import { useState, useEffect, useCallback } from 'react';

export interface User { id: string; name: string }
export interface Preferences { theme?: 'light' | 'dark' }
export interface Notification { id: string; read: boolean }
export interface Message { id: string; to: string; content: string }

export const __api = {
  fetchUser: async (): Promise<User> => ({ id: 'u1', name: 'Alice' }),
  fetchPreferences: async (_uid: string): Promise<Preferences> => ({ theme: 'light' }),
  fetchNotifications: async (_uid: string): Promise<Notification[]> => [
    { id: 'n1', read: false },
    { id: 'n2', read: false },
  ],
  fetchMessages: async (_uid: string): Promise<Message[]> => [],
  savePreferences: async (_prefs: Partial<Preferences>): Promise<void> => {},
  markRead: async (_id: string): Promise<void> => {},
  postMessage: async (to: string, content: string): Promise<Message> => ({ id: `m-${Date.now()}`, to, content }),
};

// TODO: 이 hook 을 useCurrentUser / useUserPreferences / useUserNotifications / useUserMessages 로 분리하세요.
//       이 hook 은 제거하거나 단순 wrapping 으로 남겨도 됩니다.
export function useUser() {
  const [user, setUser] = useState<User | null>(null);
  const [preferences, setPreferences] = useState<Preferences>({});
  const [notifications, setNotifications] = useState<Notification[]>([]);
  const [messages, setMessages] = useState<Message[]>([]);

  useEffect(() => {
    __api.fetchUser().then(setUser);
  }, []);

  useEffect(() => {
    if (user) {
      __api.fetchPreferences(user.id).then(setPreferences);
      __api.fetchNotifications(user.id).then(setNotifications);
      __api.fetchMessages(user.id).then(setMessages);
    }
  }, [user?.id]);

  const updatePreferences = useCallback(async (prefs: Partial<Preferences>) => {
    await __api.savePreferences(prefs);
    setPreferences((prev) => ({ ...prev, ...prefs }));
  }, []);

  const markNotificationRead = useCallback(async (id: string) => {
    await __api.markRead(id);
    setNotifications((prev) => prev.map((n) => (n.id === id ? { ...n, read: true } : n)));
  }, []);

  const sendMessage = useCallback(async (to: string, content: string) => {
    const msg = await __api.postMessage(to, content);
    setMessages((prev) => [...prev, msg]);
  }, []);

  return { user, preferences, notifications, messages, updatePreferences, markNotificationRead, sendMessage };
}