<?php
// +----------------------------------------------------------------------
// | ThinkCache
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2012 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------
namespace Think\Cache\Driver;
/**
 * 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`)
 *    );
 * @author    liu21st <liu21st@gmail.com>
 */
class Db {

    protected $handler  =   null;
    protected $options  =   array(
        'db'            =>  '',
        'table'         =>  '',
        'prefix'        =>  '',
        'expire'        =>  0,
        'length'        =>  0,
    );

    /**
     * 架构函数
     * @param array $options 缓存参数
     * @access public
     */
    public function __construct($options=[]) {
        if(!empty($options)) {
            $this->options      =   array_merge($this->options,$options);
        }
        $this->handler   = \Think\Db::instance();
    }

    /**
     * 读取缓存
     * @access public
     * @param string $name 缓存变量名
     * @return mixed
     */
    public function get($name) {
        $name       =  $this->options['prefix'].addslashes($name);
        $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];
            $content   =  $result['data'];
            if(function_exists('gzcompress')) {
                //启用数据压缩
                $content   =   gzuncompress($content);
            }
            $content    =   unserialize($content);
            return $content;
        }
        else {
            return false;
        }
    }

    /**
     * 写入缓存
     * @access public
     * @param string $name 缓存变量名
     * @param mixed $value  存储数据
     * @param integer $expire  有效时间（秒）
     * @return boolen
     */
    public function set($name, $value,$expire=null) {
        $data   =  serialize($value);
        $name   =  $this->options['prefix'].addslashes($name);
        if(function_exists('gzcompress')) {
            //数据压缩
            $data   =   gzcompress($data,3);
        }
        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=\''.$data.'\' ,expire='.$expire.' WHERE `cachekey`=\''.$name.'\'');
        }else {
        	//新增记录
             $result  =  $this->handler->execute('INSERT INTO '.$this->options['table'].' (`cachekey`,`data`,`expire`) VALUES (\''.$name.'\',\''.$data.'\','.$expire.')');
        }
        if($result) {
            if($this->options['length']>0) {
                // 记录缓存队列
                $result   =   $this->handler->query('SELECT `data`,`datacrc` FROM `'.$this->options['table'].'` WHERE `cachekey`=\'__info__\' AND `expire` =0 LIMIT 0,1');
                $queue  =   xcache_get('__info__');
                if(!$result) {
                    $this->handler->execute('INSERT INTO '.$this->options['table'].' (`cachekey`,`data`,`expire`) VALUES (\'__info__\',\'\',0)');
                    $queue  =   [];
                }else{
                    $queue   =  unserialize($result[0]['data']);
                }
                if(false===array_search($name, $queue))  array_push($queue,$name);
                if(count($queue) > $this->options['length']) {
                    // 出列
                    $key =  array_shift($queue);
                    // 删除缓存
                    $this->handler->execute('DELETE FROM `'.$this->options['table'].'` WHERE `cachekey`=\''.$key.'\'');
                }
                $this->handler->execute('UPDATE '.$this->options['table'].' SET data=\''.serialize($queue).'\' ,expire=0 WHERE `cachekey`=\'__info__\'')
                xcache_set('__info__', $queue);
            }
            return true;
        }else {
            return false;
        }
    }

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

}