# UsersService

**Kind:** Service

**Source:** [`atloria-monorepo/apps/parser-orchestrator/test/fixtures/sample-projects/fullstack-nextjs-nestjs/backend/src/users/users.service.ts`](https://github.com/sherkety/atloria/blob/main/atloria-monorepo/apps/parser-orchestrator/test/fixtures/sample-projects/fullstack-nextjs-nestjs/backend/src/users/users.service.ts#L15)

`UsersService` encapsulates user-related backend operations for the NestJS application. It provides methods for retrieving, creating, updating, and deleting users, as well as accessing user relationships such as posts and followers.

## Methods

| Method | Signature | Returns |
|---|---|---|
| `findAll` | `findAll(paginationQuery: PaginationQueryDto)` | `unknown` |
| `findOne` | `findOne(id: string)` | `unknown` |
| `findByEmail` | `findByEmail(email: string)` | `unknown` |
| `create` | `create(createUserDto: CreateUserDto)` | `unknown` |
| `update` | `update(id: string, updateUserDto: UpdateUserDto)` | `unknown` |
| `remove` | `remove(id: string)` | `unknown` |
| `getUserPosts` | `getUserPosts(userId: string)` | `unknown` |
| `getFollowers` | `getFollowers(userId: string)` | `unknown` |

## Dependencies

- `PrismaService`
- `EventEmitter2`

## Where it refuses work

- `UsersService` stops the work with `NotFoundException` when `!user`.
- `UsersService` stops the work with `ConflictException` when `existingUser` — “User with this email already exists”.

## Diagram

```mermaid
sequenceDiagram
    participant Controller as UsersController
    participant Service as UsersService
    participant Database as Data Layer

    Controller->>Service: findOne(userId)
    Service->>Database: Query user by ID
    Database-->>Service: User record
    Service-->>Controller: User response

    Controller->>Service: getUserPosts(userId)
    Service->>Database: Query user's posts
    Database-->>Service: Posts collection
    Service-->>Controller: Posts response
```

## Usage

```ts
import { Injectable } from '@nestjs/common';
import { UsersService } from './users.service';

@Injectable()
export class ProfileService {
  constructor(private readonly usersService: UsersService) {}

  async getProfile(email: string) {
    const user = await this.usersService.findByEmail(email);

    if (!user) {
      return null;
    }

    const [posts, followers] = await Promise.all([
      this.usersService.getUserPosts(user.id),
      this.usersService.getFollowers(user.id),
    ]);

    return {
      user,
      posts,
      followers,
    };
  }
}
```

## AI Coding Instructions

- Keep user persistence and relationship queries inside `UsersService`; controllers should delegate business operations to the service.
- Use `findByEmail()` before user creation when email uniqueness must be enforced.
- Ensure `findOne()` and `findByEmail()` handle missing users consistently with the application's error-handling conventions.
- Prefer `getUserPosts()` and `getFollowers()` over duplicating relation-query logic in other services.
- Validate and sanitize create/update payloads through DTOs before calling `create()` or `update()`.

## Relationships

- DEPENDS_ON → `PrismaService`
- DEPENDS_ON → `eventemitter2`

## Referenced By

- `UsersController` (DEPENDS_ON)
- `UsersModule` (MODULE_PROVIDES)
- `UsersModule` (MODULE_EXPORTS)