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,
                   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 (?, ?, ?, ?, ?, ?, ?, datetime('now', 'localtime'), ?)
        `;
        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];
    }

    static async findByTeacher(teacherId, filters) {
        let sql = `
            SELECT g.*, s.name as student_name, c.course_name
            FROM grades g
            JOIN students s ON g.student_id = s.id
            JOIN courses c ON g.course_id = c.id
            WHERE c.teacher_id = ?
        `;
        const params = [teacherId];
        
        if (filters.courseId) {
            sql += ' AND g.course_id = ?';
            params.push(filters.courseId);
        }
        if (filters.studentName) {
            sql += ' AND (s.name LIKE ? OR s.id LIKE ?)';
            params.push(`%${filters.studentName}%`, `%${filters.studentName}%`);
        }
        return await db.query(sql, params);
    }

    static async findCourseStudentsWithGrades(courseId, teacherId) {
        const sql = `
            SELECT s.id as student_id, s.name as student_name, 
                   g.usual_score, g.midterm_score, g.final_score, g.total_score, g.grade_point, g.grade_level,
                   c.id as course_id, c.course_name
            FROM students s
            JOIN classes cl ON s.class = cl.class_name
            JOIN courses c ON c.class_id = cl.id
            LEFT JOIN grades g ON s.id = g.student_id AND g.course_id = c.id
            WHERE c.id = ? AND c.teacher_id = ?
        `;
        return await db.query(sql, [courseId, teacherId]);
    }

    static async upsert(scoreData) {
        const { 
            studentId, courseId, teacherId, 
            usual_score, midterm_score, final_score, score, 
            gradePoint, gradeLevel, remark 
        } = scoreData;
        
        const existing = await this.findByStudentAndCourse(studentId, courseId);
        
        // 处理参数：如果是 undefined 或空字符串，则设为 null
        const sanitize = (val) => (val === undefined || val === '' || val === null) ? null : val;

        const params = [
            sanitize(usual_score), 
            sanitize(midterm_score), 
            sanitize(final_score), 
            sanitize(score), 
            sanitize(gradePoint), 
            sanitize(gradeLevel), 
            sanitize(remark)
        ];
        
        if (existing) {
             const sql = `UPDATE grades SET usual_score=?, midterm_score=?, final_score=?, total_score=?, grade_point=?, grade_level=?, remark=? WHERE id=?`;
             await db.query(sql, [...params, existing.id]);
             return existing.id;
        } else {
             const sql = `INSERT INTO grades (student_id, course_id, teacher_id, usual_score, midterm_score, final_score, total_score, grade_point, grade_level, created_at, remark) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, datetime('now', 'localtime'), ?)`;
             const insertParams = [
                 studentId, courseId, teacherId,
                 ...params
             ];
             const result = await db.query(sql, insertParams);
             return result.insertId;
        }
    }
}

module.exports = Score;