Merge pull request #19 from leung018/order-service-part-2

Order-service-part-2
leung018 · Dec 10, 2024 · d900698 · d900698
2 parents f57bfa2 + e92407c
commit d900698
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Showing 10 changed files with 436 additions and 33 deletions.
diff --git a/src/main/java/com/leungcheng/spring_simple_backend/controller/MeController.java b/src/main/java/com/leungcheng/spring_simple_backend/controller/MeController.java
@@ -3,6 +3,7 @@
 import com.leungcheng.spring_simple_backend.auth.UserAuthenticatedInfoToken;
 import com.leungcheng.spring_simple_backend.domain.User;
 import com.leungcheng.spring_simple_backend.domain.UserRepository;
+import java.math.BigDecimal;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -18,5 +19,5 @@ public UserAccountInfo me(UserAuthenticatedInfoToken authToken) {
     return new UserAccountInfo(user.getUsername(), user.getBalance());
   }
 
-  public record UserAccountInfo(String username, double balance) {}
+  public record UserAccountInfo(String username, BigDecimal balance) {}
 }
diff --git a/src/main/java/com/leungcheng/spring_simple_backend/controller/ProductController.java b/src/main/java/com/leungcheng/spring_simple_backend/controller/ProductController.java
@@ -4,6 +4,7 @@
 import com.leungcheng.spring_simple_backend.domain.Product;
 import com.leungcheng.spring_simple_backend.domain.ProductRepository;
 import jakarta.validation.Valid;
+import java.math.BigDecimal;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.*;
@@ -33,5 +34,5 @@ Product one(@PathVariable String id) {
     return repository.findById(id).orElseThrow(() -> new ProductNotFoundException(id));
   }
 
-  public record CreateProductRequest(String name, double price, int quantity) {}
+  public record CreateProductRequest(String name, BigDecimal price, int quantity) {}
 }
diff --git a/src/main/java/com/leungcheng/spring_simple_backend/domain/Product.java b/src/main/java/com/leungcheng/spring_simple_backend/domain/Product.java
@@ -7,22 +7,29 @@
 import jakarta.persistence.Table;
 import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.NotBlank;
+import java.math.BigDecimal;
 
 @Entity
 @Table(name = "products")
 public class Product {
   public static class Builder {
     private String name;
-    private double price;
+    private BigDecimal price;
     private int quantity;
     private String userId;
+    private String id = java.util.UUID.randomUUID().toString();
+
+    private Builder id(String id) {
+      this.id = id;
+      return this;
+    }
 
     public Builder name(String name) {
       this.name = name;
       return this;
     }
 
-    public Builder price(double price) {
+    public Builder price(BigDecimal price) {
       this.price = price;
       return this;
     }
@@ -39,6 +46,7 @@ public Builder userId(String userId) {
 
     public Product build() {
       Product product = new Product();
+      product.id = id;
       product.name = name;
       product.price = price;
       product.quantity = quantity;
@@ -51,16 +59,20 @@ public Product build() {
 
   private Product() {}
 
+  public Builder toBuilder() {
+    return new Builder().name(name).price(price).quantity(quantity).userId(userId).id(id);
+  }
+
   @Id
   @JsonProperty(access = JsonProperty.Access.READ_ONLY)
-  private String id = java.util.UUID.randomUUID().toString();
+  private String id;
 
   private String userId;
 
   @NotBlank private String name;
 
   @Min(0)
-  private double price;
+  private BigDecimal price;
 
   @Min(0)
   private int quantity;
@@ -77,7 +89,7 @@ public String getName() {
     return name;
   }
 
-  public double getPrice() {
+  public BigDecimal getPrice() {
     return price;
   }
 

diff --git a/src/main/java/com/leungcheng/spring_simple_backend/domain/User.java b/src/main/java/com/leungcheng/spring_simple_backend/domain/User.java
@@ -8,6 +8,7 @@
 import jakarta.persistence.Table;
 import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.NotBlank;
+import java.math.BigDecimal;
 import java.util.Collection;
 import java.util.List;
 import org.springframework.security.core.GrantedAuthority;
@@ -16,12 +17,18 @@
 @Entity
 @Table(name = "users")
 public class User implements UserDetails {
-  public static final double INITIAL_BALANCE = 100;
+  public static final BigDecimal INITIAL_BALANCE = new BigDecimal(100);
 
   public static class Builder {
     private String username;
     private String password;
-    private double balance;
+    private BigDecimal balance;
+    private String id = java.util.UUID.randomUUID().toString();
+
+    private Builder id(String id) {
+      this.id = id;
+      return this;
+    }
 
     public Builder username(String username) {
       this.username = username;
@@ -33,13 +40,15 @@ public Builder password(String password) {
       return this;
     }
 
