
        }

        if ($this->isExpired($document)) {
            $this->doDelete($id);
            return false;
        }

        return unserialize($document[self::DATA_FIELD]->bin);
    }

    /**
     * {@inheritdoc}
     */
    protected function doContains($id)
    {
        $document = $this->collection->findOne(array('_id' => $id), array(self::EXPIRATION_FIELD));

        if ($document === null) {
            return false;
        }

        if ($this->isExpired($document)) {
            $this->doDelete($id);
            return false;
        }

        return true;
    }

    /**
     * {@inheritdoc}
     */
    protected function doSave($id, $data, $lifeTime = 0)
    {
        $result = $this->collection->update(
            array('_id' => $id),
            array('$set' => array(
                self::EXPIRATION_FIELD => ($lifeTime > 0 ? new MongoDate(time() + $lifeTime) : null),
                self::DATA_FIELD => new MongoBinData(serialize($data), MongoBinData::BYTE_ARRAY),
            )),
            array('upsert' => true, 'multiple' => false)
        );

        return isset($result['ok']) ? $result['ok'] == 1 : true;
    }

    /**
     * {@inheritdoc}
     */
    protected function doDelete($id)
    {
        $result = $this->collection->remove(array('_id' => $id));

        return isset($result['ok']) ? $result['ok'] == 1 : true;
    }

    /**
     * {@inheritdoc}
     */
    protected function doFlush()
    {
        // Use remove() in lieu of drop() to maintain any collection indexes
        $result = $this->collection->remove();

        return isset($result['ok']) ? $result['ok'] == 1 : true;
    }

    /**
     * {@inheritdoc}
     */
    protected function doGetStats()
    {
        $serverStatus = $this->collection->db->command(array(
            'serverStatus' => 1,
            'locks' => 0,
            'metrics' => 0,
            'recordStats' => 0,
            'repl' => 0,
        ));

        $collStats = $this->collection->db->command(array('collStats' => 1));

        return array(
            Cache::STATS_HITS => null,
            Cache::STATS_MISSES => null,
            Cache::STATS_UPTIME => (isset($serverStatus['uptime']) ? (int) $serverStatus['uptime'] : null),
            Cache::STATS_MEMORY_USAGE => (isset($collStats['size']) ? (int) $collStats['size'] : null),
            Cache::STATS_MEMORY_AVAILABLE  => null,
        );
    }

    /**
     * Check if the document is expired.
     *
     * @param array $document
     * @return boolean
     */
    private function isExpired(array $document)
    {
        return isset($document[self::EXPIRATION_FIELD]) &&
            $document[self::EXPIRATION_FIELD] instanceof MongoDate &&
            $document[self::EXPIRATION_FIELD]->sec < time();
    }
}