bad_liskov_substitution_principle.ts

type Order = {
  id: number;
  value: number;
  customer: string;
};

class Payment {
  private discount: number;
  private fee: number;
  private order: Order;

  constructor(discount: number, fee: number, order: Order) {
    this.discount = discount;
    this.fee = fee;
    this.order = order;
  }

  public getDiscount(value: number): number {
    return (value * this.discount) / 100;
  }

  public getFee(value: number): number {
    return (value * this.fee) / 100;
  }

  public getFinalValue(): number {
    const discount = this.getDiscount(this.order.value);

    let currentValue = this.order.value;

    if (discount > 0) {
      currentValue = currentValue - discount;
    }

    const fee = this.getFee(currentValue);

    if (fee > 0) {
      return currentValue + fee;
    }

    return currentValue;
  }

  public getOrder(): Order {
    return this.order;
  }
}

class CreditPayment extends Payment {
  constructor(discount: number, fee: number, order: Order) {
    super(discount, fee, order);
  }

  public getDiscount(value: number): number {
    throw new Error("not implemented discount in credit payment method");
  }
}

class PixPayment extends Payment {
  constructor(discount: number, fee: number, order: Order) {
    super(discount, fee, order);
  }

  public getFee(value: number): number {
    throw new Error("not implemented fee in pix payment method");
  }
}