const dotenv = require('dotenv');
const parsed = dotenv.config().parsed;
if (parsed) {
  for (const key in parsed) {
    process.env[key] = parsed[key];
  }
}
// ── Startup Validations ──────────────────────────────────────────────────────
if (!process.env.JWT_SECRET) {
  console.warn('⚠️  WARNING: JWT_SECRET is not set in .env — authentication will fail. Set it before using auth routes.');
}

const express = require('express');
const cors = require('cors');
const connectDB = require('./config/db');
const authRoutes = require('./routes/authRoutes');
const contractRoutes = require('./routes/contractRoutes');
const paymentRoutes = require('./routes/paymentRoutes');
const feedbackRoutes = require('./routes/feedbackRoutes');
const adminRoutes = require('./routes/adminRoutes');
const ApiError = require('./utils/ApiError');
const helmet = require('helmet');
const rateLimit = require('express-rate-limit');
const User = require('./models/User');

const app = express();
app.set('trust proxy', 1);
const PORT = process.env.PORT || 7860;

// ── Database ─────────────────────────────────────────────────────────────────
connectDB();

// ── Middleware ────────────────────────────────────────────────────────────────
app.use(helmet({
  frameguard: false,
  contentSecurityPolicy: false,
}));
app.use(rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 1000, // limit each IP to 1000 requests per windowMs
  handler: (req, res) => {
    res.status(429).json({
      success: false,
      message: 'Too many requests, please try again later.',
      errors: []
    });
  }
}));
const allowedOrigins = [
  'http://localhost:5173',
  'http://localhost:5174',
  'https://lexguard.vercel.app',
  'https://adity251105-lexguard-backend.hf.space',
  process.env.FRONTEND_URL,  // Allow custom override via env
].filter(Boolean);

app.use(cors({
  origin: (origin, cb) => {
    // Allow requests with no origin (server-to-server, curl, mobile apps)
    if (!origin || allowedOrigins.includes(origin)) return cb(null, true);
    cb(null, false);
  },
  credentials: true
}));
app.use(express.json({ limit: '11mb' }));
app.use(express.urlencoded({ extended: true, limit: '11mb' }));

// ── Routes ────────────────────────────────────────────────────────────────────
app.use('/api/auth', authRoutes);
app.use('/api/contracts', contractRoutes);
app.use('/api/payments', paymentRoutes);
app.use('/api/feedback', feedbackRoutes);
app.use('/api/admin', adminRoutes);

// Root landing endpoint to prevent 404 in Hugging Face Space iframe
app.get('/', (_req, res) => {
  res.status(200).json({
    status: 'ok',
    message: 'Welcome to LexGuard API backend. Use /health for service health status.',
    documentation: 'https://github.com/Aditya2514/LexGuard',
  });
});

// Health check endpoint
app.get('/health', (_req, res) => {
  res.status(200).json({
    status: 'ok',
    service: 'LexGuard API',
    version: '1.0.0',
    phase: 'Phase 1 – Core Backend & Parsing',
  });
});

// ── 404 Handler ───────────────────────────────────────────────────────────────
app.use((req, res) => {
  res.status(404).json({
    success: false,
    message: `Route ${req.method} ${req.originalUrl} not found.`,
  });
});

// ── Global Error Handler ──────────────────────────────────────────────────────
// eslint-disable-next-line no-unused-vars
app.use((err, _req, res, _next) => {
  // Multer file size exceeded
  if (err.code === 'LIMIT_FILE_SIZE') {
    return res.status(413).json({
      success: false,
      message: 'File too large. Maximum allowed upload size is 10 MB.',
    });
  }

  // Multer fileFilter rejection (plain Error with statusCode set in fileFilter)
  if (err.statusCode && !(err instanceof ApiError)) {
    return res.status(err.statusCode).json({
      success: false,
      message: err.message,
    });
  }

  // Known application errors
  if (err instanceof ApiError) {
    return res.status(err.statusCode).json({
      success: false,
      message: err.message,
      errors: err.errors,
    });
  }

  // Mongoose: invalid ObjectId format in URL params (e.g. /api/contracts/bad-id)
  if (err.name === 'CastError') {
    return res.status(400).json({
      success: false,
      message: `Invalid ID format: "${err.value}" is not a valid resource ID.`,
    });
  }

  // Mongoose: buffering timed out — DB is unreachable
  if (err.name === 'MongooseError' && err.message.includes('buffering timed out')) {
    return res.status(503).json({
      success: false,
      message: 'Database is currently unavailable. Please try again shortly.',
    });
  }

  // Mongoose validation errors (e.g. required field missing)
  if (err.name === 'ValidationError') {
    const messages = Object.values(err.errors).map((e) => e.message);
    return res.status(400).json({
      success: false,
      message: 'Validation failed.',
      errors: messages,
    });
  }

  // Unknown/unexpected errors — log stack for debugging, hide details from client
  console.error('Unhandled error:', err);
  return res.status(500).json({
    success: false,
    message: 'An unexpected internal error occurred. Please try again later.',
  });
});

// ── Start Server ──────────────────────────────────────────────────────────────
if (!process.env.VERCEL) {
  app.listen(PORT, () => {
    console.log(`🚀 LexGuard API running at http://localhost:${PORT}`);
    console.log(`📋 Health check: http://localhost:${PORT}/health`);
    
    // Start background job queue processor
    const jobQueueService = require('./services/jobQueueService');
    jobQueueService.startQueueWorker();
    
    // Removed warmEmbeddingCache as it is no longer used
    
    // Daily quota reset cron (runs every hour)
    setInterval(async () => {
      try {
        const now = new Date();
        const result = await User.updateMany(
          { quotaResetDate: { $lte: now } },
          { 
            usedThisMonth: 0, 
            quotaResetDate: new Date(now.getTime() + 30 * 86400000) 
          }
        );
        if (result.modifiedCount > 0) {
          console.log(`[Cron] Reset quotas for ${result.modifiedCount} users.`);
        }
      } catch (err) {
        console.error('[Cron] Error resetting quotas:', err);
      }
    }, 60 * 60 * 1000);
  });
}

module.exports = app;