Restructured files to avoid circular imports

mongomap/base.py

@@ -0,0 +1,101 @@
+
+class ValidationError(Exception):
+    pass
+
+
+class BaseField(object):
+    """A base class for fields in a MongoDB document. Instances of this class
+    may be added to subclasses of `Document` to define a document's schema.
+    """
+    
+    def __init__(self, name=None, default=None):
+        self.name = name
+        self.default = default
+
+    def __get__(self, instance, owner):
+        """Descriptor for retrieving a value from a field in a document. Do 
+        any necessary conversion between Python and MongoDB types.
+        """
+        if instance is None:
+            # Document class being used rather than a document object
+            return self
+
+        # Get value from document instance if available, if not use default
+        value = instance._data.get(self.name)
+        if value is not None:
+            value = self._to_python(value)
+        elif self.default is not None:
+            value = self.default
+            if callable(value):
+                value = value()
+        return value
+
+    def __set__(self, instance, value):
+        """Descriptor for assigning a value to a field in a document. Do any 
+        necessary conversion between Python and MongoDB types.
+        """
+        if value is not None:
+            try:
+                value = self._to_python(value)
+                self._validate(value)
+                value = self._to_mongo(value)
+            except ValueError:
+                raise ValidationError('Invalid value for field of type "' +
+                                      self.__class__.__name__ + '"')
+        instance._data[self.name] = value
+
+    def _to_python(self, value):
+        """Convert a MongoDB-compatible type to a Python type.
+        """
+        return unicode(value)
+
+    def _to_mongo(self, value):
+        """Convert a Python type to a MongoDB-compatible type.
+        """
+        return self._to_python(value)
+
+    def _validate(self, value):
+        """Perform validation on a value.
+        """
+        return value
+
+
+class DocumentMetaclass(type):
+    """Metaclass for all documents.
+    """
+
+    def __new__(cls, name, bases, attrs):
+        doc_fields = {}
+
+        # Include all fields present in superclasses
+        for base in bases:
+            if hasattr(base, '_fields'):
+                doc_fields.update(base._fields)
+
+        # Add the document's fields to the _fields attribute
+        for attr_name, attr_val in attrs.items():
+            if issubclass(attr_val.__class__, BaseField):
+                if not attr_val.name:
+                    attr_val.name = attr_name
+                doc_fields[attr_name] = attr_val
+        attrs['_fields'] = doc_fields
+
+        return type.__new__(cls, name, bases, attrs)
+
+
+class BaseDocument(object):
+
+    def __init__(self, **values):
+        self._data = {}
+        # Assign initial values to instance
+        for attr_name, attr_value in self._fields.items():
+            if attr_name in values:
+                setattr(self, attr_name, values.pop(attr_name))
+            else:
+                # Use default value
+                setattr(self, attr_name, getattr(self, attr_name))
+
+    def __iter__(self):
+        # Use _data rather than _fields as iterator only looks at names so
+        # values don't need to be converted to Python types
+        return iter(self._data)