package com.tourguide.modules.system.service;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.tourguide.common.exception.BusinessException;
import com.tourguide.modules.system.dto.GuideNotificationResponse;
import com.tourguide.modules.system.entity.GuideNoticeRead;
import com.tourguide.modules.system.entity.SystemNotice;
import com.tourguide.modules.system.mapper.GuideNoticeReadMapper;
import com.tourguide.modules.system.mapper.SystemNoticeMapper;
import org.springframework.stereotype.Service;

import java.time.LocalDateTime;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

@Service
public class GuideNotificationService {
    private final SystemNoticeMapper noticeMapper;
    private final GuideNoticeReadMapper readMapper;

    public GuideNotificationService(SystemNoticeMapper noticeMapper, GuideNoticeReadMapper readMapper) {
        this.noticeMapper = noticeMapper;
        this.readMapper = readMapper;
    }

    public long unreadCount(Long guideId) {
        List<SystemNotice> notices = publishedNotices();
        if (notices.isEmpty()) return 0L;
        Set<Long> readIds = readNoticeIds(guideId, notices);
        return notices.stream().filter(notice -> !readIds.contains(notice.getId())).count();
    }

    public List<GuideNotificationResponse> list(Long guideId) {
        List<SystemNotice> notices = publishedNotices();
        Set<Long> readIds = readNoticeIds(guideId, notices);
        return notices.stream()
                .map(notice -> new GuideNotificationResponse(notice, readIds.contains(notice.getId())))
                .collect(Collectors.toList());
    }

    public void markRead(Long guideId, Long noticeId) {
        SystemNotice notice = noticeMapper.selectOne(new LambdaQueryWrapper<SystemNotice>()
                .eq(SystemNotice::getId, noticeId)
                .eq(SystemNotice::getStatus, 1)
                .last("LIMIT 1"));
        if (notice == null) throw new BusinessException(404, "Notification not found");
        Long count = readMapper.selectCount(new LambdaQueryWrapper<GuideNoticeRead>()
                .eq(GuideNoticeRead::getGuideId, guideId)
                .eq(GuideNoticeRead::getNoticeId, noticeId));
        if (count > 0) return;
        GuideNoticeRead read = new GuideNoticeRead();
        read.setGuideId(guideId);
        read.setNoticeId(noticeId);
        read.setReadAt(LocalDateTime.now());
        readMapper.insert(read);
    }

    private List<SystemNotice> publishedNotices() {
        return noticeMapper.selectList(new LambdaQueryWrapper<SystemNotice>()
                .eq(SystemNotice::getStatus, 1)
                .isNotNull(SystemNotice::getPublishTime)
                .le(SystemNotice::getPublishTime, LocalDateTime.now())
                .orderByDesc(SystemNotice::getPublishTime));
    }

    private Set<Long> readNoticeIds(Long guideId, List<SystemNotice> notices) {
        if (notices.isEmpty()) return Collections.emptySet();
        List<Long> noticeIds = notices.stream().map(SystemNotice::getId).collect(Collectors.toList());
        return readMapper.selectList(new LambdaQueryWrapper<GuideNoticeRead>()
                        .eq(GuideNoticeRead::getGuideId, guideId)
                        .in(GuideNoticeRead::getNoticeId, noticeIds))
                .stream().map(GuideNoticeRead::getNoticeId).collect(Collectors.toSet());
    }
}