feat: Add Backends For Frontends (BFF) pattern (#300) (#3543)

* Add Backends For Frontends pattern (#300) Implements the BFF pattern with two client-specific gateways (MobileBff, DesktopBff) aggregating shared downstream services (AuthService, CartService, OrderService, SupplierService) into client-tailored response shapes. Closes #300 * Rename SupplierService lookup key to productName for clarity The service is looked up by product name throughout the codebase, not an actual product ID as the previous naming implied. * Address review feedback: remove unnecessary compact constructors, add InMemory* service tests
2026-09-03 08:18:55 +00:00 · 2026-08-16 21:56:51 +03:00
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commit 1673930bc0
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 ---
 title: "Backends For Frontends Pattern in Java: Tailoring APIs to Client Needs"
 shortTitle: Backends For Frontends
 description: "Learn the Backends For Frontends (BFF) design pattern in Java. Understand how to give each client type its own dedicated backend service, with real-world examples, code, and diagrams."
 category: Architectural
 language: en
 tag:
  - API design
  - Architecture
  - Client-server
  - Decoupling
  - Microservices
 ---
 ## Also known as
 * Backend For Frontend
 * BFF Pattern
 ## Intent of Backends For Frontends Pattern
 Provide each client-side application (mobile, desktop, chatbot, and so on) with its own dedicated
 backend service, so every client gets an API shaped exactly for its own needs instead of sharing
 one general-purpose backend with every other client.
 ## Detailed Explanation of Backends For Frontends Pattern with Real-World Examples
 Real-world example
 > Imagine a retail company whose mobile app, desktop back-office tool, and support chatbot all
 > need customer, cart, order and supplier data -- but a phone screen wants a short summary while
 > the back-office desktop tool wants full order and stock detail. Rather than exposing one shared
 > API that every client has to filter or over-fetch from, the company stands up a small BFF service
 > for the mobile clients and a separate BFF service for the intranet clients. Each BFF calls only
 > the downstream microservices its client needs and returns a payload shaped for that client.
 In plain words
 > Give every kind of client its own tailor-made backend, instead of forcing all clients through one
 > one-size-fits-all API.
 Sam Newman, who popularized the pattern, says
 > Create separate backend services to be consumed by specific frontend applications or interfaces.
 ## Architecture Diagram
 ```
 node mobile{
 component iosapp as "ios app"
 component androidapp as "android app"
 }
 node intranet{
 component desktop as "desktop app"
 component chatbot
 }
 component bff as "BFF server"{
 component iosbff as "ios BFF"
 component androidbff as "android BFF"
 component chatbotbff as "chatbot BFF"
 component desktopbff as "desktop BFF"
 }
 node intranetserv as "intranet services server"{
 component ss as "supplier service API"
 }
 cloud onlypublic as "public cloud"{
 component cas as "customer authentication service API"
 component cs as "cart service API"
 }
 cloud cloudserv as "managed cloud"{
 component os as "order service API"
 }
 iosapp -- iosbff
 androidapp -- androidbff
 chatbot -- chatbotbff
 desktop -- desktopbff
 iosbff -- cas
 androidbff -- cas
 iosbff -- cs
 androidbff -- cs
 iosbff -- os
 androidbff -- os
 chatbotbff -- os
 desktopbff -- os
 chatbotbff -- ss
 desktopbff -- ss
 ```
 This example implements a simplified version of the diagram above with two client-facing BFFs
 instead of four, to keep the demo focused: a **Mobile BFF** standing in for the ios/android BFFs,
 and a **Desktop BFF** standing in for the desktop/chatbot BFFs. Both call into the same shared
 downstream services (`AuthService`, `OrderService`), while `CartService` is only used by the
 Mobile BFF and `SupplierService` is only reachable from the Desktop BFF, matching the fan-out
 shown in the diagram.
 ## Class Diagram
 ![Backends For Frontends class diagram](./etc/backends-for-frontends.png)
 ## When to Use the Backends For Frontends Pattern in Java
 * Different client types (mobile, web, desktop, voice/chat) need meaningfully different shapes,
  granularity, or aggregation of the same underlying data.
 * A single shared API has grown a large number of client-specific conditional branches, optional
  fields, or query parameters to accommodate every consumer.
 * Different client teams need to iterate on their own API independently without coordinating
  changes through one shared backend team.
 * Some clients (e.g. mobile) need aggressively trimmed payloads for bandwidth/latency reasons,
  while others (e.g. an internal desktop tool) need much richer data.
 ## Benefits and Trade-offs of Backends For Frontends Pattern
 Benefits:
 * Each client gets an API optimized for its own needs, improving performance and simplicity on
  the client side.
