package nju.seec.helper.service.impl;

import cn.hutool.core.util.StrUtil;
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.question.StudentAnswerDTO;
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.QuestionService;
import nju.seec.helper.service.QuizStudentAnswerService;
import nju.seec.helper.vo.question.BaseQuestionVO;
import nju.seec.helper.vo.quiz.QuizStudentAnswerStatisticVO;
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.AtomicInteger;

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

    private final QuestionService questionService;

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

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

        switch (quiz.getState()) {
            case NOT_STARTED:
                throw HelperException.of(ExceptionType.FORBIDDEN, "测试未开始，无法提交");
            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, StrUtil.format("已达最大提交次数{}次，无法再提交", quiz.getMaxSubmitNumber()));
        }

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

        AtomicInteger correct = new AtomicInteger();

        Map<String, StudentAnswerDTO.AnswerRecordDTO> records = studentAnswerDTO.getRecords();
        questionVOList.forEach(baseQuestionVO -> {
            String questionId = baseQuestionVO.getId();
            Object answer;
            if (records.get(questionId) != null) {
                answer = records.get(questionId).getAnswer();
            } else {
                answer = quizStudentAnswer.getAnswers().get(questionId);
            }
            if (baseQuestionVO.pass(answer)) {
                correct.getAndIncrement();
            }
            quizStudentAnswer.getAnswers().put(questionId, answer);
        });

        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)
                .setSubmitNumber(quizStudentAnswer.getSubmitNumber() + 1)
                .setScore(score);

        questionService.record(user, studentAnswerDTO);

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

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

    @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.getQuestionsByIds(quizDAO.findQuizById(quizId).getQuestions())))
                .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);
    }
}