const express = require("express");
const mongoose = require("mongoose");
const Reward = require("../models/Reward");
const User = require("../models/User");
const auth = require("../middleware/auth");
const { asyncHandler } = require("../middleware/errorHandler");
const {
  createRewardValidation,
  rewardIdValidation,
} = require("../middleware/validators/rewardValidator");
const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
const { deductRewardPoints } = require("../services/gamificationService");

const router = express.Router();

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

    const rewards = await Reward.find()
      .sort({ cost: 1 })
      .skip(skip)
      .limit(limit);

    const totalCount = await Reward.countDocuments();

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

// Create a reward
router.post(
  "/",
  auth,
  createRewardValidation,
  asyncHandler(async (req, res) => {
    const { name, description, cost, isPremium } = req.body;

    const newReward = new Reward({
      name,
      description,
      cost,
      isPremium,
    });

    const reward = await newReward.save();
    res.json(reward);
  }),
);

// Redeem a reward
router.post(
  "/redeem/:id",
  auth,
  rewardIdValidation,
  asyncHandler(async (req, res) => {
    const session = await mongoose.startSession();
    session.startTransaction();

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

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

      if (user.points < reward.cost) {
        await session.abortTransaction();
        session.endSession();
        return res.status(400).json({ msg: "Not enough points" });
      }

      if (reward.isPremium && !user.isPremium) {
        await session.abortTransaction();
        session.endSession();
        return res.status(403).json({ msg: "Premium reward not available" });
      }

      // Deduct points using gamification service
      const { transaction } = await deductRewardPoints(
        req.user.id,
        reward._id,
        reward.cost,
        session
      );

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

      res.json({
        msg: "Reward redeemed successfully",
        pointsDeducted: Math.abs(transaction.amount),
        newBalance: transaction.balanceAfter,
      });
    } catch (err) {
      await session.abortTransaction();
      session.endSession();
      throw err;
    }
  }),
);

module.exports = router;