 * Client teams can evolve their BFF independently, reducing cross-team coordination.
 * Downstream microservices stay generic and reusable; client-specific logic lives in the BFF
  layer instead of leaking into shared services.
 Trade-offs:
 * Introduces additional services to build, deploy, and operate.
 * Logic that is genuinely shared across clients can end up duplicated across BFFs if not
  carefully factored out.
 * Adds an extra network hop between the client and the downstream services.
 ## How to Implement Backends For Frontends Pattern in Java
 1. Identify the distinct client types that need meaningfully different data shapes.
 2. Define the downstream services each client's data actually depends on (`AuthService`,
   `CartService`, `OrderService`, `SupplierService` in this example).
 3. Create one BFF per client type, implementing a shared `ClientBff<T>` contract, where each BFF
   only depends on the downstream services its client needs.
 4. Have each BFF aggregate and reshape the downstream data into a response DTO tailored to its
   client (`MobileDashboardResponse`, `DesktopDashboardResponse`).
 5. Wire the client applications to call their own BFF rather than the downstream services
   directly.
 ## Source Code
 * [Pattern: Backends For Frontends](https://samnewman.io/patterns/architectural/bff/) by Sam Newman
 * [Microservices Patterns: With examples in Java](https://www.amazon.com/Microservices-Patterns-examples-Chris-Richardson/dp/1617294543) by Chris Richardson
 ## References and Credits
 * [Building Microservices](https://www.oreilly.com/library/view/building-microservices-2nd/9781492034018/) by Sam Newman
 * [Pattern: Backend for frontend (microservices.io)](https://microservices.io/patterns/apigateway.html)
@@ -0,0 +1,130 @@
@startuml
 package com.iluwatar.bff {
  class App {
    - LOGGER : Logger {static}
    - USER_ID : String {static}
    - PRODUCT_ID : String {static}
    - DEMO_PRICE_USD : double {static}
    - DEMO_STOCK_LEVEL : int {static}
    + App()
    + main(args : String[]) {static}
  }
 }
 package com.iluwatar.bff.bff {
  interface ClientBff<T> {
    + getDashboard(userId : String) : T {abstract}
  }
  class DesktopBff {
    - authService : AuthService
    - orderService : OrderService
    - supplierService : SupplierService
    + DesktopBff(auth : AuthService, orders : OrderService, suppliers : SupplierService)
    + getDashboard(userId : String) : DesktopDashboardResponse
  }
  class MobileBff {
    - MAX_RECENT_ORDERS : int {static}
    - authService : AuthService
    - cartService : CartService
    - orderService : OrderService
    + MobileBff(auth : AuthService, cart : CartService, orders : OrderService)
    + getDashboard(userId : String) : MobileDashboardResponse
  }
 }
 package com.iluwatar.bff.dto {
  class DesktopDashboardResponse {
    - greeting : String
    - loyaltyTier : String
    - orderStatuses : List<String>
    - supplierStockSummaries : List<String>
    + DesktopDashboardResponse(greeting : String, loyaltyTier : String, orderStatuses : List<String>, supplierStockSummaries : List<String>)
  }
  class MobileDashboardResponse {
    - greeting : String
    - cartItemCount : int
    - cartTotalUsd : double
    - recentOrderSummaries : List<String>
    + MobileDashboardResponse(greeting : String, cartItemCount : int, cartTotalUsd : double, recentOrderSummaries : List<String>)
  }
 }
 package com.iluwatar.bff.model {
  class CartItem {
    - product : Product
    - quantity : int
    + CartItem(product : Product, quantity : int)
    + lineTotal() : double
  }
  class Order {
    - id : String
    - productName : String
    - status : String
    + Order(id : String, productName : String, status : String)
  }
  class Product {
    - id : String
    - name : String
    - priceUsd : double
    + Product(id : String, name : String, priceUsd : double)
  }
  class SupplierRecord {
    - productId : String
    - supplierName : String
    - stockLevel : int
    + SupplierRecord(productId : String, supplierName : String, stockLevel : int)
  }
  class User {
    - id : String
    - displayName : String
    - loyaltyTier : String
    + User(id : String, displayName : String, loyaltyTier : String)
  }
 }
 package com.iluwatar.bff.service {
  interface AuthService {
    + getUser(userId : String) : User {abstract}
  }
  interface CartService {
    + getCart(userId : String) : List<CartItem> {abstract}
  }
  interface OrderService {
    + getOrders(userId : String) : List<Order> {abstract}
  }
  interface SupplierService {
    + getSupplierRecords(productId : String) : List<SupplierRecord> {abstract}
  }
 }
 package com.iluwatar.bff.service.impl {
  class InMemoryAuthService {
    - users : Map<String, User>
    + InMemoryAuthService(userData : Map<String, User>)
    + getUser(userId : String) : User
  }
  class InMemoryCartService {
    - cartsByUserId : Map<String, List<CartItem>>
    + InMemoryCartService(carts : Map<String, List<CartItem>>)
    + getCart(userId : String) : List<CartItem>
  }
  class InMemoryOrderService {
    - ordersByUserId : Map<String, List<Order>>
    + InMemoryOrderService(orders : Map<String, List<Order>>)
    + getOrders(userId : String) : List<Order>
  }
