package nju.seec.helper.service.impl;

import com.google.common.collect.ImmutableSet;
import lombok.Cleanup;
import lombok.SneakyThrows;
import nju.seec.helper.dao.ChooseDAO;
import nju.seec.helper.dao.CourseDAO;
import nju.seec.helper.dao.SlideDAO;
import nju.seec.helper.dto.LoginUser;
import nju.seec.helper.dto.ModifySlideDTO;
import nju.seec.helper.dto.SlideDTO;
import nju.seec.helper.dto.SlideStateDTO;
import nju.seec.helper.entity.Course;
import nju.seec.helper.entity.Slide;
import nju.seec.helper.service.AuthUtil;
import nju.seec.helper.service.SlideService;
import nju.seec.helper.util.CacheUtils;
import nju.seec.helper.util.Consts;
import nju.seec.helper.util.FileUtils;
import nju.seec.helper.util.enums.ExceptionType;
import nju.seec.helper.util.enums.SlideState;
import nju.seec.helper.util.exception.HelperException;
import nju.seec.helper.vo.SlideVO;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.multipart.MultipartFile;

import java.io.InputStream;
import java.time.LocalDateTime;
import java.util.Objects;
import java.util.concurrent.TimeUnit;

/**
 * @author cst
 */
@Service
public class SlideServiceImpl implements SlideService {
    private static final long SLIDE_URL_LIVING_SECONDS = 20 * 60;

    private final CourseDAO courseDAO;
    private final SlideDAO slideDAO;
    private final ChooseDAO chooseDAO;

    private final FileUtils fileUtils;
    private final CacheUtils cacheUtils;

    public SlideServiceImpl(CourseDAO courseDAO, SlideDAO slideDAO, ChooseDAO chooseDAO, FileUtils fileUtils, CacheUtils cacheUtils) {
        this.courseDAO = courseDAO;
        this.slideDAO = slideDAO;
        this.chooseDAO = chooseDAO;
        this.fileUtils = fileUtils;
        this.cacheUtils = cacheUtils;
    }

    @Transactional(rollbackFor = Exception.class)
    @SneakyThrows
    @Override
    public SlideVO createSlide(LoginUser teacher, SlideDTO slideDTO) {
        Course course = courseDAO.findCourseById(slideDTO.getCourseId());
        AuthUtil.checkDataAuth(teacher.getId(), course.getTeacherId(), "您无权创建该课程的幻灯片");

        Slide slide = new Slide()
                .setCourseId(slideDTO.getCourseId())
                .setCourseName(course.getName())
                .setTeacherId(teacher.getId())
                .setTeacherName(teacher.getName())
                .setName(slideDTO.getName())
                .setState(slideDTO.getState());

        // 解析文件页数
        MultipartFile file = slideDTO.getFile();
        int pages;
        switch (Objects.requireNonNull(file.getContentType())) {
            // pdf
            case "application/pdf":
                @Cleanup InputStream fileInputStream = file.getInputStream();
                PDDocument doc = PDDocument.load(fileInputStream);
                pages = doc.getNumberOfPages();
                break;
            default:
                throw HelperException.of(ExceptionType.FORBIDDEN, "不支持的文件类型");
        }

        slide.setPages(pages);

        // 上传文件
        String objectName = fileUtils.upload(LocalDateTime.now().toString() + "-" + file.getOriginalFilename(), file.getInputStream());
        slide.setObjectName(objectName);

        return new SlideVO(slideDAO.save(slide));
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public SlideVO modifySlide(LoginUser user, ModifySlideDTO modifySlideDTO) {
        Slide slide = slideDAO.findSlideById(modifySlideDTO.getId());
        AuthUtil.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权修改该幻灯片");

        slide.setName(modifySlideDTO.getName());
        slide = slideDAO.save(slide);
        return new SlideVO(slide);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void modifySlideState(LoginUser user, SlideStateDTO slideStateDTO) {
        Slide slide = slideDAO.findSlideById(slideStateDTO.getId());
        AuthUtil.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权修改该幻灯片状态");

        slide.setState(slideStateDTO.getState());
        slideDAO.save(slide);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void removeSlide(LoginUser user, Integer slideId) {
        Slide slide = slideDAO.findSlideById(slideId);
        AuthUtil.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权删除该幻灯片");

        slide.setDeleteAt(System.currentTimeMillis());
        slideDAO.save(slide);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<SlideVO> teacherGetSlides(LoginUser teacher, String key, Pageable pageable) {
        return slideDAO.findByTeacherIdAndNameContains(teacher.getId(), key, pageable).map(SlideVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<SlideVO> teacherGetSlidesByCourse(LoginUser teacher, Integer courseId, String key, Pageable pageable) {
        return slideDAO.findByCourseIdAndTeacherIdAndNameContains(courseId, teacher.getId(), key, pageable).map(SlideVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<SlideVO> studentGetSlidesByCourse(LoginUser student, Integer courseId, String key, Pageable pageable) {
        if (!chooseDAO.existsByStudentIdAndCourseId(student.getId(), courseId)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "你无权查看该课程下的幻灯片");
        }

        return slideDAO.findByCourseIdAndStateNotInAndNameContains(courseId, ImmutableSet.of(SlideState.DRAFT), key, pageable).map(SlideVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public String getSlideUrl(LoginUser user, Integer slideId) {
        Slide slide = slideDAO.findSlideById(slideId);
        checkDataAccessAuth(user, slide);

        String url = cacheUtils.get(Consts.SLIDE_URL_CACHE_NAME, slide.getObjectName());
        if (url != null) {
            return url;
        }
        url = fileUtils.getUrl(slide.getObjectName(), SLIDE_URL_LIVING_SECONDS);
        cacheUtils.set(Consts.SLIDE_URL_CACHE_NAME, slide.getObjectName(), url, SLIDE_URL_LIVING_SECONDS, TimeUnit.SECONDS);
        return url;
    }

    @Transactional(readOnly = true)
    @Override
    public SlideVO getOneSlide(LoginUser user, Integer slideId) {
        Slide slide = slideDAO.findSlideById(slideId);
        checkDataAccessAuth(user, slide);
        return new SlideVO(slide);
    }

    private void checkDataAccessAuth(LoginUser user, Slide slide) {
        HelperException forbiddenEx = HelperException.of(ExceptionType.FORBIDDEN, "您无权访问该幻灯片");

        switch (user.getType()) {
            case TEACHER:
                if (!slide.getTeacherId().equals(user.getId())) {
                    throw forbiddenEx;
                }
                break;
            case STUDENT:
                if (!chooseDAO.existsByStudentIdAndCourseId(user.getId(), slide.getCourseId())
                        || slide.getState() == SlideState.DRAFT) {
                    throw forbiddenEx;
                }
                break;
            default:
                throw forbiddenEx;
        }
    }
}