package nju.seec.helper.service.impl;

import cn.hutool.core.util.StrUtil;
import lombok.SneakyThrows;
import nju.seec.helper.aspect.auth.LoginUser;
import nju.seec.helper.dao.CourseDAO;
import nju.seec.helper.dao.CourseFileDAO;
import nju.seec.helper.dto.coursefile.CourseFileDTO;
import nju.seec.helper.entity.Course;
import nju.seec.helper.entity.CourseFile;
import nju.seec.helper.enums.ExceptionType;
import nju.seec.helper.exception.HelperException;
import nju.seec.helper.service.CourseFileService;
import nju.seec.helper.service.CourseService;
import nju.seec.helper.util.OssUtils;
import nju.seec.helper.vo.CourseFileVO;
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;

/**
 * @author cst
 */
@Service
public class CourseFileServiceImpl implements CourseFileService {
    private static final String COURSE_FILE_STORE_DIR = "course_file";

    private final CourseDAO courseDAO;
    private final CourseFileDAO courseFileDAO;

    private final CourseService courseService;

    private final OssUtils ossUtils;

    public CourseFileServiceImpl(CourseDAO courseDAO, CourseFileDAO courseFileDAO, CourseService courseService, OssUtils ossUtils) {
        this.courseDAO = courseDAO;
        this.courseFileDAO = courseFileDAO;
        this.courseService = courseService;
        this.ossUtils = ossUtils;
    }

    @Transactional(rollbackFor = Exception.class)
    @SneakyThrows
    @Override
    public void uploadCourseFile(LoginUser user, CourseFileDTO courseFileDTO) {
        Course course = courseDAO.findCourseById(courseFileDTO.getCourseId());

        MultipartFile file = courseFileDTO.getFile();
        String fileName = file.getOriginalFilename();
        String objectName = getCourseFileObjectName(course.getId(), fileName);

        CourseFile courseFile = new CourseFile()
                .setCourseId(course.getId())
                .setTeacherId(user.getId())
                .setFileName(fileName)
                .setObjectName(objectName);

        if (!existsAddAuth(user, courseFile)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权上传该附件");
        }

        if (courseFileDAO.existsByCourseIdAndFileName(courseFileDTO.getCourseId(), fileName)) {
            throw HelperException.of(ExceptionType.CONFLICT, "该课程已有同名附件");
        }

        courseFileDAO.save(courseFile);

        ossUtils.upload(objectName, file.getInputStream());
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void deleteCourseFile(LoginUser user, Long courseFileId) {
        CourseFile courseFile = courseFileDAO.findCourseFileById(courseFileId);

        if (!existsDelAuth(user, courseFile)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权删除该附件");
        }

        courseFileDAO.delete(courseFile);
        ossUtils.delete(courseFile.getObjectName());
    }

    @Transactional(readOnly = true)
    @Override
    public Page<CourseFileVO> getCourseFilesByCourse(LoginUser user, Long courseId, String key, Pageable pageable) {
        if (!courseService.existsGetAuth(user, courseDAO.findCourseById(courseId))) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权访问该课程的附件");
        }

        return courseFileDAO.findByCourseIdAndFileNameContains(courseId, key, pageable).map(CourseFileVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public String getCourseFileUrl(LoginUser user, Long courseFileId) {
        CourseFile courseFile = courseFileDAO.findCourseFileById(courseFileId);

        if (!existsGetAuth(user, courseFile)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权获取该附件的链接");
        }

        return ossUtils.getUrl(courseFile.getObjectName());
    }

    private String getCourseFileObjectName(Long courseId, String fileName) {
        return StrUtil.join(File.separator, COURSE_FILE_STORE_DIR, courseId, fileName);
    }

    @Override
    public boolean existsAddAuth(LoginUser user, CourseFile courseFile) {
        return courseDAO.findCourseById(courseFile.getCourseId()).getTeacher().getId().equals(user.getId());
    }

    @Override
    public boolean existsDelAuth(LoginUser user, CourseFile courseFile) {
        return courseFile.getTeacherId().equals(user.getId());
    }

    @Override
    public boolean existsUpdateAuth(LoginUser user, CourseFile courseFile) {
        return courseFile.getTeacherId().equals(user.getId());
    }

    @Override
    public boolean existsGetAuth(LoginUser user, CourseFile courseFile) {
        return courseService.existsGetAuth(user, courseDAO.findCourseById(courseFile.getCourseId()));
    }
}