package nju.seec.helper.service.impl;

import com.google.common.collect.Maps;
import nju.seec.helper.aspect.auth.LoginUser;
import nju.seec.helper.dao.QuizDAO;
import nju.seec.helper.dao.QuizStudentAnswerDAO;
import nju.seec.helper.dao.UserDAO;
import nju.seec.helper.dto.quiz.QuizStudentAnswerDTO;
import nju.seec.helper.entity.Quiz;
import nju.seec.helper.entity.QuizStudentAnswer;
import nju.seec.helper.entity.User;
import nju.seec.helper.enums.ExceptionType;
import nju.seec.helper.exception.HelperException;
import nju.seec.helper.service.CourseService;
import nju.seec.helper.service.QuestionService;
import nju.seec.helper.service.QuizStudentAnswerService;
import nju.seec.helper.vo.QuizStudentAnswerStatisticVO;
import nju.seec.helper.vo.question.BaseQuestionVO;
import nju.seec.helper.vo.quiz.QuizStudentAnswerVO;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;

/**
 * @author cst
 */
@Service
public class QuizStudentAnswerServiceImpl implements QuizStudentAnswerService {
    private final QuizDAO quizDAO;
    private final UserDAO userDAO;
    private final QuizStudentAnswerDAO quizStudentAnswerDAO;

    private final QuestionService questionService;
    private final CourseService courseService;

    public QuizStudentAnswerServiceImpl(QuizDAO quizDAO, UserDAO userDAO, QuizStudentAnswerDAO quizStudentAnswerDAO, QuestionService questionService, CourseService courseService) {
        this.quizDAO = quizDAO;
        this.userDAO = userDAO;
        this.quizStudentAnswerDAO = quizStudentAnswerDAO;
        this.questionService = questionService;
        this.courseService = courseService;
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public QuizStudentAnswerVO submitQuizStudentAnswer(LoginUser user, Long quizId, QuizStudentAnswerDTO quizStudentAnswerDTO) {
        Quiz quiz = quizDAO.findQuizById(quizId);

        if (!courseService.existsCourseResourcesAuth(user, quiz.getCourse().getId())) {
            throw HelperException.of(ExceptionType.FORBIDDEN, "您无权提交该测试的作答");
        }

        switch (quiz.getState()) {
            case NOT_STARTED:
                throw HelperException.of(ExceptionType.FORBIDDEN, "测试暂未开始");
            case CLOSED:
                throw HelperException.of(ExceptionType.FORBIDDEN, "测试已关闭，无法提交");
            default:
                break;
        }

        User student = userDAO.findUserById(user.getId());

        QuizStudentAnswer quizStudentAnswer = quizStudentAnswerDAO.findByQuizAndStudent(quiz, student).orElse(new QuizStudentAnswer());

        if (quizStudentAnswer.getSubmitNumber() >= quiz.getMaxSubmitNumber()) {
            throw HelperException.of(ExceptionType.FORBIDDEN, String.format("已达最大提交次数%d次，无法再提交", quiz.getMaxSubmitNumber()));
        }

        // 计算得分
        List<BaseQuestionVO> questionVOList = questionService.getQuestionsByQuiz(quiz);

        AtomicReference<Integer> correct = new AtomicReference<>(0);

        Map<String, Object> answers = quizStudentAnswerDTO.getAnswers();
        questionVOList.forEach(baseQuestionVO -> {
            Object answer;
            if ((answer = answers.get(baseQuestionVO.getId())) != null && baseQuestionVO.pass(answer)) {
                correct.getAndSet(correct.get() + 1);
            }
        });

        BigDecimal score = BigDecimal.valueOf(correct.get() * 100).divide(BigDecimal.valueOf(questionVOList.size()), 2, RoundingMode.HALF_UP);
        // 计算完毕

        quizStudentAnswer.setQuiz(quiz)
                .setStudent(student)
                .setAnswers(quizStudentAnswerDTO.getAnswers())
                .setSubmitNumber(quizStudentAnswer.getSubmitNumber() + 1)
                .setAnswers(answers)
                .setScore(score);

        return new QuizStudentAnswerVO(quizStudentAnswerDAO.save(quizStudentAnswer), questionVOList);
    }

    @Transactional(readOnly = true)
    @Override
    public Page<QuizStudentAnswerVO> getQuizStudentAnswers(LoginUser user, Long quizId, Pageable pageable) {
        return quizStudentAnswerDAO.findByQuiz(quizDAO.findQuizById(quizId), pageable).map(quizStudentAnswer -> new QuizStudentAnswerVO(quizStudentAnswer, questionService.getQuestionsByQuiz(quizDAO.findQuizById(quizId))));
    }

    @Transactional(readOnly = true)
    @Override
    public QuizStudentAnswerVO getQuizStudentAnswer(LoginUser user, Long quizId) {
        return quizStudentAnswerDAO
                .findByQuizAndStudent(quizDAO.findQuizById(quizId), userDAO.findUserById(user.getId()))
                .map(quizStudentAnswer -> new QuizStudentAnswerVO(quizStudentAnswer, questionService.getQuestionsByQuiz(quizDAO.findQuizById(quizId))))
                .orElse(null);
    }

    @Transactional(readOnly = true)
    @Override
    public QuizStudentAnswerStatisticVO getQuizStudentAnswerStatistic(LoginUser user, Long quizId) {
        List<QuizStudentAnswer> quizStudentAnswers = quizStudentAnswerDAO.findByQuiz(quizDAO.findQuizById(quizId));

        Map<BigDecimal, Integer> scores = Maps.newHashMapWithExpectedSize(quizStudentAnswers.size());
        Map<Integer, Integer> submitNums = Maps.newHashMapWithExpectedSize(quizStudentAnswers.size());

        quizStudentAnswers.forEach(
                quizStudentAnswer -> {
                    scores.merge(quizStudentAnswer.getScore(), 1, Integer::sum);
                    submitNums.merge(quizStudentAnswer.getSubmitNumber(), 1, Integer::sum);
                }
        );

        return QuizStudentAnswerStatisticVO.of(quizId, scores, submitNums);
    }
}