require('dotenv').config();
const express = require('express');
const multer = require('multer');
const { google } = require('googleapis');
const fs = require('fs');
const cors = require('cors');

const app = express();
const upload = multer({ dest: 'uploads/' });

app.use(cors({ origin: '*', credentials: true, allowedHeaders: ['Content-Type', 'Authorization', 'x-refresh-token'] }));
app.use(express.json());

const GOOGLE_CLIENT_ID = process.env.GOOGLE_CLIENT_ID;
const GOOGLE_CLIENT_SECRET = process.env.GOOGLE_CLIENT_SECRET;
const REDIRECT_URI = process.env.REDIRECT_URI;

let adminRefreshToken = null;

const oauth2Client = new google.auth.OAuth2(GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, REDIRECT_URI);

async function getAccessToken(req) {
    if (!adminRefreshToken && req && req.headers['x-refresh-token']) {
        console.log('Restoring session from client header...');
        adminRefreshToken = req.headers['x-refresh-token'];
    }
    if (!adminRefreshToken) throw new Error('Chưa đăng nhập Admin (Session expired)');
    
    oauth2Client.setCredentials({ refresh_token: adminRefreshToken });
    const { credentials } = await oauth2Client.refreshAccessToken();
    return credentials.access_token;
}

// Hàm Tìm hoặc Tạo Folder (Đã khôi phục)
async function findOrCreateFolder(drive, name, parentId = 'root') {
    const q = `mimeType='application/vnd.google-apps.folder' and name='${name}' and '${parentId}' in parents and trashed=false`;
    const res = await drive.files.list({ q, fields: 'files(id, name)' });
    
    if (res.data.files.length > 0) return res.data.files[0];

    const folder = await drive.files.create({
        resource: { name, mimeType: 'application/vnd.google-apps.folder', parents: [parentId] },
        fields: 'id, name'
    });
    return folder.data;
}

// === CẤU HÌNH CHO UPTIMEROBOT & TRANG CHỦ ===
// 1. Xử lý HEAD request (UptimeRobot ping): Trả về 200 OK nhanh, không tốn tài nguyên render HTML
app.head('/', (req, res) => {
    res.status(200).end();
});

// 2. Xử lý GET request (Người dùng truy cập): Hiển thị giao diện chào mừng
app.get('/', (req, res) => {
    res.send(`
        <div style="font-family: sans-serif; text-align: center; padding-top: 50px;">
            <h1 style="color: green;">QLVB Server is Running! 🚀</h1>
            <p>Backend API đang hoạt động bình thường.</p>
            <p>Trạng thái Google Auth: ${adminRefreshToken ? '<b style="color:blue">Đã kết nối</b>' : '<b style="color:red">Chưa đăng nhập</b>'}</p>
        </div>
    `);
});
// ================================================

// 1. Login
app.post('/api/oauth/token', async (req, res) => {
    try {
        const { code, redirect_uri } = req.body;
        const client = new google.auth.OAuth2(GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, redirect_uri || REDIRECT_URI);
        const { tokens } = await client.getToken(code);
        if (tokens.refresh_token) adminRefreshToken = tokens.refresh_token;
        res.json(tokens);
    } catch (error) {
        res.status(500).json({ error: error.message });
    }
});

// 2. Upload (Đã sửa logic tạo thư mục lồng nhau)
app.post('/api/upload', upload.array('files'), async (req, res) => {
    try {
        await getAccessToken(req); // Khôi phục session
        const drive = google.drive({ version: 'v3', auth: oauth2Client });
        
        const { docName, type, month } = req.body;
        
        // Tạo cấu trúc thư mục
        const rootFolder = await findOrCreateFolder(drive, 'QLVB-DATA');
        const typeFolder = await findOrCreateFolder(drive, type === 'incoming' ? 'VanBanDen' : 'VanBanDi', rootFolder.id);
        const monthFolder = await findOrCreateFolder(drive, month || 'Khac', typeFolder.id);
        const docFolder = await findOrCreateFolder(drive, `${docName} - ${Date.now()}`, monthFolder.id);

        const uploadedFiles = [];
        for (const file of req.files) {
            const media = { mimeType: file.mimetype, body: fs.createReadStream(file.path) };
            const driveFile = await drive.files.create({
                resource: { name: file.originalname, parents: [docFolder.id] },
                media: media,
                fields: 'id, name, webViewLink, webContentLink'
            });
            uploadedFiles.push(driveFile.data);
            fs.unlinkSync(file.path);
        }
        res.json({ folderId: docFolder.id, files: uploadedFiles });
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: error.message });
    }
});

// 3. Delete
app.delete('/api/delete/:fileId', async (req, res) => {
    try {
        await getAccessToken(req);
        const drive = google.drive({ version: 'v3', auth: oauth2Client });
        await drive.files.delete({ fileId: req.params.fileId });
        res.json({ success: true });
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: error.message });
    }
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));