  class InMemorySupplierService {
    - recordsByProductId : Map<String, List<SupplierRecord>>
    + InMemorySupplierService(records : Map<String, List<SupplierRecord>>)
    + getSupplierRecords(productId : String) : List<SupplierRecord>
  }
 }
 DesktopBff ..|> ClientBff
 MobileBff ..|> ClientBff
 DesktopBff --> "-authService" AuthService
 DesktopBff --> "-orderService" OrderService
 DesktopBff --> "-supplierService" SupplierService
 MobileBff --> "-authService" AuthService
 MobileBff --> "-cartService" CartService
 MobileBff --> "-orderService" OrderService
 InMemoryAuthService ..|> AuthService
 InMemoryCartService ..|> CartService
 InMemoryOrderService ..|> OrderService
 InMemorySupplierService ..|> SupplierService
 CartItem --> "-product" Product
@enduml
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 <?xml version="1.0" encoding="UTF-8"?>
 <!--
    This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
    The MIT License
    Copyright © 2014-2022 Ilkka Seppälä
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    THE SOFTWARE.
 -->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>com.iluwatar</groupId>
    <artifactId>java-design-patterns</artifactId>
    <version>1.26.0-SNAPSHOT</version>
  </parent>
  <artifactId>backends-for-frontends</artifactId>
  <dependencies>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-engine</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
          <archive>
            <manifest>
              <mainClass>com.iluwatar.bff.App</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>
    </plugins>
  </build>
 </project>
@@ -0,0 +1,109 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff;
 import com.iluwatar.bff.bff.DesktopBff;
 import com.iluwatar.bff.bff.MobileBff;
 import com.iluwatar.bff.model.CartItem;
 import com.iluwatar.bff.model.Order;
 import com.iluwatar.bff.model.Product;
 import com.iluwatar.bff.model.SupplierRecord;
 import com.iluwatar.bff.model.User;
 import com.iluwatar.bff.service.impl.InMemoryAuthService;
 import com.iluwatar.bff.service.impl.InMemoryCartService;
 import com.iluwatar.bff.service.impl.InMemoryOrderService;
 import com.iluwatar.bff.service.impl.InMemorySupplierService;
 import java.util.List;
 import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 /**
 * {@link App} demonstrates the Backends For Frontends (BFF) pattern.
 *
 * <p>A single set of downstream microservices (customer authentication, cart, order and supplier
 * services) is shared by every client. Two different client-facing gateways -- {@link MobileBff}
 * for the mobile apps and {@link DesktopBff} for the intranet desktop/chatbot clients -- each call
 * a different subset of those services and reshape the results into a response tailored to what
 * their own client actually needs, rather than exposing one one-size-fits-all API to every client.
 */
 public final class App {
  /** Logger for this class. */
  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
  /** User id used in the demonstration. */
  private static final String USER_ID = "u-1";
  /** Product id used in the demonstration. */
  private static final String PRODUCT_ID = "p-42";
  /** Unit price of the demo product in US dollars. */
  private static final double DEMO_PRICE_USD = 79.99;
  /** Supplier stock level used in the demonstration. */
  private static final int DEMO_STOCK_LEVEL = 120;
  private App() {
    // utility class
  }
  /**
   * Program entry point.
   *
   * @param args no argument sent
   */
  public static void main(final String[] args) {
    // shared downstream microservices, as drawn in the pattern diagram
    var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
    var product = new Product(PRODUCT_ID, "Wireless Headphones", DEMO_PRICE_USD);
    var cartService = new InMemoryCartService(Map.of(USER_ID, List.of(new CartItem(product, 2))));
    var orderService =
        new InMemoryOrderService(
            Map.of(
                USER_ID,
                List.of(
                    new Order("o-1", "Wireless Headphones", "DELIVERED"),
                    new Order("o-2", "USB-C Cable", "IN_TRANSIT"))));
    var supplierService =
        new InMemorySupplierService(
            Map.of(
                "Wireless Headphones",
                List.of(new SupplierRecord(PRODUCT_ID, "Acme Audio Co.", DEMO_STOCK_LEVEL))));
    // client-specific BFFs, each calling only the services their client needs
    var mobileBff = new MobileBff(authService, cartService, orderService);
    var desktopBff = new DesktopBff(authService, orderService, supplierService);
    var mobileResponse = mobileBff.getDashboard(USER_ID);
    LOGGER.info("Mobile BFF response: {}", mobileResponse);
    var desktopResponse = desktopBff.getDashboard(USER_ID);
    LOGGER.info("Desktop BFF response: {}", desktopResponse);
  }
 }
@@ -0,0 +1,44 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.bff;
 /**
 * Common contract every client-specific Backend For Frontend implements: given a user id, build
 * whatever response shape ({@code T}) that particular client needs. Each implementation is free to
 * call a different subset of downstream services and aggregate them differently -- that freedom is
 * the entire point of the pattern.
