<?php
// +----------------------------------------------------------------------
// | YwxApp [ WE CAN DO IT JUST THINK ]
// +----------------------------------------------------------------------
// | Copyright (c) 2026-2036 http://ywxapp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Author: ywxapp<admin@ywxapp.cn>
// +----------------------------------------------------------------------

declare (strict_types = 1);

namespace ywxapp\library;

use think\facade\Db;

/**
 * 数据库备份 / 还原（纯 PHP 实现）
 *
 * 运行环境禁用了 exec / shell_exec，无法调用 mysqldump、mysql 命令行，
 * 因此这里全部走 PDO：
 *   备份：SHOW CREATE TABLE 导出结构 + 分块 SELECT 生成 INSERT，边生成边写文件（支持分卷）
 *   还原：流式读取 .sql，按分号切句逐条执行
 *   优化：OPTIMIZE TABLE
 *
 * 备份落地结构：runtime/backup/<备份名>/<备份名>-1.sql、<备份名>-2.sql …
 *
 * @author ywxapp <admin@ywxapp.cn>
 */
class DbBackup
{
    /**
     * 备份根目录
     */
    protected string $dir;

    /**
     * 单卷最大字节数
     */
    protected int $partSize;

    /**
     * 每次读取的数据行数
     */
    protected int $chunk;

    /**
     * @param string|null $dir      备份根目录，默认 runtime/backup
     * @param int         $partSize 单卷字节数，默认 2MB
     * @param int         $chunk    每次取数行数
     */
    public function __construct(?string $dir = null, int $partSize = 2097152, int $chunk = 500)
    {
        $this->dir      = $dir ?: runtime_path() . 'backup';
        $this->partSize = max(65536, $partSize);
        $this->chunk    = max(50, $chunk);
    }

    /**
     * 备份根目录
     */
    public function dir(): string
    {
        return $this->dir;
    }

    /**
     * 数据表清单（不含视图）
     *
     * @return array{name:string,rows:int,size:int,comment:string,engine:string}[]
     */
    public function tables(): array
    {
        $prefix = $this->prefix();
        try {
            $rows = Db::query('SHOW TABLE STATUS');
        } catch (\Throwable $e) {
            return [];
        }
        $list = [];
        foreach ($rows as $row) {
            $row = array_change_key_case($row, CASE_LOWER);
            $list[] = [
                'name'    => $row['name'] ?? '',
                'rows'    => (int) ($row['rows'] ?? 0),
                'size'    => (int) (($row['data_length'] ?? 0) + ($row['index_length'] ?? 0)),
                'comment' => (string) ($row['comment'] ?? ''),
                'engine'  => (string) ($row['engine'] ?? ''),
                'prefix'  => $prefix,
            ];
        }
        return $list;
    }

    /**
     * 执行备份
     *
     * @param array       $tables  表名（不带前缀也可）；空数组=全部表
     * @param string|null $name    备份名，默认按时间生成
     * @return array{name:string,files:array,size:int,tables:int,rows:int}
     */
    public function backup(array $tables = [], ?string $name = null): array
    {
        $all = $this->tables();
        $map = [];
        foreach ($all as $t) {
            $map[$t['name']] = $t;
        }
        // 允许用户传不带前缀的表名
        $chosen = [];
        foreach ($tables as $t) {
            $t = (string) $t;
            if (isset($map[$t])) {
                $chosen[] = $t;
            } else {
                $full = $this->prefix() . $t;
                if (isset($map[$full])) {
                    $chosen[] = $full;
                }
            }
        }
        if ($chosen === []) {
            $chosen = array_column($all, 'name');
        }

        $name  = $name ?: date('Ymd_His') . '_' . substr(md5(uniqid('', true)), 0, 6);
        $name  = preg_replace('/[^a-zA-Z0-9_\-]/', '', $name) ?: date('Ymd_His');
        $dir   = $this->dir . DIRECTORY_SEPARATOR . $name;
        if (!is_dir($dir) && !mkdir($dir, 0755, true) && !is_dir($dir)) {
            throw new \RuntimeException('备份目录不可写：' . $dir);
        }

        $files = [];
        $part  = 1;
        $size  = 0;
        $rows  = 0;
        $fh    = null;
        $cur   = '';

