const express = require('express');
const multer = require('multer');
const cors = require('cors');
const fs = require('fs');
const path = require('path');
const morgan = require('morgan');

const app = express();
const port = 3000;

// Middleware
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.');
        }
    });
});

// 路由
app.get('/api/hello', (req, res) => {
    res.send('Hello, world!');
});

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