actually the whole code has been refactored

orchestrator/model/resources.py

+import copy
+import json
 import uuid
 
 from enum import Enum
-from voluptuous import Schema, Invalid, MultipleInvalid
+from voluptuous import Schema, Invalid, MultipleInvalid, Any, ALLOW_EXTRA, PREVENT_EXTRA
 
 
 class Resource(object):
     DEFAULT_ID_LENGTH = 8
+    ADDITIONAL_SCHEMA = {}
+
+    def __new__(cls, *args, **kwargs):
+        attributes = cls.__attributes_from_dict(args[0] if len(args) else kwargs)
+        resource_type = attributes['type'].value
+        if resource_type is Resource:
+            raise InvalidResourceException('Resource class is abstract')
+        cls.__validate_attributes(attributes, cls.__schema(resource_type, extend=True))
+        instance = super(Resource, resource_type).__new__(resource_type)
+        instance._attributes = attributes  # pylint: disable=protected-access
+        return instance
 
-    def __init__(self, *args, **kwargs):
-        if len(args):
-            resource = args[0]
-            if isinstance(resource, Resource):
-                self.__id = resource.id
-                self.__type = Resource.Type[resource.type]
-            else:
-                self.__attributes_from_dict(resource)
-        else:
-            self.__attributes_from_dict(kwargs)
-
-    def __attributes_from_dict(self, attributes):
-        schema = Schema({
-            'id': str,
-            'type': Resource.Type.validate
-        })
+    @classmethod
+    def __attributes_from_dict(cls, attributes):
+        cls.__validate_attributes(attributes, cls.__schema(extend=False))
+        attributes = copy.deepcopy(attributes)
+        attributes['id'] = attributes.get('id', Resource.__generate_random_id())
+        attributes['type'] = ResourceType.validate(attributes.get('type', cls))
+        return attributes
+
+    @classmethod
+    def __validate_attributes(cls, attributes, schema):
         try:
             schema(attributes)
-            self.__id = attributes.get('id', Resource._random_id())
-            self.__type = Resource.Type[attributes.get('type', 'null')]
         except MultipleInvalid as invalid:
             raise InvalidResourceException(invalid)
 
-    @property
-    def id(self):
-        return self.__id
+    @classmethod
+    def __schema(cls, resource_type=None, extend=False):
+        try:
+            string_validator = Any(str, unicode)
+        except NameError:
+            string_validator = Any(str)
+
+        schema = Schema(schema={'id': string_validator, 'type': ResourceType.validate}, extra=ALLOW_EXTRA)
+        if extend:
+            additional = resource_type.ADDITIONAL_SCHEMA if resource_type else cls.ADDITIONAL_SCHEMA
+            schema = schema.extend(additional, extra=PREVENT_EXTRA)
+        return schema
 
     @property
     def type(self):
-        return self.__type.name
+        return str(self._attributes['type'])
+
+    def __getattr__(self, item):
+        try:
+            return self._attributes[item]
+        except KeyError:
+            raise AttributeError('Attribute (%s) is not set on resource')
 
     @staticmethod
-    def _random_id():
+    def __generate_random_id():
         return uuid.uuid4().hex[:Resource.DEFAULT_ID_LENGTH]
 
     def __eq__(self, other):
-        return isinstance(other, Resource) and \
-               self.id == other.id and \
-               self.type == other.type
+        try:
+            for attr, other_value in other.items():
+                value = self._attributes.get(attr)
+                if value is None or value != other_value:
+                    return False
+            return True
+        except AttributeError:
+            return False
 
     def __repr__(self):
-        return "%s(%s)" % (self.__class__.__name__, self.id)
+        return json.dumps(self, default=Resource.json_encoder)
 
-    def __hash__(self):
-        return hash(self.__repr__())
+    def __iter__(self):
+        return self._attributes.__iter__()
 
