<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         2.2.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */

namespace Cake\Cache\Engine;

use Cake\Cache\CacheEngine;
use Redis;
use RedisException;

/**
 * Redis storage engine for cache.
 *
 */
class RedisEngine extends CacheEngine
{

    /**
     * Redis wrapper.
     *
     * @var \Redis
     */
    protected $_Redis = null;

    /**
     * The default config used unless overridden by runtime configuration
     *
     * - `database` database number to use for connection.
     * - `duration` Specify how long items in this cache configuration last.
     * - `groups` List of groups or 'tags' associated to every key stored in this config.
     *    handy for deleting a complete group from cache.
     * - `password` Redis server password.
     * - `persistent` Connect to the Redis server with a persistent connection
     * - `port` port number to the Redis server.
     * - `prefix` Prefix appended to all entries. Good for when you need to share a keyspace
     *    with either another cache config or another application.
     * - `probability` Probability of hitting a cache gc cleanup. Setting to 0 will disable
     *    cache::gc from ever being called automatically.
     * - `server` URL or ip to the Redis server host.
     * - `timeout` timeout in seconds (float).
     * - `unix_socket` Path to the unix socket file (default: false)
     *
     * @var array
     */
    protected $_defaultConfig = [
        'database' => 0,
        'duration' => 3600,
        'groups' => [],
        'password' => false,
        'persistent' => true,
        'port' => 6379,
        'prefix' => 'cake_',
        'probability' => 100,
        'host' => null,
        'server' => '127.0.0.1',
        'timeout' => 0,
        'unix_socket' => false,
    ];

    /**
     * Initialize the Cache Engine
     *
     * Called automatically by the cache frontend
     *
     * @param array $config array of setting for the engine
     * @return bool True if the engine has been successfully initialized, false if not
     */
    public function init(array $config = [])
    {
        if (!extension_loaded('redis')) {
            return false;
        }

        if (!empty($config['host'])) {
            $config['server'] = $config['host'];
        }

        parent::init($config);
        return $this->_connect();
    }

    /**
     * Connects to a Redis server
     *
     * @return bool True if Redis server was connected
     */
    protected function _connect()
    {
        try {
            $this->_Redis = new Redis();
            if (!empty($this->_config['unix_socket'])) {
                $return = $this->_Redis->connect($this->_config['unix_socket']);
            } elseif (empty($this->_config['persistent'])) {
                $return = $this->_Redis->connect($this->_config['server'], $this->_config['port'], $this->_config['timeout']);
            } else {
                $persistentId = $this->_config['port'] . $this->_config['timeout'] . $this->_config['database'];
                $return = $this->_Redis->pconnect($this->_config['server'], $this->_config['port'], $this->_config['timeout'], $persistentId);
            }
        } catch (RedisException $e) {
            return false;
        }
        if ($return && $this->_config['password']) {
            $return = $this->_Redis->auth($this->_config['password']);
        }
        if ($return) {
            $return = $this->_Redis->select($this->_config['database']);
        }
        return $return;
    }

    /**
     * Write data for key into cache.
     *
     * @param string $key Identifier for the data
     * @param mixed $value Data to be cached
     * @return bool True if the data was successfully cached, false on failure
     */
    public function write($key, $value)
    {
        $key = $this->_key($key);

        if (!is_int($value)) {
            $value = serialize($value);
        }

        $duration = $this->_config['duration'];
        if ($duration === 0) {
            return $this->_Redis->set($key, $value);
        }

        return $this->_Redis->setex($key, $duration, $value);
    }

    /**
     * Read a key from the cache
     *
     * @param string $key Identifier for the data
     * @return mixed The cached data, or false if the data doesn't exist, has expired, or if there was an error fetching it
     */
    public function read($key)
    {
        $key = $this->_key($key);

        $value = $this->_Redis->get($key);
        if (ctype_digit($value)) {
            $value = (int)$value;
        }
        if ($value !== false && is_string($value)) {
            $value = unserialize($value);
        }
        return $value;
    }

    /**
     * Increments the value of an integer cached key
     *
     * @param string $key Identifier for the data
     * @param int $offset How much to increment
     * @return bool|int New incremented value, false otherwise
     */
    public function increment($key, $offset = 1)
    {
        $key = $this->_key($key);

        return (int)$this->_Redis->incrBy($key, $offset);
    }

    /**
     * Decrements the value of an integer cached key
     *
     * @param string $key Identifier for the data
     * @param int $offset How much to subtract
     * @return bool|int New decremented value, false otherwise
     */
    public function decrement($key, $offset = 1)
    {
        $key = $this->_key($key);

        return (int)$this->_Redis->decrBy($key, $offset);
    }

    /**
     * Delete a key from the cache
     *
     * @param string $key Identifier for the data
     * @return bool True if the value was successfully deleted, false if it didn't exist or couldn't be removed
     */
    public function delete($key)
    {
        $key = $this->_key($key);

        return $this->_Redis->delete($key) > 0;
    }

    /**
     * Delete all keys from the cache
     *
     * @param bool $check If true will check expiration, otherwise delete all.
     * @return bool True if the cache was successfully cleared, false otherwise
     */
    public function clear($check)
    {
        if ($check) {
            return true;
        }
        $keys = $this->_Redis->getKeys($this->_config['prefix'] . '*');
        $this->_Redis->del($keys);

        return true;
    }

    /**
     * Write data for key into cache if it doesn't exist already.
     * If it already exists, it fails and returns false.
     *
     * @param string $key Identifier for the data.
     * @param mixed $value Data to be cached.
     * @return bool True if the data was successfully cached, false on failure.
     * @link https://github.com/phpredis/phpredis#setnx
     */
    public function add($key, $value)
    {
        $duration = $this->_config['duration'];
        $key = $this->_key($key);

        if (!is_int($value)) {
            $value = serialize($value);
        }

        // setnx() doesn't have an expiry option, so overwrite the key with one
        if ($this->_Redis->setnx($key, $value)) {
            return $this->_Redis->setex($key, $duration, $value);
        }
        return false;
    }

    /**
     * Returns the `group value` for each of the configured groups
     * If the group initial value was not found, then it initializes
     * the group accordingly.
     *
     * @return array
     */
    public function groups()
    {
        $result = [];
        foreach ($this->_config['groups'] as $group) {
            $value = $this->_Redis->get($this->_config['prefix'] . $group);
            if (!$value) {
                $value = 1;
                $this->_Redis->set($this->_config['prefix'] . $group, $value);
            }
            $result[] = $group . $value;
        }
        return $result;
    }

    /**
     * Increments the group value to simulate deletion of all keys under a group
     * old values will remain in storage until they expire.
     *
     * @param string $group name of the group to be cleared
     * @return bool success
     */
    public function clearGroup($group)
    {
        return (bool)$this->_Redis->incr($this->_config['prefix'] . $group);
    }

    /**
     * Disconnects from the redis server
     */
    public function __destruct()
    {
        if (empty($this->_config['persistent']) && $this->_Redis instanceof Redis) {
            $this->_Redis->close();
        }
    }
}
