coplete Change model for editor

src/c3nav/editor/models.py

@@ -1,9 +1,11 @@
+import typing
+
+from django.apps import apps
 from django.conf import settings
+from django.core.exceptions import ObjectDoesNotExist, ValidationError
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
 
-from c3nav.mapdata.fields import JSONField
-
 
 class ChangeSet(models.Model):
     author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.PROTECT, verbose_name=_('Author'))
@@ -20,12 +22,124 @@ class ChangeSet(models.Model):
 
 
 class Change(models.Model):
+    ACTIONS = (
+        ('delchange', _('delete change')),
+        ('create', _('create object')),
+        ('delete', _('delete object')),
+        ('update', _('update attribute')),
+        ('m2m_add', _('add many to many relation')),
+        ('m2m_remove', _('add many to many relation')),
+    )
     changeset = models.ForeignKey(ChangeSet, on_delete=models.CASCADE, verbose_name=_('Change Set'))
     author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.PROTECT, verbose_name=_('Author'))
     created = models.DateTimeField(auto_now_add=True, verbose_name=_('created'))
-    content = JSONField()
+    action = models.CharField(max_length=16, choices=ACTIONS, verbose_name=_('action'))
+    deletes_change = models.OneToOneField('Change', null=True, on_delete=models.CASCADE, related_name='deleted_by',
+                                          verbose_name=_('deletes change'))
+    model_name = models.CharField(max_length=50, null=True, verbose_name=_('model name'))
+    existing_object_pk = models.PositiveIntegerField(null=True, verbose_name=_('id of existing object'))
+    created_object = models.ForeignKey('Change', null=True, on_delete=models.CASCADE, related_name='changed_by',
+                                       verbose_name=_('changed object'))
+    field_name = models.CharField(max_length=50, null=True, verbose_name=_('field name'))
+    field_value = models.TextField(null=True, verbose_name=_('new field value'))
 
     class Meta:
         verbose_name = _('Change')
         verbose_name_plural = _('Changes')
         default_related_name = 'changes'
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._set_object = None
+
+    @property
+    def model_class(self) -> typing.Type[models.Model]:
+        if self.model_name is None:
+            raise TypeError('model_name is not set, can not get model')
+        return apps.get_model('mapdata', self.model_name)
+
+    @model_class.setter
+    def model_class(self, value: typing.Type[models.Model]):
+        if not issubclass(value, models.Model):
+            raise ValueError('value is not a django model')
+        if value._meta.abstract:
+            raise ValueError('value is an abstract model')
+        if value._meta.app_label != 'mapdata':
+            raise ValueError('value is not a mapdata model')
+        self.model_name = value.__name__
+
+    @property
+    def object(self) -> models.Model:
+        if self.existing_object_pk is not None:
+            if self.created_object is not None:
+                raise TypeError('existing_object_pk and created_object can not both be set.')
+            if self._set_object is not None:
+                if isinstance(self._set_object, self.model_class) and self._set_object.pk != self.existing_object_pk:
+                    return self._set_object
+                self._set_object = None
+            self._set_object = self.model_class.objects.get(pk=self.existing_object_pk)
+            return self._set_object
+        elif self.created_object is not None:
+            if self.created_object.model_class != self.model_class:
+                raise TypeError('created_object model and change model do not match.')
+            if self.created_object.changeset_id != self.changeset_id:
+                raise TypeError('created_object belongs to a different changeset.')
+            return self.created_object
+        raise TypeError('existing_model_pk or created_object have to be set.')
+
+    @object.setter
+    def object(self, value: models.Model):
+        if isinstance(value, Change):
+            if self.created_object.changeset_id != self.changeset_id:
+                raise ValueError('value is a Change instance but belongs to a different changeset.')
+            if value.action != 'create':
+                raise ValueError('value is a Change instance but has action not set to create')
+            self.model_class = value.model_class
+            self.created_object = value
+            self.existing_object_pk = None
+            return
+
+        model_class_before = self.model_class
+        self.model_class = value.__class__
+        if value.pk is None:
+            self.model_class = model_class_before
+            raise ValueError('object is not saved yet and cannot be referenced')
+        self.existing_object_pk = value.pk
+        self.created_object = None
+
+    def clean(self):
+        if self.action == 'delchange':
+            if self.deletes_change is None:
+                raise ValidationError('deletes_change has to be set if action is delchange.')
+            if self.deletes_change.changeset_id != self.changeset_id:
+                raise ValidationError('deletes_change refers to a change from a different changeset.')
+
+            for field_name in ('model_name', 'existing_object_pk', 'created_object', 'field_name', 'field_value'):
+                if getattr(self, field_name) is not None:
+                    raise ValidationError('%s must not be set if action is delchange.' % field_name)
+            return
+
+        if self.deletes_change is not None:
+            raise ValidationError('deletes_change can only be set if action is delchange.')
+
+        if self.model_name is None:
+            raise ValidationError('model_name has to be set if action is not delchange.')
+
+        try:
+            object = self.object  # noqa
+        except TypeError as e:
+            raise ValidationError(str(e))
+        except ObjectDoesNotExist:
+            raise ValidationError('model_name has to be set if action is not delchange.')
+
+        if self.existing_object_pk is None:
+            if self.created_object is None:
+                raise ValidationError('existing_model_pk or created_object have to be set if action is not delchange.')
+        else:
+            if self.created_object is not None:
+                raise ValidationError('existing_model_pk and created_object can not both be set.')
+
+        if self.action in ('create', 'delete'):
+            for field_name in ('field_name', 'field_value'):
+                if getattr(self, field_name) is not None:
+                    raise ValidationError('%s must not be set if action is create or delete.' % field_name)