from django.contrib.contenttypes.admin import GenericInlineModelAdmin
from django.contrib.contenttypes.models import ContentType
from django.utils.functional import cached_property

from polymorphic.formsets import polymorphic_child_forms_factory, BasePolymorphicGenericInlineFormSet, PolymorphicGenericFormSetChild
from .inlines import PolymorphicParentInlineModelAdmin, PolymorphicChildInlineModelAdmin


class PolymorphicParentGenericInlineModelAdmin(PolymorphicParentInlineModelAdmin, GenericInlineModelAdmin):
    """
    Variation for inlines based on generic foreign keys.
    """
    formset = BasePolymorphicGenericInlineFormSet

    def get_formset(self, request, obj=None, **kwargs):
        """
        Construct the generic inline formset class.
        """
        # Construct the FormSet class. This is almost the same as parent version,
        # except that a different super is called so generic_inlineformset_factory() is used.
        # NOTE that generic_inlineformset_factory() also makes sure the GFK fields are excluded in the form.
        FormSet = GenericInlineModelAdmin.get_formset(self, request, obj=obj, **kwargs)

        FormSet.child_forms = polymorphic_child_forms_factory(
            formset_children=self.get_formset_children(request, obj=obj)
        )
        return FormSet


class PolymorphicChildGenericInlineModelAdmin(PolymorphicChildInlineModelAdmin):
    """
    Variation for generic inlines.
    """
    # Make sure that the GFK fields are excluded from the child forms
    formset_child = PolymorphicGenericFormSetChild
    ct_field = "content_type"
    ct_fk_field = "object_id"

    @cached_property
    def content_type(self):
        """
        Expose the ContentType that the child relates to.
        This can be used for the ``polymorphic_ctype`` field.
        """
        return ContentType.objects.get_for_model(self.model)

    def get_formset_child(self, request, obj=None, **kwargs):
        # Similar to GenericInlineModelAdmin.get_formset(),
        # make sure the GFK is automatically excluded from the form
        defaults = {
            "ct_field": self.ct_field,
            "fk_field": self.ct_fk_field,
        }
        defaults.update(kwargs)
        return super(PolymorphicChildGenericInlineModelAdmin, self).get_formset_child(request, obj=obj, **defaults)