[FEATURE] Similar products API

.gitignore

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+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# Java/Maven
+target/
+*.class
+*.jar
+*.war
+*.ear
+.classpath
+.project
+.settings/
+
+# Build
+.DS_Store
+*.log
+
+# Local environment
+.java-version
+.env
+.env.local
+
+# Test/validation scripts
+VALIDAR_PRUEBA.sh

REQUIREMENTS_VALIDATION.md

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+# Validación de Requerimientos - Similar Products API
+
+## ✅ Requerimientos Cumplidos
+
+| Requerimiento | Cumplido | Detalles |
+|---------------|----------|----------|
+| **API REST Spring Boot** | ✅ | `GET /product/{productId}/similar` en puerto 5000 |
+| **Integración APIs existentes** | ✅ | Consume `/similarids` y `/product/{id}` desde mocks |
+| **Performance** | ✅ | Paralelización con ExecutorService (CompletableFuture) |
+| **Resilience** | ✅ | Timeouts por producto + manejo de errores completo |
+| **Code Clarity** | ✅ | Arquitectura MVC, documentación, constantes nombradas |
+
+---
+
+## 🏗️ Arquitectura
+
+```
+GET /product/{productId}/similar (Puerto 5000)
+    ↓
+SimilarProductsController (validación)
+    ↓
+SimilarProductsService (orquestación)
+    ↓ [En Paralelo - ExecutorService]
+    ├→ getSimilarProductIds() → IDs
+    ├→ getProductDetail() × N (paralelo)
+    └→ getProductDetail() × N (paralelo)
+    ↓
+Retornar List<ProductDetail>
+```
+
+**Capas:**
+- **Controller**: HTTP endpoint + validación
+- **Service**: Orquestación paralela
+- **ExternalApiService**: Integración con APIs externas
+- **Model**: DTO ProductDetail
+
+---
+
+## 🚀 Performance: Paralelización
+
+**Problema:** 5 productos × 10 seg/producto = 50 segundos
+
+**Solución - Paralelo con CompletableFuture:**
+```java
+List<CompletableFuture<ProductDetail>> futures = new ArrayList<>();
+for (String id : similarIds) {
+    futures.add(CompletableFuture.supplyAsync(
+        () -> externalApiService.getProductDetail(id), 
+        executorService  // Thread pool de 10
+    ));
+}
+```
+
+**Resultado:** 5 productos en ~10 segundos (máximo del grupo)  
+**Mejora:** **5x más rápido**
+
+---
+
+## 🛡️ Resilience: Tolerancia a Fallos
+
+✅ **Timeout por producto:** 15 segundos max  
+✅ **Si uno falla, otros continúan:** Retorna resultados parciales  
+✅ **Timeout HTTP:** Connect 5s + Read 10s  
+✅ **Never crashes:** Nunca retorna 500 Error  
+✅ **Validación input:** productId no vacío  
+✅ **Logging:** Todos los errores se registran en logs para debugging  
+
+**Ejemplo:**
+- Productos: 5
+- Uno tarda 20 seg (timeout 15s)
+- Retorna: 4 productos (no falla)
+- Log: WARN/ERROR en logs con detalles para debugging
+
+---
+
+## 📂 Estructura del Código
+
+```
+app/src/main/java/com/similarproducts/
+├── Application.java
+├── controller/ → SimilarProductsController
+├── service/ → SimilarProductsService, ExternalApiService
+└── model/ → ProductDetail
+
+app/src/main/resources/
+└── application.yml (puerto 5000)
+```
+
+---
+
+## 🧪 Ejemplo de Uso
+
+```bash
+# Request
+GET http://localhost:5000/product/1/similar
+
+# Response (200 OK)
+[
+  {
+    "id": "2",
+    "name": "Similar Product",
+    "price": 29.99,
+    "availability": true
+  }
+]
+
+# Si no hay similares (200 OK - nunca falla)
+[]
+```
+
+---
+
+## 🔧 Configuración
+
+- **Puerto:** 5000 ✅
+- **Framework:** Spring Boot 3.3.8
+- **Java:** 21 LTS
+- **Build:** Maven
+- **Thread Pool:** 10 threads
+- **Timeouts:** Configurables

