discount codes (step3)

Author: Félix Carpena

src/main/java/group/rohlik/application/CartDiscountAdder.java

@@ -0,0 +1,26 @@
+package group.rohlik.application;
+
+import group.rohlik.entity.Cart;
+import group.rohlik.entity.CartRepository;
+import group.rohlik.entity.Discount;
+import group.rohlik.entity.DiscountRepository;
+import lombok.AllArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@AllArgsConstructor
+@Service
+@Transactional
+public class CartDiscountAdder {
+
+    private final CartRepository cartRepository;
+    private final DiscountRepository discountRepository;
+
+    public void add(long cartId, String code) {
+        Cart cart = cartRepository.findById(cartId).orElseThrow();
+        Discount discount = discountRepository.findByCode(code).orElseThrow();
+        cart.applyDiscount(discount);
+
+        cartRepository.save(cart);
+    }
+}

src/main/java/group/rohlik/application/CartLineAdder.java

@@ -22,7 +22,7 @@ public void add(long cartId, String sku, int quantity) {
         Cart cart = cartRepository.findById(cartId).orElseThrow();
         Product product = productRepository.findById(sku).orElseThrow();
         cart.addLine(product, quantity);
-        cart.recalculateDiscounts(discountRepository.findAll());
+        cart.recalculateAutomaticDiscounts(discountRepository.findAllAutomatics());
 
         cartRepository.save(cart);
     }

src/main/java/group/rohlik/controller/CartController.java

@@ -1,6 +1,7 @@
 package group.rohlik.controller;
 
 import com.fasterxml.jackson.databind.JsonNode;
+import group.rohlik.application.CartDiscountAdder;
 import group.rohlik.application.CartLineAdder;
 import lombok.AllArgsConstructor;
 import org.springframework.http.HttpStatus;
@@ -15,6 +16,7 @@
 public class CartController {
 
     private final CartLineAdder cartLineAdder;
+    private final CartDiscountAdder cartDiscountAdder;
 
     @PostMapping(path = "/carts/{id}/lines", consumes = "application/json", produces = "application/json")
     public ResponseEntity addLine(@PathVariable long id, @RequestBody JsonNode payload) {
@@ -25,4 +27,13 @@ public ResponseEntity addLine(@PathVariable long id, @RequestBody JsonNode paylo
 
         return new ResponseEntity<>(HttpStatus.OK);
     }
+
+    @PostMapping(path = "/carts/{id}/discounts", consumes = "application/json", produces = "application/json")
+    public ResponseEntity addDiscount(@PathVariable long id, @RequestBody JsonNode payload) {
+        String code = payload.get("code").textValue();
+
+        cartDiscountAdder.add(id, code);
+
+        return new ResponseEntity<>(HttpStatus.OK);
+    }
 }

src/main/java/group/rohlik/entity/Cart.java

@@ -80,11 +80,13 @@ private double totalDiscountsPrice() {
                 .sum();
     }
 
-    public void recalculateDiscounts(List<Discount> discounts) {
-        this.discounts.clear();
+    public void recalculateAutomaticDiscounts(List<Discount> discounts) {
+        List<Discount> toBeDeleted = this.discounts.stream().filter(Discount::isAutomatic).toList();
+        toBeDeleted.forEach(this.discounts::remove);
         double price = totalLinesPrice();
         discounts
                 .stream()
+                .filter(Discount::isAutomatic)
                 .filter(discount -> discount.getMinPrice() < price)
                 .forEach(this.discounts::add);
     }
@@ -108,6 +110,12 @@ public boolean hasDiscount(long id) {
                 .anyMatch(line -> line.getId() == id);
     }
 
+    public boolean hasDiscount(String name) {
+        return discounts
+                .stream()
+                .anyMatch(line -> line.getName().equals(name));
+    }
+
     public Integer quantityOfProduct(String sku) {
         return lines
                 .stream()
@@ -116,4 +124,10 @@ public Integer quantityOfProduct(String sku) {
                 .map(CartLine::getQuantity)
                 .orElse(0);
     }
+    public void applyDiscount(Discount discount) {
+        Assert.isTrue(!discount.isAutomatic(), "Discount can not be of type automatic");
+        Assert.isTrue(!discounts.contains(discount), "Discount already applied");
+
+        discounts.add(discount);
+    }
 }

src/main/java/group/rohlik/entity/Discount.java

@@ -1,18 +1,21 @@
 package group.rohlik.entity;
 
