import express from 'express';
import cors from 'cors';
import path from 'path';
import fs from 'fs';
import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const app = express();
const port = process.env.PORT || 3001;

// Middlewares
app.use(cors());
app.use(express.json({ limit: '50mb' }));

// Data Directory for JSON files
const dataDir = path.resolve(__dirname, 'data');
if (!fs.existsSync(dataDir)) {
  fs.mkdirSync(dataDir, { recursive: true });
}

// =======================
// API Routes
// =======================

// Mock PPT APIs (Windows GUI features are not supported on Linux/Docker)
app.get('/api/ppt/check', (req, res) => {
  res.json({ success: true, hasPpt: false, ppts: [] });
});

app.post('/api/ppt/control', (req, res) => {
  res.json({ success: false, error: 'Not supported on server environment' });
});

// Local File Storage APIs
app.post('/api/local-file/save', (req, res) => {
  try {
    const { key, data } = req.body;
    if (!key || !data) throw new Error('Missing key or data');
    
    // Sanitize key
    const safeKey = String(key).replace(/[^a-zA-Z0-9_-]/g, '_');
    const filePath = path.join(dataDir, `${safeKey}.json`);
    
    fs.writeFileSync(filePath, JSON.stringify(data, null, 2));
    res.json({ success: true });
  } catch (e) {
    res.status(500).json({ success: false, error: e.message });
  }
});

app.get('/api/local-file/load', (req, res) => {
  try {
    const key = req.query.key;
    if (!key) {
      return res.status(400).json({ success: false, error: 'Missing key' });
    }
    
    const safeKey = String(key).replace(/[^a-zA-Z0-9_-]/g, '_');
    const filePath = path.join(dataDir, `${safeKey}.json`);
    
    if (fs.existsSync(filePath)) {
      const data = fs.readFileSync(filePath, 'utf-8');
      res.json({ success: true, data: JSON.parse(data) });
    } else {
      res.status(404).json({ success: false, error: 'Not found' });
    }
  } catch (e) {
    res.status(500).json({ success: false, error: e.message });
  }
});

app.get('/api/local-file/keys', (req, res) => {
  try {
    const files = fs.readdirSync(dataDir);
    const keys = files
      .filter(f => f.endsWith('.json'))
      .map(f => f.replace('.json', ''));
    res.json({ success: true, keys });
  } catch (e) {
    res.status(500).json({ success: false, error: e.message });
  }
});

// =======================
// Static Files & SPA
// =======================
const staticDir = path.resolve(__dirname, 'dist');

if (fs.existsSync(staticDir)) {
  // Serve static files
  app.use(express.static(staticDir, {
    setHeaders: (res, path, stat) => {
      // Prevent caching for sw.js and index.html
      if (path.endsWith('sw.js') || path.endsWith('index.html')) {
        res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
        res.setHeader('Pragma', 'no-cache');
        res.setHeader('Expires', '0');
      } else {
        // Cache other static assets
        res.setHeader('Cache-Control', 'public, max-age=3600');
      }
    }
  }));
  
  // Catch-all route for SPA fallback
  app.get('*', (req, res) => {
    res.sendFile(path.join(staticDir, 'index.html'));
  });
} else {
  // Fallback if dist doesn't exist yet
  app.get('*', (req, res) => {
    res.send('<h3>Frontend not found!</h3><p>Please build the Vue frontend (<code>npm run build</code>) and copy the <code>dist</code> folder into the <code>docker-server</code> directory before running.</p>');
  });
}

// Start Server
app.listen(port, () => {
  console.log(`ClassHomeworkBoard Server running on port ${port}`);
  console.log(`Data directory: ${dataDir}`);
  console.log(`Static files directory: ${staticDir}`);
});