import { Injectable } from '@nestjs/common';
import { RedisService } from '../infra/redis.service';
import { FamilyService } from './family.service';

const ONLINE_KEY_PREFIX = 'ws:user:';
const LAST_SEEN_KEY_PREFIX = 'ws:last_seen:';

@Injectable()
export class PresenceService {
  constructor(
    private readonly redis: RedisService,
    private readonly family: FamilyService
  ) {}

  async isUserOnline(userId: string) {
    const value = await this.redis.client.get(`${ONLINE_KEY_PREFIX}${userId}`);
    return value === 'online';
  }

  async getUserLastSeen(userId: string) {
    return this.redis.client.get(`${LAST_SEEN_KEY_PREFIX}${userId}`);
  }

  async getFamilyPresence(requesterId: string, groupId: string) {
    const group = await this.family.assertFamilyMember(groupId, requesterId);
    const members = await Promise.all(
      group.members.map(async (member) => {
        const online = await this.isUserOnline(member.userId);
        const lastSeenRaw = online ? null : await this.getUserLastSeen(member.userId);
        return {
          userId: member.userId,
          displayName: member.user.displayName,
          online,
          lastSeenAt: online ? new Date().toISOString() : lastSeenRaw ?? undefined
        };
      })
    );

    return {
      members,
      onlineCount: members.filter((member) => member.online).length
    };
  }
}