Break up the login flow and expose the authorization URL to the libra…

…ry user

schwab/auth.py

@@ -1,6 +1,7 @@
 from authlib.integrations.httpx_client import AsyncOAuth2Client, OAuth2Client
 from prompt_toolkit import prompt
 
+import collections
 import contextlib
 import httpx
 import json
@@ -27,7 +28,7 @@ def get_logger():
     return logging.getLogger(__name__)
 
 
-def __update_token(token_path):
+def __make_update_token_func(token_path):
     def update_token(t, *args, **kwargs):
         get_logger().info('Updating token to file %s', token_path)
 
@@ -119,51 +120,6 @@ def wrap_token_in_metadata(self, token):
         }
 
 
-def __fetch_and_register_token_from_redirect(
-        oauth, redirected_url, api_key, app_secret, token_path,
-        token_write_func, asyncio, enforce_enums=True):
-    token = oauth.fetch_token(
-        TOKEN_ENDPOINT,
-        authorization_response=redirected_url,
-        client_id=api_key, auth=(api_key, app_secret))
-
-    # Don't emit token details in debug logs
-    register_redactions(token)
-
-    # Set up token writing and perform the initial token write
-    update_token = (
-        __update_token(token_path) if token_write_func is None
-        else token_write_func)
-    metadata_manager = TokenMetadata(token, int(time.time()), update_token)
-    update_token = metadata_manager.wrapped_token_write_func()
-    update_token(token)
-
-    # The synchronous and asynchronous versions of the OAuth2Client are similar
-    # enough that can mostly be used interchangeably. The one currently known
-    # exception is the token update function: the synchronous version expects a
-    # synchronous one, the asynchronous requires an async one. The
-    # oauth_client_update_token variable will contain the appropriate one.
-    if asyncio:
-        async def oauth_client_update_token(t, *args, **kwargs):
-            update_token(t, *args, **kwargs)  # pragma: no cover
-        session_class = AsyncOAuth2Client
-        client_class = AsyncClient
-    else:
-        oauth_client_update_token = update_token
-        session_class = OAuth2Client
-        client_class = Client
-
-    # Return a new session configured to refresh credentials
-    return client_class(
-        api_key,
-        session_class(api_key,
-                      client_secret=app_secret,
-                      token=token,
-                      update_token=oauth_client_update_token,
-                      leeway=300),
-        token_metadata=metadata_manager, enforce_enums=enforce_enums)
-
-
 ################################################################################
 # client_from_login_flow
 
@@ -351,9 +307,7 @@ def callback_server():
             time.sleep(0.1)
 
         # Open the browser
-        oauth = OAuth2Client(api_key, redirect_uri=callback_url)
-        authorization_url, state = oauth.create_authorization_url(
-            'https://api.schwabapi.com/v1/oauth/authorize')
+        auth_context = get_auth_context(api_key, callback_url)
 
         print()
         print('***********************************************************************')
@@ -363,7 +317,7 @@ def callback_server():
         print('browser, captures the resulting OAuth callback, and creates a token')
         print('using the result. The authorization URL is:')
         print()
-        print('>>', authorization_url)
+        print('>>', auth_context.authorization_url)
         print()
         print('IMPORTANT: Your browser will give you a security warning about an')
         print('invalid certificate prior to issuing the redirect. This is because')
@@ -388,7 +342,7 @@ def callback_server():
                   'this method with interactive=False to skip this input.')
 
         controller = webbrowser.get(requested_browser)
-        controller.open(authorization_url)
+        controller.open(auth_context.authorization_url)
 
         # Wait for a response
         now = __TIME_TIME()
@@ -420,9 +374,13 @@ def callback_server():
                     'can set a longer timeout by passing a value of ' +
                     'callback_timeout to client_from_login_flow.')
 
-        return __fetch_and_register_token_from_redirect(
-            oauth, received_url, api_key, app_secret, token_path,
-            token_write_func, asyncio, enforce_enums=enforce_enums)
+        token_write_func = (
+            __make_update_token_func(token_path) if token_write_func is None
+            else token_write_func)
+
+        return client_from_received_url(
+                api_key, app_secret, auth_context, received_url, 
+                token_write_func, asyncio, enforce_enums)
 
 
 ################################################################################
@@ -455,8 +413,8 @@ def client_from_token_file(token_path, api_key, app_secret, asyncio=False,
     load = __token_loader(token_path)
 
     return client_from_access_functions(
-        api_key, app_secret, load, __update_token(token_path), asyncio=asyncio,
-        enforce_enums=enforce_enums)
+        api_key, app_secret, load, __make_update_token_func(token_path),
+        asyncio=asyncio, enforce_enums=enforce_enums)
 
