from django.db import migrations, transaction


def migrate_slots(apps, schema_editor, forward=True):
    from djangocms_alias.models import AliasContent as AliasContentModelClass

    AliasContent = apps.get_model("djangocms_alias", "AliasContent")
    ContentType = apps.get_model("contenttypes", "ContentType")
    Placeholder = apps.get_model("cms", "Placeholder")

    default_slot_name = AliasContentModelClass.placeholder_slotname

    db_alias = schema_editor.connection.alias
    content_type = ContentType.objects.filter(app_label="djangocms_alias", model="aliascontent").first()
    if content_type is None:
        return
    placeholder_qs = Placeholder.objects.using(db_alias).filter(content_type=content_type)
    qs = AliasContent._default_manager.using(db_alias).prefetch_related("alias").exclude(alias__static_code="")

    with transaction.atomic(using=db_alias):
        for alias_content in qs:
            slots = list(placeholder_qs.filter(object_id=alias_content.pk))
            if len(slots) == 1:
                placeholder = slots[0]
                # Ensure the placeholder exists with the correct slot name
                if forward and placeholder.slot == default_slot_name:
                    # If migrating forward, we use the static code or the placeholder slot name
                    placeholder.slot = alias_content.alias.static_code or default_slot_name
                    placeholder.save()
                elif placeholder.slot != default_slot_name:
                    # If migrating backward, we revert to the original placeholder slot name
                    placeholder.slot = default_slot_name
                    placeholder.save()
            elif len(slots) > 1:
                print(
                    f"AliasContent {alias_content.pk} has multiple placeholders, expected only one. "
                    "Skipping migration for this instance:\n"
                    f"{alias_content.alias.static_code or alias_content.name} "
                    f"({alias_content.language}, pk={alias_content.pk})",
                )
                for placeholder in slots:
                    print(f" - Placeholder {placeholder.pk} with slot '{placeholder.slot}'")


class Migration(migrations.Migration):
    dependencies = [
        ("djangocms_alias", "0004_alter_aliascontent_language"),
    ]

    operations = [
        migrations.RunPython(
            code=lambda apps, schema_editor: migrate_slots(apps, schema_editor, forward=True),
            reverse_code=lambda apps, schema_editor: migrate_slots(apps, schema_editor, forward=False),
            elidable=True,
        ),
    ]