zeller-test.ts

const DISCOUNT_TYPES = {
    BUY_2_GET_3: "BUY_2_GET_3",
    BULK: "BULK",
}

const ITEM_LIST = {
   APPLE_TV: "atv",
   SUPER_IPAD: "ipd"
}

type item  = {
    name: string,
    price: number,
    sku: string
}


// we can create multiple objects of PriceRules containing different kinds of discounts
class PriceRules {
    prices: Map<string,number>;

    constructor(priceList: Map<string,number>){
      this.prices = priceList
    }

    // function will get the price of items with discounts applied if applicable
    public getTotalPrice(item: string, quantity: number): number{
        let price = 0;

        // discount for item tv
        if(item === ITEM_LIST.APPLE_TV && quantity === 3){
            price = this.prices.get(item) * 2;
        }
        // discount for ipad
        else if(item === ITEM_LIST.SUPER_IPAD && quantity === 4  ){
          // 9.09% less
          let newPrice = this.prices.get(item) - (this.prices.get(item)/100)*9.09;
          price =  newPrice * quantity;
        }
        // return other prices
        else{
          price = this.prices.get(item) * quantity;
        }

        return price;
    }

}

class Checkout {
    private cart:Map<string,number>;
    private priceRules: PriceRules

    constructor(priceRules: PriceRules){
      this.priceRules = priceRules;
    }


    public scan(item: string): void{
        this.cart.has(item) ? this.cart.set(item, this.cart.get(item)+1) : this.cart.set(item,1);
    }

    public total(): number{
        let total = 0;
        for(let key of this.cart.keys()){
          // get price of each item
          let itemPrice = this.priceRules.getTotalPrice(key,this.cart.get(key));
          total += itemPrice;
        }
        return total;
    }

}




// MAIN

// get the itemlist
// { ipd: 549.99, atv: 109.50 }
let itemPrices = new Map<string,number>([ [ "ipd", 549.99 ], [ "atv", 109.50 ]])

// create different pricerules
let priceRule = new PriceRules(itemPrices);
const co = new Checkout(priceRule);
co.scan();
co.scan(item2);
const total = co.total();