 
 ################################################################################
@@ -494,9 +452,7 @@ def client_from_manual_flow(api_key, app_secret, callback_url, token_path,
     get_logger().info('Creating new token with callback URL \'%s\' ' +
                        'and token path \'%s\'', callback_url, token_path)
 
-    oauth = OAuth2Client(api_key, redirect_uri=callback_url)
-    authorization_url, state = oauth.create_authorization_url(
-        'https://api.schwabapi.com/v1/oauth/authorize')
+    auth_context = get_auth_context(api_key, callback_url)
 
     print('\n**************************************************************\n')
     print('This is the manual login and token creation flow for schwab-py.')
@@ -505,7 +461,7 @@ def client_from_manual_flow(api_key, app_secret, callback_url, token_path,
     print(' 1. Open the following link by copy-pasting it into the browser')
     print('    of your choice:')
     print()
-    print('        ' + authorization_url)
+    print('        ' + auth_context.authorization_url)
     print()
     print(' 2. Log in with your account credentials. You may be asked to')
     print('    perform two-factor authentication using text messaging or')
@@ -529,11 +485,15 @@ def client_from_manual_flow(api_key, app_secret, callback_url, token_path,
                'and update your callback URL to begin with \'https\' ' +
                'to stop seeing this message.').format(callback_url))
 
-    redirected_url = prompt('Redirect URL> ').strip()
+    received_url = prompt('Redirect URL> ').strip()
+
+    token_write_func = (
+        __make_update_token_func(token_path) if token_write_func is None
+        else token_write_func)
 
-    return __fetch_and_register_token_from_redirect(
-        oauth, redirected_url, api_key, app_secret, token_path, token_write_func,
-        asyncio, enforce_enums=enforce_enums)
+    return client_from_received_url(
+            api_key, app_secret, auth_context, received_url, token_write_func, 
+            asyncio, enforce_enums)
 
 
 ################################################################################
@@ -611,6 +571,68 @@ async def oauth_client_update_token(t, *args, **kwargs):
         enforce_enums=enforce_enums)
 
 
+################################################################################
+# Tools for incorporating token generation into webapp workflows
+
+
+AuthContext = collections.namedtuple(
+        'AuthContext', ['callback_url', 'authorization_url', 'state'])
+
+def get_auth_context(api_key, callback_url):
+    oauth = OAuth2Client(api_key, redirect_uri=callback_url)
+    authorization_url, state = oauth.create_authorization_url(
+        'https://api.schwabapi.com/v1/oauth/authorize')
+
+    return AuthContext(callback_url, authorization_url, state)
+
+
+def client_from_received_url(
+        api_key, app_secret, auth_context, received_url, token_write_func, 
+        asyncio=False, enforce_enums=True):
+    # XXX: The AuthContext must be serializable, which means the original 
+    #      OAuth2Client created in get_auth_context cannot be passed around. 
+    #      Instead, we reconstruct it here.
+    oauth = OAuth2Client(api_key, redirect_uri=auth_context.callback_url)
+
+    token = oauth.fetch_token(
+        TOKEN_ENDPOINT,
+        authorization_response=received_url,
+        client_id=api_key, auth=(api_key, app_secret))
+
+    # Don't emit token details in debug logs
+    register_redactions(token)
+
+    # Set up token writing and perform the initial token write
+    metadata_manager = TokenMetadata(token, int(time.time()), token_write_func)
+    token_write_func = metadata_manager.wrapped_token_write_func()
+    token_write_func(token)
+
+    # The synchronous and asynchronous versions of the OAuth2Client are similar
+    # enough that can mostly be used interchangeably. The one currently known
+    # exception is the token update function: the synchronous version expects a
+    # synchronous one, the asynchronous requires an async one. The
+    # oauth_client_update_token variable will contain the appropriate one.
+    if asyncio:
+        async def oauth_client_update_token(t, *args, **kwargs):
+            token_write_func(t, *args, **kwargs)  # pragma: no cover
+        session_class = AsyncOAuth2Client
+        client_class = AsyncClient
+    else:
+        oauth_client_update_token = token_write_func
+        session_class = OAuth2Client
+        client_class = Client
+
+    # Return a new session configured to refresh credentials
+    return client_class(
+        api_key,
+        session_class(api_key,
+                      client_secret=app_secret,
+                      token=token,
+                      update_token=oauth_client_update_token,
+                      leeway=300),
+        token_metadata=metadata_manager, enforce_enums=enforce_enums)
+
+
 ################################################################################
 # easy_client