From 5c715424eee6d3bf602d854fb3acc99f0c8aa46e Mon Sep 17 00:00:00 2001
From: Sonny Bakker <sonny@maykinmedia.nl>
Date: Wed, 14 Sep 2022 12:25:54 +0200
Subject: [PATCH] [#210] Add query param extension

---
 vng_api_common/inspectors/__init__.py |  1 +
 vng_api_common/inspectors/query.py    | 83 +++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 vng_api_common/inspectors/query.py

diff --git a/vng_api_common/inspectors/__init__.py b/vng_api_common/inspectors/__init__.py
index c04ec423..ce12021e 100644
--- a/vng_api_common/inspectors/__init__.py
+++ b/vng_api_common/inspectors/__init__.py
@@ -5,3 +5,4 @@
     ReadOnlyFieldExtension,
 )
 from .polymorphic import PolymorphicSerializerExtension
+from .query import FilterExtension
diff --git a/vng_api_common/inspectors/query.py b/vng_api_common/inspectors/query.py
new file mode 100644
index 00000000..a3bb72e8
--- /dev/null
+++ b/vng_api_common/inspectors/query.py
@@ -0,0 +1,83 @@
+from django.db import models
+from django.utils.encoding import force_text
+from django.utils.translation import gettext as _
+
+from django_filters.filters import BaseCSVFilter, ChoiceFilter
+from drf_spectacular.extensions import OpenApiFilterExtension
+from rest_framework.filters import OrderingFilter
+
+from vng_api_common.filters import URLModelChoiceFilter
+from vng_api_common.inspectors.utils import get_target_field
+from vng_api_common.oas import TYPE_ARRAY, TYPE_STRING
+from vng_api_common.utils import underscore_to_camel
+
+
+class FilterExtension(OpenApiFilterExtension):
+    target_class = "vng_api_common.filters.Backend"
+    match_subclasses = True
+
+    def get_schema_operation_parameters(self, auto_schema, *args, **kwargs):
+        default_parameters = self.target.get_schema_operation_parameters(
+            auto_schema.view
+        )
+        filterset_class = getattr(auto_schema.view, "filterset_class", None)
+
+        if isinstance(self.target, OrderingFilter) or not filterset_class:
+            # TODO: OrderingFilter not present in ZRC, test in other components
+            return default_parameters
+
+        queryset = auto_schema.view.get_queryset()
+
+        for parameter in default_parameters:
+            filter_field = filterset_class.base_filters[parameter["name"]]
+            model_field = get_target_field(queryset.model, parameter["name"])
+
+            parameter_name = underscore_to_camel(parameter["name"])
+
+            original_description = parameter.get("description")
+            help_text = filter_field.extra.get(
+                "help_text",
+                getattr(model_field, "help_text", "") if model_field else "",
+            )
+
+            if isinstance(filter_field, BaseCSVFilter):
+                schema = {
+                    "type": TYPE_ARRAY,
+                    "items": {
+                        "type": TYPE_STRING,
+                    },
+                }
+
+                if "choices" in filter_field.extra:
+                    schema["items"]["enum"] = (
+                        [choice[0] for choice in filter_field.extra["choices"]],
+                    )
+
+                parameter["type"] = TYPE_ARRAY
+                parameter["schema"] = schema
+                parameter["style"] = "form"
+                parameter["explode"] = False
+            elif isinstance(filter_field, URLModelChoiceFilter):
+                description = _("URL to the related {resource}").format(
+                    resource=parameter_name
+                )
+                parameter["description"] = help_text or description
+                parameter["format"] = "uri"
+            elif isinstance(filter_field, ChoiceFilter):
+                parameter["schema"]["enum"] = [
+                    choice[0] for choice in filter_field.extra["choices"]
+                ]
+            elif model_field and isinstance(model_field, models.URLField):
+                parameter["format"] = "uri"
+
+            if parameter["description"] == original_description and help_text:
+                parameter["description"] = force_text(help_text)
+
+            if "max_length" in filter_field.extra:
+                parameter["max_length"] = filter_field.extra["max_length"]
+            if "min_length" in filter_field.extra:
+                parameter["min_length"] = filter_field.extra["min_length"]
+
+            parameter["name"] = parameter_name
+
+        return default_parameters