package com.tcm.training.admin.app.home.service;

import cn.hutool.core.util.StrUtil;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.tcm.training.admin.app.live.support.AppLiveCourseDisplaySupport;
import com.tcm.training.admin.app.home.vo.AppHomeLiveCourseVO;
import com.tcm.training.admin.live.entity.LiveCourse;
import com.tcm.training.admin.live.entity.LiveSession;
import com.tcm.training.admin.live.mapper.LiveCourseMapper;
import com.tcm.training.admin.live.mapper.LiveSessionMapper;
import org.springframework.stereotype.Service;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * APP 首页养生直播聚合服务。
 */
@Service
public class AppHomeLiveCourseService {

    private static final int COURSE_STATUS_ENABLED = 1;
    private static final long NEXT_START_DELAY_MINUTES = 10L;
    private static final int HOME_CARD_LIMIT = 2;
    private static final DateTimeFormatter START_TIME_FORMATTER = DateTimeFormatter.ofPattern("MM月dd日 HH:mm 开播");

    private final LiveCourseMapper liveCourseMapper;
    private final LiveSessionMapper liveSessionMapper;
    private final AppLiveCourseDisplaySupport appLiveCourseDisplaySupport;

    /**
     * 注入首页直播所需的课程与场次查询能力。
     */
    public AppHomeLiveCourseService(LiveCourseMapper liveCourseMapper,
                                    LiveSessionMapper liveSessionMapper,
                                    AppLiveCourseDisplaySupport appLiveCourseDisplaySupport) {
        this.liveCourseMapper = liveCourseMapper;
        this.liveSessionMapper = liveSessionMapper;
        this.appLiveCourseDisplaySupport = appLiveCourseDisplaySupport;
    }

    /**
     * 查询 APP 首页展示的养生直播卡片。
     */
    public List<AppHomeLiveCourseVO> listHomeLiveCourses() {
        List<LiveCourse> courses = liveCourseMapper.selectList(new LambdaQueryWrapper<LiveCourse>()
                .eq(LiveCourse::getDeleted, 0)
                .eq(LiveCourse::getStatus, COURSE_STATUS_ENABLED)
                .orderByDesc(LiveCourse::getId));
        if (courses == null || courses.isEmpty()) {
            return Collections.emptyList();
        }

        Map<Long, List<LiveSession>> sessionMap = loadSessionMap(courses);
        LocalDateTime now = LocalDateTime.now();
        List<HomeLiveCourseCard> cards = new ArrayList<HomeLiveCourseCard>(courses.size());
        for (LiveCourse course : courses) {
            cards.add(buildHomeCard(course, sessionMap.get(course.getId()), now));
        }
        cards.sort(new Comparator<HomeLiveCourseCard>() {
            @Override
            public int compare(HomeLiveCourseCard left, HomeLiveCourseCard right) {
                return compareCards(left, right);
            }
        });

        List<AppHomeLiveCourseVO> result = new ArrayList<AppHomeLiveCourseVO>(Math.min(cards.size(), HOME_CARD_LIMIT));
        for (int i = 0; i < cards.size() && i < HOME_CARD_LIMIT; i++) {
            result.add(cards.get(i).getCard());
        }
        return result;
    }

    /**
     * 批量加载首页直播课程的全部场次。
     */
    private Map<Long, List<LiveSession>> loadSessionMap(List<LiveCourse> courses) {
        List<Long> courseIds = new ArrayList<Long>(courses.size());
        for (LiveCourse course : courses) {
            courseIds.add(course.getId());
        }
        List<LiveSession> sessions = liveSessionMapper.selectList(new LambdaQueryWrapper<LiveSession>()
                .in(LiveSession::getLiveCourseId, courseIds)
                .eq(LiveSession::getDeleted, 0)
                .orderByAsc(LiveSession::getStartTime)
                .orderByAsc(LiveSession::getId));
        return appLiveCourseDisplaySupport.groupSessionsByCourseId(sessions);
    }

    /**
     * 根据课程与场次快照构造首页直播卡片。
     */
    private HomeLiveCourseCard buildHomeCard(LiveCourse course, List<LiveSession> sessions, LocalDateTime now) {
        HomeLiveCourseCard homeCard = new HomeLiveCourseCard();
        AppHomeLiveCourseVO card = new AppHomeLiveCourseVO();
        String coverImage = appLiveCourseDisplaySupport.trimToNull(course.getCoverImg());
        String liveImage = appLiveCourseDisplaySupport.resolveLiveImage(course);
        card.setCourseId(course.getId());
        card.setTitle(appLiveCourseDisplaySupport.trimToNull(course.getTitle()));
        card.setCoverImage(coverImage);
        card.setLiveImage(liveImage);
        card.setHasPassword(StrUtil.isNotBlank(course.getPassword()));
        homeCard.setCard(card);

