/**
 * ONLYOFFICE Integration Service
 * 
 * Standard ONLYOFFICE Document Server integration for inline .docx editing.
 * 
 * Architecture:
 *   - Backend serves .docx files and receives save callbacks from ONLYOFFICE
 *   - JWT-signed config ensures secure communication
 *   - Document key is based on file content hash + timestamp for cache-busting
 * 
 * Docker Networking:
 *   - Public URL (browser -> ONLYOFFICE): http://<host>:8080
 *   - Internal URL (backend -> ONLYOFFICE): http://onlyoffice-server/
 *   - Backend URL (ONLYOFFICE -> backend): http://<host>:8771
 */

const express = require('express');
const jwt = require('jsonwebtoken');
const axios = require('axios');
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

const router = express.Router();

// ============================================================
// CONFIGURATION
// ============================================================

const ONLYOFFICE_PUBLIC_URL = process.env.ONLYOFFICE_PUBLIC_URL || 'http://localhost:8080';
const ONLYOFFICE_INTERNAL_URL = process.env.ONLYOFFICE_INTERNAL_URL || ONLYOFFICE_PUBLIC_URL;
const BACKEND_PUBLIC_URL = process.env.BACKEND_PUBLIC_URL || 'http://localhost:8771';
const JWT_SECRET = process.env.JWT_SECRET || 'cvapp_onlyoffice_jwt_secret_2026';

const TEMPLATES_DIR = path.join(__dirname, 'carbone-templates');
fs.mkdirSync(TEMPLATES_DIR, { recursive: true });

const REGISTRY_PATH = path.join(TEMPLATES_DIR, 'registry.json');
function loadRegistry() {
  try { return JSON.parse(fs.readFileSync(REGISTRY_PATH, 'utf-8')); }
  catch { return []; }
}
function saveRegistry(registry) {
  fs.writeFileSync(REGISTRY_PATH, JSON.stringify(registry, null, 2));
}

// ============================================================
// HELPERS
// ============================================================

function signToken(payload) {
  return jwt.sign(payload, JWT_SECRET, { expiresIn: '1h' });
}

function verifyToken(token) {
  try {
    if (token && token.startsWith('Bearer ')) token = token.substring(7);
    return jwt.verify(token, JWT_SECRET);
  } catch { return null; }
}

/**
 * Generate a document key. ONLYOFFICE uses this for caching — a new key
 * means ONLYOFFICE treats it as a new document and fetches the file fresh.
 * We combine templateId + file modification time + random hash so every
 * edit session after a save gets a unique key.
 */
function generateDocKey(templateId, fileMtime) {
  return `cv_${templateId}_${Math.floor(fileMtime)}_${crypto.randomBytes(4).toString('hex')}`;
}

// ============================================================
// GET /:templateId/config — JWT-signed editor config
// ============================================================

router.get('/:templateId/config', (req, res) => {
  const templateId = req.params.templateId;
  const registry = loadRegistry();
  const template = registry.find(t => t.id === templateId);
  
  if (!template) return res.status(404).json({ error: 'Template not found' });
  if (!fs.existsSync(template.path)) return res.status(404).json({ error: 'Template file missing' });
  
  res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
  res.setHeader('Pragma', 'no-cache');
  res.setHeader('Expires', '0');
  
  const fileStats = fs.statSync(template.path);
  const fileMtime = fileStats.mtimeMs;
  const docKey = generateDocKey(templateId, fileMtime);
  const fileName = template.originalName || template.name + '.docx';
  
  const documentUrl = `${BACKEND_PUBLIC_URL}/api/onlyoffice/${templateId}/download?cb=${Date.now()}`;
  const callbackUrl = `${BACKEND_PUBLIC_URL}/api/onlyoffice/${templateId}/callback`;
  
  const config = {
    document: {
      fileType: 'docx',
      key: docKey,
      title: fileName,
      url: documentUrl,
      permissions: { edit: true, download: true, review: true, print: false },
    },
    editorConfig: {
      mode: 'edit',
      lang: 'en',
      callbackUrl: callbackUrl,
      user: { id: 'cv-app-user', name: 'CV App Editor' },
      customization: {
        autosave: true,
        forcesave: true,
        compactHeader: false,
        hideRightMenu: true,
        chat: false,
        feedback: false,
        goback: false,
      },
    },
    documentType: 'text',
  };
  
  config.token = signToken(config);
  
  res.json({
    config,
    onlyofficeUrl: ONLYOFFICE_PUBLIC_URL,
    templateId,
    templateName: template.name,
  });
});

