Use a chain of objects for getting a session

example.py

@@ -28,39 +28,114 @@ def print_devices(devices):
         print(device['alias'])
 
 
+class Gateway(object):
+    def __init__(self, oauth_base, api_root):
+        self.oauth_base = oauth_base
+        self.api_root = api_root
+
+    @classmethod
+    def discover(cls):
+        gw = wideq.gateway_info()
+        return cls(gw['empUri'], gw['thinqUri'])
+
+    @classmethod
+    def load(cls, data):
+        return cls(data['oauth_base'], data['api_root'])
+
+    def dump(self):
+        return {'oauth_base': self.oauth_base, 'api_root': self.api_root}
+
+    def oauth_url(self):
+        return wideq.oauth_url(self.oauth_base)
+
+
+class Auth(object):
+    def __init__(self, gateway, access_token):
+        self.gateway = gateway
+        self.access_token = access_token
+
+    def start_session(self):
+        """Start an API session for the logged-in user. Return the
+        Session object and the user's devices.
+        """
+
+        session_info = wideq.login(self.gateway.api_root, self.access_token)
+        session_id = session_info['jsessionId']
+        return Session(self, session_id), session_info['item']
+
+    def dump(self):
+        return self.access_token
+
+    @classmethod
+    def load(cls, gateway, data):
+        return cls(gateway, data)
+
+
+class Session(object):
+    def __init__(self, auth, session_id):
+        self.auth = auth
+        self.session_id = session_id
+
+    def get_devices(self):
+        return wideq.get_devices(self.auth.gateway.api_root,
+                                 self.auth.access_token,
+                                 self.session_id)
+
+    def dump(self):
+        return self.session_id
+
+    @classmethod
+    def load(cls, auth, data):
+        return cls(auth, data)
+
+
+def authenticate(gateway):
+    login_url = gateway.oauth_url()
+    print('Log in here:')
+    print(login_url)
+    print('Then paste the URL where the browser is redirected:')
+    callback_url = input()
+    access_token = wideq.parse_oauth_callback(callback_url)
+    return Auth(gateway, access_token)
+
+
 def example():
     state = load_state()
 
-    # Get the URLs for the API.
-    if 'oauth_base' not in state and 'api_root' not in state:
-        gw = wideq.gateway_info()
-        state['oauth_base'] = gw['empUri']
-        state['api_root'] = gw['thinqUri']
-        save_state(state)
-    oauth_base = state['oauth_base']
-    api_root = state['api_root']
+    # Get the gateway, which contains the base URLs and hostnames for
+    # accessing the API.
+    if 'gateway' in state:
+        gateway = Gateway.load(state['gateway'])
+    else:
+        gateway = Gateway.discover()
 
-    # If we don't have an access token, authenticate.
-    if 'access_token' not in state:
-        login_url = wideq.oauth_url(oauth_base)
-        print('Log in here:')
-        print(login_url)
-        print('Then paste the URL where the browser is redirected:')
-        callback_url = input()
-        state['access_token'] = wideq.parse_oauth_callback(callback_url)
+        state['gateway'] = gateway.dump()
         save_state(state)
-    access_token = state['access_token']
 
-    # If we don't have a session, log in.
-    if 'session_id' not in state:
-        session_info = wideq.login(api_root, access_token)
-        state['session_id'] = session_info['jsessionId']
+    # Authenticate the user.
+    if 'auth' in state:
+        auth = Auth.load(gateway, state['auth'])
+    else:
+        auth = authenticate(gateway)
+
+        state['auth'] = auth.dump()
         save_state(state)
-        print_devices(session_info['item'])
-    session_id = state['session_id']
 
-    # Request a list of devices.
-    devices = wideq.get_devices(api_root, access_token, session_id)
+    # Start a session.
+    if 'session' in state:
+        session = Session.load(auth, state['session'])
+        devices = None
+    else:
+        session, devices = auth.start_session()
+
+        state['session'] = session.dump()
+        save_state(state)
+
+    # Request a list of devices, if we didn't get them "for free"
+    # already by starting the session.
+    if not devices:
+        devices = session.get_devices()
+
     print_devices(devices)