const express = require('express');
const cors = require('cors');
const path = require('path');
const multer = require('multer');
const jwt = require('jsonwebtoken');
const bcrypt = require('bcryptjs');
const db = require('./database');
const { extractFirstTwoPages } = require('./utils/pdfProcessor');
const fs = require('fs');

const app = express();
const PORT = 3000;
const JWT_SECRET = 'super-secret-key-pdf-preview';

app.use(cors());
app.use(express.json());
app.use('/uploads/processed', express.static(path.join(__dirname, 'uploads/processed')));
// Serve the built frontend from the public folder
app.use(express.static(path.join(__dirname, 'public')));

// Ensure upload directories exist
const uploadDirOrig = path.join(__dirname, 'uploads/original');
const uploadDirProc = path.join(__dirname, 'uploads/processed');
if (!fs.existsSync(uploadDirOrig)) fs.mkdirSync(uploadDirOrig, { recursive: true });
if (!fs.existsSync(uploadDirProc)) fs.mkdirSync(uploadDirProc, { recursive: true });

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    // 使用绝对路径，避免服务器 CWD 不在项目目录时写入失败
    cb(null, path.join(__dirname, 'uploads/original/'));
  },
  filename: function (req, file, cb) {
    const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1E9);
    cb(null, uniqueSuffix + '.pdf');
  }
});
const upload = multer({ storage: storage });

// Middleware for auth
const authenticateJWT = (req, res, next) => {
  const authHeader = req.headers.authorization;
  if (authHeader) {
    const token = authHeader.split(' ')[1];
    jwt.verify(token, JWT_SECRET, (err, user) => {
      if (err) return res.sendStatus(403);
      req.user = user;
      next();
    });
  } else {
    res.sendStatus(401);
  }
};

// Admin Login Route
app.post('/api/admin/login', (req, res) => {
  const { username, password } = req.body;
  const user = db.prepare('SELECT * FROM users WHERE username = ?').get(username);
  
  if (user && bcrypt.compareSync(password, user.password)) {
    const token = jwt.sign({ username: user.username }, JWT_SECRET, { expiresIn: '24h' });
    res.json({ token });
  } else {
    res.status(401).json({ message: 'Username or password incorrect' });
  }
});

// Upload PDF Route
app.post('/api/admin/upload', authenticateJWT, upload.single('document'), async (req, res) => {
  if (!req.file) return res.status(400).json({ message: 'No file uploaded' });
  
  const originalPath = req.file.path;
  const processedFilename = 'processed-' + req.file.filename;
  const processedPathRelative = 'uploads/processed/' + processedFilename;
  const processedPath = path.join(__dirname, processedPathRelative);
  const title = req.body.title || req.file.originalname;

  try {
    await extractFirstTwoPages(originalPath, processedPath);
    
    const stmt = db.prepare('INSERT INTO documents (title, original_path, processed_path) VALUES (?, ?, ?)');
    const info = stmt.run(title, originalPath, processedPathRelative);
    
    res.json({ message: 'Upload successful', documentId: info.lastInsertRowid });
  } catch (error) {
    // 输出完整堆栈到服务器日志，便于排查
    console.error('Upload error details:', error.stack || error);
    res.status(500).json({
      message: 'Error processing PDF',
      error: error.message || error.toString(),
      stack: process.env.NODE_ENV !== 'production' ? error.stack : undefined
    });
  }
});

// Delete PDF Route
app.delete('/api/admin/documents/:id', authenticateJWT, (req, res) => {
    const doc = db.prepare('SELECT * FROM documents WHERE id = ?').get(req.params.id);
    if (!doc) return res.status(404).json({ message: 'Not found' });

    try {
        if (fs.existsSync(path.join(__dirname, doc.original_path))) fs.unlinkSync(path.join(__dirname, doc.original_path));
        if (fs.existsSync(path.join(__dirname, doc.processed_path))) fs.unlinkSync(path.join(__dirname, doc.processed_path));
    } catch(e) { }

    db.prepare('DELETE FROM documents WHERE id = ?').run(req.params.id);
    res.json({ message: 'Deleted successfully' });
});

// Public List Documents Route
app.get('/api/documents', (req, res) => {
  const docs = db.prepare('SELECT id, title, processed_path, created_at FROM documents ORDER BY created_at DESC').all();
  // Map processed_path to a URL
  const responseData = docs.map(doc => ({
    id: doc.id,
    title: doc.title,
    created_at: doc.created_at,
    url: `/${doc.processed_path}`
  }));
  res.json(responseData);
});

// Public Get Single Document
app.get('/api/documents/:id', (req, res) => {
  const doc = db.prepare('SELECT id, title, processed_path, created_at FROM documents WHERE id = ?').get(req.params.id);
  if (!doc) return res.status(404).json({ message: 'Document not found' });
  
  res.json({
    id: doc.id,
    title: doc.title,
    created_at: doc.created_at,
    url: `/${doc.processed_path}`
  });
});

app.listen(PORT, () => {
  console.log(`Backend server running on http://localhost:${PORT}`);
});

// SPA fallback: must be after all API routes so Vue Router can handle client-side routing
// Note: app.use() (not app.get('*')) is required for Express 5 compatibility
app.use((req, res) => {
  const indexPath = path.join(__dirname, 'public', 'index.html');
  if (fs.existsSync(indexPath)) {
    res.sendFile(indexPath);
  } else {
    res.status(404).send('Frontend not built yet. Run: cd frontend && npm run build');
  }
});