const express = require('express');
const { v4: uuidv4 } = require('uuid');
require('dotenv').config();

// Import utilities
const redisClient = require('./src/utils/redis-client');
const fallbackStore = require('./src/utils/fallback-store');
const logger = require('./src/utils/logger');
const pdfGenerator = require('./src/utils/pdf-generator');

const app = express();
const port = process.env.PORT || 3049;

// Middleware
app.use(express.json());
app.use(express.static('public'));

// Request logging middleware
app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    const responseTime = Date.now() - start;
    logger.logRequest(req, res, responseTime);
  });
  next();
});

// Global error handler
app.use((err, req, res, next) => {
  logger.error('Unhandled error:', err);
  res.status(500).json({ 
    success: false, 
    message: 'Internal Server Error',
    error: process.env.NODE_ENV === 'development' ? err.message : undefined
  });
});

// Health check endpoint
app.get('/health', async (req, res) => {
  const redisHealthy = redisClient.isHealthy();
  const fallbackActive = fallbackStore.isActive;
  
  res.json({
    status: 'ok',
    timestamp: new Date().toISOString(),
    redis: {
      connected: redisHealthy,
      fallbackActive: fallbackActive
    },
    uptime: process.uptime()
  });
});

// Get all events endpoint
app.get('/events', async (req, res) => {
  try {
    let events;
    
    if (redisClient.isHealthy()) {
      events = await redisClient.getAllEvents();
    } else {
      events = fallbackStore.getAllEvents();
    }
    
    res.json({
      success: true,
      events,
      usingFallback: fallbackStore.isActive
    });
  } catch (error) {
    logger.error('Error fetching events:', error);
    res.status(500).json({ 
      success: false, 
      message: 'Failed to fetch events' 
    });
  }
});

// Get specific event stats
app.get('/events/:eventId', async (req, res) => {
  try {
    const eventId = req.params.eventId;
    let eventStats;
    
    if (redisClient.isHealthy()) {
      eventStats = await redisClient.getEventStats(eventId);
    } else {
      eventStats = fallbackStore.getEventStats(eventId);
    }
    
    if (!eventStats) {
      return res.status(404).json({ 
        success: false, 
        message: 'Event not found' 
      });
    }
    
    res.json({
      success: true,
      event: eventStats,
      usingFallback: fallbackStore.isActive
    });
  } catch (error) {
    logger.error('Error fetching event stats:', error);
    res.status(500).json({ 
      success: false, 
      message: 'Failed to fetch event stats' 
    });
  }
});

// Purchase ticket endpoint (multi-event)
app.post('/buy/:eventId', async (req, res) => {
  const startTime = Date.now();
  const eventId = req.params.eventId;
  const purchaseId = uuidv4();
  const timestamp = new Date().toISOString();
  
  try {
    let result;
    
    // Try Redis first
    if (redisClient.isHealthy()) {
      try {
        const luaResult = await redisClient.purchaseTicket(eventId, purchaseId, timestamp);
        
        if (luaResult[0]) {
          // Success - generate PDF ticket
          try {
            // Get event details for PDF
            const eventStats = await redisClient.getEventStats(eventId);
            
            const pdfResult = await pdfGenerator.generateTicketPDF({
              ticketId: luaResult[0],
              eventId,
              purchaseId,
              eventName: eventStats?.name || `Event ${eventId}`,
              eventDescription: eventStats?.description || 'Event description not available',
              timestamp,
              soldCount: luaResult[2]
            });
            
            result = {
              success: true,
              ticket: luaResult[0],
              purchaseId,
              eventId,
              soldCount: luaResult[2],
              message: 'Ticket purchased successfully!',
              usingFallback: false,
              pdf: {
                generated: pdfResult.success,
                filename: pdfResult.filename,
                downloadUrl: `/tickets/${purchaseId}`
              }
            };
            
            logger.logPurchase(eventId, luaResult[0], purchaseId, true);
            logger.info(`PDF ticket generated for purchase ${purchaseId}`);
            
          } catch (pdfError) {
            logger.error('PDF generation failed:', pdfError);
            
