const express = require('express');
const cors = require('cors');
const mongoose = require('mongoose');
const dotenv = require('dotenv');
const rateLimit = require('express-rate-limit');

// Import routes
const { router: authRoutes } = require('./routes/auth');
const sourceTextRoutes = require('./routes/sourceTexts');
const submissionRoutes = require('./routes/submissions');
const searchRoutes = require('./routes/search');
const subtitleRoutes = require('./routes/subtitles');
const subtitleSubmissionRoutes = require('./routes/subtitleSubmissions');
const weeklyPracticeFilesRoutes = require('./routes/weeklyPracticeFiles');
const dictionaryRoutes = require('./routes/dictionary');
const icibaRoutes = require('./routes/iciba');
const oneRoutes = require('./routes/one');
const mtRoutes = require('./routes/mt');
const slidesRoutes = require('./routes/slides');
const messagesRoutes = require('./routes/messages');
const refinityRoutes = require('./routes/refinity');
const tutorialRefinityRoutes = require('./routes/tutorial-refinity');
const linksRoutes = require('./routes/links');
const docsRoutes = require('./routes/docs');
const adminWeeksRoutes = require('./routes/admin-weeks');

dotenv.config();

// Global error handlers to prevent crashes
process.on('uncaughtException', (error) => {
  console.error('Uncaught Exception:', error);
  // Don't exit immediately, try to log and continue
  console.error('Stack trace:', error.stack);
});

process.on('unhandledRejection', (reason, promise) => {
  console.error('Unhandled Rejection at:', promise, 'reason:', reason);
  // Don't exit immediately, try to log and continue
  console.error('Stack trace:', reason?.stack);
});

// Memory leak prevention
process.on('warning', (warning) => {
  console.warn('Node.js warning:', warning.name, warning.message);
});

const app = express();
const PORT = process.env.PORT || 5000;

// Trust proxy for rate limiting
app.set('trust proxy', 1);

// Rate limiting - Increased limits to prevent 429 errors
const limiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 1000, // Increased from 100 to 1000 requests per windowMs
  message: { error: 'Too many requests, please try again later.' },
  standardHeaders: true,
  legacyHeaders: false,
  skip: (req) => {
    // Skip rate limiting for health checks
    return req.path === '/health' || req.path === '/api/health';
  }
});

// Middleware
app.use(cors());
app.use(express.json({ limit: '10mb' }));
// Global request logger for debugging
app.use((req, res, next) => {
  if (req.url.includes('tutorial-refinity')) {
    console.log('[Backend Global] Request:', req.method, req.url, req.path);
  }
  next();
});
app.use(limiter);

// Database connection with better error handling
// Normalize MongoDB URI for Atlas usage and ensure TLS in SRV connection
const RAW_MONGO_URI = process.env.MONGODB_URI || 'mongodb://localhost:27017/transcreation-sandbox';
let NORMALIZED_MONGO_URI = RAW_MONGO_URI;
try {
  if (RAW_MONGO_URI.startsWith('mongodb+srv://')) {
    const hasDb = /mongodb\+srv:\/\/[^/]+\//.test(RAW_MONGO_URI) && !/mongodb\+srv:\/\/[^/]+\/$/.test(RAW_MONGO_URI);
    if (!hasDb) {
      NORMALIZED_MONGO_URI = RAW_MONGO_URI.replace(/mongodb\+srv:\/\/([^/]+)\/?/, 'mongodb+srv://$1/transhub');
    }
    if (!NORMALIZED_MONGO_URI.includes('tls=') && !NORMALIZED_MONGO_URI.includes('ssl=')) {
      NORMALIZED_MONGO_URI += (NORMALIZED_MONGO_URI.includes('?') ? '&' : '?') + 'tls=true';
    }
    if (!NORMALIZED_MONGO_URI.includes('retryWrites=')) {
      NORMALIZED_MONGO_URI += (NORMALIZED_MONGO_URI.includes('?') ? '&' : '?') + 'retryWrites=true&w=majority';
    }
  }
} catch {}

mongoose.connect(NORMALIZED_MONGO_URI, {
  maxPoolSize: 10,
  serverSelectionTimeoutMS: 15000,
  socketTimeoutMS: 45000,
})
.then(() => {
  console.log('Connected to MongoDB');
})
.catch(err => {
  console.error('MongoDB connection error:', err);
  // Don't exit immediately, try to reconnect
  setTimeout(() => {
    console.log('Attempting to reconnect to MongoDB...');
    mongoose.connect(NORMALIZED_MONGO_URI);
  }, 5000);
});

// Handle MongoDB connection errors
mongoose.connection.on('error', (err) => {
  console.error('MongoDB connection error:', err);
});

mongoose.connection.on('disconnected', () => {
  console.log('MongoDB disconnected');
});

// Routes
app.use('/api/auth', authRoutes);
app.use('/api/source-texts', sourceTextRoutes);
app.use('/api/submissions', submissionRoutes);
app.use('/api/search', searchRoutes);
app.use('/api/subtitles', subtitleRoutes);
app.use('/api/subtitle-submissions', subtitleSubmissionRoutes);
app.use('/api/weekly-practice-files', weeklyPracticeFilesRoutes);
app.use('/api/dictionary', dictionaryRoutes);
app.use('/api/iciba', icibaRoutes);
app.use('/api/one', oneRoutes);
app.use('/api/mt', mtRoutes);
app.use('/api/slides', slidesRoutes);
app.use('/api/messages', messagesRoutes);
app.use('/api/links', linksRoutes);
app.use('/api/docs', docsRoutes);
app.use('/api/refinity', refinityRoutes);
// Add logging middleware for ALL requests to help debug
app.use((req, res, next) => {
  if (req.url.includes('tutorial-refinity')) {
    console.log('[Backend] ALL middleware - tutorial-refinity request:', req.method, req.url, req.path, 'headers:', req.headers['x-user-role']);
  }
  next();
});
app.use('/api/tutorial-refinity', (req, res, next) => {
  console.log('[Backend] tutorial-refinity middleware:', req.method, req.path, req.url, 'body:', req.body);
  next();
}, tutorialRefinityRoutes);
app.use('/api', adminWeeksRoutes);

