1 files changed, 75 insertions, 0 deletions
diff --git a/django-simple-history/simple_history/manager.py b/django-simple-history/simple_history/manager.py
new file mode 100755
index 000000000..923b310eb
--- /dev/null
+++ b/django-simple-history/simple_history/manager.py
@@ -0,0 +1,75 @@
+from django.db import models
+
+
+class HistoryDescriptor(object):
+    def __init__(self, model):
+        self.model = model
+
+    def __get__(self, instance, owner):
+        if instance is None:
+            return HistoryManager(self.model)
+        return HistoryManager(self.model, instance)
+
+
+class HistoryManager(models.Manager):
+    def __init__(self, model, instance=None):
+        super(HistoryManager, self).__init__()
+        self.model = model
+        self.instance = instance
+
+    def get_query_set(self):
+        if self.instance is None:
+            return super(HistoryManager, self).get_query_set()
+
+        if isinstance(self.instance._meta.pk, models.OneToOneField):
+            filter = {self.instance._meta.pk.name + "_id": self.instance.pk}
+        else:
+            filter = {self.instance._meta.pk.name: self.instance.pk}
+        return super(HistoryManager, self).get_query_set().filter(**filter)
+
+    def most_recent(self):
+        """
+        Returns the most recent copy of the instance available in the history.
+        """
+        if not self.instance:
+            raise TypeError("Can't use most_recent() without a %s instance." %
+                            self.instance._meta.object_name)
+        tmp = []
+        for field in self.instance._meta.fields:
+            if isinstance(field, models.ForeignKey):
+                tmp.append(field.name + "_id")
+            else:
+                tmp.append(field.name)
+        fields = tuple(tmp)
+        try:
+            values = self.values_list(*fields)[0]
+        except IndexError:
+            raise self.instance.DoesNotExist("%s has no historical record." %
+                                             self.instance._meta.object_name)
+        return self.instance.__class__(*values)
+
+    def as_of(self, date):
+        """
+        Returns an instance of the original model with all the attributes set
+        according to what was present on the object on the date provided.
+        """
+        if not self.instance:
+            raise TypeError("Can't use as_of() without a %s instance." %
+                            self.instance._meta.object_name)
+        tmp = []
+        for field in self.instance._meta.fields:
+            if isinstance(field, models.ForeignKey):
+                tmp.append(field.name + "_id")
+            else:
+                tmp.append(field.name)
+        fields = tuple(tmp)
+        qs = self.filter(history_date__lte=date)
+        try:
+            values = qs.values_list('history_type', *fields)[0]
+        except IndexError:
+            raise self.instance.DoesNotExist("%s had not yet been created." %
+                                             self.instance._meta.object_name)
+        if values[0] == '-':
+            raise self.instance.DoesNotExist("%s had already been deleted." %
+                                             self.instance._meta.object_name)
+        return self.instance.__class__(*values[1:])