-import lombok.Data;
+import lombok.Getter;
 import lombok.NoArgsConstructor;
 
 import javax.persistence.Column;
 import javax.persistence.Entity;
+import javax.persistence.EnumType;
+import javax.persistence.Enumerated;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 
 @Entity(name = "discounts")
-@Data
+@Getter
 @NoArgsConstructor
 public class Discount {
+
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private long id;
@@ -22,4 +25,39 @@ public class Discount {
     private float minPrice;
     @Column(nullable = false)
     private float amount;
+    @Column
+    private String code;
+    @Column
+    @Enumerated(EnumType.STRING)
+    private DiscountType type;
+
+    public enum DiscountType {
+        CODE, MIN_PRICE
+    }
+
+    public static Discount minimumPriceDiscount(String name, float amount, float minPrice) {
+        Discount discount = new Discount();
+        discount.name = name;
+        discount.amount = amount;
+        discount.minPrice = minPrice;
+        discount.code = null;
+        discount.type = DiscountType.MIN_PRICE;
+
+        return discount;
+    }
+
+    public static Discount codeDiscount(String name, float amount, String code) {
+        Discount discount = new Discount();
+        discount.name = name;
+        discount.amount = amount;
+        discount.minPrice = 0;
+        discount.code = code;
+        discount.type = DiscountType.CODE;
+
+        return discount;
+    }
+
+    public boolean isAutomatic() {
+        return !type.equals(DiscountType.CODE);
+    }
 }

src/main/java/group/rohlik/entity/DiscountRepository.java

@@ -1,6 +1,15 @@
 package group.rohlik.entity;
 
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+
+import java.util.List;
+import java.util.Optional;
 
 public interface DiscountRepository extends JpaRepository<Discount, Long> {
+
+    Optional<Discount> findByCode(String code);
+
+    @Query("SELECT d FROM discounts d WHERE d.type in ('MIN_PRICE')")
+    List<Discount> findAllAutomatics();
 }

src/test/java/group/rohlik/acceptance/steps/CartSteps.java

@@ -89,13 +89,35 @@ public void thereShouldBeDiscountInCart(long discountId) {
         Assertions.assertTrue(cart.hasDiscount(discountId), String.format("Discount %s should be present", discountId));
     }
 
+    @Then("there should be discount {string} in my cart")
+    public void thereShouldBeDiscountByNameInCart(String name) {
+        Cart cart = currentCart();
+
+        Assertions.assertTrue(cart.hasDiscount(name), String.format("Discount %s should be present", name));
+    }
+
     @Then("there shouldn't be discounts in my cart")
     public void thereShouldNotBeDiscountsInCart() {
         Cart cart = currentCart();
 
         Assertions.assertEquals(0, cart.getDiscounts().size());
     }
 
+    @When("I apply {string} discount to my cart")
+    public void iApplyDiscountToMyCart(String code) {
+        JsonObject body = new JsonObject();
+        body.add("code", code);
+        HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.APPLICATION_JSON);
+
+        template.exchange(
+                String.format("/carts/%d/discounts", currentCartId),
+                HttpMethod.POST,
+                new HttpEntity<>(body.toString(), headers),
+                String.class
+        );
+    }
+
     private Cart currentCart() {
         return cartRepository.findById(currentCartId).orElseThrow();
     }

src/test/java/group/rohlik/acceptance/steps/DiscountSteps.java

@@ -2,22 +2,26 @@
 
 import group.rohlik.entity.Discount;
 import group.rohlik.entity.DiscountRepository;
-import io.cucumber.java.en.And;
 import io.cucumber.java.en.Given;
 import lombok.AllArgsConstructor;
 import org.springframework.transaction.annotation.Transactional;
 
 @AllArgsConstructor
 public class DiscountSteps {
+
     private final DiscountRepository discountRepository;
 
     @Given("there is a cart discount {string} for {float} euros with a minimum total price of {float} euros")
     @Transactional
     public void thereIsACartDiscountWithAMinimumTotalPrice(String name, float amount, float minPrice) {
-        Discount discount = new Discount();
-        discount.setName(name);
-        discount.setAmount(amount);
-        discount.setMinPrice(minPrice);
+        Discount discount = Discount.minimumPriceDiscount(name, amount, minPrice);
+        discountRepository.save(discount);
+    }
+
+    @Given("there is a cart discount {string} for {float} euros with code {string}")
+    @Transactional
+    public void thereIsACartDiscountWithCode(String name, float amount, String code) {
+        Discount discount = Discount.codeDiscount(name, amount, code);
         discountRepository.save(discount);
     }
 }

src/test/resources/features/add_discount_to_cart.feature

@@ -0,0 +1,41 @@
+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 "Amazing discount" for 1 euros with a minimum total price of 6 euros
+    And I have a 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: Mix automatic and code discounts
+    Given I add 3 units of product "001" to my cart
+    When I apply "FREE-SHIPPING" discount to my cart
+    Then the cart's total cost should be 5.5 euros
+    And there should be discount "free shipping" in my cart
+    And there should be discount "Amazing discount" in my cart
+
+  Scenario: Code discounts are no recalculated
+    Given I add 2 units of product "001" to my cart
+    And I add 2 units of product "002" to my cart
+    And I apply "FREE-SHIPPING" discount to my cart
+    When I remove product "002" of my cart
+    Then the cart's total cost should be 4.0 euros
+    And there should be discount "free shipping" in my cart