// server.js - Node.js Backend with Express and Tesseract OCR
const express = require('express');
const multer = require('multer');
const Tesseract = require('tesseract.js');
const path = require('path');
const fs = require('fs');

const app = express();
const PORT = process.env.PORT || 7860;

// Multer configuration for file uploads
const upload = multer({ 
  dest: 'uploads/',
  limits: { fileSize: 10 * 1024 * 1024 } // 10MB limit
});

// Middleware
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
app.use(express.static('public'));

// Database configuration
const DB_FILE = './database.json';
const ADMIN_PASSWORD = 'BTXHZ';
const ADMIN_TOKEN = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhZG1pbiI6dHJ1ZX0.dummytoken';

// Initialize database file if doesn't exist
if (!fs.existsSync(DB_FILE)) {
  fs.writeFileSync(DB_FILE, JSON.stringify([]));
  console.log('📁 Database file created');
}

// Initialize uploads folder if doesn't exist
if (!fs.existsSync('uploads')) {
  fs.mkdirSync('uploads');
  console.log('📁 Uploads folder created');
}

// Database helper functions
const getDB = () => {
  try {
    const data = fs.readFileSync(DB_FILE, 'utf8');
    return JSON.parse(data);
  } catch (error) {
    console.error('Error reading database:', error);
    return [];
  }
};

const saveDB = (data) => {
  try {
    fs.writeFileSync(DB_FILE, JSON.stringify(data, null, 2));
    return true;
  } catch (error) {
    console.error('Error saving database:', error);
    return false;
  }
};

// Authentication middleware
const authMiddleware = (req, res, next) => {
  const authHeader = req.headers.authorization;
  
  if (!authHeader || !authHeader.startsWith('Bearer ')) {
    return res.status(401).json({ 
      success: false, 
      error: 'Unauthorized - No token provided' 
    });
  }
  
  const token = authHeader.replace('Bearer ', '');
  
  if (token !== ADMIN_TOKEN) {
    return res.status(401).json({ 
      success: false, 
      error: 'Unauthorized - Invalid token' 
    });
  }
  
  next();
};

// ============================================
// HTML ROUTES
// ============================================

// Root route - redirect to home
app.get('/', (req, res) => {
  res.redirect('/home');
});

// Home page
app.get('/home', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'home.html'));
});

// Admin create page
app.get('/home/admin/create', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'admin.html'));
});

// Verification page
app.get('/home/url/:name/:id', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'verify.html'));
});

// ============================================
// API ROUTES
// ============================================

// Login endpoint
app.post('/api/login', (req, res) => {
  const { password } = req.body;
  
  if (!password) {
    return res.status(400).json({ 
      success: false, 
      error: 'Password is required' 
    });
  }
  
  if (password === ADMIN_PASSWORD) {
    res.json({ 
      success: true, 
      token: ADMIN_TOKEN,
      message: 'Login successful'
    });
  } else {
    res.status(401).json({ 
      success: false, 
      error: 'Invalid password' 
    });
  }
});

// Create short link endpoint (protected)
app.post('/api/create', authMiddleware, (req, res) => {
  const { title, redirect, name, verify } = req.body;
  
  // Validation
  if (!title || !redirect || !name) {
    return res.status(400).json({ 
      success: false, 
      error: 'Title, redirect, and name are required' 
    });
  }
  
  // Check if name already exists
  const db = getDB();
  const existingLink = db.find(link => link.name === name);
  
  if (existingLink) {
    return res.status(400).json({ 
      success: false, 
      error: 'Short name already exists' 
    });
  }
  
  // Create new link
  const id = Date.now().toString();
  const newLink = {
    id,
    title,
    redirect,
    name,
    verify: verify === true,
    createdAt: new Date().toISOString()
  };
  
  db.push(newLink);
  
  if (saveDB(db)) {
    console.log(`✅ New link created: ${name} (ID: ${id})`);
    res.json({ 
      success: true, 
      link: newLink,
      message: 'Short link created successfully'
    });
  } else {
    res.status(500).json({ 
      success: false, 
      error: 'Failed to save link' 
    });
  }
});

// Get all links endpoint
app.get('/api/links', (req, res) => {
  const db = getDB();
  res.json(db);
});

// Get specific link endpoint
app.get('/api/link/:name/:id', (req, res) => {
  const { name, id } = req.params;
  const db = getDB();
  
  const link = db.find(l => l.name === name && l.id === id);
  
  if (link) {
    res.json(link);
  } else {
    res.status(404).json({ 
      error: 'Link not found',
      message: 'The requested short link does not exist'
    });
  }
});