-    class Type(Enum):
-        null = 0
-        instance = 1
+    def keys(self):
+        return self._attributes.keys()
 
-        @classmethod
-        def validate(cls, value):
-            try:
-                cls[value]
-            except KeyError:
-                raise Invalid('The given resource type (%s) is not valid' % value)
-            return True
+    def values(self):
+        return self._attributes.values()
 
+    def items(self):
+        return self._attributes.items()
 
-class Instance(Resource):
-    def __init__(self, *args, **kwargs):
-        kwargs['type'] = Resource.Type.instance.name
-        super(Instance, self).__init__(*args, **kwargs)
+    def __getitem__(self, item):
+        return self._attributes[item]
 
+    def __add__(self, other):
+        return ResourceGroup(resources=[self, other])
+
+    @staticmethod
+    def json_encoder(data):
+        if isinstance(data, ResourceType):
+            return str(data)
+        return dict(data)
+
+
+class ResourceGroup(Resource):
+    ADDITIONAL_SCHEMA = {
+        'resources': Any(list, set, tuple)
+    }
+
+    def __init__(self, *_, **__):
+        self.__resources = {}
+        if 'resources' in self._attributes.keys():
+            for resource in self._attributes['resources']:
+                self.add(resource)
+        self._attributes['resources'] = self.resources
+
+    def add(self, resource):
+        if not isinstance(resource, Resource):
+            try:
+                resource = Resource(resource)
+            except InvalidResourceException:
+                raise InvalidResourceException('ResourceGroup can only store resources')
+        self.__resources[resource.id] = resource
 
-class ResourceGroup(object):
-    def __init__(self, *args):
-        self.__resources = set()
-        if len(args):
-            for argument in args:
+    def remove(self, resource):
         try:
-                    self.__iadd__(argument)
+            del self.__resources[Resource(resource).id]
         except InvalidResourceException:
-                    for resource in argument:
-                        self.__iadd__(resource)
+            del self.__resources[resource.id]
 
     @property
     def resources(self):
-        return list(self.__resources)
+        return list(self.__resources.values())
 
-    def __add__(self, other):
-        if isinstance(other, dict):
-            return ResourceGroup(Resource(other), *self.resources)
-        if isinstance(other, Resource):
-            return ResourceGroup(other, *self.resources)
-        if isinstance(other, ResourceGroup):
-            resources = other.resources + self.resources
-            return ResourceGroup(*resources)
-        raise InvalidResourceException()
-
-    def __iadd__(self, other):
-        if isinstance(other, dict):
-            self.__resources.add(Resource(other))
-            return self
-        if isinstance(other, Resource):
-            self.__resources.add(other)
-            return self
-        if isinstance(other, ResourceGroup):
-            self.__resources.union(other.resources)
-            return self
-        raise InvalidResourceException()
 
-    def __iter__(self):
-        return self.__resources.__iter__()
+class Instance(Resource):
+    ADDITIONAL_SCHEMA = {
+        'number_of_cores': int
+    }
 
-    def __eq__(self, other):
-        return self.__resources == set(other.resources)
+
+class ResourceType(Enum):
+    null = Resource
+    group = ResourceGroup
+    instance = Instance
+
+    @classmethod
+    def validate(cls, value):
+        if isinstance(value, cls):
+            return value
+        try:
+            return cls[value]
+        except KeyError:
+            return cls(value)
+        except ValueError:
+            raise Invalid('The given resource type (%s) is not valid' % value)
+
+    def __str__(self):
+        return str(self.name)
+
+    def __repr__(self):
+        return '%s(%s)' % (self.__class__.__name__, str(self))
 
 
 class InvalidResourceException(Exception):

tests/test_resources.py

+import json
 from unittest.case import TestCase
 
-from voluptuous import Invalid
-
-from orchestrator.model.resources import Resource, ResourceGroup, Instance, InvalidResourceException
+from orchestrator.model.resources import Resource, ResourceGroup, Instance, InvalidResourceException, ResourceType
 
