feat: implement coupon and campaign applications over ShoppingCartSer…

…vice

- Improve interface
- Add required fields
- Add unit tests

src/main/java/io/github/akadir/casestudy/discount/coupon/ConcreteCoupon.java

@@ -7,7 +7,7 @@
 import java.util.Map;
 
 public class ConcreteCoupon extends Coupon {
-    protected ConcreteCoupon(Double minimumCartAmount, DiscountType discountType, double discountAmount) {
+    public ConcreteCoupon(double minimumCartAmount, DiscountType discountType, double discountAmount) {
         super(minimumCartAmount, discountType, discountAmount);
     }
 

src/main/java/io/github/akadir/casestudy/discount/coupon/base/Coupon.java

@@ -10,11 +10,11 @@
 public abstract class Coupon {
     protected final Logger log = LoggerFactory.getLogger(this.getClass());
 
-    protected final Double minimumCartAmount;
+    protected final double minimumCartAmount;
     protected final DiscountType discountType;
     protected final double discountAmount;
 
-    protected Coupon(Double minimumCartAmount, DiscountType discountType, double discountAmount) {
+    protected Coupon(double minimumCartAmount, DiscountType discountType, double discountAmount) {
         this.minimumCartAmount = minimumCartAmount;
         this.discountType = discountType;
         this.discountAmount = discountAmount;

src/main/java/io/github/akadir/casestudy/shopping/service/ShoppingCartService.java

@@ -1,5 +1,7 @@
 package io.github.akadir.casestudy.shopping.service;
 
+import io.github.akadir.casestudy.discount.campaign.base.Campaign;
+import io.github.akadir.casestudy.discount.coupon.base.Coupon;
 import io.github.akadir.casestudy.product.model.Product;
 
 import java.util.Map;
@@ -14,5 +16,13 @@ public interface ShoppingCartService {
 
     void removeProduct(Product product, int amount);
 
+    boolean applyCoupon(Coupon coupon);
+
+    boolean applyCampaign(Campaign campaign);
+
+    double getCartPrice();
+
+    double getDiscounts();
+
     Map<Product, Integer> getProducts();
 }

src/main/java/io/github/akadir/casestudy/shopping/service/impl/ConcreteShoppingCartServiceImpl.java

@@ -1,10 +1,12 @@
 package io.github.akadir.casestudy.shopping.service.impl;
 
+import io.github.akadir.casestudy.discount.campaign.base.Campaign;
+import io.github.akadir.casestudy.discount.coupon.base.Coupon;
 import io.github.akadir.casestudy.product.model.Product;
+import io.github.akadir.casestudy.shopping.service.ShoppingCartService;
 import io.github.akadir.casestudy.shopping.validator.CartEventValidator;
 import io.github.akadir.casestudy.shopping.validator.impl.AmountValidator;
 import io.github.akadir.casestudy.shopping.validator.impl.ProductValidator;
-import io.github.akadir.casestudy.shopping.service.ShoppingCartService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -17,6 +19,9 @@ public class ConcreteShoppingCartServiceImpl implements ShoppingCartService {
 
     private final Map<Product, Integer> products;
     private final CartEventValidator validator;
+    private Coupon appliedCoupon;
+    private Campaign appliedCampaign;
+    private double discount;
 
     public ConcreteShoppingCartServiceImpl() {
         this.products = new HashMap<>();
@@ -56,11 +61,113 @@ public void removeProduct(Product product, int amount) {
                 products.put(product, alreadyAdded - amount);
                 log.info("{} {} removed from cart. new amount is: {}", amount, product.getTitle(), alreadyAdded - amount);
             }
+
+            checkDiscounts();
         } else {
             log.warn("{} with amount: {} could not be removed from chart", product.getTitle(), amount);
         }
     }
 
+    private void checkDiscounts() {
+        double newDiscount = 0;
+
+        if (appliedCampaign != null) {
+            double campaignDiscount = appliedCampaign.calculateDiscount(products);
+
+            if (campaignDiscount == 0) {
+                this.appliedCampaign = null;
+                log.info("Campaign removed from cart");
+            }
+
+            newDiscount += campaignDiscount;
+        }
+
+        if (appliedCoupon != null) {
+            double couponDiscount = appliedCoupon.calculateDiscount(products);
+
+            if (couponDiscount == 0) {
+                this.appliedCoupon = null;
+                log.info("Coupon removed from cart");
+            }
+
+            newDiscount += couponDiscount;
+        }
+
+        this.discount = newDiscount;
+    }
+
+    @Override
+    public boolean applyCoupon(Coupon coupon) {
+        if (appliedCoupon != null) {
+            log.warn("You have already applied another coupon");
+            return false;
+        }
+
+        if (coupon != null) {
+            double couponDiscount = coupon.calculateDiscount(this.getProducts());
+
+            if (couponDiscount == 0) {
+                log.warn("Coupon has no effect on total price of cart");
+                return false;
+            }
+
+            double cartPrice = getCartPrice();
+
+            if (cartPrice < couponDiscount + this.discount) {
+                log.warn("Discounts exceeded cart price. Add more products into your cart to use this coupon");
+                return false;
+            }
+
+            this.discount += couponDiscount;
+            this.appliedCoupon = coupon;
+            return true;
+        }
+
+        return false;
+    }
+
+    @Override
+    public boolean applyCampaign(Campaign campaign) {
+        if (appliedCampaign != null) {
+            log.warn("You have already applied another campaign");
+            return false;
+        }
+
+        if (campaign != null) {
+            double campaignDiscount = campaign.calculateDiscount(this.getProducts());
+
+            if (campaignDiscount == 0) {
+                log.warn("Campaign has no effect on total price of cart");
+                return false;
+            }
+
+            double cartPrice = getCartPrice();
+
+            if (cartPrice < campaignDiscount + this.discount) {
+                log.warn("Discounts exceeded cart price. Add more products into your cart to use this campaign");
+                return false;
+            }
+
+            this.discount += campaignDiscount;
+            this.appliedCampaign = campaign;
+
+            return true;
+        }
+
+        return false;
+    }
+
+    @Override
+    public double getCartPrice() {
+        return products.entrySet().stream()
+                .mapToDouble(e -> e.getKey().getPrice() * e.getValue()).sum();
+    }
+
+    @Override
+    public double getDiscounts() {
+        return discount;
+    }
+
     public Map<Product, Integer> getProducts() {
         return Collections.unmodifiableMap(products);
     }