// OCR Verification endpoint
app.post('/api/verify', upload.single('image'), async (req, res) => {
  if (!req.file) {
    return res.status(400).json({ 
      success: false, 
      error: 'No image file uploaded' 
    });
  }
  
  const filePath = req.file.path;
  console.log(`🔍 Processing OCR for file: ${req.file.originalname}`);
  
  try {
    // Perform OCR using Tesseract
    const { data: { text } } = await Tesseract.recognize(
      filePath,
      'eng',
      {
        logger: info => {
          if (info.status === 'recognizing text') {
            console.log(`OCR Progress: ${Math.round(info.progress * 100)}%`);
          }
        }
      }
    );
    
    console.log('📝 OCR Text extracted:', text.substring(0, 100) + '...');
    
    // Clean up uploaded file
    fs.unlinkSync(filePath);
    
    // Normalize text for better matching
    const normalizedText = text.toLowerCase();
    
    // Check for required conditions
    const hasNotmebotz = normalizedText.includes('notmebotz') || 
                        normalizedText.includes('notme botz');
    
    const hasFollowButton = normalizedText.includes('follow channel') || 
                           normalizedText.includes('follow') && normalizedText.includes('channel');
    
    const hasPrivacy = normalizedText.includes('added privacy') || 
                      normalizedText.includes('this channel has added privacy');
    
    // Verification logic
    const verified = hasNotmebotz && !hasFollowButton && !hasPrivacy;
    
    console.log(`✅ Verification result: ${verified ? 'PASSED' : 'FAILED'}`);
    console.log(`   - Channel: ${hasNotmebotz ? 'NOTMEBOTZ ✓' : 'NOT FOUND ✗'}`);
    console.log(`   - Follow Button: ${hasFollowButton ? 'PRESENT ✗' : 'ABSENT ✓'}`);
    console.log(`   - Privacy Text: ${hasPrivacy ? 'PRESENT ✗' : 'ABSENT ✓'}`);
    
    res.json({
      success: true,
      verified,
      channelName: hasNotmebotz ? 'NOTMEBOTZ' : 'UNKNOWN',
      hasFollowButton,
      hasPrivacy,
      extractedText: text.substring(0, 200) // Return first 200 chars for debugging
    });
    
  } catch (error) {
    console.error('❌ OCR Error:', error);
    
    // Clean up file if it still exists
    if (fs.existsSync(filePath)) {
      fs.unlinkSync(filePath);
    }
    
    res.status(500).json({ 
      success: false, 
      error: 'OCR processing failed',
      message: error.message 
    });
  }
});

// Delete link endpoint (optional - for admin)
app.delete('/api/link/:id', authMiddleware, (req, res) => {
  const { id } = req.params;
  const db = getDB();
  
  const index = db.findIndex(link => link.id === id);
  
  if (index !== -1) {
    const deletedLink = db.splice(index, 1)[0];
    saveDB(db);
    
    console.log(`🗑️ Link deleted: ${deletedLink.name} (ID: ${id})`);
    
    res.json({ 
      success: true, 
      message: 'Link deleted successfully',
      deletedLink 
    });
  } else {
    res.status(404).json({ 
      success: false, 
      error: 'Link not found' 
    });
  }
});

// Health check endpoint
app.get('/api/health', (req, res) => {
  res.json({ 
    status: 'OK', 
    uptime: process.uptime(),
    timestamp: new Date().toISOString()
  });
});

// ============================================
// ERROR HANDLING
// ============================================

// 404 handler
app.use((req, res) => {
  res.status(404).json({ 
    error: 'Not Found',
    message: 'The requested endpoint does not exist',
    path: req.path
  });
});

// Global error handler
app.use((err, req, res, next) => {
  console.error('❌ Server Error:', err);
  
  res.status(err.status || 500).json({
    error: 'Internal Server Error',
    message: err.message || 'Something went wrong'
  });
});

// ============================================
// START SERVER
// ============================================

app.listen(PORT, () => {
  console.log('');
  console.log('╔════════════════════════════════════════╗');
  console.log('║   🚀 ShortLink OCR Server Running     ║');
  console.log('╚════════════════════════════════════════╝');
  console.log('');
  console.log(`🌐 Server: http://localhost:${PORT}`);
  console.log(`📊 Admin Panel: http://localhost:${PORT}/home/admin/create`);
  console.log(`🔐 Admin Password: ${ADMIN_PASSWORD}`);
  console.log('');
  console.log('📁 Database:', DB_FILE);
  console.log('📂 Uploads:', path.join(__dirname, 'uploads'));
  console.log('');
  console.log('Press Ctrl+C to stop the server');
  console.log('');
});