horse-minimal-api

Development

Guide for building lightweight, low-boilerplate, and rapid HTTP services (Minimal APIs) in Horse.

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Horse Minimal API

For focused microservices, mock APIs, or rapid prototyping, you can leverage Horse's lightweight routing and configuration DSL to build complete HTTP services in a single file with minimal boilerplate.

1. Single-File Bootstrap Design (Delphi)

A Minimal API structures all route registrations, basic logic, and middleware imports directly within the main .dpr bootstrap file using inline anonymous procedures:

program MinimalAPI;

{$APPTYPE CONSOLE}

uses
  System.SysUtils,
  System.JSON,
  Horse,
  Horse.Jhonson;

begin
  // 1. Fluent Middleware Configuration
  THorse.Use(Jhonson);

  // 2. Inline Route Mappings
  THorse.Get('/ping',
    procedure(Req: THorseRequest; Res: THorseResponse)
    begin
      Res.Send('pong');
    end);

  THorse.Get('/hello/:name',
    procedure(Req: THorseRequest; Res: THorseResponse)
    begin
      Res.Send('Hello, ' + Req.Params.Field('name').AsString + '!');
    end);

  // 3. Fast JSON response
  THorse.Get('/status',
    procedure(Req: THorseRequest; Res: THorseResponse)
    var
      LStatus: TJSONObject;
    begin
      LStatus := TJSONObject.Create(TJSONPair.Create('status', 'online'));
      Res.Send(LStatus); // Johnson takes ownership
    end);

  // 4. Port Listening
  THorse.Listen(9000);
end.

2. Best Practices for Minimal APIs

Although Minimal APIs promote rapid development, follow these principles to avoid "spaghetti code":

Extract Complex Handlers: If a route handler exceeds 25 lines of code or requires database calls, do not write it inline. Extract it to a local unit procedure.
Use Radix Router: Opt-in to THorse.UseRadixRouter; to ensure maximum matching speed if your API contains path parameters.
Keep it Focused: A Minimal API should serve a single responsibility (Microservice). If you need to manage multiple domains (e.g. Users, Products, Invoices) in the same project, migrate to modular controllers.

3. When to Transition to MVC Architecture

Transition from a Minimal API to a structured MVC/Modular architecture when:

You start mixing database logic (queries) and HTML rendering/formatting inside the .dpr file.
Your project grows beyond 10 HTTP endpoints.
You need to reuse database layers across multiple CLI, daemon, or GUI applications.
You need to write structured unit/integration tests without bootstrap coupling.