refactoring (step2)

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

@@ -0,0 +1,26 @@
+package group.rohlik.application;
+
+import group.rohlik.entity.Cart;
+import group.rohlik.entity.CartRepository;
+import group.rohlik.entity.Product;
+import group.rohlik.entity.ProductRepository;
+import lombok.AllArgsConstructor;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+@AllArgsConstructor
+@Service
+@Transactional
+public class CartLineAdder {
+
+    private final CartRepository cartRepository;
+    private final ProductRepository productRepository;
+
+    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);
+
+        cartRepository.save(cart);
+    }
+}

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

@@ -2,11 +2,7 @@
 
 import com.fasterxml.jackson.databind.JsonNode;
 import group.rohlik.application.CartDiscountAdder;
-import group.rohlik.entity.Cart;
-import group.rohlik.entity.CartLine;
-import group.rohlik.entity.CartRepository;
-import group.rohlik.entity.Product;
-import group.rohlik.entity.ProductRepository;
+import group.rohlik.application.CartLineAdder;
 import lombok.AllArgsConstructor;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -19,44 +15,15 @@
 @AllArgsConstructor
 public class CartController {
 
-    private final CartRepository cartRepository;
-    private final ProductRepository productRepository;
+    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) {
         String sku = payload.get("sku").textValue();
         int quantity = payload.get("quantity").intValue();
 
-        if (quantity < 0) {
-            throw new IllegalArgumentException("Negative quantity not allowed");
-        }
-
-        Cart cart = cartRepository.findById(id).orElseThrow();
-        Product product = productRepository.findById(sku).orElseThrow();
-        CartLine cartLine = cart.getLines()
-                .stream()
-                .filter(currentCartLine -> currentCartLine.getProduct().equals(product))
-                .findFirst()
-                .orElse(null);
-
-        if (cartLine == null) {
-            if (quantity > 0) {
-                cartLine = new CartLine();
-                cartLine.setProduct(product);
-                cartLine.setQuantity(quantity);
-                cartLine.setCart(cart);
-                cart.getLines().add(cartLine);
-            }
-        } else {
-            if (quantity == 0) {
-                cart.getLines().remove(cartLine);
-            } else {
-                cartLine.setQuantity(quantity);
-            }
-        }
-
-        cartRepository.save(cart);
+        cartLineAdder.add(id, sku, quantity);
 
         return new ResponseEntity<>(HttpStatus.OK);
     }

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

@@ -1,8 +1,9 @@
 package group.rohlik.entity;
 
-import lombok.Data;
 import lombok.EqualsAndHashCode;
+import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.springframework.util.Assert;
 
 import javax.persistence.CascadeType;
 import javax.persistence.Entity;
@@ -14,11 +15,13 @@
 import javax.persistence.ManyToMany;
 import javax.persistence.OneToMany;
 import javax.persistence.Table;
+import java.math.BigDecimal;
+import java.math.RoundingMode;
 import java.util.HashSet;
 import java.util.Set;
 
 @Entity
-@Data
+@Getter
 @NoArgsConstructor
 @Table(name = "carts")
 public class Cart {
@@ -37,4 +40,60 @@ public class Cart {
     )
     @EqualsAndHashCode.Exclude
     private Set<Discount> discounts = new HashSet<>();
+
+    public void addLine(Product product, int quantity) {
+        Assert.isTrue(quantity >= 0, "Line quantity must be positive");
+
+        CartLine cartLine = lines
+                .stream()
+                .filter(currentCartLine -> currentCartLine.getProduct().equals(product))
+                .findFirst()
+                .orElse(null);
+
+        if (cartLine == null) {
+            if (quantity > 0) {
+                cartLine = new CartLine();
+                cartLine.setProduct(product);
+                cartLine.setQuantity(quantity);
+                cartLine.setCart(this);
+                lines.add(cartLine);
+            }
+        } else {
+            if (quantity == 0) {
+                lines.remove(cartLine);
+            } else {
+                cartLine.setQuantity(quantity);
+            }
+        }
+    }
+
+    private double totalLinesPrice() {
+        return lines
+                .stream()
+                .mapToDouble(currentCartLine -> currentCartLine.getQuantity() * currentCartLine.getProduct().getPrice())
+                .sum();
+    }
+
+    private double totalDiscountsPrice() {
+        return discounts
+                .stream()
+                .mapToDouble(Discount::getValue)
+                .sum();
+    }
+
+    public double totalPrice() {
+        return BigDecimal
+                .valueOf(totalLinesPrice() - totalDiscountsPrice())
+                .setScale(2, RoundingMode.CEILING)
+                .doubleValue();
+    }
+
+    public Integer quantityOfProduct(String sku) {
+        return lines
+                .stream()
+                .filter(line -> line.getProduct().getSku().equals(sku))
+                .findFirst()
+                .map(CartLine::getQuantity)
+                .orElse(0);
+    }
 }

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

@@ -64,41 +64,23 @@ public void removeProductOfMyCart(String sku) {
     @Then("the cart's total cost should be {double} euro(s)")
     public void cartTotalCost(double amount) {
         Cart cart = currentCart();
-        double totalProducts = cart
-                .getLines()
-                .stream()
-                .mapToDouble(currentCartLine -> currentCartLine.getQuantity() * currentCartLine.getProduct().getPrice())
-                .sum();
-        double totalDiscounts = cart.getDiscounts().stream().mapToDouble(Discount::getValue).sum();
-        double totalPrice = totalProducts - totalDiscounts;
-
-        Assertions.assertEquals(amount, BigDecimal.valueOf(totalPrice).setScale(2, RoundingMode.CEILING).doubleValue());
+        double totalPrice = cart.totalPrice();
 
+        Assertions.assertEquals(amount, totalPrice);
     }
 
     @Then("there should be {int} unit(s) of product {string} in my cart")
     public void thereShouldBeProductUnitsInMyCart(int quantity, String sku) {
         Cart cart = currentCart();
-        CartLine cartLine = cart.getLines()
-                .stream()
-                .filter(currentCartLine -> currentCartLine.getProduct().getSku().equals(sku))
-                .findFirst()
-                .orElse(null);
-
-        Assertions.assertNotNull(cartLine, String.format("Product %s not found", sku));
-        Assertions.assertEquals(quantity, cartLine.getQuantity());
+
+        Assertions.assertEquals(quantity, cart.quantityOfProduct(sku));
     }
 
     @Then("there shouldn't be product {string} in my cart")
     public void thereShouldNotBeProductInCart(String sku) {
         Cart cart = currentCart();
-        CartLine cartLine = cart.getLines()
-                .stream()
-                .filter(currentCartLine -> currentCartLine.getProduct().getSku().equals(sku))
-                .findFirst()
-                .orElse(null);
 
-        Assertions.assertNull(cartLine, String.format("Product %s should not be present", sku));
+        Assertions.assertTrue(cart.quantityOfProduct(sku) == 0, String.format("Product %s should not be present", sku));
     }
 
     private Cart currentCart() {