const express = require('express');
const router = express.Router();
const { google } = require('googleapis');
const { requireAuth } = require('../middleware/auth');

// Google Calendar configuration
const SCOPES = ['https://www.googleapis.com/auth/calendar.readonly'];

// OAuth2 client setup
const getOAuth2Client = () => {
  return new google.auth.OAuth2(
    process.env.GOOGLE_CLIENT_ID,
    process.env.GOOGLE_CLIENT_SECRET,
    process.env.GOOGLE_REDIRECT_URI || 'http://localhost:3002/api/calendar/oauth/callback'
  );
};

// GET /api/calendar/auth - Start OAuth flow (Demo mode)
router.get('/auth', requireAuth, (req, res) => {
  try {
    // Check if Google credentials are configured
    if (!process.env.GOOGLE_CLIENT_ID || !process.env.GOOGLE_CLIENT_SECRET) {
      // Demo mode - simulate successful connection
      console.log('Demo mode: Simulating Google Calendar connection for user:', req.currentUser.id);
      
      // Simulate the callback redirect with success
      const frontendUrl = process.env.FRONTEND_URL || 'http://localhost:8080';
      return res.json({ 
        authUrl: `${frontendUrl}/calendar?demo=true&connected=true`,
        demo: true,
        message: 'Demo mode: Google Calendar integration simulated'
      });
    }

    // Production mode with real Google OAuth
    const oauth2Client = getOAuth2Client();
    
    const authUrl = oauth2Client.generateAuthUrl({
      access_type: 'offline',
      scope: SCOPES,
      state: JSON.stringify({ userId: req.currentUser.id })
    });

    res.json({ authUrl });
  } catch (error) {
    console.error('Error generating auth URL:', error);
    res.status(500).json({ error: 'Failed to generate authorization URL' });
  }
});

// GET /api/calendar/oauth/callback - Handle OAuth callback
router.get('/oauth/callback', async (req, res) => {
  try {
    const { code, state } = req.query;
    
    if (!code) {
      return res.status(400).json({ error: 'Authorization code not provided' });
    }

    const oauth2Client = getOAuth2Client();
    const { tokens } = await oauth2Client.getToken(code);
    
    // Parse state to get user ID
    const { userId } = JSON.parse(state);
    
    // Here you would typically save the tokens to the database
    // For now, we'll just return them (in production, store securely)
    console.log('Google Calendar tokens received for user:', userId);
    console.log('Tokens:', tokens);
    
    // TODO: Save tokens to database associated with user
    // await saveGoogleTokensForUser(userId, tokens);

    // Redirect to frontend with success
    res.redirect(`${process.env.FRONTEND_URL || 'http://localhost:8080'}/calendar?connected=true`);
  } catch (error) {
    console.error('Error handling OAuth callback:', error);
    res.redirect(`${process.env.FRONTEND_URL || 'http://localhost:8080'}/calendar?error=auth_failed`);
  }
});

// GET /api/calendar/status - Check connection status
router.get('/status', requireAuth, async (req, res) => {
  try {
    // Check if we're in demo mode or have real Google integration
    if (!process.env.GOOGLE_CLIENT_ID || !process.env.GOOGLE_CLIENT_SECRET) {
      // Demo mode - check if user has been "connected" in this session
      // For demo purposes, we'll simulate connection status
      res.json({ 
        connected: false, // Will be set to true after demo connection
        email: null,
        demo: true
      });
      return;
    }

    // TODO: Check if user has valid Google Calendar tokens in database
    // const tokens = await getGoogleTokensForUser(req.currentUser.id);
    
    res.json({ 
      connected: false, // Change to true when tokens exist and are valid
      email: null // Return connected Google account email when available
    });
  } catch (error) {
    console.error('Error checking calendar status:', error);
    res.status(500).json({ error: 'Failed to check calendar status' });
  }
});

// GET /api/calendar/events - Get events from Google Calendar
router.get('/events', requireAuth, async (req, res) => {
  try {
    const { start, end } = req.query;
    
    // TODO: Get tokens from database
    // const tokens = await getGoogleTokensForUser(req.currentUser.id);
    // if (!tokens) {
    //   return res.status(401).json({ error: 'Google Calendar not connected' });
    // }

    // For now, return sample data
    const sampleEvents = [
      {
        id: 'google-1',
        title: 'Google Calendar Event',
        start: new Date().toISOString(),
        end: new Date(Date.now() + 60 * 60 * 1000).toISOString(),
        type: 'google',
        color: '#ea4335'
      }
    ];

    res.json({ events: sampleEvents });

    // TODO: Implement actual Google Calendar API call
    /*
    const oauth2Client = getOAuth2Client();
    oauth2Client.setCredentials(tokens);

    const calendar = google.calendar({ version: 'v3', auth: oauth2Client });
    
    const response = await calendar.events.list({
      calendarId: 'primary',
      timeMin: start || new Date().toISOString(),
      timeMax: end || new Date(Date.now() + 30 * 24 * 60 * 60 * 1000).toISOString(),
      maxResults: 100,
      singleEvents: true,
      orderBy: 'startTime',
    });

    const events = response.data.items.map(event => ({
      id: event.id,
      title: event.summary,
      start: event.start.dateTime || event.start.date,
      end: event.end.dateTime || event.end.date,
      type: 'google',
      color: '#ea4335',
      description: event.description,
      location: event.location
    }));

    res.json({ events });
    */
  } catch (error) {
    console.error('Error fetching calendar events:', error);
    res.status(500).json({ error: 'Failed to fetch calendar events' });
  }
});

// POST /api/calendar/disconnect - Disconnect Google Calendar
router.post('/disconnect', requireAuth, async (req, res) => {
  try {
    // TODO: Remove tokens from database
    // await removeGoogleTokensForUser(req.currentUser.id);
    
    res.json({ success: true, message: 'Google Calendar disconnected' });
  } catch (error) {
    console.error('Error disconnecting calendar:', error);
    res.status(500).json({ error: 'Failed to disconnect calendar' });
  }
});

module.exports = router;