require('dotenv').config();
const express = require('express');
const cors = require('cors');
const helmet = require('helmet');
const morgan = require('morgan');
const rateLimit = require('express-rate-limit');
const { testConnection, getDatabaseStats } = require('./config/db');
const { validateEnvironment } = require('./validate-env');

// Validate environment configuration on startup
console.log('\n🔧 Validating environment configuration...');
const isEnvValid = validateEnvironment();
if (!isEnvValid) {
  console.error('❌ Environment validation failed. Please fix errors and restart.');
  process.exit(1);
}

const app = express();

// Configuration
const config = require('./config/config');
const PORT = config.server.port;
const API_PREFIX = config.server.apiPrefix;
const NODE_ENV = config.server.nodeEnv;

// Security middleware
app.use(helmet());

// CORS configuration
app.use(cors(config.cors));

// Body parser middleware
app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ extended: true, limit: '10mb' }));

// Logging middleware
if (NODE_ENV === 'development') {
  app.use(morgan('dev'));
} else {
  app.use(morgan('combined'));
}

// Rate limiting
const limiter = rateLimit({
  windowMs: config.rateLimit.windowMs,
  max: config.rateLimit.maxRequests,
  message: config.rateLimit.message,
  standardHeaders: true,
  legacyHeaders: false,
});

app.use(API_PREFIX, limiter);

// Health check endpoint
app.get('/health', async (req, res) => {
  const dbStats = await getDatabaseStats();
  
  res.status(200).json({
    status: 'OK',
    message: 'Interview Quiz API is running',
    timestamp: new Date().toISOString(),
    environment: NODE_ENV,
    database: dbStats
  });
});

// API routes
const authRoutes = require('./routes/auth.routes');
const guestRoutes = require('./routes/guest.routes');
const categoryRoutes = require('./routes/category.routes');
const questionRoutes = require('./routes/question.routes');
const adminRoutes = require('./routes/admin.routes');
const quizRoutes = require('./routes/quiz.routes');
const userRoutes = require('./routes/user.routes');

app.use(`${API_PREFIX}/auth`, authRoutes);
app.use(`${API_PREFIX}/guest`, guestRoutes);
app.use(`${API_PREFIX}/categories`, categoryRoutes);
app.use(`${API_PREFIX}/questions`, questionRoutes);
app.use(`${API_PREFIX}/admin`, adminRoutes);
app.use(`${API_PREFIX}/quiz`, quizRoutes);
app.use(`${API_PREFIX}/users`, userRoutes);

// Root endpoint
app.get('/', (req, res) => {
  res.json({
    message: 'Welcome to Interview Quiz API',
    version: '2.0.0',
    documentation: '/api-docs'
  });
});

// 404 handler
app.use((req, res, next) => {
  res.status(404).json({
    success: false,
    message: 'Route not found',
    path: req.originalUrl
  });
});

// Global error handler
app.use((err, req, res, next) => {
  console.error('Error:', err);

  const statusCode = err.statusCode || 500;
  const message = err.message || 'Internal Server Error';

  res.status(statusCode).json({
    success: false,
    message: message,
    ...(NODE_ENV === 'development' && { stack: err.stack })
  });
});

// Start server
app.listen(PORT, async () => {
  console.log(`
╔════════════════════════════════════════╗
║   Interview Quiz API - MySQL Edition  ║
╚════════════════════════════════════════╝
  
🚀 Server running on port ${PORT}
🌍 Environment: ${NODE_ENV}
🔗 API Endpoint: http://localhost:${PORT}${API_PREFIX}
📊 Health Check: http://localhost:${PORT}/health
  `);
  
  // Test database connection on startup
  console.log('🔌 Testing database connection...');
  const connected = await testConnection();
  if (!connected) {
    console.warn('⚠️  Warning: Database connection failed. Server is running but database operations will fail.');
  }
});

// Handle unhandled promise rejections
process.on('unhandledRejection', (err) => {
  console.error('Unhandled Promise Rejection:', err);
  // Close server & exit process
  process.exit(1);
});

module.exports = app;