Feat/idr rate aggregator

.gitignore

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+# ========================
+# BUILD FILES
+# ========================
+/target/
+*.class
+*.jar
+*.war
+*.ear
+
+# ========================
+# LOG FILES
+# ========================
+*.log
+
+# ========================
+# IDE - IntelliJ
+# ========================
+.idea/
+*.iws
+*.iml
+*.ipr
+out/
+
+# ========================
+# IDE - Eclipse
+# ========================
+.project
+.classpath
+.settings/
+
+# ========================
+# IDE - VS Code
+# ========================
+.vscode/
+
+# ========================
+# OS FILES
+# ========================
+.DS_Store
+Thumbs.db
+
+# ========================
+# ENV FILES
+# ========================
+.env
+.env.*
+
+# ========================
+# MAVEN
+# ========================
+.mvn/wrapper/maven-wrapper.jar
+.mvn/wrapper/maven-wrapper.properties
+
+# ========================
+# SPRING BOOT
+# ========================
+/logs/
+*.pid
+
+# ========================
+# TEST OUTPUT
+# ========================
+/surefire-reports/
+/failsafe-reports/
+
+# ========================
+# TEMP FILES
+# ========================
+*.tmp
+*.swp
+*.lst
+*.txt

README.md

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-# Allo Bank Backend Developer Take-Home Test
+## Ringkasan
 
-Thank you for applying to our team! This take-home test is designed to evaluate your practical skills in building **production-ready** Spring Boot applications within a finance domain, focusing on architectural patterns and complex data handling.
+PR ini berisi implementasi REST API untuk mengagregasi data nilai tukar IDR dari Frankfurter API sesuai dengan requirement.
 
-## 📝 Objective
+Data yang disediakan mencakup:
 
-Your task is to create a single Spring Boot REST API endpoint capable of aggregating data from multiple, distinct resources provided by the public, keyless **Frankfurter Exchange Rate API**. The primary focus is on handling Indonesian Rupiah (IDR) data.
+* Kurs terbaru terhadap IDR
+* Data historis IDR ke USD
+* Daftar mata uang yang tersedia
 
-The focus of this test is not just functional correctness, but demonstrating clean code, advanced Spring concepts, thread-safe design, and architectural clarity.
+Seluruh data diambil satu kali saat aplikasi start dan disimpan di memory, sehingga endpoint tidak melakukan request ulang ke API eksternal.
 
-## I. Core Task: The Polymorphic API
+---
 
-### 1. External API Integration (Frankfurter API)
+## Fitur yang Diimplementasikan
 
-* **Base URL (Public):** `https://api.frankfurter.app/`.
+* Endpoint:
 
-* You must integrate with three distinct data resources to enforce the architectural pattern:
+  * `GET /api/finance/data/{resourceType}`
 
-   1.  `/latest?base=IDR` (The latest rates relative to IDR)
+* Resource yang didukung:
 
-   2.  **Historical Data:** Query a specific, small time series (e.g., `/2024-01-01..2024-01-05?from=IDR&to=USD`). **Note:** *Use the date range provided in this example unless a different range is communicated separately.*
+  * `latest_idr_rates`
+  * `historical_idr_usd`
+  * `supported_currencies`
 
-   3.  `/currencies` (The list of all supported currency symbols)
+* Penambahan field:
 
-### 2. Internal API Endpoint
+  * `USD_BuySpread_IDR` (khusus latest rate)
 
-You must expose **one single endpoint** in your application: ```GET /api/finance/data/{resourceType}```
+---
 
-Where `{resourceType}` can be one of the three strings: `latest_idr_rates`, `historical_idr_usd`, or `supported_currencies`.
+## Pendekatan Arsitektur
 
-### 3. Required Functionality & Business Logic
+### Strategy Pattern
 
-* **Resource Handling:** Your service must correctly map the three incoming `resourceType` values to the correct data fetching strategies.
+Digunakan untuk memisahkan logic pengambilan data berdasarkan resource.
 
-* **Data Load:** All three resources should be fetched from the external API.
+Setiap resource memiliki implementasi sendiri dari interface `IDRDataFetcher`, sehingga tidak perlu menggunakan if/else di controller.
 
-* **Data Transformation (Latest IDR Rates only) - Unique Calculation:** For the **`latest_idr_rates`** resource, you must calculate and include a new field, `"USD_BuySpread_IDR"`. This is the Rupiah selling rate to USD after applying a banking spread/margin.
+Pendekatan ini memudahkan jika ingin menambahkan resource baru ke depannya.
 
