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

class Course {
    static async findByTeacherId(teacherId) {
        const sql = `
            SELECT c.*, cl.class_name, 
                   (SELECT COUNT(*) FROM students s WHERE s.class = cl.class_name) as student_count
            FROM courses c
            LEFT JOIN classes cl ON c.class_id = cl.id
            WHERE c.teacher_id = ?
            ORDER BY c.course_code
        `;
        return await db.query(sql, [teacherId]);
    }
    
    static async findById(id) {
        const rows = await db.query('SELECT * FROM courses WHERE id = ?', [id]);
        return rows[0];
    }

    static async findDetailsById(id) {
        const sql = `
            SELECT c.*, u.name as teacher_name, cl.class_name
            FROM courses c
            JOIN users u ON c.teacher_id = u.id
            JOIN classes cl ON c.class_id = cl.id
            WHERE c.id = ?
        `;
        const rows = await db.query(sql, [id]);
        return rows[0];
    }

    static async findByStudentId(studentId) {
        const sql = `
            SELECT c.*, u.name as teacher_name
            FROM courses c
            JOIN classes cl ON c.class_id = cl.id
            JOIN students s ON cl.class_name = s.class
            JOIN users u ON c.teacher_id = u.id
            WHERE s.id = ?
            ORDER BY c.course_code
        `;
        return await db.query(sql, [studentId]);
    }

    static async getClasses() {
        return await db.query('SELECT * FROM classes');
    }

    static async create(data) {
        const { course_name, course_code, credit, teacher_id, semester, class_id, category } = data;
        const sql = `INSERT INTO courses (course_name, course_code, credit, teacher_id, semester, class_id, category) VALUES (?, ?, ?, ?, ?, ?, ?)`;
        const result = await db.query(sql, [course_name, course_code, credit, teacher_id, semester, class_id, category]);
        return result.insertId;
    }

    static async update(id, data) {
        const { course_name, course_code, credit, semester, class_id } = data;
        const sql = `
            UPDATE courses 
            SET course_name = ?, course_code = ?, credit = ?, semester = ?, class_id = ?
            WHERE id = ?
        `;
        const result = await db.query(sql, [course_name, course_code, credit, semester, class_id, id]);
        return result.affectedRows > 0;
    }
}

module.exports = Course;