export interface ProductPricing {
  price: number;
  benefitAmount?: number | null;
}

export function calcBenefitAmount(product: ProductPricing): number {
  return product.benefitAmount ?? product.price;
}

export function validateMinPurchase(
  deliveryType: 'LOCAL' | 'CROSS_CITY',
  quantity: number,
  localMinQty: number,
  crossMinQty: number,
): { ok: boolean; message?: string } {
  const min = deliveryType === 'LOCAL' ? localMinQty : crossMinQty;
  if (quantity < min) {
    return {
      ok: false,
      message:
        deliveryType === 'LOCAL'
          ? `同城配送至少购买 ${min} 瓶`
          : `跨城配送至少购买 ${min} 瓶（1箱）`,
    };
  }
  return { ok: true };
}

export function validateRedeemAmount(
  balance: number,
  amount: number,
  documentAmount?: number | null,
): { ok: boolean; message?: string } {
  if (amount <= 0) return { ok: false, message: '核销金额必须大于 0' };
  if (amount > balance) return { ok: false, message: '核销金额不能超过可用余额' };
  if (documentAmount != null && amount > documentAmount) {
    return { ok: false, message: '核销金额不能超过该核销单可用金额' };
  }
  return { ok: true };
}

export interface BenefitCouponBalance {
  id: string;
  balance: number;
  createdAt: number;
}

/** FIFO 跨多张权益券分配核销金额（购酒按单发券，展示为总余额） */
export function allocateBenefitCoupons(
  coupons: BenefitCouponBalance[],
  amount: number,
  documentAmount?: number | null,
): { ok: true; allocations: Array<{ couponId: string; amount: number }> } | { ok: false; message: string } {
  const active = coupons
    .filter((c) => c.balance > 0)
    .sort((a, b) => a.createdAt - b.createdAt);
  const totalBalance = active.reduce((sum, c) => sum + c.balance, 0);
  const check = validateRedeemAmount(totalBalance, amount, documentAmount);
  if (!check.ok) return { ok: false, message: check.message! };

  let remaining = amount;
  const allocations: Array<{ couponId: string; amount: number }> = [];
  for (const coupon of active) {
    if (remaining <= 0) break;
    const take = Math.min(coupon.balance, remaining);
    allocations.push({ couponId: coupon.id, amount: take });
    remaining = Math.round((remaining - take) * 100) / 100;
  }

  if (remaining > 0) {
    return { ok: false, message: '权益余额不足' };
  }

  return { ok: true, allocations };
}

export function calcBenefitSummary(
  balances: number[],
): { totalBalance: number; maxRedeemAmount: number; activeCouponCount: number } {
  const totalBalance = Math.round(balances.reduce((sum, b) => sum + b, 0) * 100) / 100;
  return {
    totalBalance,
    maxRedeemAmount: totalBalance,
    activeCouponCount: balances.length,
  };
}

export function calcRedeemSettleAmount(amount: number, settlementRate: number): number {
  return Math.round(amount * settlementRate * 100) / 100;
}

export function generateUserNo(): string {
  const suffix = Math.floor(10000000 + Math.random() * 90000000);
  return `DK${suffix}`;
}

export function generateOrderNo(): string {
  const now = new Date();
  const y = now.getFullYear();
  const m = String(now.getMonth() + 1).padStart(2, '0');
  const d = String(now.getDate()).padStart(2, '0');
  const rand = String(Math.floor(Math.random() * 100000)).padStart(5, '0');
  return `DK${y}${m}${d}${rand}`;
}

export function generateCouponNo(): string {
  return `BC${Date.now()}${Math.floor(Math.random() * 1000)}`;
}

export function generateRedeemNo(): string {
  return `RD${Date.now()}${Math.floor(Math.random() * 1000)}`;
}

export function orderTabToStatuses(tab: string): string[] | undefined {
  switch (tab) {
    case 'pending_pay':
      return ['PENDING_PAY'];
    case 'pending_ship':
      return ['PENDING_SHIP', 'OUT_WAREHOUSE'];
    case 'pending_receive':
      return ['SHIPPING', 'PENDING_RECEIVE'];
    case 'completed':
      return ['COMPLETED'];
    default:
      return undefined;
  }
}