RaftLabs User API Client

A .NET 9.0 solution demonstrating Clean Architecture principles for interacting with external APIs. This project implements a robust, generic API client for the reqres.in service with comprehensive error handling, retry logic, caching, and extensive testing.

[This README is generated with the help of an AI tool but the project is handmade by a human developer :) ]

Architecture Overview

This solution follows Clean Architecture principles with a generic, reusable design that can support multiple entity types:

├── src/
│   ├── RaftLabs.Domain/          # Core business entities and interfaces
│   ├── RaftLabs.Application/     # Use cases and application services  
│   ├── RaftLabs.Infrastructure/  # Generic HTTP client and repository patterns
│   └── RaftLabs.Presentation/    # Web API controllers and endpoints
├── tests/
│   └── RaftLabs.UnitTests/       # Comprehensive unit tests (11 tests)
├── samples/
│   └── RaftLabs.Console/         # Interactive demo console application
└── README.md

Architecture Layers

Domain Layer (innermost): Contains core business entities, domain exceptions, and repository interfaces
Application Layer: Implements use cases, business logic, and coordinates between layers
Infrastructure Layer: Generic HTTP client, repository base classes, caching, and retry policies
Presentation Layer: REST API endpoints with global exception handling and Swagger documentation

Generic Architecture Benefits

Extensible Design: Easily add new entity types (Products, Orders, etc.) without code duplication
Type-Safe Generic Patterns: IRepository<T, TId> and ExternalRepositoryBase<T, TId, TExternal, TExternalPage>
Reusable HTTP Client: Generic IApiClient supporting any endpoint and response type
Consistent Patterns: All repositories follow the same structure and behavior

Features

Core Functionality

Generic HTTP Client: IApiClient using IHttpClientFactory with named client registration
Generic Repository Pattern: IRepository<T, TId> and ExternalRepositoryBase<T, TId, TExternal, TExternalPage>
Options Pattern: Strongly-typed configuration with IOptions<ApiSettings>
Async/Await Patterns: Full asynchronous implementation throughout the solution
Pagination Support: Handles paginated data retrieval and aggregation
Type-Safe Mapping: Clean mapping between external API models and domain entities

Resilience & Performance

Retry Logic: Implements exponential backoff using Polly library
Timeout Handling: Configurable request timeouts per named HttpClient
In-Memory Caching: Reduces API calls with configurable cache expiration
Error Handling: Comprehensive exception handling with domain-specific exceptions

Configuration & Monitoring

Configurable Settings: External API settings via appsettings.json with Options pattern
Structured Logging: Comprehensive logging with named HttpClient identification
Health Monitoring: Built-in error tracking and retry monitoring
Global Exception Handling: Centralized exception middleware

API Documentation & Testing

Swagger/OpenAPI: Interactive API documentation with API key authentication
Unit Testing: 11 comprehensive unit tests with 100% pass rate
Mocking Strategy: Clean mocking of IApiClient and other dependencies
XML Documentation: Comprehensive code documentation

API Endpoints

The solution exposes the following REST endpoints:

Users Controller

Method	Endpoint	Description
`GET`	`/api/users/{id}`	Get a specific user by ID
`GET`	`/api/users`	Get all users (aggregated from all pages)
`GET`	`/api/users/page/{page}`	Get users for a specific page

Example Responses

Get User by ID:

{
  "id": 2,
  "email": "[email protected]",
  "firstName": "Janet",
  "lastName": "Weaver",
  "avatar": "https://reqres.in/img/faces/2-image.jpg",
  "fullName": "Janet Weaver"
}

Get Users Page:

{
  "page": 1,
  "per_page": 6,
  "total": 12,
  "total_pages": 2,
  "data": [...],
  "has_next_page": true,
  "has_previous_page": false
}

Quick Start

Prerequisites

.NET 9.0 SDK or later (Download here)
IDE: Visual Studio 2022, VS Code, or JetBrains Rider
Internet Connection: Required for external API calls to reqres.in

Getting Started

1. Clone and Setup

# Clone the repository
git clone <repository-url>
cd RaftLabs

# Restore all packages
dotnet restore

# Build the entire solution
dotnet build

2. Run the Interactive Console Demo

# Navigate to console project
cd samples/RaftLabs.Console

# Run the demo (shows all features)
dotnet run

Expected Output:

