import { Exception, SafePromise, SafeResult } from "@rolesvillesoftware/tools/dist";

import { Calculator } from "./";
import { ExamDim, ExamStat, ExamContext, ExamFact } from "../models";
import { Logger } from "../Logger";

export class ExamCalculator extends Calculator<ExamDim, ExamStat> {
    private async getExamStat(exam: ExamDim): Promise<ExamStat> {
        const query = this.processResults(
            await SafePromise.run(() => this.context.examStat.selectOrCreate((i, b) => i.examDimId === b.examDimId, { examDimId: exam.id } as ExamStat))
        );
        if ( query.count === 0) { throw new Exception("Unable to create exam stat record"); }
        return query.toArray()[0];
    }
    private async getExamStudents(exam: ExamDim): Promise<ExamFact[]> {
        const students = this.processResults(
            await SafePromise.run(() =>
                this.context.examFact
                    .where((i, b) => i.examDimId === b.id, exam)
                    .execute()
                    .toPromise()
            )
        ).toArray();
        if (students.length === 0) {
            throw new Exception("No exam, student, question data exists");
        }
        if (!students.every((v, i) => i === 0 || v.examDimId === students[i - 1].examDimId)) {
            throw new Exception("Not all question facts are for the same question.");
        }
        return students;
    }

    async calculate(input?: ExamDim): Promise<ExamStat> {
        if (input == null) {
            return null;
        }

        Logger.log(`Loading Student Answers`);
        const students = this.processResults(await SafePromise.run(() => this.getExamStudents(input)));
        Logger.log(`Loading or creating Exam Stat Record`);
        const examStat = this.processResults(await SafePromise.run(() => this.getExamStat(input)));

        Logger.log(`Calculating initial exam statistics`);
        examStat.populate(input, students);

        return examStat;
    }
}