 *
 * @param <T> the response DTO shape this BFF returns to its client
 */
 public interface ClientBff<T> {
  /**
   * Builds the dashboard response for a given user, tailored to this BFF's client.
   *
   * @param userId identifier of the user requesting their dashboard
   * @return the client-specific response
   */
  T getDashboard(String userId);
 }
@@ -0,0 +1,94 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.bff;
 import com.iluwatar.bff.dto.DesktopDashboardResponse;
 import com.iluwatar.bff.service.AuthService;
 import com.iluwatar.bff.service.OrderService;
 import com.iluwatar.bff.service.SupplierService;
 import java.util.ArrayList;
 import java.util.List;
 /**
 * Backend For Frontend serving the intranet clients (desktop app, chatbot) from the diagram. It
 * aggregates the auth, order and supplier services and reshapes the results into a richer,
 * back-office style payload. Unlike {@link MobileBff}, it does not touch the cart service at all
 * and it does reach into the intranet-only supplier service, matching the fan-out drawn in the
 * pattern diagram.
 */
 public final class DesktopBff implements ClientBff<DesktopDashboardResponse> {
  /** The customer authentication service. */
  private final AuthService authService;
  /** The order service. */
  private final OrderService orderService;
  /** The supplier service (intranet-only). */
  private final SupplierService supplierService;
  /**
   * Creates a desktop BFF wired to the downstream services it depends on.
   *
   * @param auth the customer authentication service
   * @param orders the order service
   * @param suppliers the supplier service
   */
  public DesktopBff(
      final AuthService auth, final OrderService orders, final SupplierService suppliers) {
    this.authService = auth;
    this.orderService = orders;
    this.supplierService = suppliers;
  }
  @Override
  public DesktopDashboardResponse getDashboard(final String userId) {
    var user = authService.getUser(userId);
    var orders = orderService.getOrders(userId);
    var orderStatuses =
        orders.stream()
            .map(order -> order.id() + ": " + order.productName() + " [" + order.status() + "]")
            .toList();
    var supplierStockSummaries = new ArrayList<String>();
    for (var order : orders) {
      for (var supplierRecord : supplierService.getSupplierRecords(order.productName())) {
        supplierStockSummaries.add(
            supplierRecord.supplierName()
                + ": "
                + supplierRecord.stockLevel()
                + " units of "
                + order.productName());
      }
    }
    return new DesktopDashboardResponse(
        "Welcome back, " + user.displayName(),
        user.loyaltyTier(),
        List.copyOf(orderStatuses),
        List.copyOf(supplierStockSummaries));
  }
 }
@@ -0,0 +1,86 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.bff;
 import com.iluwatar.bff.dto.MobileDashboardResponse;
 import com.iluwatar.bff.service.AuthService;
 import com.iluwatar.bff.service.CartService;
 import com.iluwatar.bff.service.OrderService;
 import java.util.List;
 /**
 * Backend For Frontend serving the mobile clients (iOS app, Android app) from the diagram. It
 * aggregates the auth, cart and order services and reshapes the results into a small payload suited
 * to a phone screen and a limited-bandwidth connection. It never calls the supplier service: a
 * mobile shopper has no use for back-office stock data, so this BFF simply does not expose it,
 * rather than sending it and letting the client ignore it.
 */
 public final class MobileBff implements ClientBff<MobileDashboardResponse> {
  /** Maximum number of recent order summaries to include in the mobile response. */
  private static final int MAX_RECENT_ORDERS = 3;
  /** The customer authentication service. */
  private final AuthService authService;
  /** The cart service. */
  private final CartService cartService;
  /** The order service. */
  private final OrderService orderService;
  /**
   * Creates a mobile BFF wired to the downstream services it depends on.