=== RaftLabs User API Client Demo ===

Demo 1: Getting user with ID 2...
Found user: Janet Weaver ([email protected])

Demo 2: Getting users from page 1...
Page 1 of 2 (Total: 12 users)

Demo 3: Getting all users...
Retrieved 12 total users

Demo 4: Testing error handling...
Correctly handled non-existent user

Demo 5: Testing caching...
First call: 250ms, Second call: 0ms
   Cache working: Yes

3. Run the Web API

# From solution root
dotnet run --project src/RaftLabs.Presentation

# Or with specific URL
dotnet run --project src/RaftLabs.Presentation --urls "http://localhost:5000"

API will be available at:

Swagger UI: http://localhost:5000 (interactive documentation)
API Base: http://localhost:5000/api/users

4. Run All Unit Tests

# From solution root
dotnet test

# Expected output:
# Test run for RaftLabs.UnitTests.dll (.NET 9.0)
# Total tests: 11
# Passed: 11
# Failed: 0
# Skipped: 0

5. Test API Endpoints

# Get user by ID
curl http://localhost:5000/api/users/2

# Get all users (aggregated from all pages)  
curl http://localhost:5000/api/users

# Get specific page
curl http://localhost:5000/api/users/page/1

# Test error handling
curl http://localhost:5000/api/users/999

Build and Development

Build Commands

# Clean and rebuild entire solution
dotnet clean && dotnet build

# Build specific project
dotnet build src/RaftLabs.Infrastructure

# Build in Release mode
dotnet build --configuration Release

# Restore packages only
dotnet restore

Running Projects

# Run Web API (default: https://localhost:7042, http://localhost:5000)
dotnet run --project src/RaftLabs.Presentation

# Run Console Demo
dotnet run --project samples/RaftLabs.Console

# Run with specific profile
dotnet run --project src/RaftLabs.Presentation --launch-profile "https"

Testing Commands

# Run all tests
dotnet test

# Run tests with detailed output
dotnet test --verbosity normal

# Run tests with coverage (requires coverage tools)
dotnet test --collect:"XPlat Code Coverage"

# Run specific test class
dotnet test --filter "ExternalUserRepositoryTests"

# Run specific test method
dotnet test --filter "GetUserByIdAsync_WithValidUser_ReturnsUser"

Development Workflow

# 1. Make changes to code
# 2. Build to check for compilation errors
dotnet build

# 3. Run tests to ensure functionality
dotnet test

# 4. Test the console app
dotnet run --project samples/RaftLabs.Console

# 5. Test the API
dotnet run --project src/RaftLabs.Presentation

Configuration

API Settings (`appsettings.json`)

{
  "ApiSettings": {
    "BaseUrl": "https://reqres.in/api/",
    "ApiKey": "reqres-free-v1", 
    "TimeoutSeconds": 30,
    "RetryAttempts": 3,
    "RetryDelayMs": 1000,
    "CacheExpirationMinutes": 5
  }
}

Configuration Options

Setting	Description	Default	Location
`BaseUrl`	External API base URL	`https://reqres.in/api/`	Both Console & API
`ApiKey`	API key for authentication	`reqres-free-v1`	HTTP Header `x-api-key`
`TimeoutSeconds`	HTTP request timeout	`30`	HttpClient configuration
`RetryAttempts`	Number of retry attempts	`3`	Polly retry policy
`RetryDelayMs`	Delay between retries (ms)	`1000`	Exponential backoff base
`CacheExpirationMinutes`	Cache expiration time	`5`	IMemoryCache settings

HttpClient Configuration

The solution uses named HttpClient registration with the Options pattern:

// Named client registration
builder.Services.AddHttpClient("ReqresApiClient");

// ApiClient uses IHttpClientFactory internally
public ApiClient(IHttpClientFactory httpClientFactory, ILogger<ApiClient> logger, IOptions<ApiSettings> apiSettings)
{
    _httpClient = httpClientFactory.CreateClient("ReqresApiClient");
    _httpClient.BaseAddress = new Uri(_apiSettings.BaseUrl);
    _httpClient.Timeout = TimeSpan.FromSeconds(_apiSettings.TimeoutSeconds);
    _httpClient.DefaultRequestHeaders.Add("x-api-key", _apiSettings.ApiKey);
}

Testing Strategy

Unit Test Coverage

The solution includes 11 comprehensive unit tests covering:

ExternalUserRepository Tests (6 tests)

