From 2e2fc09617f256ee2525e4b9f7b8a7b1a5831af0 Mon Sep 17 00:00:00 2001
From: Birger Schacht <birger.schacht@oeaw.ac.at>
Date: Mon, 27 Jan 2025 16:25:04 +0100
Subject: [PATCH] feat(generic): add a collections filter

Closes: #1557
---
 apis_core/generic/filtersets.py               | 51 +++++++++++++++++++
 apis_core/generic/forms/fields.py             | 29 ++++++++++-
 .../widgets/includeexclude_multiwidget.html   |  4 ++
 3 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 apis_core/generic/templates/widgets/includeexclude_multiwidget.html

diff --git a/apis_core/generic/filtersets.py b/apis_core/generic/filtersets.py
index febcc39d8..72a8553e7 100644
--- a/apis_core/generic/filtersets.py
+++ b/apis_core/generic/filtersets.py
@@ -1,7 +1,47 @@
+import logging
+
+import django_filters
+from django.apps import apps
+from django.contrib.contenttypes.models import ContentType
 from django_filters.filterset import FilterSet
 
+from apis_core.generic.forms.fields import IncludeExcludeField
+
 from .forms import GenericFilterSetForm
 
+logger = logging.getLogger(__name__)
+
+
+class CollectionsFilter(django_filters.filters.ModelMultipleChoiceFilter):
+    """
+    A simple filter for connections to collections. It provides an `include`/`exclude`
+    selector, which allows to define what the filter should do.
+    """
+
+    @property
+    def field(self):
+        return IncludeExcludeField(super().field, required=self.extra["required"])
+
+    def filter(self, queryset, value):
+        value, include_exclude = value
+        if value:
+            content_type = ContentType.objects.get_for_model(queryset.model)
+            try:
+                skoscollectioncontentobject = apps.get_model(
+                    "collections.SkosCollectionContentObject"
+                )
+                scco = skoscollectioncontentobject.objects.filter(
+                    content_type=content_type, collection__in=value
+                ).values("object_id")
+                match include_exclude:
+                    case "include":
+                        return queryset.filter(id__in=scco)
+                    case "exclude":
+                        return queryset.exclude(id__in=scco)
+            except LookupError as e:
+                logger.debug("Not filtering for collections: %s", e)
+        return queryset
+
 
 class GenericFilterSet(FilterSet):
     """
@@ -12,3 +52,14 @@ class GenericFilterSet(FilterSet):
 
     class Meta:
         form = GenericFilterSetForm
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        try:
+            skoscollection = apps.get_model("collections.SkosCollection")
+            if skoscollection.objects.exists():
+                self.filters["collections"] = CollectionsFilter(
+                    queryset=skoscollection.objects.all(),
+                )
+        except LookupError as e:
+            logger.debug("Not adding collections filter to form: %s", e)
diff --git a/apis_core/generic/forms/fields.py b/apis_core/generic/forms/fields.py
index 42e39e2d9..e7567894a 100644
--- a/apis_core/generic/forms/fields.py
+++ b/apis_core/generic/forms/fields.py
@@ -1,5 +1,5 @@
 from django.core.exceptions import ValidationError
-from django.forms import ModelChoiceField
+from django.forms import ChoiceField, ModelChoiceField, MultiValueField, MultiWidget
 from django.utils.translation import gettext as _
 
 from apis_core.utils.helpers import create_object_from_uri
@@ -16,3 +16,30 @@ def to_python(self, value):
                 params={"value": value, "exception": e},
             )
         return result or super().to_python(value)
+
+
+class IncludeExcludeMultiWidget(MultiWidget):
+    template_name = "widgets/includeexclude_multiwidget.html"
+    use_fieldset = False
+
+    def decompress(self, value):
+        return [value, value]
+
+
+class IncludeExcludeField(MultiValueField):
+    """
+    This is a custom MultiValueField that adds a ChoiceField that only provides two
+    choices, namely `exclude` and `include`. It can be used for django-filter filters
+    to specify which action should be done with the filter.
+    """
+
+    def __init__(self, field, *args, **kwargs):
+        fields = (
+            field,
+            ChoiceField(choices=[("include", "include"), ("exclude", "exclude")]),
+        )
+        kwargs["widget"] = IncludeExcludeMultiWidget(widgets=[f.widget for f in fields])
+        super().__init__(fields=fields, *args, **kwargs)
+
+    def compress(self, data_list):
+        return data_list
diff --git a/apis_core/generic/templates/widgets/includeexclude_multiwidget.html b/apis_core/generic/templates/widgets/includeexclude_multiwidget.html
new file mode 100644
index 000000000..7500c2072
--- /dev/null
+++ b/apis_core/generic/templates/widgets/includeexclude_multiwidget.html
@@ -0,0 +1,4 @@
+<div class="row">
+  <div class="col">{% include widget.subwidgets.0.template_name with widget=widget.subwidgets.0 %}</div>
+  <div class="col-auto">{% include widget.subwidgets.1.template_name with widget=widget.subwidgets.1 %}</div>
+</div>