id = Column(db.Integer, primary_key=True)

# 'object' defined in GFKBase

object_version = Column(db.Integer, default=0)

user_id = Column(db.Integer, db.ForeignKey("users.id"))

user = db.relationship("User", backref='changes')

change = Column(PseudoJSON)

created_at = Column(db.DateTime(True), default=db.func.now())

__tablename__ = 'changes'

def to_dict(self, full=True):

d = {

'id': self.id,

'object_id': self.object_id,

'object_type': self.object_type,

'change_type': self.change_type,

'object_version': self.object_version,

'change': self.change,

'created_at': self.created_at

}

if full:

d['user'] = self.user.to_dict()

else:

d['user_id'] = self.user_id

return d

@classmethod

def last_change(cls, obj):

return cls.query.filter(

cls.object_id == obj.id,

cls.object_type == obj.__class__.__tablename__

).order_by(

cls.object_version.desc()

skipped_fields = ('id', 'created_at', 'updated_at', 'version')

_clean_values = None

def __init__(self, *a, **kw):

super(ChangeTrackingMixin, self).__init__(*a, **kw)

self.record_changes(self.user)

def prep_cleanvalues(self):

self.__dict__['_clean_values'] = {}

for attr in inspect(self.__class__).column_attrs:

col, = attr.columns

# 'query' is col name but not attr name

self._clean_values[col.name] = None

def __setattr__(self, key, value):

if self._clean_values is None:

self.prep_cleanvalues()

for attr in inspect(self.__class__).column_attrs:

col, = attr.columns

previous = getattr(self, attr.key, None)

self._clean_values[col.name] = previous

super(ChangeTrackingMixin, self).__setattr__(key, value)

def record_changes(self, changed_by):

db.session.add(self)

db.session.flush()

changes = {}

for attr in inspect(self.__class__).column_attrs:

col, = attr.columns

if attr.key not in self.skipped_fields:

changes[col.name] = {'previous': self._clean_values[col.name],

'current': getattr(self, attr.key)}

db.session.add(Change(object=self,

object_version=self.version,

user=changed_by,