feat: 实现成绩管理系统核心功能

添加响应工具、错误处理中间件和数据库模型
创建用户、学生、课程和成绩相关服务
实现管理员、教师和学生控制器的基本功能
重构路由处理并优化数据库查询

backend/models/Course.js

@@ -0,0 +1,17 @@
+const db = require('../config/database');
+
+class Course {
+    static async findByTeacherId(teacherId) {
+        return await db.query(
+            'SELECT * FROM courses WHERE teacher_id = ? ORDER BY course_code',
+            [teacherId]
+        );
+    }
+    
+    static async findById(id) {
+        const rows = await db.query('SELECT * FROM courses WHERE id = ?', [id]);
+        return rows[0];
+    }
+}
+
+module.exports = Course;

backend/models/Score.js

@@ -0,0 +1,55 @@
+const db = require('../config/database');
+
+class Score {
+    static async findByStudentId(studentId) {
+        const sql = `
+            SELECT s.*, c.course_code, c.course_name, c.credit,
+                   u.name as teacher_name
+            FROM scores s
+            JOIN courses c ON s.course_id = c.id
+            JOIN users u ON s.teacher_id = u.id
+            WHERE s.student_id = ?
+            ORDER BY s.created_at DESC
+        `;
+        return await db.query(sql, [studentId]);
+    }
+
+    static async findDetailsById(scoreId, studentId) {
+        const sql = `
+            SELECT s.*, c.course_code, c.course_name, c.credit, c.semester,
+                   u.name as teacher_name, u.email as teacher_email,
+                   st.id as student_number, st.class as class_name
+            FROM scores s
+            JOIN courses c ON s.course_id = c.id
+            JOIN users u ON s.teacher_id = u.id
+            JOIN students st ON s.student_id = st.id
+            WHERE s.id = ? AND st.id = ?
+        `;
+        const rows = await db.query(sql, [scoreId, studentId]);
+        return rows[0];
+    }
+
+    static async create(scoreData) {
+        const { studentId, courseId, teacherId, score, gradePoint, gradeLevel, examDate, remark } = scoreData;
+        const sql = `
+            INSERT INTO scores (student_id, course_id, teacher_id, score, 
+            grade_point, grade_level, created_at, remark) 
+            VALUES (?, ?, ?, ?, ?, ?, NOW(), ?)
+        `;
+        // 注意：这里用 created_at 替代了 examDate，如果数据库有 examDate 列可以改回去
+        const result = await db.pool.execute(sql, [
+            studentId, courseId, teacherId, score, gradePoint, gradeLevel, remark
+        ]);
+        return result[0].insertId;
+    }
+
+    static async findByStudentAndCourse(studentId, courseId) {
+        const rows = await db.query(
+            'SELECT * FROM scores WHERE student_id = ? AND course_id = ?',
+            [studentId, courseId]
+        );
+        return rows[0];
+    }
+}
+
+module.exports = Score;

backend/models/Student.js

@@ -0,0 +1,23 @@
+const db = require('../config/database');
+
+class Student {
+    static async findByUserId(userId) {
+        const students = await db.query('SELECT * FROM students WHERE user_id = ?', [userId]);
+        return students[0];
+    }
+    
+    static async findById(studentId) {
+        const students = await db.query('SELECT * FROM students WHERE student_id = ?', [studentId]);
+        return students[0];
+    }
+
+    static async create(studentData) {
+        const { id, name, className, userId } = studentData;
+        await db.query(
+            'INSERT INTO students (id, name, class, user_id) VALUES (?, ?, ?, ?)',
+            [id, name, className, userId]
+        );
+    }
+}
+
+module.exports = Student;

backend/models/User.js

@@ -0,0 +1,33 @@
+const db = require('../config/database');
+const bcrypt = require('bcryptjs');
+
+class User {
+    static async findById(id) {
+        const users = await db.query('SELECT * FROM users WHERE id = ?', [id]);
+        return users[0];
+    }
+
+    static async findByIdAndRole(id, role) {
+        const users = await db.query('SELECT * FROM users WHERE id = ? AND role = ?', [id, role]);
+        return users[0];
+    }
+
+    static async create(userData) {
+        const { id, name, password, role, className } = userData;
+        const salt = await bcrypt.genSalt(10);
+        const hashedPassword = await bcrypt.hash(password, salt);
+        
+        await db.query(
+            'INSERT INTO users (id, name, password, role, class) VALUES (?, ?, ?, ?, ?)',
+            [id, name, hashedPassword, role, className || null]
+        );
+        
+        return { id, name, role, class: className };
+    }
+
+    static async verifyPassword(plainPassword, hashedPassword) {
+        return await bcrypt.compare(plainPassword, hashedPassword);
+    }
+}
+
+module.exports = User;