<?php
// +------------------------------------------------+
// | http://www.cjango.com                          |
// +------------------------------------------------+
// | 修复BUG不是一朝一夕的事情，等我喝醉了再说吧！  |
// +------------------------------------------------+
// | Author: 小陈叔叔 <Jason.Chen>                  |
// +------------------------------------------------+
namespace tools;

/**
 * 数据导出工具
 */
class Database
{
    /**
     * 文件指针
     * @var resource
     */
    private $fp;

    /**
     * 备份文件信息 part - 卷号，name - 文件名
     * @var array
     */
    private $file;

    /**
     * 当前打开文件大小
     * @var integer
     */
    private $size = 0;

    /**
     * 备份配置
     * @var integer
     */
    private $config = [
        'path'     => '', // 数据库备份根路径
        'part'     => 2097152, // 数据库备份卷大小 2Mb
        'compress' => true, // 数据库备份文件是否启用压缩
        'level'    => 9, // 数据库备份文件压缩级别
        'line'     => 1000,
    ];

    /**
     * 数据库备份构造方法
     * @param array  $file   备份或还原的文件信息
     * @param array  $config 备份配置信息
     */
    public function __construct($file, $config)
    {
        $this->file   = $file;
        $this->config = array_merge($this->config, $config);
    }

    /**
     * 打开一个卷，用于写入数据
     * @param  integer $size 写入数据的大小
     */
    private function open($size)
    {
        if ($this->fp) {
            $this->size += $size;
            if ($this->size > $this->config['part']) {
                $this->config['compress'] ? @gzclose($this->fp) : @fclose($this->fp);
                $this->fp = null;
                $this->file['part']++;
                session('backup_file', $this->file);
                $this->create();
            }
        } else {
            $backuppath = $this->config['path'];
            $filename   = "{$backuppath}{$this->file['name']}-{$this->file['part']}.sql";
            if ($this->config['compress']) {
                $filename = "{$filename}.gz";
                $this->fp = @gzopen($filename, "a{$this->config['level']}");
            } else {
                $this->fp = @fopen($filename, 'a');
            }
            $this->size = filesize($filename) + $size;
        }
    }

    /**
     * 写入初始数据
     * @return boolean true - 写入成功，false - 写入失败
     */
    public function create()
    {
        $sql = "-- -----------------------------\n";
        $sql .= "-- c.Jango MySQL Data Transfer\n";
        $sql .= "--\n";
        $sql .= "-- Host     : " . \think\Config::get('database.hostname') . "\n";
        $sql .= "-- UserName : " . \think\Config::get('database.username') . "\n";
        $sql .= "-- Database : " . \think\Config::get('database.database') . "\n";
        $sql .= "--\n";
        $sql .= "-- Part : #{$this->file['part']}\n";
        $sql .= "-- Date : " . date("Y-m-d H:i:s") . "\n";
        $sql .= "-- -----------------------------\n\n";
        return $this->write($sql);
    }

    /**
     * 写入SQL语句
     * @param  string $sql 要写入的SQL语句
     * @return boolean     true - 写入成功，false - 写入失败！
     */
    private function write($sql)
    {
        $size = strlen($sql);
        // 由于压缩原因，无法计算出压缩后的长度，这里假设压缩率为50%，
        // 一般情况压缩率都会高于50%；
        $size = $this->config['compress'] ? $size / 2 : $size;
        $this->open($size);
        return $this->config['compress'] ? @gzwrite($this->fp, $sql) : @fwrite($this->fp, $sql);
    }

    /**
     * 备份表结构
     * @param  string  $table 表名
     * @param  integer $start 起始行数
     * @return boolean        false - 备份失败
     */
    public function backup($table, $start)
    {
        // 创建DB对象
        $db = \think\Loader::db();

        // 备份表结构
        if (0 == $start) {
            $result = $db->query("SHOW CREATE TABLE `{$table}`");
            $result = array_change_key_case($result[0]);

            $sql = "\n";
            $sql .= "-- -----------------------------\n";
            $sql .= "-- Table structure for `{$table}`\n";
            $sql .= "-- -----------------------------\n";
            $sql .= "SET FOREIGN_KEY_CHECKS = 0;\n";
            $sql .= "DROP TABLE IF EXISTS `{$table}`;\n";
            $sql .= trim($result['create table']) . ";\n\n";
            if (false === $this->write($sql)) {
                return false;
            }
        }

        // 数据总数
        $result = $db->query("SELECT COUNT(*) AS count FROM `{$table}`");
        $count  = $result[0]['count'];
        $line   = $this->config['line'];

        // 备份表数据
        if ($count) {
            // 写入数据注释
            if (0 == $start) {
                $sql = "-- -----------------------------\n";
                $sql .= "-- Records of `{$table}`\n";
                $sql .= "-- -----------------------------\n";
                $this->write($sql);
            }

            // 备份数据记录
            $result  = $db->query("SELECT * FROM `{$table}` LIMIT {$start}, $line");
            $columns = $db->query("SHOW COLUMNS FROM `{$table}`");
            $columns = array_column($columns, 'Field');
            $columns = implode('`, `', $columns);

            $sql = "INSERT INTO `{$table}` (`{$columns}`) VALUES\r\n";

            foreach ($result as $row) {
                $sql .= "('" . str_replace(["\r", "\n"], ['\r', '\n'], implode("', '", $row)) . "'),\r\n";
            }

            $sql = rtrim(rtrim($sql), ',') . ";\r\n";

            if (false === $this->write($sql)) {
                return false;
            }

            // 还有更多数据
            if ($count > $start + $line) {
                return [$start + $line, $count];
            }
        }

        // 备份下一表
        return 0;
    }

    /**
     * 还原数据库
     * @param  integer $start [description]
     * @return [type]         [description]
     */
    public function import($start = 0)
    {
        //还原数据
        $db = \think\Loader::db();
        if ($this->config['compress']) {
            $gz   = gzopen($this->file[1], 'r');
            $size = 0;
        } else {
            $size = filesize($this->file[1]);
            $gz   = fopen($this->file[1], 'r');
        }
        $sql = '';
        if ($start) {
            $this->config['compress'] ? gzseek($gz, $start) : fseek($gz, $start);
        }

        for ($i = 0; $i < 1000; $i++) {
            $sql .= $this->config['compress'] ? gzgets($gz) : fgets($gz);
            if (preg_match('/.*;$/', trim($sql))) {
                if (false !== $db->execute($sql)) {
                    $start += strlen($sql);
                } else {
                    return false;
                }
                $sql = '';
            } elseif ($this->config['compress'] ? gzeof($gz) : feof($gz)) {
                return 0;
            }
        }

        return [$start, $size];
    }

    /**
     * 析构方法，用于关闭文件资源
     */
    public function __destruct()
    {
        if ($this->config['compress'] && !is_null($this->fp)) {
            @gzclose($this->fp);
        } elseif (!is_null($this->fp)) {
            @fclose($this->fp);
        } else {

        }
    }
}