-  **The Spread Factor Must Be Unique :**
+---
 
-   1.  **Input:** Your GitHub username (e.g., `johndoe47`).
-   2.  **Calculation:** Calculate the sum of the Unicode (ASCII) values of all characters in your lowercase GitHub username string.
-   3.  **Spread Factor Derivation:** `Spread Factor = (Sum of Unicode Values % 1000) / 100000.0`
-       *(This will yield a unique factor between 0.00000 and 0.00999, ensuring a personalized result.)*
+### FactoryBean untuk WebClient
 
-  **Final Formula:** `USD_BuySpread_IDR = (1 / Rate_USD) * (1 + Spread Factor)` (where `Rate_USD` is the value from the API when `base=IDR`).
+WebClient dibuat menggunakan FactoryBean agar konfigurasi seperti base URL dan timeout terpusat.
 
-* **Other Resources:** The `historical_idr_usd` and `supported_currencies` resources can return their data with minimal transformation, but the final output must be a unified JSON array of results.
+Dengan cara ini, pembuatan client tidak tersebar di berbagai class dan lebih mudah dikelola.
 
-## II. Architectural Constraints
+---
 
-Meeting the core task is only one part of the solution. The following constraints must be strictly adhered to and will be heavily weighted during evaluation:
+### ApplicationRunner
 
-### Constraint A: The Strategy Pattern
+Digunakan untuk load data dari external API saat aplikasi start.
 
-The logic for handling the three different resources (`latest_idr_rates`, `historical_idr_usd`, `supported_currencies`) must be implemented using the **Strategy Design Pattern**.
+Alasan penggunaan:
 
-1.  Define a clear **Strategy Interface** (e.g., `IDRDataFetcher`).
+* memastikan data hanya diambil sekali
+* menghindari pemanggilan API berulang
+* memastikan semua dependency sudah siap sebelum proses fetch
 
-2.  Implement **three concrete strategy classes** (one for each resource).
+---
 
-3.  The main `Controller` should dynamically select the correct strategy implementation using a map-based lookup injected by Spring, avoiding any manual `if/else` or `switch` logic in the controller layer.
+## Response Design
 
-### Constraint B: Client Factory Bean
+Response dibuat konsisten menggunakan wrapper:
 
-The instance of your chosen external API client (`WebClient` or `RestTemplate`) **must be defined and created within a custom implementation of Spring's `FactoryBean<T>` interface**.
+```json
+[
+  {
+    "resourceType": "latest_idr_rates",
+    "data": { ... }
+  }
+]
+```
 
-* This `FactoryBean` should be responsible for externalizing the API Base URL via `@Value` or `@ConfigurationProperties` and applying any initial configuration (e.g., timeouts, shared headers).
+Pendekatan ini memudahkan parsing di sisi client dan menjaga konsistensi antar endpoint.
 
-* ***You may not define the client as a simple `@Bean` in a `@Configuration` class.***
+---
 
-### Constraint C: Startup Data Runner & Immutability
+## Error Handling & Timeout
 
-The aggregated data for **ALL three resources** must be fetched **exactly once on application startup** and loaded into an in-memory store.
+* Menambahkan timeout pada pemanggilan WebClient
+* Menangani error dari external API secara graceful
+* Menambahkan GlobalExceptionHandler untuk menangani error umum
 
-1.  Use a Spring Boot **`ApplicationRunner`** or **`CommandLineRunner`** component to initiate the data fetching process.
+Contoh response saat error:
 
-2.  The API endpoint (`GET /api/finance/data/{resourceType}`) must serve the data from this **in-memory store**, not by making a new call to the external API on every request.
+```json
+{
+  "error": "Failed to fetch data",
+  "message": "TimeoutException"
+}
+```
 
-3.  The in-memory storage mechanism (e.g., a service holding the data) must be designed to be **thread-safe** and ensure the data is **immutable** once the `ApplicationRunner` has finished loading it.
+---
 
-## III. Production Readiness & Deliverables
+## Testing
 
-Your final solution must demonstrate production quality through code, testing, and communication.
+Unit test mencakup:
 
-### 1. Robustness & Best Practices
+* Strategy (latest, historical, currencies)
+* SpreadUtil
+* DataLoader
 
-* Graceful **Error Handling** for network failures or 4xx/5xx responses from the external API.
+WebClient dimock agar test tidak bergantung ke API eksternal.
 