-    public Builder balance(double balance) {
+    public Builder balance(BigDecimal balance) {
       this.balance = balance;
       return this;
     }
 
     public User build() {
       User user = new User();
+
+      user.id = id;
       user.username = username;
       user.password = password;
       user.balance = balance;
@@ -51,9 +60,13 @@ public User build() {
 
   private User() {}
 
+  public User.Builder toBuilder() {
+    return new User.Builder().username(username).password(password).balance(balance).id(id);
+  }
+
   @Id
   @JsonProperty(access = JsonProperty.Access.READ_ONLY)
-  private String id = java.util.UUID.randomUUID().toString();
+  private String id;
 
   @Column(unique = true)
   @NotBlank
@@ -62,7 +75,7 @@ private User() {}
   @NotBlank private String password;
 
   @Min(0)
-  private double balance;
+  private BigDecimal balance;
 
   @Override
   public Collection<? extends GrantedAuthority> getAuthorities() {
@@ -83,7 +96,7 @@ public String getUsername() {
     return username;
   }
 
-  public double getBalance() {
+  public BigDecimal getBalance() {
     return balance;
   }
 }
diff --git a/src/main/java/com/leungcheng/spring_simple_backend/domain/order/Order.java b/src/main/java/com/leungcheng/spring_simple_backend/domain/order/Order.java
@@ -8,17 +8,22 @@
 @Table(name = "orders")
 public class Order {
   @Id private final String id = java.util.UUID.randomUUID().toString();
-  private String userId;
+  private String buyerUserId;
   private PurchaseItems purchaseItems;
 
   private Order() {}
 
+  Order(String buyerUserId, PurchaseItems purchaseItems) {
+    this.buyerUserId = buyerUserId;
+    this.purchaseItems = purchaseItems;
+  }
+
   public String getId() {
     return id;
   }
 
-  public String getUserId() {
-    return userId;
+  public String getBuyerUserId() {
+    return buyerUserId;
   }
 
   public PurchaseItems getPurchaseItems() {

diff --git a/src/main/java/com/leungcheng/spring_simple_backend/domain/order/OrderService.java b/src/main/java/com/leungcheng/spring_simple_backend/domain/order/OrderService.java
@@ -1,8 +1,16 @@
 package com.leungcheng.spring_simple_backend.domain.order;
 
+import com.google.common.collect.ImmutableMap;
+import com.leungcheng.spring_simple_backend.domain.Product;
 import com.leungcheng.spring_simple_backend.domain.ProductRepository;
+import com.leungcheng.spring_simple_backend.domain.User;
 import com.leungcheng.spring_simple_backend.domain.UserRepository;
+import java.math.BigDecimal;
+import java.util.Map;
+import java.util.Optional;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Isolation;
+import org.springframework.transaction.annotation.Transactional;
 
 @Service
 public class OrderService {
@@ -19,7 +27,77 @@ public OrderService(
     this.orderRepository = orderRepository;
   }
 