            // Still return success for ticket purchase, but note PDF failure
            result = {
              success: true,
              ticket: luaResult[0],
              purchaseId,
              eventId,
              soldCount: luaResult[2],
              message: 'Ticket purchased successfully! (PDF generation failed)',
              usingFallback: false,
              pdf: {
                generated: false,
                error: 'PDF generation failed'
              }
            };
            
            logger.logPurchase(eventId, luaResult[0], purchaseId, true);
          }
        } else {
          // Failed - handle specific error
          const errorCode = luaResult[1];
          let statusCode = 400;
          let message = 'Purchase failed';
          
          switch (errorCode) {
            case 'EVENT_NOT_FOUND':
              statusCode = 404;
              message = 'Event not found';
              break;
            case 'NO_TICKETS_AVAILABLE':
              statusCode = 409;
              message = 'No tickets available for this event';
              break;
          }
          
          logger.logPurchase(eventId, null, purchaseId, false, errorCode);
          return res.status(statusCode).json({ 
            success: false, 
            message,
            errorCode,
            eventId,
            purchaseId
          });
        }
      } catch (redisError) {
        logger.error('Redis purchase failed, attempting fallback:', redisError);
        // Activate fallback if not already active
        if (!fallbackStore.isActive) {
          fallbackStore.activate('Redis purchase operation failed');
        }
        throw redisError; // Will be caught by outer try-catch for fallback
      }
    } else {
      throw new Error('Redis not available');
    }
    
    const responseTime = Date.now() - startTime;
    result.responseTime = `${responseTime}ms`;
    
    res.json(result);
    
  } catch (error) {
    // Fallback to in-memory store
    try {
      if (!fallbackStore.isActive) {
        fallbackStore.activate('Redis connection failed during purchase');
      }
      
      const fallbackResult = fallbackStore.purchaseTicket(eventId, purchaseId);
      
      if (fallbackResult.success) {
        // Generate PDF for fallback purchase
        try {
          const eventStats = fallbackStore.getEventStats(eventId);
          
          const pdfResult = await pdfGenerator.generateTicketPDF({
            ticketId: fallbackResult.ticket,
            eventId,
            purchaseId,
            eventName: eventStats?.name || `Event ${eventId}`,
            eventDescription: eventStats?.description || 'Event description not available',
            timestamp,
            soldCount: fallbackResult.soldCount
          });
          
          const responseTime = Date.now() - startTime;
          res.json({
            success: true,
            ticket: fallbackResult.ticket,
            purchaseId,
            eventId,
            soldCount: fallbackResult.soldCount,
            message: 'Ticket purchased successfully (fallback mode)!',
            usingFallback: true,
            responseTime: `${responseTime}ms`,
            pdf: {
              generated: pdfResult.success,
              filename: pdfResult.filename,
              downloadUrl: `/tickets/${purchaseId}`
            }
          });
          
          logger.info(`PDF ticket generated for fallback purchase ${purchaseId}`);
          
        } catch (pdfError) {
          logger.error('PDF generation failed in fallback mode:', pdfError);
          
          const responseTime = Date.now() - startTime;
          res.json({
            success: true,
            ticket: fallbackResult.ticket,
            purchaseId,
            eventId,
            soldCount: fallbackResult.soldCount,
            message: 'Ticket purchased successfully (fallback mode, PDF generation failed)!',
            usingFallback: true,
            responseTime: `${responseTime}ms`,
            pdf: {
              generated: false,
              error: 'PDF generation failed'
            }
          });
        }
      } else {
        let statusCode = 400;
        let message = 'Purchase failed';
        
        switch (fallbackResult.error) {
          case 'EVENT_NOT_FOUND':
            statusCode = 404;
            message = 'Event not found';
            break;
          case 'NO_TICKETS_AVAILABLE':
            statusCode = 409;
            message = 'No tickets available for this event';
            break;
        }
        
        logger.logPurchase(eventId, null, purchaseId, false, fallbackResult.error);
        res.status(statusCode).json({ 
          success: false, 
          message,
          errorCode: fallbackResult.error,
          eventId,
          purchaseId,
          usingFallback: true
        });
      }
    } catch (fallbackError) {
      logger.error('Both Redis and fallback failed:', fallbackError);
      logger.logPurchase(eventId, null, purchaseId, false, fallbackError);
      
      res.status(500).json({ 
        success: false, 
        message: 'System temporarily unavailable',
        eventId,
        purchaseId
      });
    }
  }
});

