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

class StudentService {
    static async getStudentCourses(userId) {
        const student = await Student.findById(userId);
        if (!student) {
            throw new Error('学生信息不存在');
        }

        const courses = await Course.findByStudentId(userId);
        return courses;
    }

    static async getCourseDetails(courseId) {
        const course = await Course.findDetailsById(courseId);
        if (!course) {
            throw new Error('课程不存在');
        }
        return course;
    }

    static async getStudentGrades(userId) {
        // 确认学生是否存在
        const student = await Student.findById(userId);
        if (!student) {
            throw new Error('学生信息不存在');
        }

        const grades = await Score.findByStudentId(userId);

        // 计算统计信息
        let totalCredits = 0;
        let totalGradePoints = 0;
        const totalCourses = grades.length;

        grades.forEach(grade => {
            const credit = parseFloat(grade.credit);
            totalCredits += credit;
            if (grade.grade_point) {
                totalGradePoints += parseFloat(grade.grade_point) * credit;
            }
        });

        const gpa = totalCredits > 0 ? (totalGradePoints / totalCredits).toFixed(2) : 0;
        const averageScore = totalCourses > 0 ? 
            (grades.reduce((sum, g) => sum + parseFloat(g.score || 0), 0) / totalCourses).toFixed(1) : 0;

        return {
            grades,
            statistics: {
                totalCourses,
                totalCredits,
                gpa,
                averageScore
            }
        };
    }

    static async getGradeDetails(scoreId, userId) {
        const grade = await Score.findDetailsById(scoreId, userId);
        if (!grade) {
            throw new Error('成绩不存在');
        }
        return grade;
    }
}

module.exports = StudentService;