import express from 'express';
import cors from 'cors';
import helmet from 'helmet';
import session from 'express-session';
import rateLimit from 'express-rate-limit';
import dotenv from 'dotenv';
import { testConnection } from './config.js';
import { sessionConfig, securityConfig, serverConfig } from './config.js';
import { notFoundHandler, errorHandler } from './middleware/errorHandler.js';

// Routes
import authRoutes from './routes/auth.js';
import analyzeRoutes from './routes/analyze.js';
import adminRoutes from './routes/admin.js';
import llmConfigRoutes from './routes/llmConfig.js';

// 載入環境變數
dotenv.config();

const app = express();
const PORT = serverConfig.port;

// ============================================
// Middleware Setup
// ============================================

// Security Headers
app.use(helmet({
  contentSecurityPolicy: false, // 暫時關閉 CSP 以便開發
}));

// CORS
app.use(cors({
  origin: [`http://localhost:${serverConfig.clientPort}`, 'http://localhost:5173'],
  credentials: true
}));

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

// Session
app.use(session({
  secret: sessionConfig.secret,
  resave: sessionConfig.resave,
  saveUninitialized: sessionConfig.saveUninitialized,
  cookie: sessionConfig.cookie,
  name: '5why.sid'
}));

// Rate Limiting
const limiter = rateLimit({
  windowMs: securityConfig.rateLimitWindowMs,
  max: securityConfig.rateLimitMax,
  message: {
    success: false,
    error: '請求過於頻繁，請稍後再試'
  },
  standardHeaders: true,
  legacyHeaders: false
});

app.use('/api/', limiter);

// Request Logging (Development)
if (process.env.NODE_ENV === 'development') {
  app.use((req, res, next) => {
    console.log(`${new Date().toISOString()} - ${req.method} ${req.path}`);
    next();
  });
}

// ============================================
// Routes
// ============================================

// Health Check
app.get('/health', (req, res) => {
  res.json({
    status: 'ok',
    message: 'Server is running',
    timestamp: new Date().toISOString(),
    environment: process.env.NODE_ENV || 'development'
  });
});

// Database Health Check
app.get('/health/db', async (req, res) => {
  try {
    const isConnected = await testConnection();
    res.json({
      status: isConnected ? 'ok' : 'error',
      database: isConnected ? 'connected' : 'disconnected'
    });
  } catch (error) {
    res.status(500).json({
      status: 'error',
      database: 'error',
      message: error.message
    });
  }
});

// API Routes
app.use('/api/auth', authRoutes);
app.use('/api/analyze', analyzeRoutes);
app.use('/api/admin', adminRoutes);
app.use('/api/llm-config', llmConfigRoutes);

// Root Endpoint
app.get('/', (req, res) => {
  res.json({
    message: '5 Why Root Cause Analyzer API',
    version: '1.0.0',
    endpoints: {
      health: '/health',
      auth: {
        login: 'POST /api/auth/login',
        logout: 'POST /api/auth/logout',
        me: 'GET /api/auth/me'
      },
      analyze: {
        create: 'POST /api/analyze',
        history: 'GET /api/analyze/history',
        detail: 'GET /api/analyze/:id',
        translate: 'POST /api/analyze/translate'
      },
      admin: {
        dashboard: 'GET /api/admin/dashboard',
        users: 'GET /api/admin/users',
        analyses: 'GET /api/admin/analyses',
        auditLogs: 'GET /api/admin/audit-logs'
      },
      llmConfig: {
        list: 'GET /api/llm-config',
        active: 'GET /api/llm-config/active',
        create: 'POST /api/llm-config',
        update: 'PUT /api/llm-config/:id',
        activate: 'PUT /api/llm-config/:id/activate',
        delete: 'DELETE /api/llm-config/:id',
        test: 'POST /api/llm-config/test'
      }
    }
  });
});

// ============================================
// Error Handling
// ============================================

// 404 Handler
app.use(notFoundHandler);

// Global Error Handler
app.use(errorHandler);

// ============================================
// Server Startup
// ============================================

async function startServer() {
  try {
    console.log('\n╔════════════════════════════════════════════╗');
    console.log('║  5 Why Analyzer - Server Starting...     ║');
    console.log('╚════════════════════════════════════════════╝\n');

    // Test database connection
    console.log('📡 Testing database connection...');
    const dbConnected = await testConnection();

    if (!dbConnected) {
      console.warn('⚠️  Warning: Database connection failed');
      console.warn('   Server will start but database features will not work');
    }

    // Start server
    app.listen(PORT, () => {
      console.log('\n✅ Server is running!');
      console.log(`   URL: http://localhost:${PORT}`);
      console.log(`   Environment: ${process.env.NODE_ENV || 'development'}`);
      console.log(`   Database: ${dbConnected ? 'Connected ✓' : 'Disconnected ✗'}`);
      console.log(`\n📚 API Documentation: http://localhost:${PORT}/`);
      console.log(`🔍 Health Check: http://localhost:${PORT}/health`);
      console.log('\n💡 Press Ctrl+C to stop the server\n');
    });

  } catch (error) {
    console.error('\n❌ Failed to start server:');
    console.error('   Error:', error.message);
    process.exit(1);
  }
}

// Handle uncaught exceptions
process.on('uncaughtException', (error) => {
  console.error('Uncaught Exception:', error);
  process.exit(1);
});

// Handle unhandled promise rejections
process.on('unhandledRejection', (reason, promise) => {
  console.error('Unhandled Rejection at:', promise, 'reason:', reason);
  process.exit(1);
});

// Graceful shutdown
process.on('SIGTERM', () => {
  console.log('\n📴 SIGTERM received. Shutting down gracefully...');
  process.exit(0);
});

process.on('SIGINT', () => {
  console.log('\n📴 SIGINT received. Shutting down gracefully...');
  process.exit(0);
});

// Start the server
startServer();