import { create } from 'zustand';
import { getUnreadCount, listMessages, markRead, type MessageInfo } from '../api/messages';

interface MessageState {
  unreadCount: number;
  recentMessages: MessageInfo[];
  fetchUnreadCount: () => Promise<void>;
  fetchRecentMessages: () => Promise<void>;
  markAsRead: (id: string) => Promise<void>;
  connectSSE: () => () => void;
}

// 请求去重：记录正在进行的请求，防止并发重复调用
let unreadCountPromise: Promise<void> | null = null;
let recentMessagesPromise: Promise<void> | null = null;

export const useMessageStore = create<MessageState>((set, get) => ({
  unreadCount: 0,
  recentMessages: [],

  fetchUnreadCount: async () => {
    // 如果已有进行中的请求，复用该 Promise
    if (unreadCountPromise) {
      await unreadCountPromise;
      return;
    }
    unreadCountPromise = (async () => {
      try {
        const result = await getUnreadCount();
        set({ unreadCount: result.count });
      } catch {
        // 静默失败，不影响用户体验
      } finally {
        unreadCountPromise = null;
      }
    })();
    await unreadCountPromise;
  },

  fetchRecentMessages: async () => {
    if (recentMessagesPromise) {
      await recentMessagesPromise;
      return;
    }
    recentMessagesPromise = (async () => {
      try {
        const result = await listMessages({ page: 1, page_size: 5 });
        set({ recentMessages: result.data });
      } catch {
        // 静默失败
      } finally {
        recentMessagesPromise = null;
      }
    })();
    await recentMessagesPromise;
  },

  markAsRead: async (id: string) => {
    const prev = { unreadCount: get().unreadCount, recentMessages: get().recentMessages };
    set((state) => ({
      unreadCount: Math.max(0, state.unreadCount - 1),
      recentMessages: state.recentMessages.map((m) =>
        m.id === id ? { ...m, is_read: true } : m,
      ),
    }));
    try {
      await markRead(id);
    } catch {
      set({ unreadCount: prev.unreadCount, recentMessages: prev.recentMessages });
    }
  },

  connectSSE: () => {
    const baseUrl = import.meta.env.VITE_API_BASE_URL || '/api/v1';
    const token = localStorage.getItem('token');
    if (!token) return () => {};

    const url = `${baseUrl}/messages/stream?token=${encodeURIComponent(token)}`;
    const es = new EventSource(url);

    es.addEventListener('message', () => {
      get().fetchUnreadCount();
      get().fetchRecentMessages();
    });

    es.addEventListener('alert', () => {
      get().fetchUnreadCount();
    });

    es.addEventListener('vital_update', () => {
      // 体征数据更新事件 — 预留：未来可触发趋势图刷新
    });

    es.onerror = () => {
      // SSE 连接断开时 EventSource 会自动重连
    };

    return () => {
      es.close();
    };
  },
}));