// Health check endpoint
app.get('/api/health', (req, res) => {
  res.json({ status: 'OK', message: 'TransHub API is running - Auth middleware fixed for time code editing' });
});

// Simple health check for Hugging Face Spaces
app.get('/health', (req, res) => {
  res.status(200).send('OK');
});

// Error handling middleware
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ error: 'Something went wrong!' });
});

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
  // Seed default links if empty (best-effort)
  (async () => {
    try {
      const Link = require('./models/Link');
      const count = await Link.countDocuments();
      if (count === 0) {
        await Link.insertMany([
          { title: 'AI工具集', url: 'https://ai-bot.cn', desc: 'AI tools directory and learning resources.' },
          { title: 'Proz.com', url: 'https://www.proz.com', desc: 'Translators community and job marketplace.' },
          { title: 'Translators without Borders', url: 'https://translatorswithoutborders.org', desc: 'Volunteer translation for humanitarian causes.' },
          { title: 'TED Translator', url: 'https://www.ted.com/participate/translate', desc: 'Volunteer to translate TED talks.' },
          { title: 'Matecat', url: 'https://www.matecat.com', desc: 'Free web-based CAT tool with TM/MT support.' }
        ]);
        console.log('Seeded default Useful Links');
      }
    } catch (e) {
      console.warn('Unable to seed Useful Links:', e?.message);
    }
  })();
  
  // Initialize week 1 tutorial tasks and weekly practice by default
  const initializeWeek1 = async () => {
    try {
      const SourceText = require('./models/SourceText');
      
      // Check if week 1 tutorial tasks exist
      const existingTutorialTasks = await SourceText.find({ 
        category: 'tutorial', 
        weekNumber: 1 
      });
      
      if (existingTutorialTasks.length === 0) {
        console.log('Initializing week 1 tutorial tasks...');
        const tutorialTasks = [
          {
            title: 'Tutorial Task 1 - Introduction',
            content: '欢迎来到我们的翻译课程。今天我们将学习如何翻译产品介绍。',
            category: 'tutorial',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese',
            translationBrief: 'You have been asked to translate the following for marketing the product in a country where your LOTE is spoken.'
          },
          {
            title: 'Tutorial Task 2 - Development',
            content: '这个产品具有独特的设计理念，融合了传统与现代元素。',
            category: 'tutorial',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese',
            translationBrief: 'You have been asked to translate the following for marketing the product in a country where your LOTE is spoken.'
          },
          {
            title: 'Tutorial Task 3 - Conclusion',
            content: '我们相信这个产品能够满足您的所有需求，为您提供最佳体验。',
            category: 'tutorial',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese',
            translationBrief: 'You have been asked to translate the following for marketing the product in a country where your LOTE is spoken.'
          }
        ];
        await SourceText.insertMany(tutorialTasks);
        console.log('Week 1 tutorial tasks initialized successfully');
      }
      
      // Check if week 1 weekly practice exists
      const existingWeeklyPractice = await SourceText.find({ 
        category: 'weekly-practice', 
        weekNumber: 1 
      });
      
      if (existingWeeklyPractice.length === 0) {
        console.log('Initializing week 1 weekly practice...');
        const weeklyPractice = [
          {
            title: 'Chinese Pun 1',
            content: '为什么睡前一定要吃夜宵？因为这样才不会做饿梦。',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese'
          },
          {
            title: 'Chinese Pun 2',
            content: '女娲用什么补天？强扭的瓜。',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese'
          },
          {
            title: 'Chinese Pun 3',
            content: '你知道如何区分真假大象吗？把他们仍进水中，真相会浮出水面的。',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'Chinese',
            sourceCulture: 'Chinese'
          },
          {
            title: 'English Pun 1',
            content: 'What if Soy milk is just regular milk introducing itself in Spanish.',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'English',
            sourceCulture: 'Western'
          },
          {
            title: 'English Pun 2',
            content: 'I can\'t believe I got fired from the calendar factory. All I did was take a day off.',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'English',
            sourceCulture: 'Western'
          },
          {
            title: 'English Pun 3',
            content: 'When life gives you melons, you might be dyslexic.',
            category: 'weekly-practice',
            weekNumber: 1,
            sourceLanguage: 'English',
            sourceCulture: 'Western'
          }
        ];
        await SourceText.insertMany(weeklyPractice);
        console.log('Week 1 weekly practice initialized successfully');
      }
    } catch (error) {
      console.error('Error initializing week 1 data:', error);
    }
  };
  
  // Auto-initialization disabled to prevent overwriting definitive data
  // initializeWeek1();
});

// Graceful shutdown
process.on('SIGTERM', async () => {
  console.log('SIGTERM received, shutting down gracefully');
  try {
    await mongoose.connection.close();
    console.log('MongoDB connection closed');
    process.exit(0);
  } catch (error) {
    console.error('Error closing MongoDB connection:', error);
    process.exit(1);
  }
});

process.on('SIGINT', async () => {
  console.log('SIGINT received, shutting down gracefully');
  try {
    await mongoose.connection.close();
    console.log('MongoDB connection closed');
    process.exit(0);
  } catch (error) {
    console.error('Error closing MongoDB connection:', error);
    process.exit(1);
  }
});