/**
 * 用户信息缓存服务
 * 管理用户信息的缓存和获取
 */

import type { MessageResponse, UserDTO } from '../../../types/dto';
import { api } from '../../../services/api';
import { getUserCache, saveUserCache } from '../../../services/database';
import type { IUserCacheService } from '../types';

export class UserCacheService implements IUserCacheService {
  // 正在获取用户信息的请求映射（用于去重）
  private pendingUserRequests: Map<string, Promise<UserDTO | null>> = new Map();

  /**
   * 获取用户信息（带缓存和去重）
   */
  async getSenderInfo(userId: string): Promise<UserDTO | null> {
    // 1. 先检查本地缓存
    const cachedUser = await getUserCache(userId);
    if (cachedUser) {
      return cachedUser;
    }

    // 2. 检查是否已有正在进行的请求
    const pendingRequest = this.pendingUserRequests.get(userId);
    if (pendingRequest) {
      return pendingRequest;
    }

    // 3. 发起新请求
    const request = this.fetchUserInfo(userId);
    this.pendingUserRequests.set(userId, request);

    try {
      const user = await request;
      return user;
    } finally {
      // 请求完成后清理
      this.pendingUserRequests.delete(userId);
    }
  }

  /**
   * 从服务器获取用户信息
   */
  private async fetchUserInfo(userId: string): Promise<UserDTO | null> {
    try {
      const response = await api.get<UserDTO>(`/users/${userId}`);
      if (response.code === 0 && response.data) {
        // 缓存到本地数据库
        await saveUserCache(response.data);
        return response.data;
      }
      return null;
    } catch (error) {
      console.error(`[UserCacheService] 获取用户信息失败: ${userId}`, error);
      return null;
    }
  }

  /**
   * 批量异步填充消息的 sender 信息
   * 填充完成后调用 notifyUpdate 更新内存并通知订阅者
   */
  enrichMessagesWithSenderInfo(
    conversationId: string,
    messages: MessageResponse[],
    notifyUpdate: (conversationId: string, messages: MessageResponse[]) => void
  ): void {
    // 收集所有需要查询的唯一 sender_id（排除系统用户）
    const senderIds = [...new Set(
      messages
        .filter(m => m.sender_id && m.sender_id !== '10000' && !m.sender)
        .map(m => m.sender_id)
    )];

    if (senderIds.length === 0) return;

    // 并发获取所有 sender 信息
    Promise.all(senderIds.map(id => this.getSenderInfo(id).then(user => ({ id, user }))))
      .then(results => {
        const senderMap = new Map<string, UserDTO>();
        results.forEach(({ id, user }) => {
          if (user) senderMap.set(id, user);
        });

        if (senderMap.size === 0) return;

        let changed = false;
        const updated = messages.map(m => {
          if (!m.sender && m.sender_id && senderMap.has(m.sender_id)) {
            changed = true;
            return { ...m, sender: senderMap.get(m.sender_id) };
          }
          return m;
        });

        if (!changed) return;

        // 调用回调通知更新
        notifyUpdate(conversationId, updated);
      })
      .catch(error => {
        console.error('[UserCacheService] 批量获取 sender 信息失败:', error);
      });
  }

  /**
   * 清除所有待处理的请求
   * 用于测试或需要重置的场景
   */
  reset(): void {
    this.pendingUserRequests.clear();
  }
}

// 单例导出
export const userCacheService = new UserCacheService();