 
 class ResourceTest(TestCase):
     def test_resource_without_args(self):
-        # when
-        resource = Resource()
-
-        # then
-        self.assertIsInstance(resource.id, str)
-        self.assertEqual(Resource.DEFAULT_ID_LENGTH, len(resource.id))
-        self.assertEqual('null', resource.type)
+        with self.assertRaises(InvalidResourceException):
+            Resource()
 
     def test_resource_from_args(self):
         # given
         expected_id = 'dummy_resource'
-        expected_type = 'null'
+        expected_type = ResourceType.instance
 
         # when
         result = Resource(id=expected_id, type=expected_type)
 
         # then
         self.assertEqual(expected_id, result.id)
-        self.assertEqual(expected_type, result.type)
+        self.assertEqual(expected_type.name, result.type)
 
     def test_resource_from_dict(self):
         # given
-        resource_dict = dict(id='dummy_resource', type='null')
+        resource_dict = {'id': 'dummy_resource', 'type': 'instance'}
 
         # when
         result = Resource(resource_dict)
@@ -50,12 +44,20 @@ class ResourceTest(TestCase):
         with self.assertRaises(InvalidResourceException):
             Resource(invalid_attributes)
 
-    def test_resource_type_validate(self):
-        self.assertTrue(Resource.Type.validate('instance'))
+    def test_resource_type_validation(self):
+        self.assertTrue(ResourceType.validate('instance'))
+        self.assertTrue(ResourceType.validate(Instance))
+        self.assertTrue(ResourceType.validate(ResourceType.instance))
+        self.assertIsInstance(Resource(type='instance'), Instance)
+        self.assertIsInstance(Resource(type=Instance), Instance)
+        self.assertIsInstance(Resource(type=ResourceType.instance), Instance)
+        self.assertEqual(Instance(id='some_instance'), Resource(id='some_instance', type='instance'))
+        self.assertEqual(Instance(id='some_instance'), Resource(id='some_instance', type=Instance))
+        self.assertEqual(Instance(id='some_instance'), Resource(id='some_instance', type=ResourceType.instance))
 
     def test_resource_type_invalid(self):
-        with self.assertRaises(Invalid):
-            Resource.Type.validate('nonexisting_resource_type')
+        with self.assertRaises(ValueError):
+            ResourceType.validate('nonexisting_resource_type')
 
     def test_resource_instance(self):
         # when
@@ -64,20 +66,61 @@ class ResourceTest(TestCase):
         # then
         self.assertIsInstance(instance.id, str)
         self.assertEqual(Resource.DEFAULT_ID_LENGTH, len(instance.id))
-        self.assertEqual(Resource.Type.instance.name, instance.type)
+        self.assertEqual(ResourceType.instance.name, instance.type)
 
     def test_resource_equivalence(self):
         # given
-        resource1 = Resource(id='some_resource', type='null')
-        resource2 = Resource(id='some_resource', type='null')
-        resource3 = Resource(id='some_other_resource', type='null')
-        resource4 = Resource(id='some_resource', type='instance')
+        resource1 = Resource(id='some_resource', type=Instance)
+        resource2 = Resource(id='some_resource', type=Instance)
+        resource3 = Instance(id='some_resource')
+        resource4 = Resource(id='some_other_resource', type=Instance)
+        resource5 = Resource(id='some_resource', type=ResourceGroup)
 
