/**
 * Express Server
 * HR 績效評核系統後端伺服器
 */

require('dotenv').config();
const express = require('express');
const cors = require('cors');
const helmet = require('helmet');
const morgan = require('morgan');
const path = require('path');

// Import routes
const llmRoutes = require('./routes/llm.routes');

// Import error handler
const { handleError } = require('./utils/errorHandler');

// Create Express app
const app = express();
const PORT = process.env.PORT || 3000;

// ============================================
// Middleware
// ============================================

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

// CORS configuration
app.use(cors({
  origin: process.env.FRONTEND_URL || '*',
  methods: ['GET', 'POST', 'PUT', 'DELETE', 'PATCH'],
  allowedHeaders: ['Content-Type', 'Authorization'],
  credentials: true,
}));

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

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

// Static files
app.use(express.static('public'));

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

// Health check
app.get('/health', (req, res) => {
  res.json({
    success: true,
    message: 'HR Performance System API is running',
    timestamp: new Date().toISOString(),
    environment: process.env.NODE_ENV,
  });
});

// API routes
app.use('/api/llm', llmRoutes);

// Root endpoint
app.get('/', (req, res) => {
  res.json({
    name: 'HR Performance System API',
    version: '1.0.0',
    description: '四卡循環績效管理系統',
    endpoints: {
      health: '/health',
      llm: '/api/llm',
    },
  });
});

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

// 404 handler
app.use((req, res, next) => {
  res.status(404).json({
    success: false,
    error: {
      statusCode: 404,
      message: `Cannot ${req.method} ${req.path}`,
      timestamp: new Date().toISOString(),
      path: req.path,
    },
  });
});

// Global error handler
app.use(handleError);

// ============================================
// Server Start
// ============================================

const server = app.listen(PORT, () => {
  console.log('='.repeat(50));
  console.log('🚀 HR Performance System API Server');
  console.log('='.repeat(50));
  console.log(`📡 Server running on: http://localhost:${PORT}`);
  console.log(`🌍 Environment: ${process.env.NODE_ENV || 'development'}`);
  console.log(`📅 Started at: ${new Date().toLocaleString('zh-TW')}`);
  console.log('='.repeat(50));
  console.log('\n📚 Available endpoints:');
  console.log(`   GET  /               - API information`);
  console.log(`   GET  /health         - Health check`);
  console.log(`   POST /api/llm/test/* - Test LLM connections`);
  console.log(`   POST /api/llm/generate - Generate content with LLM`);
  console.log('\n✨ Server is ready to accept connections!\n');
});

// Graceful shutdown
process.on('SIGTERM', () => {
  console.log('\n⚠️  SIGTERM received. Shutting down gracefully...');
  server.close(() => {
    console.log('✅ Server closed');
    process.exit(0);
  });
});

process.on('SIGINT', () => {
  console.log('\n⚠️  SIGINT received. Shutting down gracefully...');
  server.close(() => {
    console.log('✅ Server closed');
    process.exit(0);
  });
});

// Uncaught exception handler
process.on('uncaughtException', (error) => {
  console.error('❌ Uncaught Exception:', error);
  process.exit(1);
});

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

module.exports = app;