const express = require("express");
const mongoose = require("mongoose");
const Event = require("../models/Event");
const User = require("../models/User");
const auth = require("../middleware/auth");
const { asyncHandler } = require("../middleware/errorHandler");
const {
  createEventValidation,
  eventIdValidation,
} = require("../middleware/validators/eventValidator");
const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
const {
  awardEventParticipationPoints,
  checkAndAwardBadges,
} = require("../services/gamificationService");

const router = express.Router();

// Get all events (with pagination)
router.get(
  "/",
  paginate,
  asyncHandler(async (req, res) => {
    const { skip, limit, page } = req.pagination;

    const events = await Event.find()
      .sort({ date: -1 })
      .skip(skip)
      .limit(limit)
      .populate("participants", ["name", "profilePicture"]);

    const totalCount = await Event.countDocuments();

    res.json(buildPaginatedResponse(events, totalCount, page, limit));
  }),
);

// Create an event
router.post(
  "/",
  auth,
  createEventValidation,
  asyncHandler(async (req, res) => {
    const { title, description, date, location } = req.body;

    const newEvent = new Event({
      title,
      description,
      date,
      location,
    });

    const event = await newEvent.save();
    res.json(event);
  }),
);

// RSVP to an event
router.put(
  "/rsvp/:id",
  auth,
  eventIdValidation,
  asyncHandler(async (req, res) => {
    const session = await mongoose.startSession();
    session.startTransaction();

    try {
      const event = await Event.findById(req.params.id).session(session);
      if (!event) {
        await session.abortTransaction();
        session.endSession();
        return res.status(404).json({ msg: "Event not found" });
      }

      // Check if the user has already RSVPed
      if (
        event.participants.filter(
          (participant) => participant.toString() === req.user.id,
        ).length > 0
      ) {
        await session.abortTransaction();
        session.endSession();
        return res.status(400).json({ msg: "Already RSVPed" });
      }

      event.participants.unshift(req.user.id);
      await event.save({ session });

      // Update user's events array
      const user = await User.findById(req.user.id).session(session);
      if (!user.events.includes(event._id)) {
        user.events.push(event._id);
        await user.save({ session });
      }

      // Award points for event participation
      const { transaction } = await awardEventParticipationPoints(
        req.user.id,
        event._id,
        session
      );

      // Check and award badges
      const newBadges = await checkAndAwardBadges(req.user.id, session);

      await session.commitTransaction();
      session.endSession();

      res.json({
        participants: event.participants,
        pointsAwarded: transaction.amount,
        newBalance: transaction.balanceAfter,
        badgesEarned: newBadges,
      });
    } catch (err) {
      await session.abortTransaction();
      session.endSession();
      throw err;
    }
  }),
);

module.exports = router;