package nju.seec.helper.service.impl;

import com.google.common.collect.ImmutableSet;
import lombok.AllArgsConstructor;
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.SlideDTO;
import nju.seec.helper.dto.SlideFileDTO;
import nju.seec.helper.dto.SlideStateDTO;
import nju.seec.helper.entity.Course;
import nju.seec.helper.entity.Slide;
import nju.seec.helper.service.MessageService;
import nju.seec.helper.service.QuizService;
import nju.seec.helper.service.SlideService;
import nju.seec.helper.service.util.AuthUtils;
import nju.seec.helper.util.RedisCacheUtils;
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.MessageType;
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.beans.factory.annotation.Autowired;
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.File;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.TimeUnit;

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

    private final CourseDAO courseDAO;
    private final SlideDAO slideDAO;
    private final ChooseDAO chooseDAO;
    private final QuizService quizService;
    private final FileUtils fileUtils;
    private final RedisCacheUtils cacheUtils;

    private final MessageService messageService;

    @Autowired
    public SlideServiceImpl(CourseDAO courseDAO, SlideDAO slideDAO, ChooseDAO chooseDAO, FileUtils fileUtils, RedisCacheUtils cacheUtils, MessageService messageService, QuizService quizService) {
        this.courseDAO = courseDAO;
        this.slideDAO = slideDAO;
        this.chooseDAO = chooseDAO;
        this.fileUtils = fileUtils;
        this.cacheUtils = cacheUtils;
        this.messageService = messageService;
        this.quizService = quizService;
    }

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

        checkSameName(0L, slideDTO.getCourseId(), slideDTO.getName());

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

        MultipartFile file = slideDTO.getFile();
        FileInfo fileInfo = getFileInfo(file);
        slide.setPages(fileInfo.pages);
        slide.setObjectName("temp");
        slide = slideDAO.save(slide);

        String objectName = getObjectName(slide.getId(), slide.getName(), fileInfo.suffix);
        slide.setObjectName(objectName);
        slide = slideDAO.save(slide);

        fileUtils.upload(objectName, file.getInputStream());

        return new SlideVO(slide);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public SlideVO modifySlide(LoginUser user, SlideDTO slideDTO) {
        Slide slide = slideDAO.findSlideById(slideDTO.getId());
        AuthUtils.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权修改该课件");

        checkSameName(slide.getId(), slide.getCourseId(), slideDTO.getName());

        slide.setName(slideDTO.getName());
        String oldObjectName = slide.getObjectName();
        String newObjectName = getObjectName(slide.getId(), slide.getName(), oldObjectName.substring(oldObjectName.lastIndexOf('.') + 1));
        slide.setObjectName(newObjectName);
        slide = slideDAO.save(slide);

        if (!oldObjectName.equals(newObjectName)) {
            fileUtils.copy(oldObjectName, newObjectName);
            fileUtils.delete(oldObjectName);
        }

        return new SlideVO(slide);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void modifySlideState(LoginUser user, SlideStateDTO slideStateDTO) {
        Slide slide = slideDAO.findSlideById(slideStateDTO.getId());
        AuthUtils.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权修改该课件状态");

        slide.setState(slideStateDTO.getState());
        slide = slideDAO.save(slide);
        // 修改Slide状态同时推进quiz状态
        quizService.modifySlideState(slide);

        // 增加通知
        if (slide.getState() == SlideState.IN_CLASS) {
            Set<Long> studentIds = chooseDAO.findStudentIdsByCourseId(slide.getCourseId());
            messageService.createMessage(studentIds, MessageType.SLIDE_IN_CLASS, String.format("课程 [%s] 的课件 [%s] 已开课", slide.getCourseName(), slide.getName()), slide.getId());
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @SneakyThrows
    @Override
    public void modifySlideFile(LoginUser user, SlideFileDTO slideFileDTO) {
        Slide slide = slideDAO.findSlideById(slideFileDTO.getId());
        AuthUtils.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权修改该课件文件");

        MultipartFile file = slideFileDTO.getFile();
        FileInfo fileInfo = getFileInfo(file);
        slide.setPages(fileInfo.pages);

        String oldObjectName = slide.getObjectName();
        String newObjectName = getObjectName(slide.getId(), slide.getName(), fileInfo.suffix);
        slide.setObjectName(newObjectName);
        slideDAO.save(slide);

        fileUtils.upload(newObjectName, file.getInputStream());
        if (!oldObjectName.equals(newObjectName)) {
            fileUtils.delete(oldObjectName);
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void removeSlide(LoginUser user, Long slideId) {
        Slide slide = slideDAO.findSlideById(slideId);
        AuthUtils.checkDataAuth(user.getId(), slide.getTeacherId(), "您无权删除该课件");

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

    @SuppressWarnings("all")
    @SneakyThrows
    private FileInfo getFileInfo(MultipartFile file) {
        switch (Objects.requireNonNull(file.getContentType())) {
            case "application/pdf":
                // 解析页数
                PDDocument doc = PDDocument.load(file.getInputStream());
                return FileInfo.of(doc.getNumberOfPages(), "pdf");
            default:
                throw HelperException.of(ExceptionType.PARAM_ERROR, "不支持的文件类型");
        }
    }

    @AllArgsConstructor(staticName = "of")
    private static class FileInfo {
        private int pages;
        private String suffix;
    }

    private String getObjectName(Long slideId, String slideName, String suffix) {
        return SLIDE_STORE_DIR + File.separator + slideId + File.separator + slideName + "." + suffix;
    }

    @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, Long 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, Long 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课件");
        }

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

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

    /**
     * 检查同名课件
     */
    private void checkSameName(Long slideId, Long courseId, String name) {
        if (slideDAO.existsByCourseIdAndName(slideId, courseId, name)) {
            throw HelperException.of(ExceptionType.CONFLICT, "该课件名已使用");
        }
    }

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

        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;
        }
    }
}