cart_validation.ts

type Message = {
  text: string;
  type: 'Error' | 'Warning' | 'Info';
};
type Item = {
  product: string;
  quantity: number;
  price: number;
  total: number;
  totalGST: number;
  messages: Array<Message>;
  minimumQuantity: number;
};

type Cart = {
  lineItems: Array<Item>;
  totalQuantity: number;
  total: number;
  subtotal: number;
  totalGST: number;
  messages: Message[];
};

class CartValidation {
  private _cart: Cart;

  constructor(cart: Cart) {
    this._cart = cart;
  }

  setErrorMessage(item: Item, message: Message): void {
    item.messages.push(message);
  }

  accept(visitor: Visitor): void {
    visitor.visit(this);
  }

  get cart(): Cart {
    return this._cart;
  }

  set cart(cart) {
    this._cart = cart;
  }
}

interface Visitor {
  visit(cart: CartValidation): void;
}

class MinimumQuantityValidation implements Visitor {
  visit(cartValidation: CartValidation): void {
    for (const item of cartValidation.cart.lineItems) {
      if (item.minimumQuantity > item.quantity) {
        cartValidation.setErrorMessage(item, { text: 'Need more quantity', type: 'Error' });
      }
    }
  }
}

const cartValidation = new CartValidation({
  lineItems: [{ product: '123', quantity: 10, price: 10, messages: [], minimumQuantity: 20, total: 0, totalGST: 0 }],
  total: 0,
  totalGST: 10,
  totalQuantity: 0,
  subtotal: 0,
  messages: [],
});
const minimumQuantityValidation = new MinimumQuantityValidation();
cartValidation.accept(minimumQuantityValidation);
console.log(cartValidation.cart.lineItems[0].messages);