Todo API — C Clean Architecture

A RESTful To-Do list API built with C, following Clean Architecture principles with an in-memory database. Uses only POSIX sockets (no external dependencies).

Architecture

src/
├── entities/        Pure domain model (Todo)
├── interfaces/      Repository contract
├── usecases/        Business logic (CRUD)
├── infrastructure/  In-memory repository
└── adapters/        HTTP handlers

Each layer has a single responsibility:

Layer	Responsibility
entities/	Pure domain model (Todo)
interfaces/	Repository contract
usecases/	Business logic (CRUD)
infrastructure/	In-memory repository
adapters/	HTTP handlers

API Endpoints

Method	Endpoint	Description	Status
GET	/todos	List all todos	200
POST	/todos	Create a todo	201
GET	/todos/{id}	Get by ID	200
PUT	/todos/{id}	Update a todo	200
DELETE	/todos/{id}	Delete a todo	204

Todo Object

{
  "id": 1,
  "title": "Buy groceries",
  "completed": false,
  "created_at": "2026-03-12T11:00:00Z"
}

Requirements

• GCC or Clang
• POSIX-compatible system (Linux / macOS)

Setup & Run

make run

Server runs on http://localhost:8080.

Testing

# Unit tests
make test

# Functional tests (requires a running server on port 8080)
make functional-test