import { User } from '../types/User';

const BASE = 'https://khofmann.userpage.fu-berlin.de/phpCourse/exam/api/';

let instance: ApiImpl;

class ApiImpl {
  private token: string = '';

  constructor() {
    if (instance) {
      throw new Error('New instance cannot be created!!');
    }

    instance = this;
  }

  public logIn = async (email: string, password: string): Promise<User> => {
    const { user, token } = await (await this.post('login', { email, password })).json();
    this.token = token;

    return user;
  };

  public logOut = async (): Promise<boolean> => {
    return await (await this.postAuth('logout')).json();
  };

  private post = async (
    endpoint: string,
    body: Record<string, unknown> | undefined = undefined,
    headers: HeadersInit | undefined = undefined
  ) => {
    const response = await fetch(`${BASE}${endpoint}`, {
      mode: 'cors',
      method: 'post',
      headers,
      body: JSON.stringify(body),
    });
    if (response.ok) return response;
    throw await response.json();
  };

  private postAuth = async (
    endpoint: string,
    body: Record<string, unknown> | undefined = undefined,
    headers: HeadersInit | undefined = undefined
  ) => {
    const response = await fetch(`${BASE}${endpoint}`, {
      mode: 'cors',
      method: 'post',
      headers: { token: this.token, ...headers },
      body: JSON.stringify(body),
    });
    if (response.ok) return response;
    throw await response.json();
  };
}

const Api = new ApiImpl();
export default Api;