functional_1

functional_1.ts

type Product = {
    name: string;
    price: number;
}

type ShoppingCart = Product[];

const TAX_RATE = 0.1;
const FREE_SHIPPING_PRICE_THRESHOLD = 20;
const MINIMUM_SHIPPING_COST = 5;

let shopping_cart: ShoppingCart = [];

function add_item_to_cart(cart: ShoppingCart, item: Product) {
    return [...cart, item];
}

function calc_cart_total(cart: ShoppingCart) {
    return cart.reduce((total, product) => total + product.price, 0);
}

function calc_tax_total(cart: ShoppingCart, tax_rate: number) {
    return calc_cart_total(cart) * tax_rate;
}

function is_free_shipping(cart: ShoppingCart, price_threshold: number) {
    return calc_cart_total(cart) > price_threshold;
}

function calc_shipping_cost(cart: ShoppingCart, minimum_shipping_cost: number) {
    return cart.reduce(
        (total, product) => total, // + shipping cost calculation by each product
        minimum_shipping_cost
    );
}

function calc_order_total(cart: ShoppingCart, tax_rate: number) {
    const shipping_cost = is_free_shipping(cart, FREE_SHIPPING_PRICE_THRESHOLD) 
        ? 0 
        : calc_shipping_cost(cart, MINIMUM_SHIPPING_COST)

    return calc_cart_total(cart) 
        + calc_tax_total(cart, tax_rate) + shipping_cost;
}