Merge pull request #67 from desklab/document-cache

Measurement document cache

gcampus/core/apps.py

@@ -21,3 +21,6 @@ class GCampusCoreAppConfig(AppConfig):
     name = "gcampus.core"
     label = "gcampuscore"
     verbose_name = _("GCampus Core")
+
+    def ready(self):
+        from . import receivers  # imported to connect all receivers

gcampus/core/migrations/0005_measurement_document_cache.py

@@ -0,0 +1,23 @@
+# Generated by Django 4.0.4 on 2022-05-06 13:58
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("gcampuscore", "0004_location_help_text"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="measurement",
+            name="document",
+            field=models.FileField(
+                blank=True,
+                null=True,
+                upload_to="documents/measurement",
+                verbose_name="Document",
+            ),
+        ),
+    ]

gcampus/core/models/measurement.py

@@ -108,6 +108,15 @@ class Meta:
     #: generated column in migration ``0002_search``.
     search_vector = SearchVectorField(null=True, editable=False)
 
+    #: File field to cache the measurement detail document for this
+    #: measurement.
+    document = models.FileField(
+        verbose_name=_("Document"),
+        upload_to="documents/measurement",
+        blank=True,
+        null=True,
+    )
+
     #: Related field: List of all parameters associated with this
     #: measurement.
     parameters: List[Parameter]

gcampus/core/receivers.py

@@ -0,0 +1,86 @@
+#  Copyright (C) 2022 desklab gUG (haftungsbeschränkt)
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU Affero General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU Affero General Public License for more details.
+#
+#  You should have received a copy of the GNU Affero General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+__all__ = ["update_measurement_document", "clear_measurement_documents"]
+
+import logging
+from typing import Union, Optional
+
+from django.db.models import QuerySet
+from django.db.models.signals import post_save, post_delete
+from django.dispatch import receiver
+from django.utils.translation import get_language
+
+from gcampus.core.models import Parameter, Measurement, ParameterType, Water
+from gcampus.documents.tasks import render_cached_document_view
+
+logger = logging.getLogger("gcampus.core.receivers")
+
+
+@receiver(post_save, sender=Measurement)
+@receiver(post_save, sender=Parameter)
+@receiver(post_delete, sender=Parameter)
+def update_measurement_document(
+    sender,  # noqa
+    instance: Union[Parameter, Measurement],
+    created: bool = False,
+    update_fields: Optional[Union[tuple, list]] = None,
+    **kwargs,  # noqa
+):
+    update_fields = update_fields or ()
+
+    if isinstance(instance, Measurement):
+        if "document" in update_fields:
+            return
+        if created:
+            return
+        measurement: Measurement = instance
+    elif isinstance(instance, Parameter):
+        measurement: Measurement = instance.measurement
+    else:
+        raise NotImplementedError(f"Unhandled instance '{type(instance)}'")
+
+    if not measurement.document:
+        # Only build the document if it has been build already.
+        return
+
+    render_cached_document_view.apply_async(
+        args=(
+            "gcampus.documents.views.MeasurementDetailPDF",
+            measurement.pk,
+            get_language(),
+        ),
+    )
+
+
+@receiver(post_save, sender=ParameterType)
+def clear_measurement_documents(
+    sender,  # noqa
+    instance: ParameterType,
+    created: bool = False,
+    **kwargs,  # noqa
+):
+    if created:
+        return
+    qs: QuerySet
+    if isinstance(instance, ParameterType):
+        qs = Measurement.objects.filter(parameters__parameter_type=instance)
+    elif isinstance(instance, Water):
+        qs = Measurement.objects.filter(water=instance)
+    else:
+        raise NotImplementedError(f"Unhandled instance '{type(instance)}'")
+    # Note that the file will not be deleted from the storage backend,
+    # only its reference is removed from the database.
+    qs.update(document=None)

gcampus/documents/views/print.py

@@ -79,11 +79,12 @@ def get_filename(self):
         )
 
 
-class MeasurementDetailPDF(SingleObjectDocumentView):
+class MeasurementDetailPDF(CachedDocumentView):
     template_name = "gcampusdocuments/documents/measurement_detail.html"
     filename = gettext_lazy("gewaessercampus-measurement-detail.pdf")
     context_object_name = "measurement"
     model = Measurement
+    model_file_field = "document"
 
     def dispatch(self, request, *args, **kwargs):
         return super(MeasurementDetailPDF, self).dispatch(request, *args, **kwargs)