import {students} from "./data.js"
let passingStudents = [];

export function getPassingStudents(students, passMark = 70) {
    if (isNaN(passMark) || passMark < 0) {
        return false;
    }
    passingStudents = students.filter(student => {
        let grade = parseInt(student.grade);
        if (isNaN(grade)) return false;

        return grade >= passMark;
    });
    return passingStudents;
}

export function calculateCourseAverages(students) {
    const groupedCourses = students.reduce((accumulator, { course, grade }) => {
        if (!accumulator[course]) {
            accumulator[course] = { total: 0, count: 0 };
        }

        accumulator[course].total += Number(grade);
        accumulator[course].count += 1;

        return accumulator;
    }, {});

    return Object.entries(groupedCourses).reduce((accumulator, [course, values]) => {
        accumulator[course] = values.count === 0 ? 0 : values.total / values.count;
        return accumulator;
    }, {});
}

export function getTopPerCourse(students) {
    const topStudentsByCourse = students.reduce((accumulator, student) => {
        const currentTopStudent = accumulator[student.course];

        if (!currentTopStudent || student.grade > currentTopStudent.grade) {
            accumulator[student.course] = student;
        }

        return accumulator;
    }, {});

    return Object.values(topStudentsByCourse);
}

export function calculateOverallStatistics(students) {
    if (students.length === 0) {
        return {
            totalStudents: 0,
            averageGrade: 0,
            highestGrade: 0,
            lowestGrade: 0,
            averageAttendance: 0
        };
    }

    const totals = students.reduce((accumulator, { grade, attendance }) => {
        const numericGrade = Number(grade);
        const numericAttendance = Number(attendance);

        accumulator.totalStudents += 1;
        accumulator.gradeTotal += numericGrade;
        accumulator.attendanceTotal += numericAttendance;
        accumulator.highestGrade = Math.max(accumulator.highestGrade, numericGrade);
        accumulator.lowestGrade = Math.min(accumulator.lowestGrade, numericGrade);

        return accumulator;
    }, {
        totalStudents: 0,
        gradeTotal: 0,
        attendanceTotal: 0,
        highestGrade: -Infinity,
        lowestGrade: Infinity
    });

    return {
        totalStudents: totals.totalStudents,
        averageGrade: totals.gradeTotal / totals.totalStudents,
        highestGrade: totals.highestGrade,
        lowestGrade: totals.lowestGrade,
        averageAttendance: totals.attendanceTotal / totals.totalStudents
    };
}