        AppLiveCourseDisplaySupport.CourseDisplaySnapshot snapshot =
                appLiveCourseDisplaySupport.resolveDisplay(sessions, now, NEXT_START_DELAY_MINUTES);
        LiveSession currentSession = snapshot.getCurrentSession();
        if (currentSession != null) {
            card.setDisplayStatus(AppLiveCourseDisplaySupport.DISPLAY_STATUS_LIVING);
            card.setDisplayStatusText("直播中");
            card.setDisplayImage(appLiveCourseDisplaySupport.resolveLivingDisplayImage(coverImage, liveImage));
            card.setCurrentSessionId(currentSession.getId());
            card.setVideoUrl(appLiveCourseDisplaySupport.trimToNull(currentSession.getVideoUrl()));
            homeCard.setStatusRank(0);
            return homeCard;
        }

        homeCard.setLatestEndedAt(snapshot.getLatestEndedAt());
        if (snapshot.isEndedCooldown()) {
            card.setDisplayStatus(AppLiveCourseDisplaySupport.DISPLAY_STATUS_ENDED);
            card.setDisplayStatusText("已结束");
            card.setDisplayImage(appLiveCourseDisplaySupport.resolveStaticDisplayImage(coverImage, liveImage));
            homeCard.setStatusRank(2);
            return homeCard;
        }

        LiveSession nextSession = snapshot.getNextSession();
        if (nextSession != null) {
            card.setDisplayStatus(AppLiveCourseDisplaySupport.DISPLAY_STATUS_NOT_STARTED);
            card.setNextStartTime(nextSession.getStartTime());
            card.setDisplayStatusText(formatNextStartTime(nextSession.getStartTime()));
            card.setDisplayImage(appLiveCourseDisplaySupport.resolveStaticDisplayImage(coverImage, liveImage));
            homeCard.setStatusRank(1);
            homeCard.setNextStartTime(nextSession.getStartTime());
            return homeCard;
        }

        card.setDisplayStatus(AppLiveCourseDisplaySupport.DISPLAY_STATUS_ENDED);
        card.setDisplayStatusText("已结束");
        card.setDisplayImage(appLiveCourseDisplaySupport.resolveStaticDisplayImage(coverImage, liveImage));
        homeCard.setStatusRank(2);
        return homeCard;
    }

    /**
     * 将开播时间格式化为首页展示文案。
     */
    private String formatNextStartTime(LocalDateTime startTime) {
        if (startTime == null) {
            return "已结束";
        }
        return START_TIME_FORMATTER.format(startTime);
    }

    /**
     * 对首页直播卡片执行统一排序。
     */
    private int compareCards(HomeLiveCourseCard left, HomeLiveCourseCard right) {
        int rankCompare = Integer.compare(left.getStatusRank(), right.getStatusRank());
        if (rankCompare != 0) {
            return rankCompare;
        }

        if (left.getStatusRank() == 1) {
            int nextStartCompare = appLiveCourseDisplaySupport.compareSessionTime(left.getNextStartTime(), right.getNextStartTime());
            if (nextStartCompare != 0) {
                return nextStartCompare;
            }
        }

        if (left.getStatusRank() == 2) {
            int endedCompare = appLiveCourseDisplaySupport.compareSessionTime(right.getLatestEndedAt(), left.getLatestEndedAt());
            if (endedCompare != 0) {
                return endedCompare;
            }
        }

        return Long.compare(right.getCard().getCourseId(), left.getCard().getCourseId());
    }

    /**
     * 首页直播卡片排序中间态。
     */
    private static class HomeLiveCourseCard {

        private AppHomeLiveCourseVO card;
        private int statusRank;
        private LocalDateTime nextStartTime;
        private LocalDateTime latestEndedAt;

        /**
         * 获取首页直播卡片响应。
         */
        public AppHomeLiveCourseVO getCard() {
            return card;
        }

        /**
         * 设置首页直播卡片响应。
         */
        public void setCard(AppHomeLiveCourseVO card) {
            this.card = card;
        }

        /**
         * 获取状态优先级。
         */
        public int getStatusRank() {
            return statusRank;
        }

        /**
         * 设置状态优先级。
         */
        public void setStatusRank(int statusRank) {
            this.statusRank = statusRank;
        }

        /**
         * 获取下一次开播时间。
         */
        public LocalDateTime getNextStartTime() {
            return nextStartTime;
        }

        /**
         * 设置下一次开播时间。
         */
        public void setNextStartTime(LocalDateTime nextStartTime) {
            this.nextStartTime = nextStartTime;
        }

        /**
         * 获取最近结束时间。
         */
        public LocalDateTime getLatestEndedAt() {
            return latestEndedAt;
        }

        /**
         * 设置最近结束时间。
         */
        public void setLatestEndedAt(LocalDateTime latestEndedAt) {
            this.latestEndedAt = latestEndedAt;
        }
    }
}