import { ExamFact, ExamDim, QuestionStat } from ".";
import { mean, min, max, stdDev } from "@rolesvillesoftware/tools/dist";

export class ExamStat {
    id: number;
    examDimId: number;
    questions: number;
    mean: number;
    minScore: number;
    maxScore: number;
    scoreRange: number;
    standardDev: number;
    aav: number;
    kr20: number;
    sumOfPq: number;
    krv: number;

    students: ExamFact[];

    private calculateSumOfPq(questions: QuestionStat[]) {
        let sum = 0;
        questions.map(item => item.pq).forEach(item => sum += item);
        return sum;
    }
    private calculateKr20() {
        const N = 100 / this.questions;
        const K = this.questions;

        return (N * (K / (K - 1)) * (1 - (this.sumOfPq / (this.standardDev * this.standardDev)))) / (1 + (N - 1) * ((K / (K - 1)) * (1 - (this.sumOfPq / (this.standardDev * this.standardDev)))));
    }
    populate(exam: ExamDim, students: ExamFact[]) {
        this.students = students;

        this.examDimId = exam.id;

        this.mean = mean(students, "percentCorrect");
        this.minScore = min(students, "percentCorrect");
        this.maxScore = max(students, "percentCorrect");
        this.scoreRange = Math.abs(this.maxScore - this.minScore);
        this.standardDev = stdDev(students, "percentCorrect");

        this.aav = 1;
    }
    complete(questionStats: QuestionStat[]) {
        this.questions = questionStats.length;
        this.sumOfPq = this.calculateSumOfPq(questionStats);
        this.kr20 = this.calculateKr20();
        this.krv = Math.pow(this.kr20, 4) * 10;
    }
}