Voucher Validator Idea Implementation

voucher-validator.ts

const enum Gender {
  Male = "Male",
  Female = "Female",
}

interface Order {
  id: string;
  date: Date;
  totalPrice: number;
  customer: {
    id: string;
    device: {
      name: string;
      os: string;
    }
  }
}

interface Voucher {
  id: string;
  orderApplicabilityAttempt: number;
  allowedCustomerGender: Gender;
}

type ValidatorFunction = () => boolean;

function isInValidDateRange(orderDate: Date, voucherId: string): boolean {
  // TODO: check whether the `orderDate` is in valid date range specified for voucher with id `voucherId`.
  return true;
}

function isBelowMaximumAmount(orderTotalPrice: number, voucherId: string): boolean {
  // TODO: check whether an order with total price of `orderTotalPrice` exceeds voucher with id `voucherId` maximum price
  return true;
}

function isCustomerAccessingWithValidDevice(customerDeviceName: string, voucherId: string): boolean {
  // TODO: check whether customer's device name is allowed to use voucher with id `voucherId`
  return true;
}

function isValidNthOrder(orderId: string, voucherOrderAttemptApplicability: number): boolean {
  // TODO: even query order service to get customer's order attempt number, then check whether the voucher applies to current order
  return true;
}

function isCustomerGenderValid(customerId: string, voucherAllowedGender: Gender): boolean {
  // TODO: query 'users service' to retrieve user's gender, then compare with voucher allowed gender
  return true;
}

function validate(order: Order, voucher: Voucher) {
  const validators: ReadonlyArray<ValidatorFunction> = [
    () => isInValidDateRange(order.date, voucher.id),
    () => isBelowMaximumAmount(order.totalPrice, voucher.id),
    () => isCustomerAccessingWithValidDevice(order.customer.device.name, voucher.id),
    () => isValidNthOrder(order.id, voucher.orderApplicabilityAttempt),
    () => isCustomerGenderValid(order.customer.id, voucher.allowedCustomerGender),
    // Other validators can be added accordingly as needed.
    // or even, a validator can be added conditionally
    // or decide between two validators based on simple `order` or `voucher`
    // properties, then the chosen validator is added to this list.
  ];

  return validators.every((validator) => validator());
}