Logging support

apps/logs/__init__.py

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+# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+default_app_config = 'logs.apps.LogsConfig'

apps/logs/apps.py

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+# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from django.apps import AppConfig
+from django.utils.translation import gettext_lazy as _
+
+
+class LogsConfig(AppConfig):
+    name = 'logs'
+    verbose_name = _('Logs')
+
+    def ready(self):
+        # noinspection PyUnresolvedReferences
+        import logs.signals

apps/logs/models.py

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+# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from django.utils.translation import gettext_lazy as _
+from django.conf import settings
+from django.core.exceptions import ValidationError
+from django.db import models
+
+
+class Changelog(models.Model):
+    """
+    Store each modification on the database (except sessions and logging),
+    including creating, editing and deleting models.
+    """
+
+    user = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.PROTECT,
+        null=True,
+        verbose_name=_('user'),
+    )
+
+    model = models.CharField(
+        max_length=255,
+        null=False,
+        blank=False,
+        verbose_name=_('model'),
+    )
+
+    instance_pk = models.CharField(
+        max_length=255,
+        null=False,
+        blank=False,
+        verbose_name=_('identifier'),
+    )
+
+    previous = models.TextField(
+        null=True,
+        verbose_name=_('previous data'),
+    )
+
+    data = models.TextField(
+        null=True,
+        verbose_name=_('new data'),
+    )
+
+    action = models.CharField(  # create, edit or delete
+        max_length=16,
+        null=False,
+        blank=False,
+        verbose_name=_('action'),
+    )
+
+    timestamp = models.DateTimeField(
+        null=False,
+        blank=False,
+        auto_now_add=True,
+        name='timestamp',
+        verbose_name=_('timestamp'),
+    )
+
+    def delete(self, using=None, keep_parents=False):
+        raise ValidationError(_("Logs cannot be destroyed."))

apps/logs/signals.py

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+# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+import inspect
+
+from django.core import serializers
+from django.db.models.signals import pre_save, pre_delete
+from django.dispatch import receiver
+from .models import Changelog
+
+
+def get_user_in_signal(sender, **kwargs):
+    user = None
+    for entry in reversed(inspect.stack()):
+        try:
+            user = entry[0].f_locals['request'].user
+            break
+        except:
+            pass
+
+    if not user:
+        print("WARNING: Attempt to save " + str(sender) + " with no user")
+
+    return user
+
+EXCLUDED = [
+        'Changelog',
+        'Migration',
+        'Session',
+    ]
+
+@receiver(pre_save)
+def save_object(sender, instance, **kwargs):
+    model_name = sender.__name__
+    if model_name in EXCLUDED:
+        return
+
+    previous = sender.objects.filter(pk=instance.pk).all()
+
+    user = get_user_in_signal(sender, **kwargs)
+    if previous.exists:
+        previous_json = serializers.serialize('json', previous)[1:-1]
+    else:
+        previous_json = None
+    instance_json = serializers.serialize('json', [instance, ],)[1:-1]
+    Changelog.objects.create(user=user,
+                                        model=model_name,
+                                        instance_pk=instance.pk,
+                                        previous=previous_json,
+                                        data=instance_json,
+                                        action=("edit" if previous.exists() else "create")
+                                        )#.save()
+
+@receiver(pre_delete)
+def delete_object(sender, instance, **kwargs):
+    model_name = sender.__name__
+    if model_name in EXCLUDED:
+        return
+
+    user = get_user_in_signal(sender, **kwargs)
+    instance_json = serializers.serialize('json', [instance, ])[1:-1]
+    Changelog.objects.create(user=user,
+                                        model=model_name,
+                                        instance_pk=instance.pk,
+                                        previous=instance_json,
+                                        data=None,
+                                        action="delete"
+                                        ).save()

apps/logs/urls.py

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+# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+app_name = 'logs'
+
+# TODO User interface
+urlpatterns = [
+]