const Course = require('../models/Course');
const Score = require('../models/Score');
const Student = require('../models/Student');

class TeacherService {
    static async getCourses(teacherId) {
        return await Course.findByTeacherId(teacherId);
    }

    static async getClasses() {
        return await Course.getClasses();
    }

    static async getTeacherClasses(teacherId) {
        const sql = `SELECT * FROM classes WHERE teacher_id = ?`;
        const db = require('../config/database');
        return await db.query(sql, [teacherId]);
    }

    static async createCourse(teacherId, courseData) {
        return await Course.create({ ...courseData, teacher_id: teacherId });
    }

    static async updateCourse(teacherId, courseId, courseData) {
        // Verify ownership
        const course = await Course.findById(courseId);
        if (!course || course.teacher_id != teacherId) {
            throw new Error('无权修改该课程或课程不存在');
        }
        return await Course.update(courseId, courseData);
    }

    static async getGrades(teacherId, filters) {
        if (filters.courseId) {
            return await Score.findCourseStudentsWithGrades(filters.courseId, teacherId);
        } else {
            return await Score.findByTeacher(teacherId, filters);
        }
    }

    static async addScore(teacherId, scoreData) {
        let { studentId, courseId, score, usual_score, midterm_score, final_score } = scoreData;

        // 验证学生
        const student = await Student.findById(studentId);
        if (!student) {
            throw new Error('学生不存在');
        }

        // 如果没有总分但有平时/期中/期末分，尝试计算总分 (30% + 30% + 40%)
        if ((score === undefined || score === '') && (usual_score || midterm_score || final_score)) {
            const u = parseFloat(usual_score) || 0;
            const m = parseFloat(midterm_score) || 0;
            const f = parseFloat(final_score) || 0;
            score = (u * 0.3 + m * 0.3 + f * 0.4).toFixed(1);
        }

        // 计算绩点和等级
        const numericScore = parseFloat(score);
        let gradePoint = 0;
        let gradeLevel = 'F';

        if (!isNaN(numericScore)) {
            if (numericScore >= 90) { gradePoint = 4.0; gradeLevel = 'A'; }
            else if (numericScore >= 85) { gradePoint = 3.7; gradeLevel = 'A-'; }
            else if (numericScore >= 82) { gradePoint = 3.3; gradeLevel = 'B+'; }
            else if (numericScore >= 78) { gradePoint = 3.0; gradeLevel = 'B'; }
            else if (numericScore >= 75) { gradePoint = 2.7; gradeLevel = 'B-'; }
            else if (numericScore >= 72) { gradePoint = 2.3; gradeLevel = 'C+'; }
            else if (numericScore >= 68) { gradePoint = 2.0; gradeLevel = 'C'; }
            else if (numericScore >= 64) { gradePoint = 1.5; gradeLevel = 'C-'; }
            else if (numericScore >= 60) { gradePoint = 1.0; gradeLevel = 'D'; }
        } else {
            gradePoint = null;
            gradeLevel = null;
        }

        const fullScoreData = {
            ...scoreData,
            score, // 更新后的总分
            teacherId,
            gradePoint,
            gradeLevel,
            usual_score, 
            midterm_score, 
            final_score
        };

        const gradeId = await Score.upsert(fullScoreData);
        return gradeId;
    }
}

module.exports = TeacherService;