from django.db.models.signals import post_save, pre_delete
from django.dispatch import receiver
from django.contrib.contenttypes.models import ContentType
from .models import ManagedDocument, DocumentVersion, DocumentAttachment


@receiver(post_save, sender=DocumentVersion)
def document_version_post_save(sender, instance, created, **kwargs):
    """
    If a new version of a DXF file is saved and it is attached to an intersection,
    automatically generate/update the overlay PNG.
    """
    if instance.file and instance.file.name.lower().endswith('.dxf'):
        try:
            from assets.models import TrafficLightIntersection
            from assets.views.trafficlights import generate_dxf_overlay_managed_document
            
            ct_tli = ContentType.objects.get_for_model(TrafficLightIntersection)
            attachment = DocumentAttachment.objects.filter(
                document=instance.document,
                content_type=ct_tli
            ).first()
            if attachment:
                generate_dxf_overlay_managed_document(instance.document, user=instance.uploaded_by)
        except Exception:
            pass

@receiver(post_save, sender=DocumentAttachment)
def document_attachment_post_save(sender, instance, created, **kwargs):
    """
    If a document is attached to an intersection and it is a DXF file,
    automatically generate/update the overlay PNG.
    """
    try:
        from assets.models import TrafficLightIntersection
        from assets.views.trafficlights import generate_dxf_overlay_managed_document
        
        if isinstance(instance.content_object, TrafficLightIntersection):
            document = instance.document
            latest_version = document.latest_version
            if latest_version and latest_version.file and latest_version.file.name.lower().endswith('.dxf'):
                generate_dxf_overlay_managed_document(document, user=instance.attached_by)
    except Exception:
        pass