Architecture Patterns

export class UserService {
  private backendUrl: string;

  constructor(backendUrl: string) {
    this.backendUrl = backendUrl;
  }

  async register(data: RegisterDto, bearerToken?: string) {
    // Call real backend API with bearer token forwarding
    const response = await fetch(`${this.backendUrl}/api/users/register`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        ...(bearerToken && { 'Authorization': `Bearer ${bearerToken}` })
      },
      body: JSON.stringify(data)
    });

    if (!response.ok) {
      throw new Error('Backend registration failed');
    }

    const user = await response.json();

    // Transform backend data for frontend consumption
    return {
      id: user.id,
      email: user.email,
      displayName: user.firstName + ' ' + user.lastName, // Computed
      initials: (user.firstName[0] + user.lastName[0]).toUpperCase(), // UI-specific
      avatarColor: this.generateAvatarColor(user.id) // UI-specific
    };
  }

  private generateAvatarColor(id: number): string {
    const colors = ['#FF6B6B', '#4ECDC4', '#45B7D1', '#FFA07A'];
    return colors[id % colors.length];
  }
}

import { Hono } from 'hono';
import { UserService } from '../services/UserService';
import { env } from '../config/env';

const app = new Hono();
const userService = new UserService(env.BACKEND_API_URL);

app.post('/register', async (c) => {
  // Extract data and bearer token from request
  const data = await c.req.json();
  const bearerToken = c.req.header('Authorization')?.replace('Bearer ', '');

  // Just call the service - all logic is there
  const user = await userService.register(data, bearerToken);

  return c.json({ user }, 201);
});

export default app;