SAMPLE

#nullable enable
// <-------------------- PORTFOLIO CODE SAMPLE: Miniature SaaS API (BEGIN) -------------------->
// Author: [Your Name]
// Tech Stack: .NET 6+ Minimal API, C#, In-Memory Data Store
// Purpose: Demonstrates a clean, modern, and scalable approach to building a Full-Stack application backend.

// --- 1. USING STATEMENTS & GLOBAL CONFIG ---
using Microsoft.AspNetCore.Mvc;
using System.Collections.Concurrent;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// --- 2. DEPENDENCY INJECTION: Simulating Clean Architecture Layers ---

// Data Layer: Stores the application's data (in-memory for this example).
builder.Services.AddSingleton<IProductRepository, InMemoryProductRepository>();

// Service Layer (Business Logic): Contains the core application logic.
builder.Services.AddScoped<ProductService>();


var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();


// --- 3. PRESENTATION LAYER: The API Endpoints ---
// These are the public-facing endpoints that a Frontend (Vue, React, etc.) would consume.

var api = app.MapGroup("/api/products");

// GET /api/products
api.MapGet("/", (ProductService productService) => {
    return productService.GetAllProducts();
});

// GET /api/products/{id}
api.MapGet("/{id:int}", (int id, ProductService productService) => {
    var product = productService.GetProductById(id);
    return product is not null ? Results.Ok(product) : Results.NotFound();
});

// GET /api/products/premium
api.MapGet("/premium", (ProductService productService) => {
    // This simulates a feature only available to premium users.
    return productService.GetPremiumProducts();
});

app.Run();


// --- 4. DOMAIN: The Core Business Models ---
// These classes define the essential data structures of the application.

public record Product(int Id, string Name, double Price, bool IsPremium = false);


// --- 5. SERVICE LAYER: Application Business Logic ---
// This layer orchestrates data and applies business rules.

public class ProductService
{
    private readonly IProductRepository _repository;

    public ProductService(IProductRepository repository)
    {
        _repository = repository;
    }

    public IEnumerable<Product> GetAllProducts() => _repository.GetAll();
    
    public Product? GetProductById(int id) => _repository.GetById(id);
    
    public IEnumerable<Product> GetPremiumProducts()
    {
        // Business Rule: Only return products marked as premium.
        return _repository.GetAll().Where(p => p.IsPremium);
    }
}


// --- 6. DATA LAYER: Data Access and Persistence ---
// This layer is responsible for retrieving and storing data.

public interface IProductRepository
{
    IEnumerable<Product> GetAll();
    Product? GetById(int id);
}

public class InMemoryProductRepository : IProductRepository
{
    // Using a ConcurrentDictionary to be thread-safe.
    private readonly ConcurrentDictionary<int, Product> _products = new(new[]
    {
        KeyValuePair.Create(1, new Product(1, "Standard Widget", 9.99)),
        KeyValuePair.Create(2, new Product(2, "Advanced Gadget", 29.99)),
        KeyValuePair.Create(3, new Product(3, "Pro Gear", 99.99, IsPremium: true)),
        KeyValuePair.Create(4, new Product(4, "Ultimate Gizmo", 199.99, IsPremium: true)),
    });

    public IEnumerable<Product> GetAll() => _products.Values.OrderBy(p => p.Id);

    public Product? GetById(int id) => _products.GetValueOrDefault(id);
}

// <-------------------- PORTFOLIO CODE SAMPLE: Miniature SaaS API (END) -------------------->