const express = require('express');
const router = express.Router();
const db = require('../config/database');
const { requireAuth, requireRole } = require('../middleware/auth');

// 获取教师教授的课程
router.get('/courses', requireAuth, requireRole(['teacher']), async (req, res) => {
    try {
        const teacherId = req.session.user.id;
        
        const courses = await db.pool.execute(
            'SELECT * FROM courses WHERE teacher_id = ? ORDER BY course_code',
            [teacherId]
        );
        
        res.json({
            success: true,
            courses
        });
        
    } catch (error) {
        console.error('获取课程错误:', error);
        res.status(500).json({ 
            success: false, 
            message: '服务器错误' 
        });
    }
});

// 录入成绩
router.post('/grades', requireAuth, requireRole(['teacher']), async (req, res) => {
    try {
        const teacherId = req.session.user.id;
        const { studentId, courseId, score, examDate, remark } = req.body;
        
        // 验证输入
        if (!studentId || !courseId || score === undefined) {
            return res.status(400).json({ 
                success: false, 
                message: '请填写必填字段' 
            });
        }
        
        // 检查学生和课程是否存在
        const students = await db.pool.execute(
            'SELECT id FROM students WHERE student_id = ?',
            [studentId]
        );
        
        if (students[0].length === 0) {
            return res.status(404).json({ 
                success: false, 
                message: '学生不存在' 
            });
        }
        
        // 计算绩点和等级
        const numericScore = parseFloat(score);
        let gradePoint = 0;
        let gradeLevel = 'F';
        
        if (numericScore >= 90) {
            gradePoint = 4.0; gradeLevel = 'A';
        } else if (numericScore >= 80) {
            gradePoint = 3.0; gradeLevel = 'B';
        } else if (numericScore >= 70) {
            gradePoint = 2.0; gradeLevel = 'C';
        } else if (numericScore >= 60) {
            gradePoint = 1.0; gradeLevel = 'D';
        }
        
        // 插入成绩
        const result = await db.pool.execute(
            `INSERT INTO scores (student_id, course_id, teacher_id, score, 
             grade_point, grade_level, exam_date, remark) 
             VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
            [students[0][0].id, courseId, teacherId, numericScore, 
             gradePoint, gradeLevel, examDate, remark]
        );
        
        res.json({
            success: true,
            message: '成绩录入成功',
            gradeId: result.insertId
        });
        
    } catch (error) {
        console.error('录入成绩错误:', error);
        
        // 处理唯一约束错误
        if (error.code === 'ER_DUP_ENTRY') {
            return res.status(400).json({ 
                success: false, 
                message: '该学生此课程成绩已存在' 
            });
        }
        
        res.status(500).json({ 
            success: false, 
            message: '服务器错误' 
        });
    }
});

// 查询成绩（按班级、课程）
router.get('/grades', requireAuth, requireRole(['teacher']), async (req, res) => {
    try {
        const { class_name, course_id } = req.query;
        const teacherId = req.session.user.id;
        
        let query = `
            SELECT sc.*, st.student_id, st.full_name, st.class_name,
                   c.course_code, c.course_name, c.credit
            FROM scores sc
            JOIN students st ON sc.student_id = st.id
            JOIN courses c ON sc.course_id = c.id
            WHERE sc.teacher_id = ?
        `;
        
        const params = [teacherId];
        
        if (class_name) {
            query += ' AND st.class_name = ?';
            params.push(class_name);
        }
        
        if (course_id) {
            query += ' AND sc.course_id = ?';
            params.push(course_id);
        }
        
        query += ' ORDER BY st.class_name, st.student_id, sc.exam_date DESC';
        
        const grades = await db.pool.execute(query, params);
        
        res.json({
            success: true,
            grades
        });
        
    } catch (error) {
        console.error('查询成绩错误:', error);
        res.status(500).json({ 
            success: false, 
            message: '服务器错误' 
        });
    }
});

// 更新成绩
router.put('/grades/:id', requireAuth, requireRole(['teacher']), async (req, res) => {
    try {
        const gradeId = req.params.id;
        const teacherId = req.session.user.id;
        const { score, examDate, remark } = req.body;
        
        // 验证成绩是否存在且属于该教师
        const existingGrades = await db.pool.execute(
            'SELECT id FROM scores WHERE id = ? AND teacher_id = ?',
            [gradeId, teacherId]
        );
        
        if (existingGrades[0].length === 0) {
            return res.status(404).json({ 
                success: false, 
                message: '成绩不存在或无权修改' 
            });
        }
        
        // 计算新的绩点和等级
        const numericScore = parseFloat(score);
        let gradePoint = 0;
        let gradeLevel = 'F';
        
        if (numericScore >= 90) {
            gradePoint = 4.0; gradeLevel = 'A';
        } else if (numericScore >= 80) {
            gradePoint = 3.0; gradeLevel = 'B';
        } else if (numericScore >= 70) {
            gradePoint = 2.0; gradeLevel = 'C';
        } else if (numericScore >= 60) {
            gradePoint = 1.0; gradeLevel = 'D';
        }
        
        // 更新成绩
        await db.pool.execute(
            `UPDATE scores SET score = ?, grade_point = ?, grade_level = ?, 
             exam_date = ?, remark = ?, updated_at = CURRENT_TIMESTAMP 
             WHERE id = ?`,
            [numericScore, gradePoint, gradeLevel, examDate, remark, gradeId]
        );
        
        res.json({
            success: true,
            message: '成绩更新成功'
        });
        
    } catch (error) {
        console.error('更新成绩错误:', error);
        res.status(500).json({ 
            success: false, 
            message: '服务器错误' 
        });
    }
});

// 删除成绩
router.delete('/grades/:id', requireAuth, requireRole(['teacher']), async (req, res) => {
    try {
        const gradeId = req.params.id;
        const teacherId = req.session.user.id;
        
        // 验证成绩是否存在且属于该教师
        const existingGrades = await db.pool.execute(
            'SELECT id FROM scores WHERE id = ? AND teacher_id = ?',
            [gradeId, teacherId]
        );
        
        if (existingGrades[0].length === 0) {
            return res.status(404).json({ 
                success: false, 
                message: '成绩不存在或无权删除' 
            });
        }
        
        // 删除成绩
        await db.pool.execute('DELETE FROM scores WHERE id = ?', [gradeId]);
        
        res.json({
            success: true,
            message: '成绩删除成功'
        });
        
    } catch (error) {
        console.error('删除成绩错误:', error);
        res.status(500).json({ 
            success: false, 
            message: '服务器错误' 
        });
    }
});

module.exports = router;