   *
   * @param auth the customer authentication service
   * @param cart the cart service
   * @param orders the order service
   */
  public MobileBff(final AuthService auth, final CartService cart, final OrderService orders) {
    this.authService = auth;
    this.cartService = cart;
    this.orderService = orders;
  }
  @Override
  public MobileDashboardResponse getDashboard(final String userId) {
    var user = authService.getUser(userId);
    var cart = cartService.getCart(userId);
    var orders = orderService.getOrders(userId);
    var cartTotal = cart.stream().mapToDouble(item -> item.lineTotal()).sum();
    var recentOrderSummaries =
        orders.stream()
            .limit(MAX_RECENT_ORDERS)
            .map(order -> order.productName() + " (" + order.status() + ")")
            .toList();
    return new MobileDashboardResponse(
        "Hi " + user.displayName() + "!",
        cart.size(),
        cartTotal,
        List.copyOf(recentOrderSummaries));
  }
 }
@@ -0,0 +1,29 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * Client-specific Backend For Frontend implementations: one per client type (mobile, desktop) that
 * each aggregate a different subset of downstream services.
 */
 package com.iluwatar.bff.bff;
@@ -0,0 +1,42 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.dto;
 import java.util.List;
 /**
 * The shape of data the desktop back-office client renders: richer than the mobile payload,
 * including full order status and supplier stock levels that a mobile shopper never needs.
 *
 * @param greeting a short personalized greeting for the user
 * @param loyaltyTier the user's loyalty program tier
 * @param orderStatuses detailed "id: productName [status]" lines for every order
 * @param supplierStockSummaries "supplierName: stockLevel units" lines for relevant products
 */
 public record DesktopDashboardResponse(
    String greeting,
    String loyaltyTier,
    List<String> orderStatuses,
    List<String> supplierStockSummaries) {}
@@ -0,0 +1,39 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.dto;
 import java.util.List;
 /**
 * The shape of data the mobile (iOS/Android) client actually renders: a lean payload with just
 * enough for a small screen, deliberately excluding fields the desktop client needs.
 *
 * @param greeting a short personalized greeting for the user
 * @param cartItemCount number of items currently in the user's cart
 * @param cartTotalUsd total value of the user's cart in US dollars
 * @param recentOrderSummaries short human-readable summaries of the user's most recent orders
 */
 public record MobileDashboardResponse(
    String greeting, int cartItemCount, double cartTotalUsd, List<String> recentOrderSummaries) {}
@@ -0,0 +1,28 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * Response DTOs shaped by each BFF for its specific client (mobile dashboard, desktop dashboard).
 */
 package com.iluwatar.bff.dto;
@@ -0,0 +1,43 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.model;
 /**
 * A single line item inside a user's shopping cart, as returned by the cart service API.
 *
 * @param product the product being purchased
 * @param quantity number of units of the product
 */
 public record CartItem(Product product, int quantity) {
  /**
   * Computes the line total for this cart item.
   *
   * @return quantity multiplied by unit price
   */
  public double lineTotal() {
    return quantity * product.priceUsd();
  }
 }
@@ -0,0 +1,34 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.model;
 /**
 * A past order returned by the order service API.
 *
 * @param id order identifier
 * @param productName name of the ordered product
 * @param status current fulfillment status, e.g. "DELIVERED", "IN_TRANSIT"
 */
 public record Order(String id, String productName, String status) {}
@@ -0,0 +1,35 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.model;
 /**
 * Simple product record returned by the downstream Cart/Order services. Represents the data a
 * catalog or cart entry carries before each BFF trims or reshapes it for its own client.
 *
 * @param id product identifier
 * @param name display name of the product
 * @param priceUsd unit price in US dollars
 */
 public record Product(String id, String name, double priceUsd) {}
@@ -0,0 +1,35 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.model;
 /**
 * A supplier stock record returned by the supplier service API, used by the desktop back-office
 * client to show inventory information that mobile customers never need to see.
 *
 * @param productId identifier of the product this record refers to
 * @param supplierName name of the supplying vendor
 * @param stockLevel units currently available from this supplier
 */
 public record SupplierRecord(String productId, String supplierName, int stockLevel) {}
@@ -0,0 +1,35 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.model;
 /**
 * Authenticated user profile returned by the customer authentication service API. Kept
 * intentionally minimal; each BFF decides which of these fields its client actually needs.
 *
 * @param id unique user identifier
 * @param displayName human-readable name of the user
 * @param loyaltyTier loyalty program tier, e.g. "GOLD", "SILVER", "STANDARD"
 */
 public record User(String id, String displayName, String loyaltyTier) {}
@@ -0,0 +1,30 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * Domain model records shared across downstream services: User, Product, CartItem, Order, and
 * SupplierRecord. Each BFF consumes these raw domain objects and reshapes them into its own
 * client-specific DTO.
