# Entities

## Purpose

The `entities` layer defines the **core domain models of the application**.

Entities represent **business objects** used throughout the system, such as `User`, `Product`, `Project`, or `Message`.

This layer contains **pure type definitions** that describe how data is structured inside the application.  
Entities are **stable, reusable models** that can be used across any layer.

```plaintext
entities/
| --- user.ts                 # { id: string; name: string; email: string }
| --- product.ts              # { id: string; name: string; price: number }
| --- message.ts              # { id: string; content: string; createdAt: string }
| --- enums.ts                # { UserRole, ProductCategory }
```

or

```plaintext
entities/
| --- user/
|    | --- interfaces.ts      # { id: string; name: string; email: string }
|    | --- types.ts           # { id: string; name: string; email: string }
|    | --- enums.ts           # { UserRole }
|    | --- rules.ts           # MIN_ALLOWED_AGE = 18
|    | --- index.ts           # export all entity types
| --- product.ts              # { id: string; name: string; price: number }
| --- message.ts              # { id: string; content: string; createdAt: string }
```

## Responsibilities

The entities layer is responsible for:

- defining **domain models**
- defining **entity-related enums or constants**
- providing **shared types used across the application**

```ts
export type User = {
  id: number;
  name: string;
  email: string;
};

export enum UserRole {
  ADMIN = "admin",
  SIMLPE_JACK = "simple_jack",
}
```