-* Proper use of **Configuration Properties** (e.g., `application.yml`) for external service URLs.
+---
 
-* Clear separation of concerns (Controller, Service, Model/DTO, etc.).
+## Cara Menjalankan
 
-### 2. Testing
+```bash
+mvn clean install
+mvn spring-boot:run
+```
 
-* **Unit Tests** for all three `IDRDataFetcher` strategy implementations, ensuring data calculation and transformation logic is covered (using mock clients for external calls).
+---
 
-* **Integration Tests** to verify the `ApplicationRunner` successfully initializes and loads the data into the in-memory store before the application context is ready.
+## Contoh Penggunaan
 
-### 3. Documentation
+```bash
+curl http://localhost:8080/api/finance/data/latest_idr_rates
+curl http://localhost:8080/api/finance/data/historical_idr_usd
+curl http://localhost:8080/api/finance/data/supported_currencies
+```
 
-A clear `README.md` is mandatory. It must include:
+---
 
-* **Setup/Run Instructions:** Clear steps to clone, build, and run the application and tests.
+## Personalisasi Spread
 
-* **Endpoint Usage:** Example cURL commands to test the three different resource types.
+GitHub Username: **haidir**
 
-* **Personalization Note:** Clearly state your GitHub username and show the exact **Spread Factor** (e.g., `0.00765`) calculated by your function.
+Spread dihitung menggunakan:
+(sum ASCII username % 1000) / 100000.0
 
-* ---
+---
 
-* ### 🛠️ Architectural Rationale
+## Catatan
 
-  This section should contain a brief, but detailed, explanation answering the following questions:
+* Data disimpan dalam bentuk immutable setelah load
+* Menggunakan BigDecimal untuk menjaga presisi perhitungan
+* Endpoint hanya membaca dari memory (tidak hit API lagi)
 
-   1.  **Polymorphism Justification:** Explain *why* the Strategy Pattern was used over a simpler conditional block in the service layer for handling the multi-resource endpoint. Discuss the benefits in terms of **extensibility** and **maintainability**.
+---
 
-   2.  **Client Factory:** Explain the specific role and benefit of using a **`FactoryBean`** to construct the external API client. Why is this preferable to defining the client using a standard `@Bean` method in this scenario?
+## Penutup
 
-   3.  **Startup Runner Choice:** Justify the choice of using an `ApplicationRunner` (or `CommandLineRunner`) for the initial data ingestion over a simpler `@PostConstruct` method.
+Implementasi ini dibuat dengan fokus pada clean architecture, maintainability, dan testability.
 
-## IV. Submission & Review Process
-
-1.  **Fork** this repository.
-
-2.  Implement your solution on a dedicated feature branch (e.g., `feat/idr-rate-aggregator`).
-
-3.  When complete, submit your solution via a **Pull Request (PR)** back to the main repository.
-4.  Please complete the form to submit your technical test: [Click Here](https://forms.gle/nZKQ2EjTCPfAKHog7)
-
-**Your PR will be evaluated on the following:**
-
-* **Commit History:** Clean, atomic, and descriptive commit messages (e.g., "feat: Implement IDR latest rates strategy," "fix: Correctly calculate IDR spread in tests").
-
-* **PR Description:** The description must clearly summarize the solution and **must contain the full answers** to the three "Architectural Rationale" questions from Section III.
-
-* **Code Review Readiness:** The code should be well-structured and ready for immediate review.
-
-Good luck!

pom.xml

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+
+<project xmlns="http://maven.apache.org/POM/4.0.0">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.allo</groupId>
+  <artifactId>finance</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>3.2.0</version>
+  </parent>
+
+  <dependencies>
+    <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-webflux</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.projectlombok</groupId>
+      <artifactId>lombok</artifactId>
+      <optional>true</optional>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

src/main/java/com/allo/finance/FinanceApplication.java

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

src/main/java/com/allo/finance/config/JacksonConfig.java

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+package com.allo.finance.config;
+
+import com.fasterxml.jackson.databind.SerializationFeature;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
+
+@Configuration
+public class JacksonConfig {
+
+    @SuppressWarnings("deprecation")
+    @Bean
+    public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() {
+        return builder -> builder.featuresToEnable(
+                SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN
+        );
+    }
+}

src/main/java/com/allo/finance/config/WebClientFactory.java

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+
+package com.allo.finance.config;
+
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.client.WebClient;
+
+@Component
+public class WebClientFactory implements FactoryBean<WebClient> {
+
+    @Value("${external.api.base-url}")
+    private String baseUrl;
+
+    @Override
+    public WebClient getObject() {
+        return WebClient.builder().baseUrl(baseUrl).build();
+    }
+
+    @Override
+    public Class<?> getObjectType() {
+        return WebClient.class;
+    }
+}