GetUserByIdAsync_WithValidUser_ReturnsUser: Successful user retrieval
GetUserByIdAsync_WithNonExistentUser_ReturnsNull: 404 handling
GetUserByIdAsync_WithInvalidUserId_ThrowsValidationException: Input validation
GetUsersPageAsync_WithValidPage_ReturnsPagedResult: Pagination support
GetUsersPageAsync_WithInvalidPage_ThrowsValidationException: Page validation
Additional scenarios: Caching, error handling, mapping

UserService Tests (5 tests)

Service layer business logic: Coordination between repositories
Error propagation: Domain exception handling
Input validation: Parameter validation at service level
Logging verification: Structured logging validation
Mock verification: Dependency interaction verification

Test Architecture

// Clean mocking strategy using the generic IApiClient
public class ExternalUserRepositoryTests
{
    private readonly Mock<IApiClient> _mockApiClient;
    private readonly IMemoryCache _memoryCache;
    private readonly Mock<ILogger<ExternalUserRepository>> _mockLogger;
    private readonly ExternalUserRepository _repository;

    public ExternalUserRepositoryTests()
    {
        _mockApiClient = new Mock<IApiClient>();
        // ... setup with Options.Create(apiSettings)
        _repository = new ExternalUserRepository(_mockApiClient.Object, _memoryCache, _mockLogger.Object, options);
    }
}

Running Tests

Basic Test Execution

# Run all tests (11 tests)
dotnet test
# Expected: Total tests: 11, Passed: 11, Failed: 0

# Run with detailed output
dotnet test --verbosity normal

# Run with minimal output
dotnet test --verbosity quiet

Advanced Test Commands

# Run specific test class
dotnet test --filter "ExternalUserRepositoryTests"

# Run specific test method
dotnet test --filter "GetUserByIdAsync_WithValidUser_ReturnsUser"

# Run tests with logger output
dotnet test --logger "console;verbosity=detailed"

# Run tests and generate coverage report (if coverage tools installed)
dotnet test --collect:"XPlat Code Coverage"

Test Results Interpretation

Expected successful test run:
Test Run Successful.
Total tests: 11
     Passed: 11
     Failed: 0
    Skipped: 0
 Total time: ~2-3 seconds

If tests fail, check:
- Network connectivity (tests use mocked dependencies, but build needs packages)
- .NET 9.0 SDK installation
- NuGet package restoration (dotnet restore)

Test Categories

1. Unit Tests (Current - 11 tests)

Mock all external dependencies
Test business logic in isolation
Fast execution (< 3 seconds total)
No external API calls

2. Integration Tests (Future Enhancement)

Test with real HTTP calls to reqres.in
Validate end-to-end scenarios
Network dependency required

3. Performance Tests (Future Enhancement)

Cache performance validation
HTTP client connection pooling
Retry policy effectiveness

Development Decisions

Technology Choices

Clean Architecture: Ensures maintainability, testability, and separation of concerns
Generic Repository Pattern: ExternalRepositoryBase<T, TId, TExternal, TExternalPage> for reusability
HttpClientFactory with Named Clients: Prevents socket exhaustion, enables proper logging
Options Pattern: Strongly-typed configuration with IOptions<ApiSettings>
Polly for Resilience: Industry-standard library for retry policies and circuit breakers
Memory Caching: Reduces external API calls and improves performance
Structured Logging: Enables comprehensive monitoring and debugging

Error Handling Strategy

Domain Exceptions: Custom exceptions (NotFoundException, ValidationException, etc.)
HTTP Error Mapping: Proper HTTP status codes for different scenarios
Retry Logic: Exponential backoff for transient failures
Global Exception Middleware: Centralized error handling in the API layer

Generic Architecture Benefits

// Easy to extend for new entity types
public class ProductRepository : ExternalRepositoryBase<Product, int, ExternalProductResponse, ExternalProductsResponse>
{
    protected override string EndpointName => "products";
    protected override string CacheKeyPrefix => "product";
    
    // Only need to implement mapping - everything else is inherited!
    protected override Product MapFromExternalResponse(ExternalProductResponse response) => response.Data.ToProduct();
    protected override PagedResult<Product> MapFromExternalPageResponse(ExternalProductsResponse response) => response.ToPagedResult();
}

Retry Logic: Exponential backoff for transient failures
Graceful Degradation: Fallback mechanisms for service unavailability

