feat: implement dumpdata view and admin command

This feature provides ways to serialize the data of an APIS instance to
be able to import it in a freshly installed instance later on.

The main logic is implemented in the `utils.helper.datadump_serializer`
method. It serializes the important models to json - with natural
foreign keys.

There is both a view ('/api/dumpdata') and an admin command
('apisdumpdata') that output the serialized data as API Response or to
stdout.

Closes: #273

apis_core/core/management/commands/apisdumpdata.py

@@ -0,0 +1,18 @@
+from django.core.management.base import BaseCommand
+
+from apis_core.utils.helpers import datadump_serializer
+
+
+class Command(BaseCommand):
+    help = "Dump APIS data"
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            "args",
+            metavar="app_labels",
+            nargs="*",
+            help=("Optional additional app_labels."),
+        )
+
+    def handle(self, *app_labels, **options):
+        print(datadump_serializer(app_labels, "json"))

apis_core/core/views.py

@@ -0,0 +1,23 @@
+import json
+
+from rest_framework.views import APIView
+from rest_framework.response import Response
+
+from apis_core.utils.helpers import datadump_serializer
+
+
+class Dumpdata(APIView):
+    """
+    provide an API endpoint that outputs the datadump of an APIS installation
+
+    this is a bit of a hack, becaus we first use the Django JSON serializer to
+    serialize the data using natural keys, then we use json.loads to so we can
+    output it as an API reponse.
+    so basically: serialize -> deserialize -> serialize
+    """
+    def get(self, request, *args, **kwargs):
+        params = request.query_params.dict()
+        app_labels = params.pop("app_labels", [])
+        if app_labels:
+            app_labels = app_labels.split(",")
+        return Response(json.loads(datadump_serializer(app_labels, "json")))

apis_core/urls.py

@@ -16,6 +16,7 @@
 # from apis_core.apis_vocabularies.api_views import UserViewSet
 from apis_core.utils import caching
 from apis_core.apis_metainfo.viewsets import UriToObjectViewSet
+from apis_core.core.views import Dumpdata
 
 app_name = "apis_core"
 
@@ -103,7 +104,6 @@ def build_apis_mock_request(method, path, view, original_request, **kwargs):
 
 from apis_core.apis_entities.api_views import GetEntityGeneric
 
-
 urlpatterns = [
     path("", TemplateView.as_view(template_name="base.html"), name="apis_index"),
     path("admin/", admin.site.urls),
@@ -168,6 +168,7 @@ def build_apis_mock_request(method, path, view, original_request, **kwargs):
         GetEntityGeneric.as_view(),
         name="GetEntityGeneric",
     ),
+    path("api/dumpdata", Dumpdata.as_view()),
 ]
 
 if "apis_fulltext_download" in settings.INSTALLED_APPS:

apis_core/utils/helpers.py

@@ -9,7 +9,10 @@
 from apis_core.apis_entities.models import TempEntityClass
 from apis_core.apis_relations.models import Property
 
+from django.apps import apps
+from django.db import DEFAULT_DB_ALIAS, router
 from django.contrib.contenttypes.models import ContentType
+from django.core import serializers
 
 
 @functools.lru_cache
@@ -77,3 +80,55 @@ def get_member_for_entity(
         logging.debug("Found %s.%s", module, model)
         return members[0][1]
     return None
+
+
+def datadump_get_objects(models: list = [], *args, **kwargs):
+    for model in models:
+        if not model._meta.proxy and router.allow_migrate_model(
+            DEFAULT_DB_ALIAS, model
+        ):
+            objects = model._default_manager
+            queryset = objects.using(DEFAULT_DB_ALIAS).order_by(model._meta.pk.name)
+            yield from queryset.iterator()
+
+
+def datadump_get_queryset(additional_app_labels: list = []):
+    """
+    This method is loosely based on the `dumpdata` admin command.
+    It iterates throug the relevant app models and exports them using
+    a serializer and natural foreign keys.
+    Data exported this way can be reimported into a newly created Django APIS app
+    """
+
+    # get all APIS apps and all APIS models
+    apis_app_labels = ["apis_relations", "apis_metainfo"]
+    apis_app_models = [
+        model for model in apps.get_models() if model._meta.app_label in apis_app_labels
+    ]
+
+    # create a list of app labels we want to iterate
+    # this allows to extend the apps via the ?app_labels= parameter
+    app_labels = set(apis_app_labels)
+    app_labels |= set(additional_app_labels)
+
+    # look for models that inherit from APIS models and add their
+    # app label to app_labels
+    for model in apps.get_models():
+        if any(map(lambda x: issubclass(model, x), apis_app_models)):
+            app_labels.add(model._meta.app_label)
+
+    # now go through all app labels
+    app_list = {}
+    for app_label in app_labels:
+        app_config = apps.get_app_config(app_label)
+        app_list[app_config] = None
+
+    models = serializers.sort_dependencies(app_list.items(), allow_cycles=True)
+
+    yield from datadump_get_objects(models)
+
+
+def datadump_serializer(additional_app_labels: list = [], serialier_format="json"):
+    return serializers.serialize(
+        serialier_format, datadump_get_queryset(additional_app_labels), use_natural_foreign_keys=True
+    )