 */
 package com.iluwatar.bff.model;
@@ -0,0 +1,29 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * Backends For Frontends pattern: a dedicated gateway per client type (mobile, desktop) that
 * aggregates only the downstream services each client actually needs.
 */
 package com.iluwatar.bff;
@@ -0,0 +1,43 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service;
 import com.iluwatar.bff.model.User;
 /**
 * Represents the customer authentication service API from the diagram: a downstream microservice
 * shared by every client-specific BFF. Each BFF calls this the same way; only what they do with the
 * result differs.
 */
 public interface AuthService {
  /**
   * Looks up the authenticated user profile for the given id.
   *
   * @param userId identifier of the user to look up
   * @return the matching {@link User}
   */
  User getUser(String userId);
 }
@@ -0,0 +1,43 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service;
 import com.iluwatar.bff.model.CartItem;
 import java.util.List;
 /**
 * Represents the cart service API from the diagram. In this example only the mobile and android
 * clients need cart data, so only {@link com.iluwatar.bff.bff.MobileBff} calls this service.
 */
 public interface CartService {
  /**
   * Retrieves the current cart contents for a user.
   *
   * @param userId identifier of the user whose cart is requested
   * @return the list of items currently in the user's cart
   */
  List<CartItem> getCart(String userId);
 }
@@ -0,0 +1,43 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service;
 import com.iluwatar.bff.model.Order;
 import java.util.List;
 /**
 * Represents the order service API from the diagram. This downstream service is shared by every
 * client-specific BFF, matching the fan-out shown for "order service API" in the pattern diagram.
 */
 public interface OrderService {
  /**
   * Retrieves the order history for a user.
   *
   * @param userId identifier of the user whose orders are requested
   * @return the list of past orders for the user
   */
  List<Order> getOrders(String userId);
 }
@@ -0,0 +1,43 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service;
 import com.iluwatar.bff.model.SupplierRecord;
 import java.util.List;
 /**
 * Represents the supplier service API from the diagram, reachable only from the intranet services
 * server. Only back-office style clients (desktop app, chatbot) call this service.
 */
 public interface SupplierService {
  /**
   * Retrieves supplier stock records for a product.
   *
   * @param productName name of the product to check stock for
   * @return the list of supplier stock records for the product
   */
  List<SupplierRecord> getSupplierRecords(String productName);
 }
@@ -0,0 +1,58 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import com.iluwatar.bff.model.User;
 import com.iluwatar.bff.service.AuthService;
 import java.util.Map;
 /**
 * In-memory stand-in for the real customer authentication service API. Real deployments would
 * replace this with an HTTP/gRPC client; the BFFs are written against the {@link AuthService}
 * interface, so swapping the implementation later requires no change to any BFF.
 */
 public final class InMemoryAuthService implements AuthService {
  /** Users stored in memory, keyed by user id. */
  private final Map<String, User> users;
  /**
   * Creates the service with a fixed backing map of users, keyed by user id.
   *
   * @param userData the user data this service serves
   */
  public InMemoryAuthService(final Map<String, User> userData) {
    this.users = userData;
  }
  @Override
  public User getUser(final String userId) {
    var user = users.get(userId);
    if (user == null) {
      throw new IllegalArgumentException("Unknown user id: " + userId);
    }
    return user;
  }
 }
@@ -0,0 +1,51 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import com.iluwatar.bff.model.CartItem;
 import com.iluwatar.bff.service.CartService;
 import java.util.List;
 import java.util.Map;
 /** In-memory stand-in for the real cart service API. */
 public final class InMemoryCartService implements CartService {
  /** Carts stored in memory, keyed by user id. */
  private final Map<String, List<CartItem>> cartsByUserId;
  /**
   * Creates the service with a fixed backing map of carts, keyed by user id.
   *
   * @param carts the cart data this service serves
   */
  public InMemoryCartService(final Map<String, List<CartItem>> carts) {
    this.cartsByUserId = carts;
  }
  @Override
  public List<CartItem> getCart(final String userId) {
    return cartsByUserId.getOrDefault(userId, List.of());
  }
 }
@@ -0,0 +1,51 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import com.iluwatar.bff.model.Order;
 import com.iluwatar.bff.service.OrderService;
 import java.util.List;
 import java.util.Map;
 /** In-memory stand-in for the real order service API. */
 public final class InMemoryOrderService implements OrderService {
  /** Order histories stored in memory, keyed by user id. */
  private final Map<String, List<Order>> ordersByUserId;
  /**
   * Creates the service with a fixed backing map of order histories, keyed by user id.