         # then
         self.assertEqual(resource1, resource1)
         self.assertEqual(resource1, resource2)
-        self.assertNotEqual(resource1, resource3)
+        self.assertEqual(resource1, resource3)
         self.assertNotEqual(resource1, resource4)
+        self.assertNotEqual(resource1, resource5)
+        self.assertFalse(resource1 == 500)
+
+    def test_resource_str_representation(self):
+        # given
+        expected_json = '{"id": "some_resource", "type": "instance"}'
+        expected_dict = json.loads(expected_json)
+
+        # when
+        resource = Resource(expected_dict)
+        resource_dict = json.loads(str(resource))
+
+        # then
+        self.assertEqual(expected_dict, resource_dict)
+
+    def test_resource_dict_representation(self):
+        # given
+        expected_dict = {'id': 'some_resource', 'type': ResourceType.instance}
+
+        # when
+        resource = Resource(expected_dict)
+        resource_dict = dict(resource)
+
+        # then
+        self.assertEqual(expected_dict, resource_dict)
+
+    def test_dynamic_resource_type(self):
+        # when
+        resource = Resource(type='instance')
+
+        # then
+        self.__assert_is_instance(resource)
+        self.__assert_is_instance(Resource({'type': 'instance'}))
+
+        with self.assertRaises(InvalidResourceException):
+            Resource()
+
+    def __assert_is_instance(self, resource):
+        self.assertIsInstance(resource, Instance)
+        self.assertEqual(ResourceType.instance.name, resource.type)
 
 
 class ResourceGroupTest(TestCase):
@@ -90,65 +133,119 @@ class ResourceGroupTest(TestCase):
 
     def test_resource_group_from_resources(self):
         # given
-        resource1 = Resource(id='some_resource')
-        resource2 = Resource(id='some_other_resource')
+        resource1 = Instance(id='some_resource')
+        resource2 = Instance(id='some_other_resource')
 
         # then
-        self.assertEqual([resource1], ResourceGroup(resource1).resources)
-        self.assertEqual([resource1], ResourceGroup([resource1]).resources)
-        self.assertEqual([resource1], ResourceGroup([resource1, resource1]).resources)
+        self.assertEqual([resource1], ResourceGroup(resources=[resource1]).resources)
+        self.assertEqual([resource1], ResourceGroup(resources=[resource1, resource1]).resources)
         for resources in [[resource1, resource2], [resource2, resource1]]:
-            self.assertEqual(2, len(ResourceGroup(*resources).resources))
-            self.assertIn(resource1, ResourceGroup(*resources).resources)
-            self.assertIn(resource2, ResourceGroup(*resources).resources)
+            self.assertEqual(2, len(ResourceGroup(resources=resources).resources))
+            self.assertIn(resource1, ResourceGroup(resources=resources).resources)
+            self.assertIn(resource2, ResourceGroup(resources=resources).resources)
+
+    def test_resource_group_from_invalid_collection(self):
+        with self.assertRaises(InvalidResourceException):
+            ResourceGroup(resources={'invalid': 'resource'})
 
     def test_resource_group_from_dicts(self):
         # given
-        dict1 = dict(id='some_resource')
-        dict2 = dict(id='some_other_resource')
-        expected1 = Resource(dict1)
-        expected2 = Resource(dict2)
+        dict1 = dict(id='some_resource', type=Instance)
+        dict2 = dict(id='some_other_resource', type=Instance)
+        expected1 = Instance(dict1)
+        expected2 = Instance(dict2)
 
