vmesel/PyJobs

from django.db import models
from django.db.models.functions import Cast


class AssessmentQuerySet(models.QuerySet):
    def assessment_grade(self, user, assessment):
        all_answers = self.filter(
            user=user,
            question__assessment=assessment,
        )
        correct_answers = all_answers.filter(correct_answer=True).count()
        total_answers = all_answers.count()

        return correct_answers / total_answers

    def unanswered_questions(self, user, assessment):
        """
        Retrieves if the test has already been initiated
        and if the user needs to answer any other question
        """
        all_answers = self.filter(
            user=user,
        ).count()

        if assessment.question_count == all_answers:
            return True, True

        if (all_answers > 0) and (all_answers < assessment.question_count):
            return True, False

        return False, False

    def ranking(self, assessment, n=10):
        all_candidates_answers = (
            self.filter(
                question__assessment=assessment,
            )
            .values("user__username")
            .annotate(
                points=Cast(
                    models.Sum(
                        models.Case(
                            models.When(correct_answer=True, then=1),
                            default=models.Value(0),
                        )
                    ),
                    models.FloatField(),
                )
                / Cast(models.Count("correct_answer"), models.FloatField())
                * 100
            )
            .order_by("-points")[:n]
        )

        return all_candidates_answers.all()