Add sync-to-async exercise

.gitignore

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 # IntelliJ
 .idea/
 *.iml
+**/target/
+

sync_to_async/BIBLIO.adoc

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+* Docker best practices
+** https://github.com/docker/docker.github.io/blob/master/develop/develop-images/dockerfile_best-practices.md
+* Monitoring RabbitMQ with Prom
+** https://www.rabbitmq.com/prometheus.html
+** https://github.com/rabbitmq/rabbitmq-server/tree/master/deps/rabbitmq_prometheus/docker
+
+* Compose Networking with host network
+https://forums.docker.com/t/localhost-and-docker-compose-networking-issue/23100/5
+-> host.docker.internal
+

sync_to_async/docker-compose.yml

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+version: "3.9"
+volumes:
+    prometheus:
+    grafana:
+services:
+    rabbitmq:
+        # https://hub.docker.com/_/rabbitmq
+        image: rabbitmq:3.9.7-management-alpine
+        container_name: 'rabbitmq'
+        ports:
+            - 5672:5672
+            - 15672:15672 # Management
+            - 15692:15692 # Prometheus
+
+    # login : postgres/example
+    postgresql:
+        # https://hub.docker.com/_/postgres?tab=description
+        image: postgres:14.0-alpine
+        container_name: 'postgres'
+        ports:
+            - 5432:5432
+        environment:
+            POSTGRES_PASSWORD: example
+
+    adminer:
+        # https://hub.docker.com/_/adminer?tab=tags
+        image: adminer:4.8.1-standalone
+        container_name: 'adminer'
+        ports:
+            - 8080:8080
+        restart: always
+
+    prometheus:
+        # https://hub.docker.com/r/prom/prometheus/tags
+        image: prom/prometheus:v2.30.3
+        container_name: 'prometheus'
+        ports:
+            - 9090:9090
+        volumes:
+            - prometheus:/prometheus
+            - ./prometheus/prometheus.yml:/etc/prometheus/prometheus.yml
+
+    # login : guest/guest
+    grafana:
+        # https://hub.docker.com/r/grafana/grafana/tags
+        image: grafana/grafana:8.2.1
+        container_name: 'grafana'
+        ports:
+            - 3000:3000
+        volumes:
+            - grafana:/var/lib/grafana
+            - ./grafana/dashboards.yml:/etc/grafana/provisioning/dashboards/rabbitmq.yaml
+            - ./grafana/datasources.yml:/etc/grafana/provisioning/datasources/prometheus.yaml
+            - ./grafana/dashboards:/dashboards
+        environment:
+            # https://grafana.com/plugins/flant-statusmap-panel
+            # https://grafana.com/plugins/grafana-piechart-panel
+            GF_INSTALL_PLUGINS: "flant-statusmap-panel,grafana-piechart-panel"
+
+    front:
+        build : ./front
+        container_name: 'front'
+        ports:
+            - 8082:8082

sync_to_async/front/Dockerfile

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+FROM maven:3.8.3-openjdk-17 AS build
+COPY src /home/app/src
+COPY pom.xml /home/app
+RUN mvn -f /home/app/pom.xml clean package
+
+FROM eclipse-temurin:17-jdk-focal
+COPY --from=build /home/app/target/front-0.0.1-SNAPSHOT.jar /usr/local/lib/app.jar
+EXPOSE 8001
+ENTRYPOINT ["java","-jar","/usr/local/lib/app.jar"]

sync_to_async/front/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         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>
+
+    <groupId>com.github.lernejo</groupId>
+    <artifactId>front</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <properties>
+        <java.version>17</java.version>
+
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+        <maven.compiler.source>${java.version}</maven.compiler.source>
+        <maven.compiler.target>${java.version}</maven.compiler.target>
+
+        <spring-boot.version>2.5.5</spring-boot.version>
+    </properties>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-dependencies</artifactId>
+                <version>${spring-boot.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>io.micrometer</groupId>
+            <artifactId>micrometer-registry-prometheus</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <version>${spring-boot.version}</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>repackage</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

sync_to_async/front/src/main/java/com/github/lernejo/front/FrontApplication.java

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+package com.github.lernejo.front;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class FrontApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(FrontApplication.class, args);
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketController.java

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+package com.github.lernejo.front.basket;
+
+import com.github.lernejo.front.user.UserNotConnectedException;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/basket")
+record BasketController(BasketService basketService) {
+
+    @PostMapping("/add")
+    BasketInfo add(@RequestParam int productId, @RequestParam int quantity) throws ProductUnavailableException, UserNotConnectedException {
+        return basketService.add(productId, quantity);
+    }
+
+    @GetMapping
+    BasketInfo getBasketInfo() throws UserNotConnectedException {
+        return basketService.getBasketInfo();
+    }
+
+    @GetMapping("/content")
+    List<BasketProduct> getBasketContent() throws UserNotConnectedException {
+        return basketService.getBasketContent();
+    }
+
+    @PostMapping("/payment")
+    PaymentResult proceedToPayment(@RequestBody PaymentInformation info) throws RemoteServiceUnavailableException, UserNotConnectedException {
+        return basketService.proceedToPayment(info);
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketHandlerExceptionResolver.java

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+package com.github.lernejo.front.basket;
+
+import org.springframework.stereotype.Component;
+import org.springframework.web.servlet.HandlerExceptionResolver;
+import org.springframework.web.servlet.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@Component
+public class BasketHandlerExceptionResolver implements HandlerExceptionResolver {
+
+    @Override
+    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
+        return null;
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketInfo.java