         # then
-        self.assertEqual([expected1], ResourceGroup(dict1).resources)
-        self.assertEqual([expected1], ResourceGroup([dict1]).resources)
-        self.assertEqual([expected1], ResourceGroup([dict1, dict1]).resources)
+        self.assertEqual([expected1], ResourceGroup(resources=[dict1]).resources)
+        self.assertEqual([expected1], ResourceGroup(resources=[dict1, dict1]).resources)
         for resources in [[expected1, expected2], [dict2, dict1]]:
-            self.assertEqual(2, len(ResourceGroup(resources).resources))
-            self.assertIn(expected1, ResourceGroup(resources).resources)
-            self.assertIn(expected2, ResourceGroup(resources).resources)
+            self.assertEqual(2, len(ResourceGroup(resources=resources).resources))
+            self.assertIn(expected1, ResourceGroup(resources=resources).resources)
+            self.assertIn(expected2, ResourceGroup(resources=resources).resources)
+
+    def test_resource_group_from_dict(self):
+        # given
+        expected_group_id = 'some_resource_group'
+        expected_resource_id = 'some_instance'
+        group_dict = {
+            'id': expected_group_id,
+            'type': 'group',
+            'resources': [
+                {'id': expected_resource_id, 'type': 'instance'}
+            ]
+        }
+
+        # when
+        group = ResourceGroup(group_dict)
+
+        # then
+        self.assertEqual(expected_group_id, group.id)
+        self.assertEqual(1, len(group.resources))
+        self.assertEqual(expected_resource_id, group.resources[0].id)
+
+    def test_resource_group_add_resource(self):
+        # given
+        group = ResourceGroup()
+        resource = Instance()
+
+        # when
+        group.add(resource)
+
+        # then
+        self.assertEqual(1, len(group.resources))
+        self.assertIn(resource, group.resources)
+
+    def test_resource_group_remove_resource(self):
+        # given
+        resource = Instance()
+        group = ResourceGroup()
+        group.add(resource)
+
+        # when
+        group.remove(resource)
+
+        # then
+        self.assertEqual([], group.resources)
 
+    # @skip('works same way as resource addition')
     def test_resource_group_addition(self):
         # given
-        resource1 = Resource()
-        resource2 = Resource()
-        group1 = ResourceGroup(resource1)
-        group2 = ResourceGroup(resource2)
+        group1 = ResourceGroup()
+        group2 = ResourceGroup()
+        resource = Instance()
 
         # when
-        result_group = group1 + group2
+        result_group1 = group1 + group2
+        result_group2 = result_group1 + resource
 
         # then
-        self.assertEqual(2, len(result_group.resources))
-        self.assertIn(resource1, result_group.resources)
-        self.assertIn(resource2, result_group.resources)
+        self.assertIsInstance(result_group1, ResourceGroup)
+        self.assertIsInstance(result_group2, ResourceGroup)
+        self.assertEqual(2, len(result_group1.resources))
+        self.assertEqual(2, len(result_group2.resources))
+        self.assertIn(group1, result_group1.resources)
+        self.assertIn(group2, result_group1.resources)
+        self.assertIn(resource, result_group2.resources)
 
     def test_resource_group_iteration(self):
         # when
-        group = ResourceGroup(Resource(), Resource(), Resource())
+        group = ResourceGroup(resources=[Instance(), Instance(), Instance()])
 
         # then
-        for index, resource in enumerate(group):
+        for index, resource in enumerate(group.resources):
             self.assertEqual(group.resources[index], resource)
 
     def test_resource_group_equivalence(self):
         # given
-        resource1 = Resource(id='some_resource', type='null')
-        resource2 = Resource(id='some_resource', type='null')
-        resource3 = Resource(id='some_other_resource', type='null')
+        resource1 = Instance(id='some_resource')
+        resource2 = Instance(id='some_other_resource')
 
         # then
-        self.assertEqual(ResourceGroup(), ResourceGroup())
-        self.assertEqual(ResourceGroup(resource1), ResourceGroup(resource1))
-        self.assertEqual(ResourceGroup(resource1), ResourceGroup(resource2))
-        self.assertNotEqual(ResourceGroup(resource1), ResourceGroup(resource3))
+        self.assertEqual(ResourceGroup(id='some_group'),
+                         ResourceGroup(id='some_group'))
+        self.assertEqual(ResourceGroup(id='some_group', resources=[resource1]),
+                         ResourceGroup(id='some_group', resources=[resource1]))
+        self.assertNotEqual(ResourceGroup(id='some_group'),
+                            ResourceGroup(id='some_other_group'))
+        self.assertNotEqual(ResourceGroup(id='some_group', resources=[resource1]),
+                            ResourceGroup(id='some_group', resources=[resource2]))