Better support for chaining requests

vk/api.py

@@ -10,6 +10,9 @@ def __init__(self, *args, **kwargs):
         session_class = kwargs.pop('session_class', Session)
         self.session = session_class(*args, **kwargs)
 
+    def new_chain(self):
+        return Chain(self)
+
     def __getattr__(self, method_name):
         return Request(self, method_name)
 
@@ -31,3 +34,48 @@ def __getattr__(self, method_name):
     def __call__(self, **method_args):
         self._method_args = method_args
         return self._api.session.make_request(self)
+
+
+class ChainRequest(object):
+    __slots__ = ('_chain', '_method_name', '_method_args')
+
+    def __init__(self, chain, method_name):
+        self._chain = chain
+        self._method_name = method_name
+        self._method_args = {}
+
+    def __getattr__(self, method_name):
+        return ChainRequest(self._chain, self._method_name + '.' + method_name)
+
+    def __call__(self, **method_args):
+        self._method_args = method_args
+        self._chain._requests.append(self)
+        return self._chain
+
+    # repr() returns {'key': 'value'} for dicts which is unacceptable
+    def _repr_args(self):
+        result = ', '.join('"{}": "{}"'.format(k, v)
+                           for k, v in self._method_args.items())
+        return '{' + result + '}'
+
+    def get_code(self):
+        return 'API.{}({})'.format(self._method_name, self._repr_args())
+
+
+class Chain(object):
+    __slots__ = ('_requests', '_api')
+
+    def __init__(self, api):
+        self._api = api
+        self._requests = []
+
+    def execute(self):
+        return self._api.execute(code=self._get_code())
+
+    def __getattr__(self, method_name):
+        return ChainRequest(self, method_name)
+
+    def _get_code(self):
+        code = ', '.join(r.get_code() for r in self._requests)
+        code = 'return [{}];'.format(code)
+        return code