package nju.seec.helper.service.impl;

import nju.seec.helper.dao.ChooseDAO;
import nju.seec.helper.dao.CourseDAO;
import nju.seec.helper.dto.ChooseDTO;
import nju.seec.helper.dto.CourseDTO;
import nju.seec.helper.dto.LoginUser;
import nju.seec.helper.dto.modify.ModifyCourseDTO;
import nju.seec.helper.entity.Choose;
import nju.seec.helper.entity.Course;
import nju.seec.helper.service.AuthUtil;
import nju.seec.helper.service.CourseService;
import nju.seec.helper.util.EncryptUtils;
import nju.seec.helper.util.enums.ExceptionType;
import nju.seec.helper.util.exception.HelperException;
import nju.seec.helper.vo.CourseVO;
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 CourseDAO courseDAO;
    private final ChooseDAO chooseDAO;

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

    @Transactional(rollbackFor = Exception.class)
    @Override
    public CourseVO createCourse(LoginUser teacher, CourseDTO courseDTO) {
        // 检查
        checkSameCourseName(teacher.getId(), courseDTO.getName());

        Course course = new Course()
                .setTeacherId(teacher.getId())
                .setTeacherName(teacher.getName())
                .setName(courseDTO.getName())
                .setBio(courseDTO.getBio())
                .setCode(EncryptUtils.encode(courseDTO.getCode()));
        course = courseDAO.save(course);
        return new CourseVO(course);
    }

    @Override
    public CourseVO modifyCourse(LoginUser user, ModifyCourseDTO modifyCourseDTO) {
        Course course = courseDAO.findCourseById(modifyCourseDTO.getId());

        // 检查
        AuthUtil.checkDataAuth(user.getId(), course.getTeacherId(), "您无权修改该课程");
        checkSameCourseName(user.getId(), modifyCourseDTO.getName());

        course.setName(modifyCourseDTO.getName())
                .setBio(modifyCourseDTO.getBio())
                .setCode(EncryptUtils.encode(modifyCourseDTO.getCode()));
        course = courseDAO.save(course);
        return new CourseVO(course);
    }

    @Override
    public void removeCourse(LoginUser user, Integer courseId) {
        Course course = courseDAO.findCourseById(courseId);
        AuthUtil.checkDataAuth(user.getId(), course.getTeacherId(), "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, ChooseDTO chooseDTO) {
        Integer studentId = student.getId();
        if (chooseDAO.existsByStudentIdAndCourseId(studentId, chooseDTO.getCourseId())) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您已选课");
        }

        Course course = courseDAO.findCourseById(chooseDTO.getCourseId());

        if (!course.getCode().equals(EncryptUtils.encode(chooseDTO.getCode()))) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "选课码错误");
        }

        Choose choose = new Choose()
                .setCourseId(chooseDTO.getCourseId())
                .setStudentId(studentId);
        chooseDAO.save(choose);
    }

    @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> teacherGetCourses(LoginUser teacher, String key, Pageable pageable) {
        return courseDAO.findByTeacherIdAndKey(teacher.getId(), key, pageable).map(CourseVO::new);
    }

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

    /**
     * 检查同名课程
     */
    private void checkSameCourseName(Integer teacherId, String name) {
        if (courseDAO.existsByTeacherIdAndName(teacherId, name)) {
            throw HelperException.of(ExceptionType.CONFLICT, "该课程名已使用");
        }
    }
}