// Download ticket PDF endpoint
app.get('/tickets/:purchaseId', async (req, res) => {
  try {
    const purchaseId = req.params.purchaseId;
    
    if (!pdfGenerator.ticketExists(purchaseId)) {
      return res.status(404).json({
        success: false,
        message: 'Ticket not found'
      });
    }
    
    const filepath = pdfGenerator.getTicketPath(purchaseId);
    const filename = `ticket-${purchaseId}.pdf`;
    
    res.setHeader('Content-Type', 'application/pdf');
    res.setHeader('Content-Disposition', `attachment; filename="${filename}"`);
    
    const fileStream = require('fs').createReadStream(filepath);
    fileStream.pipe(res);
    
    logger.info(`PDF ticket downloaded: ${purchaseId}`);
    
  } catch (error) {
    logger.error('Error downloading ticket:', error);
    res.status(500).json({
      success: false,
      message: 'Failed to download ticket'
    });
  }
});

// PDF management endpoint
app.get('/admin/pdf-stats', async (req, res) => {
  try {
    const stats = pdfGenerator.getStats();
    res.json({
      success: true,
      stats
    });
  } catch (error) {
    logger.error('Error getting PDF stats:', error);
    res.status(500).json({
      success: false,
      message: 'Failed to get PDF statistics'
    });
  }
});

// Cleanup old tickets endpoint
app.post('/admin/cleanup-tickets', async (req, res) => {
  try {
    const maxAgeHours = req.body.maxAgeHours || 24;
    const deletedCount = await pdfGenerator.cleanupOldTickets(maxAgeHours);
    
    res.json({
      success: true,
      message: `Cleaned up ${deletedCount} old tickets`,
      deletedCount
    });
  } catch (error) {
    logger.error('Error cleaning up tickets:', error);
    res.status(500).json({
      success: false,
      message: 'Failed to cleanup tickets'
    });
  }
});

// Metrics endpoint (Prometheus compatible)
app.get('/metrics', async (req, res) => {
  try {
    let globalStats, events;
    
    if (redisClient.isHealthy()) {
      globalStats = await redisClient.getGlobalStats();
      events = await redisClient.getAllEvents();
    } else {
      globalStats = fallbackStore.getGlobalStats();
      events = fallbackStore.getAllEvents();
    }
    
    // Get PDF stats
    const pdfStats = pdfGenerator.getStats();
    
    // Calculate metrics
    const metrics = {
      timestamp: new Date().toISOString(),
      global: globalStats,
      events: events,
      system: {
        usingFallback: fallbackStore.isActive,
        redisConnected: redisClient.isHealthy(),
        uptime: process.uptime(),
        memoryUsage: process.memoryUsage()
      },
      pdf: pdfStats
    };
    
    res.json(metrics);
  } catch (error) {
    logger.error('Error generating metrics:', error);
    res.status(500).json({ 
      success: false, 
      message: 'Failed to generate metrics' 
    });
  }
});

// Initialize server
async function initializeServer() {
  try {
    // Connect to Redis
    await redisClient.connect();
    logger.info('Redis connected successfully');
    
    // Start server
    app.listen(port, () => {
      logger.info(`🚀 Ticket Microservice running on port ${port}`);
      logger.info(`📊 Health check: http://localhost:${port}/health`);
      logger.info(`📈 Metrics: http://localhost:${port}/metrics`);
      logger.info(`🎫 Events: http://localhost:${port}/events`);
    });
    
  } catch (error) {
    logger.error('Failed to initialize server:', error);
    logger.warn('Starting server with fallback store only');
    
    fallbackStore.activate('Redis connection failed at startup');
    
    app.listen(port, () => {
      logger.warn(`⚠️  Server running in FALLBACK MODE on port ${port}`);
      logger.warn('Redis connection failed - using in-memory store');
    });
  }
}

// Graceful shutdown
process.on('SIGINT', async () => {
  logger.info('Received SIGINT, shutting down gracefully...');
  try {
    await redisClient.disconnect();
    logger.info('Redis disconnected');
  } catch (error) {
    logger.error('Error disconnecting Redis:', error);
  }
  process.exit(0);
});

process.on('SIGTERM', async () => {
  logger.info('Received SIGTERM, shutting down gracefully...');
  try {
    await redisClient.disconnect();
    logger.info('Redis disconnected');
  } catch (error) {
    logger.error('Error disconnecting Redis:', error);
  }
  process.exit(0);
});

// Start the server
initializeServer();