const pool = require('../db');
const ExcelJS = require('exceljs');

async function updateScore(req, res) {
    const { student_id, points } = req.body;
    let connection; // 在try块外部声明connection

    try {
        connection = await pool.getConnection();
        
        // 更新学生的积分并增加点名次数
        const [result] = await connection.query(
            'UPDATE students SET score = score + ?, call_count = call_count + 1 WHERE student_id = ?', 
            [points, student_id]
        );

        if (result.affectedRows > 0) {
            // 查询更新后的分数
            const [rows] = await connection.query(
                'SELECT score FROM students WHERE student_id = ?', 
                [student_id]
            );
            
            if (rows.length > 0) {
                const updatedScore = rows[0].score;
                return res.send(String(updatedScore)); 
            } else {
                return res.status(404).send('学生不存在');
            }
        } else {
            return res.status(404).send('学生不存在');
        }
    } catch (error) {
        console.error('数据库操作失败:', error);
        return res.status(500).send('更新积分失败');
    } finally {
        if (connection) {
            connection.release(); // 只有在connection已被赋值时才调用release
        }
    }
}

async function getStudentScore(req, res) {
    const { student_id } = req.body;
    let connection;

    try {
        connection = await pool.getConnection();

        // 查询指定学生的分数
        const [rows] = await connection.query(
            'SELECT score FROM students WHERE student_id =?',
            [student_id]
        );

        if (rows.length > 0) {
            const score = rows[0].score;
            // 修改这里，构建包含student_id和score的对象并返回
            return res.json({ student_id, score });
        } else {
            return res.status(404).json({ message: '学生不存在' });
        }
    } catch (error) {
        console.error('数据库操作失败:', error);
        return res.status(500).json({ error: '获取分数失败' });
    } finally {
        if (connection) {
            connection.release();
        }
    }
}


async function exportScores(req, res) {
    let connection;
    try {
        connection = await pool.getConnection();

        // 查询学生的成绩
        const [rows] = await connection.query('SELECT student_name, student_id, score FROM students');

        // 创建一个工作簿和一个工作表
        const workbook = new ExcelJS.Workbook();
        const worksheet = workbook.addWorksheet('Scores');

        // 添加列标题
        worksheet.columns = [
            { header: 'Student Name', key: 'student_name', width: 20 },
            { header: 'Student ID', key: 'student_id', width: 15 },
            { header: 'Score', key: 'score', width: 10 },
        ];

        // 将数据添加到工作表中
        rows.forEach(row => {
            worksheet.addRow(row);
        });

        // 设置响应头，告知浏览器以附件形式下载文件
        res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
        res.setHeader('Content-Disposition', 'attachment; filename=scores.xlsx');

        // 生成并发送 Excel 文件
        await workbook.xlsx.write(res);
        res.end();
    } catch (error) {
        console.error('导出成绩失败:', error);
        res.status(500).send({ error: '无法导出成绩' });
    } finally {
        if (connection) connection.release();
    }
}



module.exports = { updateScore, getStudentScore,exportScores };