// ============================================================
// GET /:templateId/download — serve .docx to ONLYOFFICE
// ============================================================

router.get('/:templateId/download', (req, res) => {
  const templateId = req.params.templateId;
  const registry = loadRegistry();
  const template = registry.find(t => t.id === templateId);
  
  if (!template) return res.status(404).json({ error: 'Template not found' });
  if (!fs.existsSync(template.path)) return res.status(404).json({ error: 'Template file missing' });
  
  const fileName = template.originalName || template.name + '.docx';
  res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document');
  res.setHeader('Content-Disposition', `attachment; filename="${fileName}"`);
  res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
  res.setHeader('Pragma', 'no-cache');
  res.setHeader('Expires', '0');
  
  fs.createReadStream(template.path).pipe(res);
});

// ============================================================
// POST /:templateId/callback — ONLYOFFICE save callback
// 
// Status: 0=editing, 1=ready, 2=saved, 3=save error, 4=closed, 6=force-saved
// On status 2 or 6: download the updated file and overwrite the template.
// ============================================================

router.post('/:templateId/callback', async (req, res) => {
  const templateId = req.params.templateId;
  
  // Verify JWT if present
  const authHeader = req.headers['authorization'];
  if (authHeader) {
    if (!verifyToken(authHeader)) {
      console.error('ONLYOFFICE callback: Invalid JWT');
      return res.status(403).json({ error: 'Invalid token' });
    }
  }
  
  const { status, url: downloadUrl, key } = req.body;
  
  console.log(`ONLYOFFICE callback: template=${templateId}, status=${status}, key=${key}`);
  
  const registry = loadRegistry();
  const template = registry.find(t => t.id === templateId);
  if (!template) return res.status(404).json({ error: 'Template not found' });
  
  if ((status === 2 || status === 6) && downloadUrl) {
    try {
      console.log(`Downloading updated template: ${downloadUrl}`);
      const response = await axios.get(downloadUrl, { responseType: 'arraybuffer', timeout: 30000 });
      
      fs.writeFileSync(template.path, response.data);
      template.updatedAt = new Date().toISOString();
      saveRegistry(registry);
      
      console.log(`Template "${template.name}" saved (${response.data.length} bytes)`);
      
      // Clear ONLYOFFICE internal cache for this template
      try {
        require('child_process').execSync(
          `docker exec onlyoffice-server find /var/lib/onlyoffice/documentserver/App_Data/cache -name "cv_${templateId}*" -type d -exec rm -rf {} + 2>/dev/null || true`,
          { timeout: 5000 }
        );
      } catch (e) { /* non-fatal */ }
      
      return res.json({ error: 0, key });
    } catch (err) {
      console.error('Save failed:', err.message);
      return res.status(500).json({ error: 1, message: err.message });
    }
  }
  
  return res.json({ error: 0, key });
});

// ============================================================
// GET /health — health check
// ============================================================

router.get('/health', async (req, res) => {
  let onlyofficeStatus = 'offline';
  try {
    const resp = await axios.get(`${ONLYOFFICE_INTERNAL_URL}/healthcheck`, { timeout: 5000 });
    onlyofficeStatus = resp.status === 200 ? 'healthy' : 'unhealthy';
  } catch { /* offline */ }
  
  res.json({
    status: 'ok',
    onlyoffice: onlyofficeStatus,
    onlyofficePublicUrl: ONLYOFFICE_PUBLIC_URL,
    jwtEnabled: !!JWT_SECRET,
  });
});

module.exports = router;