Minimal APIs vs Controller-Based APIs

// ━━ Controller-based API — use for complex APIs ━━
[ApiController]                              // enables automatic model validation errors
[Route("api/v{version:apiVersion}/[controller]")]
[Produces("application/json")]
public class ProductsController(
    IProductService service,
    ILogger<ProductsController> logger) : ControllerBase
{
    [HttpGet]
    [ProducesResponseType<PagedResult<ProductDto>>(200)]
    [ProducesResponseType(400)]
    public async Task<ActionResult<PagedResult<ProductDto>>> GetAll(
        [FromQuery] ProductFilter filter,
        CancellationToken ct) =>
        Ok(await service.GetPagedAsync(filter, ct));

    [HttpGet("{id:guid}")]
    [ProducesResponseType<ProductDto>(200)]
    [ProducesResponseType(404)]
    public async Task<ActionResult<ProductDto>> GetById(Guid id, CancellationToken ct)
    {
        var product = await service.GetByIdAsync(id, ct);
        return product is null ? NotFound() : Ok(product);
    }
}

// ━━ Minimal API — use for simple microservice endpoints ━━
// Faster startup, less overhead, no controller attributes
var products = app.MapGroup("/api/products").RequireAuthorization();

products.MapGet("/", async (IProductService svc, CancellationToken ct) =>
    Results.Ok(await svc.GetAllAsync(ct)));

products.MapGet("/{id:guid}", async (Guid id, IProductService svc, CancellationToken ct) =>
{
    var product = await svc.GetByIdAsync(id, ct);
    return product is null ? Results.NotFound() : Results.Ok(product);
});

products.MapPost("/", async (
    CreateProductRequest req,   // auto-bound from body
    IProductService svc,
    CancellationToken ct) =>
{
    var result = await svc.CreateAsync(req, ct);
    return Results.Created($"/api/products/{result.Id}", result);
});

// Placeholder types
interface IProductService
{
    Task<dynamic> GetPagedAsync(dynamic f, CancellationToken ct);
    Task<dynamic?> GetByIdAsync(Guid id, CancellationToken ct);
    Task<dynamic> GetAllAsync(CancellationToken ct);
    Task<dynamic> CreateAsync(dynamic r, CancellationToken ct);
}
record PagedResult<T>(System.Collections.Generic.List<T> Items, int Total);
record ProductDto(Guid Id, string Name);
record ProductFilter(string? Category, int Page = 1, int PageSize = 20);
record CreateProductRequest(string Name, decimal Price);