from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.core.exceptions import ObjectDoesNotExist

class CommentThreadManager(models.Manager):
    """Manager for handling comment threads on both regular and historical models."""
    
    def for_instance(self, instance):
        """Get comment threads for any model instance."""
        # Get the base model class if this is a historical instance
        if instance.__class__.__name__.startswith('Historical'):
            model_class = instance.instance.__class__
            instance_id = instance.instance.pk
        else:
            model_class = instance.__class__
            instance_id = instance.pk

        ct = ContentType.objects.get_for_model(model_class)
        return self.filter(content_type=ct, object_id=instance_id)

    def create_for_instance(self, instance, **kwargs):
        """Create a comment thread for any model instance."""
        # Get the base model class if this is a historical instance
        if instance.__class__.__name__.startswith('Historical'):
            model_class = instance.instance.__class__
            instance_id = instance.instance.pk
        else:
            model_class = instance.__class__
            instance_id = instance.pk

        ct = ContentType.objects.get_for_model(model_class)
        return self.create(content_type=ct, object_id=instance_id, **kwargs)

class ThreadedModelManager(models.Manager):
    """Manager for models that have comment threads."""

    """Manager for models that have comment threads."""
    
    def get_comment_threads(self, instance):
        """Get comment threads for this instance."""
        from comments.models import CommentThread
        if not instance.pk:
            return CommentThread.objects.none()
        return CommentThread.objects.for_instance(instance)

    def add_comment_thread(self, instance, **kwargs):
        """Create a comment thread for this instance."""
        from comments.models import CommentThread
        if not instance.pk:
            raise ObjectDoesNotExist("Cannot create comment thread for unsaved instance")
        return CommentThread.objects.create_for_instance(instance, **kwargs)

    def with_comment_threads(self):
        """Get all instances with their comment threads."""
        from comments.models import CommentThread
        qs = self.get_queryset()
        content_type = ContentType.objects.get_for_model(self.model)
        
        # Get comment threads through a subquery
        threads = CommentThread.objects.filter(
            content_type=content_type,
            object_id=models.OuterRef('pk')
        )
        return qs.annotate(
            comment_count=models.Subquery(
                threads.values('object_id')
                .annotate(count=models.Count('id'))
                .values('count'),
                output_field=models.IntegerField()
            )
        )