const db = require('../config/database');

class Score {
    static async findByStudentId(studentId) {
        const sql = `
            SELECT s.id, s.student_id, s.course_id, s.teacher_id, 
                   s.total_score as score, s.grade_point, s.grade_level, s.created_at,
                   c.course_code, c.course_name, c.credit,
                   u.name as teacher_name
            FROM grades 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.id, s.student_id, s.course_id, s.teacher_id,
                   s.usual_score, s.midterm_score, s.final_score, s.total_score as score,
                   s.grade_point, s.grade_level, s.created_at, s.remark,
                   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 grades 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, remark } = scoreData;
        // 既然TeacherService只传了score，我们默认把它作为 final_score 和 total_score
        // 如果需要支持平时分/期中分，需要修改前端和Controller
        const sql = `
            INSERT INTO grades (student_id, course_id, teacher_id, final_score, total_score, 
            grade_point, grade_level, created_at, remark) 
            VALUES (?, ?, ?, ?, ?, ?, ?, NOW(), ?)
        `;
        const result = await db.pool.execute(sql, [
            studentId, courseId, teacherId, score, score, gradePoint, gradeLevel, remark
        ]);
        return result[0].insertId;
    }

    static async findByStudentAndCourse(studentId, courseId) {
        const rows = await db.query(
            'SELECT * FROM grades WHERE student_id = ? AND course_id = ?',
            [studentId, courseId]
        );
        return rows[0];
    }
}

module.exports = Score;