   *
   * @param orders the order data this service serves
   */
  public InMemoryOrderService(final Map<String, List<Order>> orders) {
    this.ordersByUserId = orders;
  }
  @Override
  public List<Order> getOrders(final String userId) {
    return ordersByUserId.getOrDefault(userId, List.of());
  }
 }
@@ -0,0 +1,51 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import com.iluwatar.bff.model.SupplierRecord;
 import com.iluwatar.bff.service.SupplierService;
 import java.util.List;
 import java.util.Map;
 /** In-memory stand-in for the real supplier service API, reachable only from the intranet. */
 public final class InMemorySupplierService implements SupplierService {
  /** Supplier records stored in memory, keyed by product name. */
  private final Map<String, List<SupplierRecord>> recordsByProductName;
  /**
   * Creates the service with a fixed backing map of supplier records, keyed by product name.
   *
   * @param records the supplier data this service serves
   */
  public InMemorySupplierService(final Map<String, List<SupplierRecord>> records) {
    this.recordsByProductName = records;
  }
  @Override
  public List<SupplierRecord> getSupplierRecords(final String productName) {
    return recordsByProductName.getOrDefault(productName, List.of());
  }
 }
@@ -0,0 +1,29 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * In-memory implementations of the downstream service API interfaces, used for the pattern
 * demonstration. Production deployments would replace these with real HTTP/gRPC clients.
 */
 package com.iluwatar.bff.service.impl;
@@ -0,0 +1,29 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 /**
 * Downstream service API interfaces shared by all BFFs: AuthService, CartService, OrderService, and
 * SupplierService. Each BFF wires in only the services its client requires.
 */
 package com.iluwatar.bff.service;
@@ -0,0 +1,41 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff;
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import org.junit.jupiter.api.Test;
 /**
 * Tests that {@link App}'s demo entry point runs end-to-end without throwing, following the
 * convention used throughout this repository for pattern demo apps.
 */
 class AppTest {
  @Test
  void mainShouldRunWithoutException() {
    assertDoesNotThrow(() -> App.main(new String[] {}));
  }
 }
@@ -0,0 +1,77 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.bff;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import com.iluwatar.bff.model.Order;
 import com.iluwatar.bff.model.SupplierRecord;
 import com.iluwatar.bff.model.User;
 import com.iluwatar.bff.service.impl.InMemoryAuthService;
 import com.iluwatar.bff.service.impl.InMemoryOrderService;
 import com.iluwatar.bff.service.impl.InMemorySupplierService;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link DesktopBff}. */
 class DesktopBffTest {
  private static final String USER_ID = "u-1";
  @Test
  void shouldAggregateOrdersAndSupplierStockIntoDesktopShape() {
    var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
    var orderService =
        new InMemoryOrderService(
            Map.of(USER_ID, List.of(new Order("o-1", "Headphones", "DELIVERED"))));
    var supplierService =
        new InMemorySupplierService(
            Map.of("Headphones", List.of(new SupplierRecord("p-1", "Acme Audio", 30))));
    var bff = new DesktopBff(authService, orderService, supplierService);
    var response = bff.getDashboard(USER_ID);
    assertEquals("Welcome back, Alice", response.greeting());
    assertEquals("GOLD", response.loyaltyTier());
    assertTrue(response.orderStatuses().get(0).contains("Headphones"));
    assertTrue(response.supplierStockSummaries().get(0).contains("Acme Audio"));
  }
  @Test
  void shouldReturnNoSupplierSummariesWhenNoOrdersExist() {
    var authService =
        new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Carol", "STANDARD")));
    var orderService = new InMemoryOrderService(Map.of(USER_ID, List.of()));
    var supplierService = new InMemorySupplierService(Map.of());
    var bff = new DesktopBff(authService, orderService, supplierService);
    var response = bff.getDashboard(USER_ID);
    assertEquals(0, response.orderStatuses().size());
    assertEquals(0, response.supplierStockSummaries().size());
  }
 }
@@ -0,0 +1,83 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.bff;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import com.iluwatar.bff.model.CartItem;
 import com.iluwatar.bff.model.Order;
 import com.iluwatar.bff.model.Product;
 import com.iluwatar.bff.model.User;
 import com.iluwatar.bff.service.impl.InMemoryAuthService;
 import com.iluwatar.bff.service.impl.InMemoryCartService;
 import com.iluwatar.bff.service.impl.InMemoryOrderService;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link MobileBff}. */
 class MobileBffTest {
  private static final String USER_ID = "u-1";
  @Test
  void shouldAggregateCartAndOrdersIntoMobileShape() {
    var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
