<?php

// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2012 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------

/**
 * 数据库方式缓存驱动
 *    CREATE TABLE think_cache (
 *      cachekey varchar(255) NOT NULL,
 *      expire int(11) NOT NULL,
 *      data blob,
 *      datacrc int(32),
 *      UNIQUE KEY `cachekey` (`cachekey`)
 *    );.
 *
 * @category   Extend
 *
 * @author    liu21st <liu21st@gmail.com>
 */
class CacheDb extends Cache
{
    /**
     * 架构函数.
     *
     * @param array $options 缓存参数
     */
    public function __construct($options = array())
    {
        if (empty($options)) {
            $options = array(
                'table' => C('DATA_CACHE_TABLE'),
            );
        }
        $this->options = $options;
        $this->options['prefix'] = isset($options['prefix']) ? $options['prefix'] : C('DATA_CACHE_PREFIX');
        $this->options['length'] = isset($options['length']) ? $options['length'] : 0;
        $this->options['expire'] = isset($options['expire']) ? $options['expire'] : C('DATA_CACHE_TIME');
        import('Db');
        $this->handler = DB::getInstance();
    }

    /**
     * 读取缓存.
     *
     * @param string $name 缓存变量名
     *
     * @return mixed
     */
    public function get($name)
    {
        $name = $this->options['prefix'].addslashes($name);
        N('cache_read', 1);
        $result = $this->handler->query('SELECT `data`,`datacrc` FROM `'.$this->options['table'].'` WHERE `cachekey`=\''.$name.'\' AND (`expire` =0 OR `expire`>'.time().') LIMIT 0,1');
        if (false !== $result) {
            $result = $result[0];
            if (C('DATA_CACHE_CHECK')) {
                //开启数据校验
                if ($result['datacrc'] != md5($result['data'])) {
                    //校验错误
                    return false;
                }
            }
            $content = $result['data'];
            if (C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
                //启用数据压缩
                $content = gzuncompress($content);
            }
            $content = unserialize($content);

            return $content;
        } else {
            return false;
        }
    }

    /**
     * 写入缓存.
     *
     * @param string $name   缓存变量名
     * @param mixed  $value  存储数据
     * @param int    $expire 有效时间（秒）
     *
     * @return boolen
     */
    public function set($name, $value, $expire = null)
    {
        $data = serialize($value);
        $name = $this->options['prefix'].addslashes($name);
        N('cache_write', 1);
        if (C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
            //数据压缩
            $data = gzcompress($data, 3);
        }
        if (C('DATA_CACHE_CHECK')) {
            //开启数据校验
            $crc = md5($data);
        } else {
            $crc = '';
        }
        if (is_null($expire)) {
            $expire = $this->options['expire'];
        }
        $expire = ($expire == 0) ? 0 : (time() + $expire); //缓存有效期为0表示永久缓存
        $result = $this->handler->query('select `cachekey` from `'.$this->options['table'].'` where `cachekey`=\''.$name.'\' limit 0,1');
        if (!empty($result)) {
            //更新记录
            $result = $this->handler->execute('UPDATE '.$this->options['table'].' SET data=\''.$data.'\' ,datacrc=\''.$crc.'\',expire='.$expire.' WHERE `cachekey`=\''.$name.'\'');
        } else {
            //新增记录
             $result = $this->handler->execute('INSERT INTO '.$this->options['table'].' (`cachekey`,`data`,`datacrc`,`expire`) VALUES (\''.$name.'\',\''.$data.'\',\''.$crc.'\','.$expire.')');
        }
        if ($result) {
            if ($this->options['length'] > 0) {
                // 记录缓存队列
                $this->queue($name);
            }

            return true;
        } else {
            return false;
        }
    }

    /**
     * 删除缓存.
     *
     * @param string $name 缓存变量名
     *
     * @return boolen
     */
    public function rm($name)
    {
        $name = $this->options['prefix'].addslashes($name);

        return $this->handler->execute('DELETE FROM `'.$this->options['table'].'` WHERE `cachekey`=\''.$name.'\'');
    }

    /**
     * 清除缓存.
     *
     * @return boolen
     */
    public function clear()
    {
        return $this->handler->execute('TRUNCATE TABLE `'.$this->options['table'].'`');
    }
}
