const express = require('express');
const cors = require('cors');
const bodyParser = require('body-parser');
const bcrypt = require('bcrypt');
const { body, validationResult } = require('express-validator');
const morgan = require('morgan');
const timeout = require('connect-timeout');
const multer = require('multer');
const path = require('path');
const fs = require('fs');
const rateLimit = require('express-rate-limit');

// 创建 Express 应用实例
const app = express();
const PORT = 3000; // 可以根据需要修改端口
const uploadDir = 'uploads/';

// 使用中间件
app.use(cors({
    origin: 'http://your-frontend-domain.com', // 修改为你前端的域名
    methods: ['GET', 'POST'],
    allowedHeaders: ['Content-Type']
}));
app.use(express.json()); // 解析 JSON 格式的请求体
app.use(morgan('combined')); // 记录 HTTP 请求日志

// 请求限制
const limiter = rateLimit({
    windowMs: 15 * 60 * 1000, // 15 分钟
    max: 100 // 每个 IP 限制 100 次请求
});
app.use(limiter); // 应用限制

// 检查并创建上传目录
if (!fs.existsSync(uploadDir)) {
    fs.mkdirSync(uploadDir, { recursive: true });
}

// 设置文件存储配置
const storage = multer.diskStorage({
    destination: (req, file, cb) => {
        cb(null, uploadDir);
    },
    filename: (req, file, cb) => {
        cb(null, Date.now() + path.extname(file.originalname));
    }
});

// 创建上传实例
const upload = multer({ 
    storage,
    limits: { fileSize: 5 * 1024 * 1024 }, // 限制文件大小为 5MB
    fileFilter: (req, file, cb) => {
        const filetypes = /jpeg|jpg|png|gif|pdf/;
        const mimetype = filetypes.test(file.mimetype);
        const extname = filetypes.test(path.extname(file.originalname).toLowerCase());

        if (mimetype && extname) {
            return cb(null, true);
        }
        cb(new Error('只允许上传 JPEG、PNG、GIF 和 PDF 文件'));
    }
});

// 模拟的用户数据（在实际应用中，这通常来自数据库）
let users = []; // 应该替换为实际的数据库

// 注册接口
app.post('/api/register', [
    body('username').notEmpty().withMessage('用户名不能为空'),
    body('password').notEmpty().withMessage('密码不能为空'),
    body('confirm_password').custom((value, { req }) => {
        if (value !== req.body.password) {
            throw new Error('密码不匹配');
        }
        return true;
    })
], async (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({ errors: errors.array() });
    }

    const { username, password } = req.body;
    const existingUser = users.find(user => user.username === username);
    if (existingUser) {
        return res.status(400).send('用户名已被注册');
    }

    const hashedPassword = await bcrypt.hash(password, 10);
    users.push({ username, password: hashedPassword });
    res.status(201).send('注册成功');
});

// 登录接口
app.post('/api/login', [
    body('username').isString().notEmpty(),
    body('password').isString().notEmpty()
], (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({ errors: errors.array() });
    }

    const { username, password } = req.body;
    const user = users.find(u => u.username === username);

    if (user && bcrypt.compareSync(password, user.password)) {
        return res.status(200).json({ message: 'Login successful!' });
    } else {
        return res.status(401).json({ message: 'Invalid username or password.' });
    }
});

// 获取数据接口
app.get('/api/data', (req, res) => {
    return res.status(200).json({ title: "欢迎使用系统", description: "这是一个模拟的系统，用于展示数据与交互" });
});
app.use(cors({
    origin: 'http://your-frontend-domain.com', // 指定允许的源
    methods: ['GET', 'POST'],
}));
app.use(express.json());
app.use(express.static(path.join(__dirname, 'public'))); // 提供静态文件
app.use(morgan('combined')); // 记录请求日志

// 创建上传目录
const uploadsDir = path.join(__dirname, 'uploads');
if (!fs.existsSync(uploadsDir)) {
    fs.mkdirSync(uploadsDir, { recursive: true });
}

// Multer setup for file uploads
const storage = multer.diskStorage({
    destination: (req, file, cb) => {
        cb(null, uploadsDir); // 确保上传目录存在
    },
    filename: (req, file, cb) => {
        cb(null, Date.now() + path.extname(file.originalname)); // Append timestamp to avoid name collisions
    }
});

const upload = multer({
    storage,
    limits: {
        fileSize: 5 * 1024 * 1024 // 限制文件大小为5MB
    },
    fileFilter: (req, file, cb) => {
        const filetypes = /csv|txt|json/; // 允许的文件类型
        const extname = filetypes.test(path.extname(file.originalname).toLowerCase());
        const mimetype = filetypes.test(file.mimetype);
        
        if (mimetype && extname) {
            return cb(null, true);
        }
        cb(new Error('Error: File type not supported!'));
    }
});

// Endpoint to handle file import
app.post('/import', upload.single('file'), (req, res) => {
    if (!req.file) {
        return res.status(400).send('No file uploaded.');
    }
    console.log(req.file);
    res.send('File imported successfully!');
});

// Endpoint to handle file export
app.get('/export', (req, res) => {
    const filePath = path.join(__dirname, 'exports', 'sample-data.csv'); // 确保该文件存在
    res.download(filePath, 'sample-data.csv', (err) => {
        if (err) {
            console.error(err);
            res.status(500).send('Error exporting file.');
        }
    });
});


// 提交成绩接口
app.post('/api/submit-grade', [
    body('grade').isNumeric()
], (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({ errors: errors.array() });
    }

    const { grade } = req.body;
    console.log(`Received grade: ${grade}`);
    return res.status(200).json({ message: 'Grade submitted successfully!', grade });
});

// 文件上传接口
app.post('/api/upload-file', upload.single('file'), (req, res) => {
    if (!req.file) {
        return res.status(400).json({ message: '没有文件上传' });
    }
    res.status(200).json({ message: '文件上传成功', filename: req.file.filename });
});

// 新增 Snum-data 接口
app.post('/api/Snum-data', (req, res) => {
    const { Number } = req.body;
    // 检查请求体中的数据
    if (typeof Number === 'undefined') {
        return res.status(400).json({ message: 'Number is required' });
    }
    console.log('Received data:', Number);

    res.status(200).json({ message: 'Data received successfully', data: { Number } });
});

// 全局错误处理
app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('服务器内部错误');
});
// 路由
app.get('/api/hello', (req, res) => {
    res.send('Hello, world!');
});


// 启动服务器
app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});