Add the __model_args__ deletion code

This adds the "deleted" fields to the models as well as a new
__model_args__ section whcih supports the option for changing the
deletion type. Deletion is now handled by choosing a deletion method
based on the __model_args__["deletion"] setting, for example if it's
soft deletion it will call Model.soft_delete()

1 files changed, 53 insertions, 1 deletions

diff --git a/mediagoblin/db/base.py b/mediagoblin/db/base.py
index 6acb0b79..a425343b 100644
--- a/mediagoblin/db/base.py
+++ b/mediagoblin/db/base.py
@@ -13,7 +13,7 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
+import datetime
 
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import inspect
@@ -26,6 +26,16 @@ if not DISABLE_GLOBALS:
 
 
 class GMGTableBase(object):
+    # Deletion types
+    HARD_DELETE = "hard-deletion"
+    SOFT_DELETE = "soft-deletion"
+
+    __default_model_args__ = {
+        "deletion": HARD_DELETE,
+        "soft_deletion_field": "deleted",
+        "soft_deletion_retain": ("id",)
+    }
+
     @property
     def _session(self):
         return inspect(self).session
@@ -37,6 +47,11 @@ class GMGTableBase(object):
     if not DISABLE_GLOBALS:
         query = Session.query_property()
 
+    def get_model_arg(self, argument):
+        model_args = self.__default_model_args__.copy()
+        model_args.update(getattr(self, "__model_args__", {}))
+        return model_args.get(argument)
+
     def get(self, key):
         return getattr(self, key)
 
@@ -56,6 +71,43 @@ class GMGTableBase(object):
             sess.flush()
 
     def delete(self, commit=True):
+        """ Delete the object either using soft or hard deletion """
+        if self.get_model_arg("deletion") == self.HARD_DELETE:
+            return self.hard_delete(commit)
+        elif self.get_model_arg("deletion") == self.SOFT_DELETE:
+            return self.soft_delete(commit)
+        else:
+            raise ValueError(
+                "__model_args__['deletion'] is an invalid value %s" % (
+                    self.get_model_arg("deletion")
+                ))
+
+    def soft_delete(self, commit):
+        # Find the deletion field
+        field_name = self.get_model_arg("soft_deletion_field")
+
+        # We can't use self.__table__.columns as it only shows it of the
+        # current model and no parent if polymorphism is being used. This
+        # will cause problems for example for the User model.
+        if field_name not in dir(type(self)):
+            raise ValueError("Cannot find soft_deletion_field")
+
+        # Store a value in the deletion field
+        setattr(self, field_name, datetime.datetime.utcnow())
+
+        # Iterate through the fields and remove data
+        retain_fields = self.get_model_arg("soft_deletion_retain")
+        for field_name in self.__table__.columns.keys():
+            # should we skip this field?
+            if field_name in retain_fields:
+                continue
+
+            setattr(self, field_name, None)
+
+        # Save the changes
+        self.save(commit)
+
+    def hard_delete(self, commit):
         """Delete the object and commit the change immediately by default"""
         sess = self._session
         assert sess is not None, "Not going to delete detached %r" % self