const Result = require('../models/Result');
const Exam = require('../models/Exam');

// 提交考试结果
exports.submitResult = async (req, res, next) => {
    try {
        const { examId, answers, timeTaken } = req.body;

        // 验证考试
        const exam = await Exam.findById(examId);
        if (!exam) {
            return res.status(404).json({ message: 'Exam not found' });
        }

        // 计算分数
        let totalScore = 0;
        const answerResults = exam.questions.map(question => {
            const userAnswer = answers[question._id];
            let isCorrect = false;
            let score = 0;

            if (question.type === 'text') {
                // 简答题默认给一半分
                if (userAnswer && userAnswer.trim().length > 0) {
                    isCorrect = true;
                    score = question.score / 2;
                }
            } else if (Array.isArray(question.answer)) {
                // 多选题
                const correctAnswers = [...question.answer].sort().toString();
                const userAns = [...userAnswer].sort().toString();
                isCorrect = correctAnswers === userAns;
                score = isCorrect ? question.score : 0;
            } else {
                // 单选题
                isCorrect = userAnswer === question.answer;
                score = isCorrect ? question.score : 0;
            }

            totalScore += score;

            return {
                questionId: question._id,
                userAnswer,
                isCorrect,
                score
            };
        });

        // 保存结果
        const result = new Result({
            exam: examId,
            user: req.user.id,
            answers: answerResults,
            totalScore,
            maxScore: exam.questions.reduce((sum, q) => sum + q.score, 0),
            timeTaken
        });

        await result.save();

        res.status(201).json(result);
    } catch (err) {
        next(err);
    }
};

// 获取用户成绩
exports.getUserResults = async (req, res, next) => {
    try {
        const results = await Result.find({ user: req.user.id })
            .populate('exam', 'title description')
            .sort({ submittedAt: -1 });

        res.json(results);
    } catch (err) {
        next(err);
    }
};

// 获取考试所有成绩 (教师/管理员)
exports.getExamResults = async (req, res, next) => {
    try {
        const results = await Result.find({ exam: req.params.id })
            .populate('user', 'username')
            .populate('exam', 'title')
            .sort({ totalScore: -1 });

        res.json(results);
    } catch (err) {
        next(err);
    }
};