-  public Order createOrder(String userId, PurchaseItems purchaseItems) {
-    throw new UnsupportedOperationException("Not implemented");
+  @Transactional(isolation = Isolation.SERIALIZABLE)
+  public Order createOrder(String buyerUserId, PurchaseItems purchaseItems) {
+    User buyer =
+        getUser(buyerUserId)
+            .orElseThrow(() -> new IllegalArgumentException("Buyer does not exist"));
+
+    BigDecimal totalCost = processPurchaseItems(purchaseItems);
+
+    if (buyer.getBalance().compareTo(totalCost) < 0) {
+      throw new IllegalArgumentException("Insufficient balance");
+    }
+    saveNewBalance(buyer, buyer.getBalance().subtract(totalCost));
+
+    return addNewOrder(buyerUserId, purchaseItems);
+  }
+
+  private Optional<User> getUser(String userId) {
+    return userRepository.findById(userId);
+  }
+
+  private void saveNewBalance(User buyer, BigDecimal newBalance) {
+    User updatedBuyer = buyer.toBuilder().balance(newBalance).build();
+    userRepository.save(updatedBuyer);
+  }
+
+  private Order addNewOrder(String buyerUserId, PurchaseItems purchaseItems) {
+    Order order = new Order(buyerUserId, purchaseItems);
+    return orderRepository.save(order);
+  }
+
+  private BigDecimal processPurchaseItems(PurchaseItems purchaseItems) {
+    ImmutableMap<String, Integer> productIdToQuantity = purchaseItems.getProductIdToQuantity();
+    if (productIdToQuantity.isEmpty()) {
+      throw new IllegalArgumentException("Purchase items cannot be empty");
+    }
+
+    BigDecimal totalCost = BigDecimal.ZERO;
+    for (Map.Entry<String, Integer> entry : productIdToQuantity.entrySet()) {
+      String productId = entry.getKey();
+      int purchaseQuantity = entry.getValue();
+      Product product = getProduct(productId);
+
+      reduceProductStock(product, purchaseQuantity);
+      addProfitToSeller(product, purchaseQuantity);
+
+      BigDecimal itemCost = product.getPrice().multiply(BigDecimal.valueOf(purchaseQuantity));
+      totalCost = totalCost.add(itemCost);
+    }
+    return totalCost;
+  }
+
+  private void reduceProductStock(Product product, int purchaseQuantity) {
+    if (purchaseQuantity > product.getQuantity()) {
+      throw new IllegalArgumentException("Insufficient stock for product: " + product.getId());
+    }
+    int newQuantity = product.getQuantity() - purchaseQuantity;
+    Product updatedProduct = product.toBuilder().quantity(newQuantity).build();
+    productRepository.save(updatedProduct);
+  }
+
+  private void addProfitToSeller(Product product, int purchaseQuantity) {
+    User seller = getUser(product.getUserId()).orElseThrow();
+    BigDecimal profit = product.getPrice().multiply(BigDecimal.valueOf(purchaseQuantity));
+    BigDecimal newBalance = seller.getBalance().add(profit);
+    saveNewBalance(seller, newBalance);
+  }
+
+  private Product getProduct(String productId) {
+    return productRepository
+        .findById(productId)
+        .orElseThrow(
+            () -> new IllegalArgumentException("Product: " + productId + " does not exist"));
   }
 }
diff --git a/src/test/java/com/leungcheng/spring_simple_backend/SpringSimpleBackendApplicationTests.java b/src/test/java/com/leungcheng/spring_simple_backend/SpringSimpleBackendApplicationTests.java
@@ -10,6 +10,7 @@
 import com.leungcheng.spring_simple_backend.domain.User;
 import com.leungcheng.spring_simple_backend.domain.UserRepository;
 import com.leungcheng.spring_simple_backend.validation.ObjectValidator.ObjectValidationException;
+import java.math.BigDecimal;
 import java.util.Optional;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -63,19 +64,20 @@ void shouldCreateAndGetProduct() throws Exception {
     useNewUserAccessToken();
 
     CreateProductParams params = CreateProductParams.sample();
+    params.price = "19.2";
     MvcResult mvcResult =
         createProduct(params)
             .andExpect(status().isCreated())
             .andExpect(jsonPath("$.name").value(params.name))
-            .andExpect(jsonPath("$.price").value(params.price))
+            .andExpect(jsonPath("$.price").value("19.2"))
             .andExpect(jsonPath("$.quantity").value(params.quantity))
             .andReturn();
     String productId = JsonPath.read(mvcResult.getResponse().getContentAsString(), "$.id");
 
     getProduct(productId)
         .andExpect(status().isOk())
         .andExpect(jsonPath("$.name").value(params.name))
-        .andExpect(jsonPath("$.price").value(params.price))
+        .andExpect(jsonPath("$.price").value("19.2"))
         .andExpect(jsonPath("$.quantity").value(params.quantity));
   }
 
@@ -100,12 +102,16 @@ void shouldHandleObjectValidationException_AndIncludeTheProperInfoInTheResponse(
     useNewUserAccessToken();
 
     CreateProductParams params = CreateProductParams.sample();
-    params.price = -1;
+    params.price = "-1";
 
     // Set up the expected exception that will be thrown when building this product
     ObjectValidationException expectedException = null;
     try {
-      new Product.Builder().name(params.name).price(params.price).quantity(params.quantity).build();
+      new Product.Builder()
+          .name(params.name)
+          .price(new BigDecimal(params.price))
+          .quantity(params.quantity)
+          .build();
     } catch (ObjectValidationException ex) {
       expectedException = ex;
     }
@@ -231,20 +237,24 @@ void shouldGetAccountInfo() throws Exception {
 
     getAccountInfo()
         .andExpect(status().isOk())
-        .andExpect(jsonPath("$.balance").value(User.INITIAL_BALANCE))
+        .andExpect(
+            jsonPath("$.balance")
+                .value(
+                    "100.0")) // FIXME: not hardcoding it. Perhaps move INITIAL_BALANCE to sth that
+        // can be accessed by tests
         .andExpect(jsonPath("$.username").value(userCredentials.username));
   }
 
   private static class CreateProductParams {
     String name;
-    double price;
+    String price;
     int quantity;
 
     private static CreateProductParams sample() {
-      return new CreateProductParams("Product 1", 1.0, 50);
+      return new CreateProductParams("Product 1", "10", 50);
     }
 
-    private CreateProductParams(String name, double price, int quantity) {
+    private CreateProductParams(String name, String price, int quantity) {
       this.name = name;
       this.price = price;
       this.quantity = quantity;