const promoService = require('./promo');
const loyaltyService = require('./loyalty');

async function buildCartPricing(items, session, userId) {
  const subtotal = items.reduce((s, i) => s + i.line_total, 0);

  let promo = null;
  let promoDiscount = 0;
  let promoError = null;

  if (session.appliedPromoCode) {
    promo = await promoService.findPromoByCode(session.appliedPromoCode);
    const check = promoService.validatePromo(promo, subtotal);
    if (!check.ok) {
      promoError = check.error;
      promo = null;
      delete session.appliedPromoCode;
    } else {
      promoDiscount = promoService.calcPromoDiscountCents(promo, subtotal);
    }
  }

  const afterPromo = Math.max(0, subtotal - promoDiscount);

  let loyaltyBalance = 0;
  let loyaltyDiscount = 0;
  let loyaltyPointsUsed = 0;

  if (userId) {
    loyaltyBalance = await loyaltyService.getBalance(userId);
    const requested = session.loyaltyPointsToUse ?? 0;
    loyaltyDiscount = loyaltyService.calcLoyaltyDiscountCents(
      requested,
      loyaltyBalance,
      afterPromo
    );
    loyaltyPointsUsed = loyaltyService.pointsForDiscount(loyaltyDiscount);
  }

  const total = Math.max(0, afterPromo - loyaltyDiscount);
  const pointsEarned =
    userId && total > 0 ? loyaltyService.calcEarnedPoints(total) : 0;

  return {
    subtotal,
    promoDiscount,
    loyaltyDiscount,
    loyaltyPointsUsed,
    loyaltyPointsUsedDisplay: loyaltyPointsUsed,
    loyaltyBalance,
    pointsEarned,
    total,
    promo: promo
      ? {
          code: promo.code,
          description: promo.description,
          discount_type: promo.discount_type,
          discount_value: promo.discount_value,
          expires_at: promo.expires_at,
        }
      : null,
    promoError,
  };
}

module.exports = { buildCartPricing };