app/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+
+<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>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>3.3.8</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.similarproducts</groupId>
+  <artifactId>app</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>app</name>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>21</maven.compiler.source>
+    <maven.compiler.target>21</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <!-- Spring Boot Web -->
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+
+    <!-- RestClient for HTTP calls -->
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webflux</artifactId>
+    </dependency>
+
+    <!-- Lombok for boilerplate reduction -->
+    <dependency>
+      <groupId>org.projectlombok</groupId>
+      <artifactId>lombok</artifactId>
+      <optional>true</optional>
+    </dependency>
+
+    <!-- Logging with Lombok -->
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-logging</artifactId>
+    </dependency>
+
+    <!-- Testing -->
+    <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>
+      </plugin>
+    </plugins>
+  </build>
+</project>

app/src/main/java/com/similarproducts/Application.java

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

app/src/main/java/com/similarproducts/controller/SimilarProductsController.java

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+package com.similarproducts.controller;
+
+import com.similarproducts.model.ProductDetail;
+import com.similarproducts.service.SimilarProductsService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@RestController
+@RequestMapping("/product")
+public class SimilarProductsController {
+
+    private static final Logger logger = LoggerFactory.getLogger(SimilarProductsController.class);
+
+    private final SimilarProductsService similarProductsService;
+
+    public SimilarProductsController(SimilarProductsService similarProductsService) {
+        this.similarProductsService = similarProductsService;
+    }
+
+    @GetMapping("/{productId}/similar")
+    public ResponseEntity<List<ProductDetail>> getSimilarProducts(
+            @PathVariable String productId) {
+        try {
+            if (productId == null || productId.trim().isEmpty()) {
+                return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(new ArrayList<>());
+            }
+
+            List<ProductDetail> similarProducts = similarProductsService.getSimilarProducts(productId);
+
+            return ResponseEntity.ok(similarProducts);
+
+        } catch (Exception e) {
+            logger.error("Unexpected error while fetching similar products for productId: {}. Error: {}", productId,
+                    e.getMessage(), e);
+            return ResponseEntity.ok(new ArrayList<>());
+        }
+    }
+}

app/src/main/java/com/similarproducts/model/ProductDetail.java

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+package com.similarproducts.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class ProductDetail {
+
+    @JsonProperty("id")
+    private String id;
+
+    @JsonProperty("name")
+    private String name;
+
+    @JsonProperty("price")
+    private Double price;
+
+    @JsonProperty("availability")
+    private Boolean availability;
+}

app/src/main/java/com/similarproducts/service/ExternalApiService.java

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+package com.similarproducts.service;
+
+import com.similarproducts.model.ProductDetail;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.client.SimpleClientHttpRequestFactory;
+import org.springframework.stereotype.Service;
+import org.springframework.web.client.RestTemplate;
+
+import java.util.concurrent.TimeUnit;
+
+@Service
+public class ExternalApiService {
+
+    private static final Logger logger = LoggerFactory.getLogger(ExternalApiService.class);
+
+    private final RestTemplate restTemplate;
+    private final String mockBaseUrl;
+
+    private static final int CONNECT_TIMEOUT_SECONDS = 5;
+    private static final int READ_TIMEOUT_SECONDS = 10;
+
+    public ExternalApiService(
+            @Value("${external.api.mock.url:http://localhost:3001}") String mockBaseUrl) {
+        this.mockBaseUrl = mockBaseUrl;
+        this.restTemplate = createRestTemplate();
+    }
+
+    public String[] getSimilarProductIds(String productId) {
+        String url = mockBaseUrl + "/product/" + productId + "/similarids";
+        try {
+            String[] ids = restTemplate.getForObject(url, String[].class);
+            return ids != null ? ids : new String[0];
+        } catch (Exception e) {
+            logger.warn("Failed to fetch similar product IDs for productId: {}. Error: {}", productId, e.getMessage());
+            return new String[0];
+        }
+    }
+
+    public ProductDetail getProductDetail(String productId) {
+        String url = mockBaseUrl + "/product/" + productId;
+        try {
+            ProductDetail detail = restTemplate.getForObject(url, ProductDetail.class);
+            return detail;
+        } catch (Exception e) {
+            logger.warn("Failed to fetch product details for productId: {}. Error: {}", productId, e.getMessage());
+            return null;
+        }
+    }
+
+    private RestTemplate createRestTemplate() {
+        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
+        factory.setConnectTimeout((int) TimeUnit.SECONDS.toMillis(CONNECT_TIMEOUT_SECONDS));
+        factory.setReadTimeout((int) TimeUnit.SECONDS.toMillis(READ_TIMEOUT_SECONDS));
+        return new RestTemplate(factory);
+    }
+}