        $open = function () use (&$fh, &$part, &$cur, &$files, $dir, $name): void {
            $cur = $dir . DIRECTORY_SEPARATOR . $name . '-' . $part . '.sql';
            $fh  = fopen($cur, 'wb');
            if ($fh === false) {
                throw new \RuntimeException('无法写入备份文件：' . $cur);
            }
            fwrite($fh, $this->header($part));
            $files[] = basename($cur);
        };
        // 写入并保证分卷：超出 partSize 就换卷
        $write = function (string $sql) use (&$fh, &$part, &$size, $open): void {
            if ($fh === null) {
                $open();
            }
            $len = strlen($sql);
            if ($this->currentSize($fh) > 0 && $this->currentSize($fh) + $len > $this->partSize) {
                fclose($fh);
                $part++;
                $open();
            }
            fwrite($fh, $sql);
        };

        try {
            foreach ($chosen as $table) {
                // 1) 表结构
                $create = Db::query('SHOW CREATE TABLE `' . $table . '`');
                $create = array_change_key_case($create[0] ?? [], CASE_LOWER);
                if (empty($create['create table'])) {
                    continue;
                }
                $write("-- -----------------------------\n");
                $write("-- 表结构：`{$table}`\n");
                $write("-- -----------------------------\n");
                $write("DROP TABLE IF EXISTS `{$table}`;\n");
                $write($create['create table'] . ";\n\n");

                // 2) 数据：分块读取，避免大表撑爆内存
                $offset   = 0;
                $hasField = false;
                while (true) {
                    $data = Db::query('SELECT * FROM `' . $table . '` LIMIT ' . $offset . ',' . $this->chunk);
                    if (empty($data)) {
                        break;
                    }
                    if (!$hasField) {
                        $write("-- -----------------------------\n");
                        $write("-- 数据：`{$table}`\n");
                        $write("-- -----------------------------\n");
                        $hasField = true;
                    }
                    $values = [];
                    foreach ($data as $row) {
                        $vals = [];
                        foreach ($row as $v) {
                            $vals[] = $this->quote($v);
                        }
                        $values[] = '(' . implode(', ', $vals) . ')';
                    }
                    $write("INSERT INTO `{$table}` VALUES\n" . implode(",\n", $values) . ";\n");
                    $rows   += count($data);
                    $offset += $this->chunk;
                    if (count($data) < $this->chunk) {
                        break;
                    }
                }
                $write("\n");
            }
            $write("SET FOREIGN_KEY_CHECKS=1;\n");
            $write("-- 备份结束 " . date('Y-m-d H:i:s') . "\n");
        } finally {
            if (is_resource($fh)) {
                fclose($fh);
            }
        }

        foreach ($files as $f) {
            $size += (int) filesize($dir . DIRECTORY_SEPARATOR . $f);
        }

        return [
            'name'   => $name,
            'files'  => $files,
            'size'   => $size,
            'tables' => count($chosen),
            'rows'   => $rows,
        ];
    }

    /**
     * 备份历史（按备份名聚合，多分卷合并为一条）
     *
     * @return array{name:string,files:array,size:int,time:int,parts:int}[]
     */
    public function backups(): array
    {
        if (!is_dir($this->dir)) {
            return [];
        }
        $list = [];
        foreach (glob($this->dir . DIRECTORY_SEPARATOR . '*', GLOB_ONLYDIR) ?: [] as $dir) {
            $name  = basename($dir);
            $files = glob($dir . DIRECTORY_SEPARATOR . '*.sql') ?: [];
            if (!$files) {
                continue;
            }
            sort($files);
            $size = 0;
            $time = 0;
            $names = [];
            foreach ($files as $f) {
                $size  += (int) filesize($f);
                $time   = max($time, (int) filemtime($f));
                $names[] = basename($f);
            }
            $list[] = [
                'name'  => $name,
                'files' => $names,
                'parts' => count($names),
                'size'  => $size,
                'time'  => $time,
            ];
        }
        usort($list, fn($a, $b) => $b['time'] <=> $a['time']);
        return $list;
    }

    /**
     * 还原备份
     *
     * @return array{files:int,sql:int}
     */
    public function restore(string $name): array
    {
        $dir = $this->safePath($name);
        if ($dir === null || !is_dir($dir)) {
            throw new \RuntimeException('备份不存在：' . $name);
        }
        $files = glob($dir . DIRECTORY_SEPARATOR . '*.sql') ?: [];
        sort($files);

        $filesCount = 0;
        $sqlCount   = 0;
        foreach ($files as $file) {
            $filesCount++;
            $sqlCount += $this->executeFile($file);
        }
        return ['files' => $filesCount, 'sql' => $sqlCount];
    }

    /**
     * 删除备份
     */
    public function delete(string $name): bool
    {
        $dir = $this->safePath($name);
        if ($dir === null || !is_dir($dir)) {
            return false;
        }
        foreach (glob($dir . DIRECTORY_SEPARATOR . '*.sql') ?: [] as $f) {
            @unlink($f);
        }
        return @rmdir($dir);
    }

