/**
 * UserManager - 用户管理核心模块（重构版）
 *
 * 使用 Zustand store 进行状态管理
 * 保持与旧 API 的向后兼容
 */

import type { UserDTO } from '../../types/dto';
import { authService } from '@/services/auth';
import { userCacheRepository } from '@/database';
import { useUserManagerStore } from './userStore';
import { createCacheEntry, isCacheExpired, DEFAULT_TTL } from '../utils/cache';
import { createDedupe } from '../utils/requestDedupe';

const dedupe = createDedupe(() => useUserManagerStore);

// 将 fetchCurrentUserFromAPI 的判别结果转为 User | null。
// 网络故障/认证失败时返回 null，由上层缓存兜底（避免空数据覆盖缓存）。
// 注意：UserManager 只负责缓存，不触发登出，登出由 authStore 统一处理。
async function fetchCurrentUserOrNull(): Promise<UserDTO | null> {
  const result = await authService.fetchCurrentUserFromAPI();
  return result.kind === 'user' ? result.user : null;
}

// ==================== UserManager 类 ====================

class UserManager {
  async getCurrentUser(forceRefresh = false): Promise<UserDTO | null> {
    const store = useUserManagerStore.getState();
    const entry = store.currentUserEntry;

    if (!forceRefresh && entry && !isCacheExpired(entry)) {
      return entry.data;
    }

    if (!forceRefresh && entry && isCacheExpired(entry)) {
      this.refreshCurrentUserInBackground();
      return entry.data;
    }

    if (!forceRefresh) {
      const cachedFromDb = await userCacheRepository.getCurrent();
      if (cachedFromDb) {
        const newEntry = createCacheEntry(cachedFromDb, DEFAULT_TTL.USER);
        store.setCurrentUserEntry(newEntry);
        this.refreshCurrentUserInBackground();
        return cachedFromDb;
      }
    }

    return dedupe('users:current', async () => {
      const user = await fetchCurrentUserOrNull();
      // 仅在拿到真实用户时刷新缓存；网络/认证失败时保留旧缓存，避免误清空
      if (user) {
        const newEntry = createCacheEntry(user, DEFAULT_TTL.USER);
        store.setCurrentUserEntry(newEntry);
        userCacheRepository.saveCurrent(user).catch(() => {});
        userCacheRepository.save(user).catch(() => {});
      }
      return user;
    });
  }

  private refreshCurrentUserInBackground(): void {
    dedupe('users:current:bg', async () => {
      const store = useUserManagerStore.getState();
      const user = await fetchCurrentUserOrNull();
      if (user) {
        const newEntry = createCacheEntry(user, DEFAULT_TTL.USER);
        store.setCurrentUserEntry(newEntry);
        userCacheRepository.saveCurrent(user).catch(() => {});
        userCacheRepository.save(user).catch(() => {});
      }
      return user;
    }).catch((error) => {
      console.error('[UserManager] refreshCurrentUserInBackground error:', error);
    });
  }

  async getUserById(userId: string, forceRefresh = false): Promise<UserDTO | null> {
    const store = useUserManagerStore.getState();
    const entry = store.usersMap.get(userId);

    if (!forceRefresh && entry && !isCacheExpired(entry)) {
      return entry.data;
    }

    if (!forceRefresh && entry && isCacheExpired(entry)) {
      this.refreshUserByIdInBackground(userId);
      return entry.data;
    }

    if (!forceRefresh) {
      const cachedFromDb = await userCacheRepository.get(userId);
      if (cachedFromDb) {
        const newEntry = createCacheEntry(cachedFromDb, DEFAULT_TTL.USER);
        store.setUser(userId, cachedFromDb);
        this.refreshUserByIdInBackground(userId);
        return cachedFromDb;
      }
    }

    return dedupe(`users:detail:${userId}`, async () => {
      const store = useUserManagerStore.getState();
      const user = await authService.fetchUserByIdFromAPI(userId);
      const newEntry = createCacheEntry(user, DEFAULT_TTL.USER);
      store.setUser(userId, user);

      if (user) {
        userCacheRepository.save(user).catch(() => {});
      }
      return user;
    });
  }

  private refreshUserByIdInBackground(userId: string): void {
    dedupe(`users:detail:bg:${userId}`, async () => {
      const store = useUserManagerStore.getState();
      const user = await authService.fetchUserByIdFromAPI(userId);
      const newEntry = createCacheEntry(user, DEFAULT_TTL.USER);
      store.setUser(userId, user);

      if (user) {
        userCacheRepository.save(user).catch(() => {});
      }
      return user;
    }).catch((error) => {
      console.error('[UserManager] refreshUserByIdInBackground error:', error);
    });
  }

  invalidateUsers(): void {
    useUserManagerStore.getState().invalidateAll();
  }
}

export const userManager = new UserManager();

export { UserManager };

export default userManager;