const express = require('express');
const { formatPrice } = require('../db');
const { getCart, cartCount, cartItems } = require('../cart');
const { requireCookieConsent } = require('../middleware/cookieConsent');
const { asyncHandler } = require('../utils/asyncHandler');
const promoService = require('../services/promo');
const loyaltyService = require('../services/loyalty');
const { buildCartPricing } = require('../services/pricing');

const router = express.Router();

router.use(requireCookieConsent);
router.use((req, res, next) => {
  res.locals.cartCount = cartCount(getCart(req));
  res.locals.formatPrice = formatPrice;
  next();
});

function cartRedirect(msg, type = 'error') {
  const param = type === 'success' ? 'promo_ok' : 'promo_error';
  return `/cart?${param}=${encodeURIComponent(msg)}`;
}

router.post(
  '/cart/promo',
  asyncHandler(async (req, res) => {
    const cart = getCart(req);
    const items = await cartItems(cart);
    if (!items.length) {
      return res.redirect(cartRedirect('Корзина пуста'));
    }

    const subtotal = items.reduce((s, i) => s + i.line_total, 0);
    const promo = await promoService.findPromoByCode(req.body.code);
    const check = promoService.validatePromo(promo, subtotal);
    if (!check.ok) {
      delete req.session.appliedPromoCode;
      return res.redirect(cartRedirect(check.error));
    }

    req.session.appliedPromoCode = promo.code;
    res.redirect(cartRedirect(`Промокод ${promo.code} применён`, 'success'));
  })
);

router.post('/cart/promo/remove', (req, res) => {
  delete req.session.appliedPromoCode;
  res.redirect(cartRedirect('Промокод удалён', 'success'));
});

router.post(
  '/cart/loyalty',
  asyncHandler(async (req, res) => {
    if (!req.session.userId) {
      return res.redirect('/login?next=/cart');
    }

    const cart = getCart(req);
    const items = await cartItems(cart);
    if (!items.length) {
      return res.redirect(cartRedirect('Корзина пуста'));
    }

    const pricing = await buildCartPricing(items, req.session, req.session.userId);
    const maxPoints = loyaltyService.pointsForDiscount(
      Math.max(0, pricing.subtotal - pricing.promoDiscount)
    );
    const balance = pricing.loyaltyBalance;

    if (req.body.use_all === '1') {
      req.session.loyaltyPointsToUse = Math.min(balance, maxPoints);
    } else {
      const pts = Math.max(0, parseInt(req.body.points, 10) || 0);
      req.session.loyaltyPointsToUse = Math.min(pts, balance, maxPoints);
    }

    res.redirect(cartRedirect('Баллы лояльности применены', 'success'));
  })
);

router.post('/cart/loyalty/remove', (req, res) => {
  delete req.session.loyaltyPointsToUse;
  res.redirect(cartRedirect('Списание баллов отменено', 'success'));
});

module.exports = router;