discount codes (step3)

features/add_discount_to_cart.feature

@@ -0,0 +1,39 @@
+Feature: Add discount to cart
+  As a Rohlik customer
+  I want to apply discounts to my cart
+  so that I can save some money
+
+  Background:
+    Given the following products exist:
+      | sku | name     | price |
+      | 001 | potatoes | 2.5   |
+      | 002 | water    | 0.95  |
+    And there is a cart discount "free shipping" for 1 euros with code "FREE-SHIPPING"
+    And there is a cart discount "special offer" for 10 euros with code "SPECIAL-OFFER"
+    And I have a cart
+
+  Scenario: No discounts
+    When I add 2 units of product "001" to my cart
+    Then the cart's total cost should be 5.0 euros
+    But there shouldn't be discounts in my cart
+
+  Scenario: Add discount
+    Given I add 2 units of product "001" to my cart
+    When I apply "FREE-SHIPPING" discount to my cart
+    Then the cart's total cost should be 4.0 euros
+    And there should be discount "free shipping" in my cart
+
+  Scenario: Add discount only apply once
+    Given I add 2 units of product "001" to my cart
+    And I apply "FREE-SHIPPING" discount to my cart
+    When I apply "FREE-SHIPPING" discount to my cart
+    Then the cart's total cost should be 4.0 euros
+    And there should be discount "free shipping" in my cart
+
+  Scenario: Cart total should be always positive
+    Given I add 2 units of product "001" to my cart
+    And I apply "FREE-SHIPPING" discount to my cart
+    When I apply "SPECIAL-OFFER" discount to my cart
+    Then the cart's total cost should be 0.0 euros
+    And there should be discount "free shipping" in my cart
+    And there should be discount "special offer" in my cart

src/application/CartDiscountAdder.ts

@@ -15,21 +15,10 @@ class CartDiscountAdder {
         const cart: Cart = await this.cartRepository.findOneByOrFail({id: cartId})
         const discount: Discount = await this.discountRepository.findOneByOrFail({code: code})
 
-        this.applyDiscount(cart, discount)
+        cart.applyDiscount(discount)
 
         await this.cartRepository.save(cart)
     }
-
-    private applyDiscount(cart: Cart, discount: Discount): void {
-        //@todo suspicious code - should we move this logic to cart entity?
-        const foundDiscount: Discount|undefined = cart.discounts.find((currentDiscount: Discount) => currentDiscount.id == discount.id)
-
-        if (foundDiscount) {
-            throw "Discount already applied"
-        }
-
-        cart.discounts.push(discount)
-    }
 }
 
 export default CartDiscountAdder

src/entity/Cart.ts

@@ -62,13 +62,31 @@ class Cart {
     }
 
     public totalPrice(): number {
-        return Math.round((this.totalLinesPrice() - this.totalDiscountsPrice()) * 100) / 100
+        return Math.max(
+            0,
+            Math.round((this.totalLinesPrice() - this.totalDiscountsPrice()) * 100) / 100
+        )
     }
 
     public quantityOfProduct(sku: string): number {
         const cartLine: CartLine|undefined = this.lines.find((cartLine: CartLine) => cartLine.product.sku == sku)
         return cartLine ? cartLine.quantity : 0
     }
+
+    public hasDiscount(name: string): boolean {
+        const discount: Discount|undefined = this.discounts.find((discount: Discount) => discount.name == name)
+        return discount ? true : false
+    }
+
+    public applyDiscount(discount: Discount): void {
+        const foundDiscount: Discount|undefined = this.discounts.find((currentDiscount: Discount) => currentDiscount.id == discount.id)
+
+        if (foundDiscount) {
+            throw "Discount already applied"
+        }
+
+        this.discounts.push(discount)
+    }
 }
 
 export default Cart

src/tests/steps/CartSteps.ts

@@ -63,6 +63,30 @@ class CartSteps {
         assert.equal(cart.quantityOfProduct(sku), 0)
     }
 
+    @then("there should be discount {string} in my cart")
+    public async thereShouldBeDiscountInCart(name: string) {
+        const cart: Cart = await this.currentCart()
+        assert.equal(cart.hasDiscount(name), true, `Discount ${name} should be present`)
+    }
+
+    @then("there shouldn't be discounts in my cart")
+    public async thereShouldNotBeDiscountsInCart() {
+        const cart: Cart = await this.currentCart()
+        assert.equal(0, cart.discounts.length);
+    }
+
+    @when("I apply {string} discount to my cart")
+    public async iApplyDiscountToMyCart(code: string) {
+        await this.axios.post(
+            `http://${process.env.WEB_HOST}:${process.env.WEB_PORT}/carts/${this.currentCartId}/discounts`,
+            { code: code },
+            {
+                headers: {'Content-Type': 'application/json'},
+                validateStatus: (status: number) => { return true }
+            }
+        )
+    }
+
     private currentCart(): Promise<Cart> {
         return this.cartRepository.findOneByOrFail({id: this.currentCartId})
     }