    var product = new Product("p-1", "Headphones", 50.0);
    var cartService = new InMemoryCartService(Map.of(USER_ID, List.of(new CartItem(product, 2))));
    var orderService =
        new InMemoryOrderService(
            Map.of(USER_ID, List.of(new Order("o-1", "Headphones", "DELIVERED"))));
    var bff = new MobileBff(authService, cartService, orderService);
    var response = bff.getDashboard(USER_ID);
    assertEquals("Hi Alice!", response.greeting());
    assertEquals(1, response.cartItemCount());
    assertEquals(100.0, response.cartTotalUsd());
    assertTrue(response.recentOrderSummaries().get(0).contains("Headphones"));
  }
  @Test
  void shouldCapRecentOrderSummariesAtThree() {
    var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Bob", "SILVER")));
    var cartService = new InMemoryCartService(Map.of(USER_ID, List.of()));
    var orderService =
        new InMemoryOrderService(
            Map.of(
                USER_ID,
                List.of(
                    new Order("o-1", "A", "DELIVERED"),
                    new Order("o-2", "B", "DELIVERED"),
                    new Order("o-3", "C", "DELIVERED"),
                    new Order("o-4", "D", "DELIVERED"))));
    var bff = new MobileBff(authService, cartService, orderService);
    var response = bff.getDashboard(USER_ID);
    assertEquals(3, response.recentOrderSummaries().size());
  }
 }
@@ -0,0 +1,54 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import com.iluwatar.bff.model.User;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link InMemoryAuthService}. */
 class InMemoryAuthServiceTest {
  private static final String USER_ID = "u-1";
  @Test
  void shouldReturnUserForKnownId() {
    var expected = new User(USER_ID, "Alice", "GOLD");
    var service = new InMemoryAuthService(Map.of(USER_ID, expected));
    var actual = service.getUser(USER_ID);
    assertEquals(expected, actual);
  }
  @Test
  void shouldThrowForUnknownId() {
    var service = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
    assertThrows(IllegalArgumentException.class, () -> service.getUser("unknown-id"));
  }
 }
@@ -0,0 +1,60 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import com.iluwatar.bff.model.CartItem;
 import com.iluwatar.bff.model.Product;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link InMemoryCartService}. */
 class InMemoryCartServiceTest {
  private static final String USER_ID = "u-1";
  @Test
  void shouldReturnCartItemsForKnownUser() {
    var product = new Product("p-1", "Headphones", 49.99);
    var item = new CartItem(product, 2);
    var service = new InMemoryCartService(Map.of(USER_ID, List.of(item)));
    var cart = service.getCart(USER_ID);
    assertEquals(1, cart.size());
    assertEquals(item, cart.get(0));
  }
  @Test
  void shouldReturnEmptyListForUnknownUser() {
    var service = new InMemoryCartService(Map.of());
    var cart = service.getCart("unknown-user");
    assertTrue(cart.isEmpty());
  }
 }
@@ -0,0 +1,58 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import com.iluwatar.bff.model.Order;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link InMemoryOrderService}. */
 class InMemoryOrderServiceTest {
  private static final String USER_ID = "u-1";
  @Test
  void shouldReturnOrdersForKnownUser() {
    var order = new Order("o-1", "Headphones", "DELIVERED");
    var service = new InMemoryOrderService(Map.of(USER_ID, List.of(order)));
    var orders = service.getOrders(USER_ID);
    assertEquals(1, orders.size());
    assertEquals(order, orders.get(0));
  }
  @Test
  void shouldReturnEmptyListForUnknownUser() {
    var service = new InMemoryOrderService(Map.of());
    var orders = service.getOrders("unknown-user");
    assertTrue(orders.isEmpty());
  }
 }
@@ -0,0 +1,58 @@
 /*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.bff.service.impl;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import com.iluwatar.bff.model.SupplierRecord;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 /** Tests for {@link InMemorySupplierService}. */
 class InMemorySupplierServiceTest {
  private static final String PRODUCT_NAME = "Headphones";
  @Test
  void shouldReturnSupplierRecordsForKnownProductName() {
    var record = new SupplierRecord("p-1", "Acme Audio", 30);
    var service = new InMemorySupplierService(Map.of(PRODUCT_NAME, List.of(record)));
    var records = service.getSupplierRecords(PRODUCT_NAME);
    assertEquals(1, records.size());
    assertEquals(record, records.get(0));
  }
  @Test
  void shouldReturnEmptyListForUnknownProductName() {
    var service = new InMemorySupplierService(Map.of());
    var records = service.getSupplierRecords("unknown-product");
    assertTrue(records.isEmpty());
  }
 }
@@ -80,6 +80,7 @@
    <module>anti-corruption-layer</module>
    <module>arrange-act-assert</module>
    <module>async-method-invocation</module>
    <module>backends-for-frontends</module>
    <module>balking</module>
    <module>bloc</module>
    <module>bridge</module>