package nju.seec.helper.service.impl;

import com.google.common.collect.ImmutableSet;
import nju.seec.helper.dao.*;
import nju.seec.helper.dto.quiz.QuizDTO;
import nju.seec.helper.dto.user.LoginUser;
import nju.seec.helper.entity.Course;
import nju.seec.helper.entity.Quiz;
import nju.seec.helper.entity.Slide;
import nju.seec.helper.service.MessageService;
import nju.seec.helper.service.QuizService;
import nju.seec.helper.service.util.AuthUtils;
import nju.seec.helper.service.util.StringUtils;
import nju.seec.helper.util.enums.*;
import nju.seec.helper.util.exception.HelperException;
import nju.seec.helper.vo.quiz.QuizVO;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;
import java.util.Set;


/**
 * @author xst
 * <p>
 * updated by cst
 */
@Service
public class QuizServiceImpl implements QuizService {
    private final SlideDAO slideDAO;
    private final QuizDAO quizDAO;
    private final QuizStudentAnswerDAO quizStudentAnswerDAO;
    private final ChooseDAO chooseDAO;
    private final CourseDAO courseDAO;
    private final UserDAO userDAO;

    private final MessageService messageService;

    @Autowired
    public QuizServiceImpl(SlideDAO slideDAO, QuizDAO quizDAO, QuizStudentAnswerDAO quizStudentAnswerDAO, ChooseDAO chooseDAO, CourseDAO courseDAO, UserDAO userDAO, MessageService messageService) {
        this.slideDAO = slideDAO;
        this.quizDAO = quizDAO;
        this.quizStudentAnswerDAO = quizStudentAnswerDAO;
        this.chooseDAO = chooseDAO;
        this.courseDAO = courseDAO;
        this.userDAO = userDAO;
        this.messageService = messageService;
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public QuizVO createQuiz(LoginUser user, QuizDTO quizDTO) {
        Slide slide = slideDAO.findSlideById(quizDTO.getSlideId());

        AuthUtils.checkDataAuth(user.getId(), slide.getTeacher().getId(), "您无权创建该课件的测试");
        checkSameName(0L, quizDTO.getSlideId(), quizDTO.getName());
        checkQuizTypeOkToSlideState(slide.getState(), quizDTO.getType());

        Quiz quiz = new Quiz()
                .setCourse(slide.getCourse())
                .setSlide(slide)
                .setTeacher(slide.getTeacher())
                .setType(quizDTO.getType())
                .setState(QuizState.getQuizStateBySlideStateAndQuizType(slide.getState(), quizDTO.getType()))
                .setName(quizDTO.getName())
                .setMaxSubmitNumber(quizDTO.getMaxSubmitTime())
                .setQuestions(quizDTO.getQuestions());

        return new QuizVO(quizDAO.save(quiz));
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public QuizVO modifyQuiz(LoginUser user, Long quizId, QuizDTO quizDTO) {
        Quiz quiz = quizDAO.findQuizById(quizId);

        AuthUtils.checkDataAuth(user.getId(), quiz.getId(), "您无权修改该测试");
        checkSubmit(quiz);

        Slide slide = quiz.getSlide();
        checkQuizTypeOkToSlideState(slide.getState(), quizDTO.getType());

        checkSameName(quiz.getId(), quizDTO.getSlideId(), quizDTO.getName());

        quiz.setType(quizDTO.getType())
                .setState(QuizState.getQuizStateBySlideStateAndQuizType(slide.getState(), quizDTO.getType()))
                .setName(quizDTO.getName())
                .setMaxSubmitNumber(quizDTO.getMaxSubmitTime())
                .setQuestions(quizDTO.getQuestions());

        return new QuizVO(quizDAO.save(quiz));
    }

    private void checkSameName(Long quizId, Long slideId, String name) {
        long exists = quizDAO.count((Specification<Quiz>) (root, query, cb) ->
                cb.and(cb.notEqual(root.get("id"), quizId),
                        cb.equal(root.get("slide").get("id"), slideId),
                        cb.equal(root.get("name"), name)
                ));
        if (exists > 0) {
            throw HelperException.of(ExceptionType.CONFLICT, "该测试名已使用");
        }
    }

    private void checkQuizTypeOkToSlideState(SlideState slideState, QuizType quizType) {
        if (!QuizType.getQuizTypesBySlideState(slideState).contains(quizType)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "课件暂时不支持创建该类型的测试，请检查课件状态");
        }
    }

