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

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.tcm.training.admin.app.home.vo.AppHomeFeaturedContentVO;
import com.tcm.training.admin.app.home.vo.AppHomeFeaturedHealthCourseVO;
import com.tcm.training.admin.app.home.vo.AppHomeFeaturedHealthPopularizationVO;
import com.tcm.training.admin.live.entity.HealthCourse;
import com.tcm.training.admin.live.entity.HealthPopularization;
import com.tcm.training.admin.live.entity.LiveCourseCategory;
import com.tcm.training.admin.live.mapper.HealthCourseMapper;
import com.tcm.training.admin.live.mapper.HealthPopularizationMapper;
import com.tcm.training.admin.live.mapper.LiveCourseCategoryMapper;
import org.springframework.stereotype.Service;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * APP 首页精选课程介绍模块聚合服务。
 */
@Service
public class AppHomeFeaturedContentService {

    private static final int STATUS_ENABLED = 1;
    private static final int HOME_RECOMMEND_ENABLED = 1;
    private final HealthCourseMapper healthCourseMapper;
    private final HealthPopularizationMapper healthPopularizationMapper;
    private final LiveCourseCategoryMapper liveCourseCategoryMapper;

    /**
     * 注入首页精选模块所需的课程、科普与分类查询能力。
     */
    public AppHomeFeaturedContentService(HealthCourseMapper healthCourseMapper,
                                         HealthPopularizationMapper healthPopularizationMapper,
                                         LiveCourseCategoryMapper liveCourseCategoryMapper) {
        this.healthCourseMapper = healthCourseMapper;
        this.healthPopularizationMapper = healthPopularizationMapper;
        this.liveCourseCategoryMapper = liveCourseCategoryMapper;
    }

    /**
     * 查询 APP 首页精选课程介绍模块数据。
     */
    public AppHomeFeaturedContentVO getFeaturedContent() {
        AppHomeFeaturedContentVO vo = new AppHomeFeaturedContentVO();
        List<HealthCourse> healthCourses = loadHomeRecommendedHealthCourses();
        vo.setHealthCourses(toHealthCourseCards(healthCourses));
        vo.setHealthPopularizations(toPopularizationCards(loadHomeRecommendedPopularizations()));
        return vo;
    }

    /**
     * 查询首页推荐的养生课程。
     */
    private List<HealthCourse> loadHomeRecommendedHealthCourses() {
        List<HealthCourse> records = healthCourseMapper.selectList(new LambdaQueryWrapper<HealthCourse>()
                .eq(HealthCourse::getDeleted, 0)
                .eq(HealthCourse::getStatus, STATUS_ENABLED)
                .eq(HealthCourse::getIsHomeRecommend, HOME_RECOMMEND_ENABLED)
                .orderByDesc(HealthCourse::getSort)
                .orderByDesc(HealthCourse::getId));
        return records == null ? Collections.<HealthCourse>emptyList() : records;
    }

    /**
     * 查询首页推荐的健康科普内容。
     */
    private List<HealthPopularization> loadHomeRecommendedPopularizations() {
        List<HealthPopularization> records = healthPopularizationMapper.selectList(new LambdaQueryWrapper<HealthPopularization>()
                .eq(HealthPopularization::getDeleted, 0)
                .eq(HealthPopularization::getStatus, STATUS_ENABLED)
                .eq(HealthPopularization::getIsHomeRecommend, HOME_RECOMMEND_ENABLED)
                .orderByAsc(HealthPopularization::getSort)
                .orderByDesc(HealthPopularization::getId));
        return records == null ? Collections.<HealthPopularization>emptyList() : records;
    }

    /**
     * 将首页推荐养生课程转换为首页卡片响应。
     */
    private List<AppHomeFeaturedHealthCourseVO> toHealthCourseCards(List<HealthCourse> courses) {
        if (courses == null || courses.isEmpty()) {
            return Collections.emptyList();
        }
        Map<Long, String> categoryNameMap = loadCategoryNameMap(courses);
        List<AppHomeFeaturedHealthCourseVO> result =
                new ArrayList<AppHomeFeaturedHealthCourseVO>(courses.size());
        for (HealthCourse course : courses) {
            AppHomeFeaturedHealthCourseVO vo = new AppHomeFeaturedHealthCourseVO();
            vo.setId(course.getId());
            vo.setTitle(trimToEmpty(course.getTitle()));
            vo.setCoverImage(trimToEmpty(course.getCoverImg()));
            vo.setLevelName(categoryNameMap.get(course.getLevelCategoryId()));
            vo.setDifficultyName(categoryNameMap.get(course.getDifficultyCategoryId()));
            vo.setSalePrice(course.getSalePrice() == null ? BigDecimal.ZERO : course.getSalePrice());
            vo.setLearnUserCount(defaultNumber(course.getLearnUserCount()));
            result.add(vo);
        }
        return result;
    }

    /**
     * 批量加载首页课程卡片需要展示的分类名称。
     */
    private Map<Long, String> loadCategoryNameMap(List<HealthCourse> courses) {
        List<Long> categoryIds = new ArrayList<Long>(courses.size() * 2);
        for (HealthCourse course : courses) {
            addCategoryId(categoryIds, course.getLevelCategoryId());
            addCategoryId(categoryIds, course.getDifficultyCategoryId());
        }
        if (categoryIds.isEmpty()) {
            return Collections.emptyMap();
        }
        List<LiveCourseCategory> categories = liveCourseCategoryMapper.selectList(new LambdaQueryWrapper<LiveCourseCategory>()
                .in(LiveCourseCategory::getId, categoryIds)
                .eq(LiveCourseCategory::getDeleted, 0));
        Map<Long, String> nameMap = new HashMap<Long, String>(categories.size());
        for (LiveCourseCategory category : categories) {
            nameMap.put(category.getId(), trimToEmpty(category.getName()));
        }
        return nameMap;
    }

    /**
     * 向分类主键列表中追加有效主键，避免空值干扰批量查询。
     */
    private void addCategoryId(List<Long> categoryIds, Long categoryId) {
        if (categoryId != null && !categoryIds.contains(categoryId)) {
            categoryIds.add(categoryId);
        }
    }

    /**
     * 将首页推荐健康科普转换为首页宫格卡片响应。
     */
    private List<AppHomeFeaturedHealthPopularizationVO> toPopularizationCards(List<HealthPopularization> items) {
        if (items == null || items.isEmpty()) {
            return Collections.emptyList();
        }
        List<AppHomeFeaturedHealthPopularizationVO> result =
                new ArrayList<AppHomeFeaturedHealthPopularizationVO>(items.size());
        for (HealthPopularization item : items) {
            AppHomeFeaturedHealthPopularizationVO vo = new AppHomeFeaturedHealthPopularizationVO();
            vo.setId(item.getId());
            vo.setTitle(trimToEmpty(item.getTitle()));
            vo.setCoverImage(trimToEmpty(item.getCoverImg()));
            vo.setContentType(item.getContentType());
            vo.setClickCount(defaultNumber(item.getClickCount()));
            result.add(vo);
        }
        return result;
    }

    /**
     * 兜底空数字字段，避免前端展示出现空值。
     */
    private Integer defaultNumber(Integer value) {
        return value == null ? 0 : value;
    }

    /**
     * 将可空文本转换为前端可直接消费的空字符串。
     */
    private String trimToEmpty(String value) {
        if (value == null) {
            return "";
        }
        String trimmed = value.trim();
        return trimmed.isEmpty() ? "" : trimmed;
    }
}