Performance Optimizations

Async Throughout: Full asynchronous implementation
HTTP Client Reuse: Efficient connection management
Response Caching: Configurable in-memory caching
Lazy Loading: Data fetched only when needed

Dependencies

Core Dependencies

Microsoft.Extensions.Http - HttpClientFactory and named client management
Microsoft.Extensions.Caching.Memory - In-memory caching with IMemoryCache
Microsoft.Extensions.Options - Options pattern for strongly-typed configuration
Polly.Extensions.Http - Retry policies and resilience patterns
Swashbuckle.AspNetCore - Swagger/OpenAPI documentation

Infrastructure Dependencies

System.Text.Json - JSON serialization/deserialization
Microsoft.Extensions.Logging - Structured logging throughout the application
Microsoft.Extensions.DependencyInjection - Dependency injection container

Test Dependencies

xUnit - Modern testing framework for .NET
Moq - Mocking framework for unit testing
Microsoft.Extensions.Logging.Abstractions - Logging abstractions for testing

Usage Examples

Console Application Demo

The included console application demonstrates all key features:

dotnet run --project samples/RaftLabs.Console

Features demonstrated:

Individual user retrieval with caching
Paginated data retrieval
Error handling for non-existent resources
Performance comparison (first call vs cached call)
Comprehensive logging output

Web API Usage

# Start the API
dotnet run --project src/RaftLabs.Presentation

# Test endpoints
curl http://localhost:5000/api/users              # Get all users
curl http://localhost:5000/api/users/2            # Get specific user  
curl http://localhost:5000/api/users/page/1       # Get users page
curl http://localhost:5000/api/users/999          # Test error handling (404)

Programmatic Usage

// Dependency injection setup (Program.cs)
builder.Services.Configure<ApiSettings>(builder.Configuration.GetSection("ApiSettings"));
builder.Services.AddHttpClient("ReqresApiClient");  
builder.Services.AddScoped<IApiClient, ApiClient>();
builder.Services.AddScoped<IUserRepository, ExternalUserRepository>();
builder.Services.AddScoped<IUserService, UserService>();

// Usage in your application
public class MyService
{
    private readonly IUserService _userService;

    public MyService(IUserService userService)
    {
        _userService = userService;
    }

    public async Task<UserDto> GetUserAsync(int id)
    {
        return await _userService.GetUserByIdAsync(id);
    }

    public async Task<PagedResult<UserDto>> GetUsersPageAsync(int page) 
    {
        return await _userService.GetUsersPageAsync(page);
    }
}

Extending for New Entity Types

// 1. Define domain entity
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

// 2. Define external models  
public class ExternalProductResponse
{
    public ExternalProductModel Data { get; set; }
}

public class ExternalProductsResponse
{
    public List<ExternalProductModel> Data { get; set; }
    // ... pagination properties
}

// 3. Create repository (inherits all functionality!)
public class ProductRepository : ExternalRepositoryBase<Product, int, ExternalProductResponse, ExternalProductsResponse>, IProductRepository
{
    protected override string EndpointName => "products";
    protected override string CacheKeyPrefix => "product";
    
    public ProductRepository(IApiClient apiClient, IMemoryCache cache, ILogger<ProductRepository> logger, IOptions<ApiSettings> apiSettings)
        : base(apiClient, cache, logger, apiSettings) { }
    
    protected override Product MapFromExternalResponse(ExternalProductResponse response) => response.Data.ToProduct();
    protected override PagedResult<Product> MapFromExternalPageResponse(ExternalProductsResponse response) => response.ToPagedResult();
}

// 4. Register in DI container
builder.Services.AddScoped<IProductRepository, ProductRepository>();

Monitoring & Observability

Logging

The application provides structured logging at multiple levels:

Information: Successful operations, HTTP requests, cache hits/misses
Warning: Retry attempts, validation warnings, cache evictions
Error: Exceptions, service failures, network timeouts

Named HttpClient Logging:

info: System.Net.Http.HttpClient.ReqresApiClient.LogicalHandler[100]
      Start processing HTTP request GET https://reqres.in/api/users/2
info: System.Net.Http.HttpClient.ReqresApiClient.ClientHandler[101]  
      Received HTTP response headers after 245ms - 200

Performance Metrics

The console demo shows real performance data:

API Response Times: Actual HTTP call duration
Cache Effectiveness: "First call: 250ms, Second call: 0ms"
Retry Monitoring: Failed attempts and retry logic execution
Error Rates: Success/failure ratios by operation type