    /**
     * 备份文件绝对路径（下载用），非法名返回 null
     */
    public function fileOf(string $name, string $file = ''): ?string
    {
        $dir = $this->safePath($name);
        if ($dir === null || !is_dir($dir)) {
            return null;
        }
        $files = glob($dir . DIRECTORY_SEPARATOR . '*.sql') ?: [];
        sort($files);
        if ($file !== '') {
            $target = $dir . DIRECTORY_SEPARATOR . basename($file);
            return is_file($target) ? $target : null;
        }
        return $files[0] ?? null;
    }

    /**
     * 优化表
     *
     * @return array{table:string,result:string}[]
     */
    public function optimize(array $tables): array
    {
        $out = [];
        foreach ($tables as $table) {
            $table = preg_replace('/[^a-zA-Z0-9_]/', '', (string) $table) ?: '';
            if ($table === '') {
                continue;
            }
            try {
                Db::execute('OPTIMIZE TABLE `' . $table . '`');
                $out[] = ['table' => $table, 'result' => 'ok'];
            } catch (\Throwable $e) {
                $out[] = ['table' => $table, 'result' => $e->getMessage()];
            }
        }
        return $out;
    }

    /* ============================ 内部方法 ============================ */

    /**
     * 备份目录（防路径穿越：只允许 [a-zA-Z0-9_-]）
     */
    protected function safePath(string $name): ?string
    {
        $name = basename($name);
        if ($name === '' || preg_match('/[^a-zA-Z0-9_\-]/', $name)) {
            return null;
        }
        return $this->dir . DIRECTORY_SEPARATOR . $name;
    }

    /**
     * 分卷文件头
     */
    protected function header(int $part): string
    {
        return "-- YwxApp 数据库备份\n"
            . "-- 生成时间：" . date('Y-m-d H:i:s') . "\n"
            . "-- 分卷：第 {$part} 卷\n"
            . "SET NAMES utf8mb4;\n"
            . "SET FOREIGN_KEY_CHECKS=0;\n"
            . "SET SQL_MODE='NO_AUTO_VALUE_ON_ZERO';\n\n";
    }

    /**
     * 当前分卷已写字节数
     *
     * @param resource $fh
     */
    protected function currentSize($fh): int
    {
        return is_resource($fh) ? (int) ftell($fh) : 0;
    }

    /**
     * 值转义：NULL / 数字 / 二进制 / 字符串
     */
    protected function quote(mixed $value): string
    {
        if ($value === null) {
            return 'NULL';
        }
        if (is_bool($value)) {
            return $value ? '1' : '0';
        }
        if (is_int($value) || is_float($value)) {
            return (string) $value;
        }
        $value = (string) $value;
        // 含控制字符的按二进制处理，避免写入时截断
        if ($value !== '' && preg_match('/[\x00-\x08\x0B\x0C\x0E-\x1F]/', $value)) {
            return '0x' . bin2hex($value);
        }
        return $this->pdoQuote($value);
    }

    protected function pdoQuote(string $value): string
    {
        try {
            $pdo = Db::connect()->getPdo();
            $q   = $pdo->quote($value);
            return $q === false ? "'" . addslashes($value) . "'" : $q;
        } catch (\Throwable $e) {
            return "'" . addslashes($value) . "'";
        }
    }

    /**
     * 流式执行一个 SQL 文件
     */
    protected function executeFile(string $file): int
    {
        $fh = fopen($file, 'rb');
        if ($fh === false) {
            throw new \RuntimeException('无法读取：' . $file);
        }
        $count  = 0;
        $buffer = '';
        while (($line = fgets($fh)) !== false) {
            $line = rtrim($line, "\r\n");
            $trim = ltrim($line);
            if ($trim === '' || str_starts_with($trim, '--') || str_starts_with($trim, '#') || str_starts_with($trim, '/*')) {
                continue;
            }
            // 存储过程/触发器依赖 DELIMITER，本实现不支持，直接跳过声明行
            if (str_starts_with(strtoupper($trim), 'DELIMITER')) {
                continue;
            }
            $buffer .= $line . "\n";
            if (substr($trim, -1) === ';' && !str_ends_with($trim, '\\;')) {
                $sql = rtrim(rtrim($buffer), ';');
                $buffer = '';
                if ($sql === '') {
                    continue;
                }
                Db::execute($sql);
                $count++;
            }
        }
        fclose($fh);
        return $count;
    }

    protected function prefix(): string
    {
        $prefix = (string) config('database.connections.mysql.prefix', '');
        return $prefix;
    }
}