const express = require("express");
const router = express.Router();
const sseAuth = require("../middleware/sseAuth");
const sseService = require("../services/sseService");
const logger = require("../utils/logger");

/**
 * @route   GET /api/sse/stream
 * @desc    SSE stream endpoint
 * @access  Private
 */
router.get("/stream", sseAuth, (req, res) => {
  const userId = req.user.id;

  // Set SSE headers
  res.setHeader("Content-Type", "text/event-stream");
  res.setHeader("Cache-Control", "no-cache");
  res.setHeader("Connection", "keep-alive");
  res.setHeader("X-Accel-Buffering", "no"); // Disable nginx buffering

  // Send initial connection success message
  res.write(`event: connected\ndata: ${JSON.stringify({ userId, timestamp: new Date().toISOString() })}\n\n`);

  // Register client
  sseService.addClient(userId, res);

  // Send heartbeat every 30 seconds to keep connection alive
  const heartbeatInterval = setInterval(() => {
    try {
      res.write(`:heartbeat\n\n`);
    } catch (error) {
      logger.error(`Heartbeat failed for user`, { userId, error: error.message });
      clearInterval(heartbeatInterval);
      sseService.removeClient(userId);
    }
  }, 30000);

  // Handle client disconnect
  req.on("close", () => {
    clearInterval(heartbeatInterval);
    sseService.removeClient(userId);
    logger.info(`SSE stream closed`, { userId });
  });

  // Handle connection errors
  req.on("error", (error) => {
    logger.error(`SSE stream error`, { userId, error: error.message });
    clearInterval(heartbeatInterval);
    sseService.removeClient(userId);
  });
});

/**
 * @route   POST /api/sse/subscribe
 * @desc    Subscribe to SSE topics
 * @access  Private
 */
router.post("/subscribe", sseAuth, (req, res) => {
  try {
    const userId = req.user.id;
    const { topics } = req.body;

    // Validate topics
    if (!topics || !Array.isArray(topics) || topics.length === 0) {
      return res.status(400).json({ 
        success: false, 
        msg: "Topics must be a non-empty array" 
      });
    }

    // Subscribe to topics
    const success = sseService.subscribe(userId, topics);

    if (!success) {
      return res.status(400).json({ 
        success: false, 
        msg: "User not connected to SSE stream" 
      });
    }

    res.json({ 
      success: true, 
      msg: "Subscribed to topics",
      topics 
    });
  } catch (error) {
    logger.error(`Subscribe error`, { error: error.message });
    res.status(500).json({ 
      success: false, 
      msg: "Server error" 
    });
  }
});

/**
 * @route   POST /api/sse/unsubscribe
 * @desc    Unsubscribe from SSE topics
 * @access  Private
 */
router.post("/unsubscribe", sseAuth, (req, res) => {
  try {
    const userId = req.user.id;
    const { topics } = req.body;

    // Validate topics
    if (!topics || !Array.isArray(topics) || topics.length === 0) {
      return res.status(400).json({ 
        success: false, 
        msg: "Topics must be a non-empty array" 
      });
    }

    // Unsubscribe from topics
    const success = sseService.unsubscribe(userId, topics);

    if (!success) {
      return res.status(400).json({ 
        success: false, 
        msg: "User not connected to SSE stream" 
      });
    }

    res.json({ 
      success: true, 
      msg: "Unsubscribed from topics",
      topics 
    });
  } catch (error) {
    logger.error(`Unsubscribe error`, { error: error.message });
    res.status(500).json({ 
      success: false, 
      msg: "Server error" 
    });
  }
});

module.exports = router;