import type { Invalidator, Subscriber, Unsubscriber } from 'svelte/store';
import type { Preference } from '../types';
import { writable, derived } from 'svelte/store';

type Nullable<T> = T | null;

interface User {
  uuid: string;
  username: string;
}

interface TokenStore {
  subscribe: (run: Subscriber<Nullable<string>>, invalidate?: Invalidator<Nullable<string>>) => Unsubscriber,
  authenticate: (newToken: string) => void,
  unauthenticate: () => void
}


interface UserStore {
  subscribe: (run: Subscriber<Nullable<User>>, invalidate?: Invalidator<Nullable<User>>) => Unsubscriber,
  setUser: (user: User) => void,
  reset: () => void
}

interface PreferenceStore {
  subscribe: (run: Subscriber<Preference>, invalidate?: Invalidator<Preference>) => Unsubscriber,
  set: (this: void, value: Preference) => void
}

function createTokenStore(): TokenStore {
  const storedToken = localStorage.getItem("token");
  const { subscribe, set } = writable<string | null>(storedToken);

  function authenticate(newToken: string): void {
    try {
      localStorage.setItem("token", newToken);
      set(newToken);
    } catch (e) {
      console.error('error', e);
    }
  }

  function unauthenticate(): void {
    localStorage.removeItem("token");
    set(null);
  }

  return {
    subscribe,
    authenticate,
    unauthenticate
  };
}

function onTokenChange($token: Nullable<string>): boolean {
  return $token ? true : false;
}

function createUserStore(): UserStore {
  const user = localStorage.getItem('user');
  const userObj: Nullable<User> = user ? JSON.parse(user) : null;
  const { subscribe, set } = writable<User | null>(userObj);

  const setUser = (user: User) => {
    localStorage.setItem('user', JSON.stringify(user));
    set(user);
  }

  const reset = () => {
    localStorage.removeItem('user');
    set(null);
  }

  return {
    subscribe,
    setUser,
    reset
  }
}


function createPreferenceStore(): PreferenceStore {
  const preferences = localStorage.getItem('preferences');
  const preferenceObj: Preference = preferences ? JSON.parse(preferences) : {
    color: "#FF0000",
    size: {
      size: 16,
      unit: 'oz'
    }
  };

  const { subscribe, set } = writable<Preference>(preferenceObj);

  return {
    subscribe,
    set
  }
}

export const token = createTokenStore();
export const authenticated = derived(token, onTokenChange);
export const user = createUserStore();
export const preferences = createPreferenceStore();