import { Injectable } from '@nestjs/common';
import * as fs from 'fs';
import * as path from 'path';

export interface User {
  id: number;
  fullName: string;
  createdAt: string;
}

@Injectable()
export class UsersService {
  private readonly filePath = path.resolve(__dirname, '..', 'data', 'users.json');

  private readUsers(): User[] {
    if (!fs.existsSync(this.filePath)) {
      return [];
    }
    const data = fs.readFileSync(this.filePath, 'utf8');
    return JSON.parse(data);
  }

  private writeUsers(users: User[]): void {
    fs.writeFileSync(this.filePath, JSON.stringify(users, null, 2), 'utf8');
  }

  findAll(): User[] {
    return this.readUsers();
  }

  create(user: User): void {
    const users = this.readUsers();
    const existingUser = users.find((u) => u.id === user.id);
    if (!existingUser) {
      users.push(user);
      this.writeUsers(users);
    }
  }
}