package nju.seec.helper.service.impl;

import nju.seec.helper.aspect.auth.LoginUser;
import nju.seec.helper.dao.ChooseDAO;
import nju.seec.helper.dao.CourseDAO;
import nju.seec.helper.dao.UserDAO;
import nju.seec.helper.dto.course.ChooseDTO;
import nju.seec.helper.dto.course.CourseDTO;
import nju.seec.helper.entity.Choose;
import nju.seec.helper.entity.Course;
import nju.seec.helper.enums.ExceptionType;
import nju.seec.helper.enums.UserType;
import nju.seec.helper.exception.HelperException;
import nju.seec.helper.service.CourseService;
import nju.seec.helper.util.EncryptUtils;
import nju.seec.helper.vo.CourseVO;
import nju.seec.helper.vo.UserVO;
import org.springframework.dao.DataIntegrityViolationException;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

/**
 * @author cst
 */
@Service
public class CourseServiceImpl implements CourseService {
    private final UserDAO userDAO;
    private final CourseDAO courseDAO;
    private final ChooseDAO chooseDAO;

    public CourseServiceImpl(UserDAO userDAO, CourseDAO courseDAO, ChooseDAO chooseDAO) {
        this.userDAO = userDAO;
        this.courseDAO = courseDAO;
        this.chooseDAO = chooseDAO;
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public CourseVO createCourse(LoginUser teacher, CourseDTO courseDTO) {
        try {
            return new CourseVO(
                    courseDAO.save(
                            new Course()
                                    .setTeacher(userDAO.findUserById(teacher.getId()))
                                    .setName(courseDTO.getName())
                                    .setBio(courseDTO.getBio())
                                    .setCode(EncryptUtils.encode(courseDTO.getCode()))
                    )
            );
        } catch (DataIntegrityViolationException e) {
            throw HelperException.of(ExceptionType.CONFLICT, "创建失败，请检查课程信息是否正确且不与已有课程冲突");
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public CourseVO modifyCourse(LoginUser user, Long courseId, CourseDTO courseDTO) {
        Course course = courseDAO.findCourseById(courseId);

        if (!existsUpdateAuth(user, course)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权修改该课程");
        }

        try {
            return new CourseVO(
                    courseDAO.save(
                            course.setName(courseDTO.getName())
                                    .setBio(courseDTO.getBio())
                                    .setCode(EncryptUtils.encode(courseDTO.getCode()))
                    )
            );
        } catch (DataIntegrityViolationException e) {
            throw HelperException.of(ExceptionType.CONFLICT, "修改失败，请检查课程信息是否正确且不与已有课程冲突");
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void deleteCourse(LoginUser user, Long courseId) {
        Course course = courseDAO.findCourseById(courseId);

        if (!existsUpdateAuth(user, course)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权删除该课程");
        }

        course.setDeleteAt(System.currentTimeMillis());
        courseDAO.save(course);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void chooseCourse(LoginUser student, Long courseId, ChooseDTO chooseDTO) {
        Long studentId = student.getId();

        if (chooseDAO.existsByStudentIdAndCourseId(studentId, courseId)) {
            throw HelperException.of(ExceptionType.CONFLICT, "您已选课");
        }

        if (!courseDAO.existsByIdAndCode(courseId, EncryptUtils.encode(chooseDTO.getCode()))) {
            throw HelperException.of(ExceptionType.NOT_FOUND, "选课码错误");
        }

        chooseDAO.save(
                new Choose()
                        .setCourseId(courseId)
                        .setStudentId(studentId)
        );
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void quitCourse(LoginUser user, Long courseId) {
        chooseDAO.deleteByStudentIdAndCourseId(user.getId(), courseId);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<CourseVO> getCourses(String key, Pageable pageable) {
        return courseDAO.findByKey(key, pageable).map(CourseVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<CourseVO> getCreatedCourses(LoginUser user, String key, Pageable pageable) {
        return courseDAO.findByTeacherAndNameContains(userDAO.findUserById(user.getId()), key, pageable).map(CourseVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<CourseVO> getChosenCourses(LoginUser user, String key, Pageable pageable) {
        return courseDAO.findByIdsAndKey(chooseDAO.findCourseIdsByStudentId(user.getId()), key, pageable).map(CourseVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public String getCourseCode(LoginUser user, Long courseId) {
        Course course = courseDAO.findCourseById(courseId);

        if (!existsGetAuth(user, course)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权获取该课程选课码");
        }

        return EncryptUtils.decode(course.getCode());
    }

    @Transactional(readOnly = true)
    @Override
    public CourseVO getOneCourse(Long courseId) {
        return new CourseVO(courseDAO.findCourseById(courseId));
    }

    @Transactional(readOnly = true)
    @Override
    public Page<UserVO> getChooseStudents(LoginUser user, Long courseId, String key, Pageable pageable) {
        Course course = courseDAO.findCourseById(courseId);

        if (!existsGetAuth(user, course)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权获取该课程的选课名单");
        }

        return userDAO.findByIdIn(chooseDAO.findStudentIdsByCourseId(courseId), pageable).map(UserVO::new);
    }

    @Override
    public boolean existsAddAuth(LoginUser user, Course course) {
        return user.getType() == UserType.TEACHER;
    }

    @Override
    public boolean existsDelAuth(LoginUser user, Course course) {
        return course.getTeacher().getId().equals(user.getId());
    }

    @Override
    public boolean existsUpdateAuth(LoginUser user, Course course) {
        return course.getTeacher().getId().equals(user.getId());
    }

    @Override
    public boolean existsGetAuth(LoginUser user, Course course) {
        return course.getTeacher().getId().equals(user.getId())
                || chooseDAO.existsByStudentIdAndCourseId(user.getId(), course.getId());
    }
}