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+package com.github.lernejo.front.basket;
+
+import java.util.List;
+
+record BasketInfo(int size, double price) {
+    public static BasketInfo from(List<BasketProduct> basket) {
+        return new BasketInfo(
+            basket.stream().mapToInt(p -> p.quantity()).sum(),
+            basket.stream().mapToDouble(p -> p.unitPrice() * p.quantity()).sum()
+        );
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketProduct.java

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+package com.github.lernejo.front.basket;
+
+record BasketProduct(String name, double unitPrice, int quantity) {
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketRepository.java

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+package com.github.lernejo.front.basket;
+
+import com.github.lernejo.front.user.SessionContext;
+import com.github.lernejo.front.user.UserNotConnectedException;
+import com.github.lernejo.front.user.UserSession;
+import org.springframework.stereotype.Repository;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Repository
+class BasketRepository {
+
+    private static final String BASKET_SESSION_KEY = "basket";
+
+    BasketInfo add(BasketProduct basketProduct) throws UserNotConnectedException {
+        List<BasketProduct> basket = getBasket();
+        basket.add(basketProduct);
+        return BasketInfo.from(basket);
+    }
+
+    public List<BasketProduct> getCurrent() throws UserNotConnectedException {
+        return getBasket();
+    }
+
+    private List<BasketProduct> getBasket() throws UserNotConnectedException {
+        UserSession userSession = SessionContext.getOrThrow();
+        List<BasketProduct> basket = userSession.get(BASKET_SESSION_KEY);
+        if (basket == null) {
+            basket = new ArrayList<>();
+            userSession.put(BASKET_SESSION_KEY, basket);
+        }
+        return basket;
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/BasketService.java

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+package com.github.lernejo.front.basket;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.github.lernejo.front.product.ProductService;
+import com.github.lernejo.front.product.StockRemovalStatus;
+import com.github.lernejo.front.user.UserNotConnectedException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+import java.time.YearMonth;
+import java.util.List;
+
+@Service
+final class BasketService {
+    private final Logger logger = LoggerFactory.getLogger(BasketService.class);
+    private final HttpClient httpClient = HttpClient.newHttpClient();
+
+    private final ProductService productService;
+    private final BasketRepository basketRepository;
+    private final String paymentServiceUrl;
+    private final ObjectMapper objectMapper;
+
+    BasketService(ProductService productService,
+                  BasketRepository basketRepository,
+                  @Value("${service.payment.url}") String paymentServiceUrl,
+                  ObjectMapper objectMapper) {
+        this.productService = productService;
+        this.basketRepository = basketRepository;
+        this.paymentServiceUrl = paymentServiceUrl;
+        this.objectMapper = objectMapper;
+    }
+
+    BasketInfo add(int productId, int quantity) throws ProductUnavailableException, UserNotConnectedException {
+        StockRemovalStatus stockRemovalStatus = productService.removeFromStock(productId, quantity);
+        if (stockRemovalStatus.status() == StockRemovalStatus.Status.REMOVED) {
+            return basketRepository.add(new BasketProduct(stockRemovalStatus.name(), stockRemovalStatus.price(), stockRemovalStatus.quantity()));
+        } else {
+            throw new ProductUnavailableException(stockRemovalStatus.name(), stockRemovalStatus.quantity());
+        }
+    }
+
+    BasketInfo getBasketInfo() throws UserNotConnectedException {
+        List<BasketProduct> current = getBasketContent();
+        return BasketInfo.from(current);
+    }
+
+    List<BasketProduct> getBasketContent() throws UserNotConnectedException {
+        return basketRepository.getCurrent();
+    }
+
+    public PaymentResult proceedToPayment(PaymentInformation info) throws RemoteServiceUnavailableException, UserNotConnectedException {
+        var payload = new PaymentServiceRequest(
+            info.firstname() + " " + info.lastname(),
+            info.cardNumber(),
+            info.expirationDate(),
+            info.cryptoCode(),
+            getBasketInfo().price()
+        );
+        HttpRequest paymentRequest = buildRequest(payload);
+        try {
+            HttpResponse<String> response = httpClient.send(paymentRequest, HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
+            return deserialize(response.body(), PaymentResult.class);
+        } catch (IOException | InterruptedException e) {
+            logger.error("Failed to proceed to payment, service unavailable", e);
+            throw new RemoteServiceUnavailableException();
+        }
+    }
+
+    private HttpRequest buildRequest(PaymentServiceRequest payload) {
+        return HttpRequest.newBuilder()
+            .uri(URI.create(paymentServiceUrl + "/api/payment"))
+            .setHeader("Accept", "application/json")
+            .setHeader("Content-Type", "application/json")
+            .POST(HttpRequest.BodyPublishers.ofString(serialize(payload)))
+            .build();
+    }
+
+    private String serialize(Object obj) {
+        try {
+            return objectMapper.writeValueAsString(obj);
+        } catch (JsonProcessingException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+
+    private <T> T deserialize(String json, Class<T> clazz) {
+        try {
+            return objectMapper.readValue(json, clazz);
+        } catch (JsonProcessingException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+
+    record PaymentServiceRequest(String creditCardOwner, String cardNumber, YearMonth expirationDate, String cryptoCode,
+                                 double amount) {
+    }
+}

sync_to_async/front/src/main/java/com/github/lernejo/front/basket/PaymentInformation.java

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+package com.github.lernejo.front.basket;
+
+import java.time.YearMonth;
+
+public record PaymentInformation(String lastname, String firstname, String cardNumber, YearMonth expirationDate,
+                                 String cryptoCode) {
+}