    private void checkSubmit(Quiz quiz) {
        if (quizStudentAnswerDAO.existsByQuiz(quiz)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "该测试已有提交，无法修改");
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void deleteQuiz(LoginUser user, Long quizId) {
        Quiz quiz = quizDAO.findQuizById(quizId);
        AuthUtils.checkDataAuth(user.getId(), quiz.getId(), "您无权删除该测试");
        quiz.setDeleteAt(System.currentTimeMillis());
        quizDAO.save(quiz);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<QuizVO> teacherGetQuizzesBySlide(LoginUser user, Long slideId, String key, Pageable pageable) {
        return findBySlideIdAndKey(slideId, key, pageable).map(QuizVO::new);
    }

    public static final Set<QuizState> STATES_NOT_GET_BY_STUDENT_SET = ImmutableSet.of(QuizState.NOT_STARTED);

    @Transactional(readOnly = true)
    @Override
    public Page<QuizVO> studentGetQuizzesBySlide(LoginUser user, Long slideId, String key, Pageable pageable) {
        return findBySlideIdAndStateNotInAndKey(slideId, STATES_NOT_GET_BY_STUDENT_SET, key, pageable).map(QuizVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<QuizVO> studentGetQuizzesByState(LoginUser user, QuizState state, String key, Pageable pageable) {
        if (STATES_NOT_GET_BY_STUDENT_SET.contains(state)) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您暂时无法获取该状态的测试");
        }
        Set<Long> courseIds = chooseDAO.findCourseIdsByStudentId(user.getId());
        return findByCourseIdInAndStateAndKey(courseIds, state, key, pageable).map(QuizVO::new);
    }

    @Transactional(readOnly = true)
    @Override
    public QuizVO getOneQuiz(LoginUser user, Long quizId) {
        Quiz quiz = quizDAO.findQuizById(quizId);
        checkDataAccessAuth(user, quiz);
        return new QuizVO(quiz);
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void modifyQuizState(Slide slide) {
        List<Quiz> quizzes = quizDAO.findAllBySlide(slide);
        Course course = slide.getCourse();
        Set<Long> chooseStudentIds = chooseDAO.findStudentIdsByCourseId(course.getId());
        quizzes.forEach(quiz -> {
            QuizState quizState = QuizState.getQuizStateBySlideStateAndQuizType(slide.getState(), quiz.getType());
            quiz.setState(quizState);
            if (quizState == QuizState.ONGOING) {
                messageService.createMessage(chooseStudentIds, MessageType.QUIZ_NEW, String.format("[%s] - [%s] 的测试 [%s] 已开放", course.getName(), slide.getName(), quiz.getName()), slide.getId());
            }
        });
    }

    private void checkDataAccessAuth(LoginUser user, Quiz quiz) {
        HelperException forbiddenEx = HelperException.of(ExceptionType.FORBIDDEN, "您无权访问该测试");

        switch (user.getType()) {
            case TEACHER:
                break;
            case STUDENT:
                if (quiz.getState() == QuizState.NOT_STARTED) {
                    throw forbiddenEx;
                }
                break;
            default:
                throw forbiddenEx;
        }
    }

    private Page<Quiz> findByCourseIdInAndStateAndKey(Set<Long> courseIds, QuizState state, String key, Pageable pageable) {
        return quizDAO.findAll(
                (Specification<Quiz>) (root, query, cb) -> cb.and(
                        root.get("course").get("id").in(courseIds),
                        cb.equal(root.get("deleteAt"), 0L),
                        cb.equal(root.get("state"), state),
                        cb.like(root.get("name"), StringUtils.keyPattern(key))),
                pageable);
    }

    private Page<Quiz> findBySlideIdAndKey(Long slideId, String key, Pageable pageable) {
        return quizDAO.findAll(
                (Specification<Quiz>) (root, query, cb) -> cb.and(
                        cb.equal(root.get("slide").get("id"), slideId),
                        cb.equal(root.get("deleteAt"), 0L),
                        cb.like(root.get("name"), StringUtils.keyPattern(key))),
                pageable);
    }


    private Page<Quiz> findBySlideIdAndStateNotInAndKey(Long slideId, Set<QuizState> exclusiveStates, String key, Pageable pageable) {
        return quizDAO.findAll(
                (Specification<Quiz>) (root, query, cb) -> cb.and(
                        cb.equal(root.get("slide").get("id"), slideId),
                        cb.equal(root.get("deleteAt"), 0L),
                        cb.like(root.get("name"), StringUtils.keyPattern(key)),
                        cb.not(root.get("state").in(exclusiveStates))),
                pageable);
    }
}