from django.db.models import Manager, Count


class LabelManager(Manager):

    def calc_label_distribution(self, examples, members, labels):
        """Calculate label distribution.

        Args:
            examples: example queryset.
            members: user queryset.
            labels: label queryset.

        Returns:
            label distribution per user.

        Examples:
            >>> self.calc_label_distribution(examples, members, labels)
            {'admin': {'positive': 10, 'negative': 5}}
        """
        distribution = {member.username: {label.text: 0 for label in labels} for member in members}
        items = self.filter(example_id__in=examples)\
            .values('user__username', 'label__text')\
            .annotate(count=Count('label__text'))
        for item in items:
            username = item['user__username']
            label = item['label__text']
            count = item['count']
            distribution[username][label] = count
        return distribution

    def get_labels(self, label, project):
        if project.collaborative_annotation:
            return self.filter(example=label.example)
        else:
            return self.filter(example=label.example, user=label.user)

    def can_annotate(self, label, project) -> bool:
        raise NotImplementedError('Please implement this method in the subclass')

    def filter_annotatable_labels(self, labels, project):
        return [label for label in labels if self.can_annotate(label, project)]


class CategoryManager(LabelManager):

    def can_annotate(self, label, project) -> bool:
        is_exclusive = project.single_class_classification
        categories = self.get_labels(label, project)
        if is_exclusive:
            return not categories.exists()
        else:
            return not categories.filter(label=label.label).exists()


class SpanManager(LabelManager):

    def can_annotate(self, label, project) -> bool:
        overlapping = getattr(project, 'allow_overlapping', False)
        spans = self.get_labels(label, project)
        if overlapping:
            return True
        for span in spans:
            if span.is_overlapping(label):
                return False
        return True


class TextLabelManager(LabelManager):

    def can_annotate(self, label, project) -> bool:
        texts = self.get_labels(label, project)
        for text in texts:
            if text.is_same_text(label):
                return False
        return True