Monitoring Capabilities

HttpClient Connection Pooling: Automatic via HttpClientFactory
Request/Response Logging: Detailed HTTP operation tracking
Cache Hit Ratios: Memory cache performance metrics
Exception Tracking: Comprehensive error logging with context

Troubleshooting

Common Issues

Build Errors

# Clean and rebuild if you encounter build issues
dotnet clean
dotnet restore  
dotnet build

Test Failures

# Ensure all packages are restored
dotnet restore
dotnet test --verbosity normal

Network Issues (Console Demo)

# Verify network connectivity
curl https://reqres.in/api/users/1

# Check configuration in appsettings.json
cat samples/RaftLabs.Console/appsettings.json

Port Conflicts (Web API)

# Use different port if 5000 is occupied
dotnet run --project src/RaftLabs.Presentation --urls "http://localhost:8080"

Debug Information

Solution: Uses .NET 9.0 target framework
Dependencies: All packages compatible with .NET 9.0
Architecture: Clean Architecture with generic patterns
Test Framework: xUnit with Moq for mocking
HTTP Client: Named client with HttpClientFactory

Performance Characteristics

Response Times (Console Demo Results)

Cold Start: ~250ms (first API call)
Cached Response: ~0ms (subsequent identical calls)
Page Retrieval: ~20-50ms (typical API response)
Error Handling: ~500ms (network timeout scenarios)

Memory Usage

Startup: Minimal footprint with DI container
Caching: Configurable memory cache (5-minute default expiration)
HTTP Connections: Pooled and reused via HttpClientFactory

Scalability Features

Connection Pooling: Automatic via HttpClientFactory
Async Operations: Full async/await throughout
Generic Design: Easy horizontal scaling for new entity types
Stateless Design: API can be deployed across multiple instances

Contributing

Fork the repository
Create a feature branch
Make your changes
Add/update tests
Ensure all tests pass
Submit a pull request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Contact

For questions or support, please contact:

Developer: @ayushwritescode
Email: [email protected]

Built with ❤️ using .NET 9.0 and Clean Architecture principles

Name		Name	Last commit message	Last commit date
Latest commit History 1 Commit
.vscode		.vscode
samples/RaftLabs.Console		samples/RaftLabs.Console
src		src
tests/RaftLabs.UnitTests		tests/RaftLabs.UnitTests
.gitignore		.gitignore
README.md		README.md
RaftLabs.sln		RaftLabs.sln
TestAuthentication.http		TestAuthentication.http
TestGlobalExceptionHandling.http		TestGlobalExceptionHandling.http

ayushwritescode/RaftLabs

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RaftLabs User API Client

Architecture Overview

Architecture Layers

Generic Architecture Benefits

Features

Core Functionality

Resilience & Performance

Configuration & Monitoring

API Documentation & Testing

API Endpoints

Users Controller

Example Responses

Quick Start

Prerequisites

Getting Started

1. Clone and Setup

2. Run the Interactive Console Demo

3. Run the Web API

4. Run All Unit Tests

5. Test API Endpoints

Build and Development

Build Commands

Running Projects

Testing Commands

Development Workflow

Configuration

API Settings (appsettings.json)

Configuration Options

HttpClient Configuration

Testing Strategy

Unit Test Coverage

ExternalUserRepository Tests (6 tests)

UserService Tests (5 tests)

Test Architecture

Running Tests

Basic Test Execution

Advanced Test Commands

Test Results Interpretation

Test Categories

1. Unit Tests (Current - 11 tests)

2. Integration Tests (Future Enhancement)

3. Performance Tests (Future Enhancement)

Development Decisions

Technology Choices

Error Handling Strategy

Generic Architecture Benefits

Performance Optimizations

Dependencies

Core Dependencies

Infrastructure Dependencies

Test Dependencies

Usage Examples

Console Application Demo

Web API Usage

Programmatic Usage

Extending for New Entity Types

Monitoring & Observability

Logging

Performance Metrics

Monitoring Capabilities

Troubleshooting

Common Issues

Build Errors

Test Failures

Network Issues (Console Demo)

Port Conflicts (Web API)

Debug Information

Performance Characteristics

Response Times (Console Demo Results)

Memory Usage

Scalability Features

Contributing

License

Contact

About

API Settings (`appsettings.json`)

Packages