Add the OAuthHelper class

- Add the `reddit` package
- Add the `OAuthHelper` class - providing the methods for the Reddit
  authorization
- Add the `http_server` configuration to the `config`
- Adjust the `isort` configuration to indent multi-line imports
  correctly

CHANGELOG.md

@@ -9,6 +9,7 @@ We follow [Semantic Versions](https://semver.org/).
 - Add `flask` to dependencies
 - Add the `http_server` module - handling the OAuth callback
 - Add `praw` to dependencies
+- Add the `OAuthHelper` class - providing the methods for the Reddit authorization
 
 
 ## Version 0.1.3

setup.cfg

@@ -47,6 +47,7 @@ default_section = FIRSTPARTY
 # See https://github.com/timothycrosley/isort#multi-line-output-modes
 multi_line_output = 3
 line_length = 80
+indent="    "
 
 
 [darglint]

slow_start_rewatch/config_default.yml

@@ -8,6 +8,11 @@ scheduled_post_file: "${home_dir}${ps}slow_start_rewatch${ps}scheduled_post.yml"
 # Temporary configuration of the Reddit username:
 username: cute_tester
 
+# Local HTTP server used for the OAuth2 callback:
+http_server:
+  hostname: "127.0.0.1"
+  port: 65000
+
 # Timer configuration:
 timer:
   refresh_interval: 200 # milliseconds

slow_start_rewatch/exceptions.py

@@ -43,3 +43,7 @@ def __init__(self):
 
 class AuthorizationError(SlowStartRewatchException):
     """Indicates an error during the authorization."""
+
+
+class RedditError(SlowStartRewatchException):
+    """Indicates error when accessing Reddit API."""

slow_start_rewatch/reddit/__init__.py

@@ -0,0 +1 @@
+# -*- coding: utf-8 -*-

slow_start_rewatch/reddit/oauth_helper.py

@@ -0,0 +1,74 @@
+# -*- coding: utf-8 -*-
+
+import uuid
+import webbrowser
+
+import click
+from praw import Reddit
+from prawcore.exceptions import PrawcoreException
+from structlog import get_logger
+
+from slow_start_rewatch.config import Config
+from slow_start_rewatch.exceptions import AuthorizationError, RedditError
+from slow_start_rewatch.http_server import http_server
+
+BAD_REQUEST_ERROR = 400
+
+log = get_logger()
+
+
+class OAuthHelper(object):
+    """Provides methods for Reddit authorization."""
+
+    def __init__(self, config: Config, reddit: Reddit) -> None:
+        """Initialize OAuthHelper."""
+        self.config = config
+        self.reddit = reddit
+
+    def authorize(self) -> None:
+        """
+        Authorize via OAuth.
+
+        Open a background browser (e.g. firefox) which is non-blocking.
+
+        The server will block until it responds to its first request. Then the
+        callback params are checked.
+        """
+        state = uuid.uuid4().hex
+        authorize_url = self.reddit.auth.url(
+            scopes=self.config["reddit.oauth_scope"],
+            state=state,
+        )
+
+        click.echo(
+            "Opening a web browser for authorization:\n" +
+            "- You will be asked to allow the Slow Start Rewatch app to " +
+            "connect with your Reddit account so that it can submit and " +
+            "edit posts on your behalf.\n" +
+            "- The app cannot access your password.\n" +
+            "- Press Ctrl+C if you would like to quit before completing " +
+            "the authorization.",
+        )
+        log.debug("webbrowser_open", url=authorize_url)
+        webbrowser.open_new(authorize_url)
+
+        code = http_server.run(
+            state=state,
+            hostname=self.config["http_server.hostname"],
+            port=self.config["http_server.port"],
+        )
+
+        log.info("oauth_authorize", code=code)
+        try:
+            refresh_token = self.reddit.auth.authorize(code)
+        except PrawcoreException as exception:
+            log.exception("oauth_authorize_failed")
+            raise RedditError(
+                "Failed to retrieve the Refresh Token.",
+            ) from exception
+
+        if not refresh_token:
+            log.error("oauth_authorize_missing_token")
+            raise AuthorizationError(
+                "Reddit hasn't provided the Refresh Token.",
+            )

tests/conftest.py

@@ -10,6 +10,7 @@
 
 import os
 from datetime import datetime
+from unittest import mock
 
 import pytest
 from dotty_dict import dotty
@@ -63,3 +64,9 @@ def post():
         title="Slow Start - Episode 1 Discussion",
         body=body,
     )
+
+
+@pytest.fixture()
+def reddit():
+    """Return mock Reddit class."""
+    return mock.Mock()

tests/test_config/config_example.yml

@@ -9,5 +9,9 @@ scheduled_post_file: "${home_dir}${ps}slow_start_rewatch${ps}scheduled_post.yml"
 
 username: cute_tester
 
+http_server:
+  hostname: "127.0.0.1"
+  port: 65000
+
 timer:
   refresh_interval: 200 # milliseconds

tests/test_oauth_helper.py

@@ -0,0 +1,88 @@
+# -*- coding: utf-8 -*-
+
+from unittest.mock import call, patch
+
+import pytest
+from prawcore.exceptions import PrawcoreException
+
+from slow_start_rewatch.exceptions import AuthorizationError, RedditError
+from slow_start_rewatch.http_server import http_server
+from slow_start_rewatch.reddit.oauth_helper import OAuthHelper
+from tests.conftest import (
+    HTTP_SERVER_HOSTNAME,
+    HTTP_SERVER_PORT,
+    OAUTH_CODE,
+    MockConfig,
+)
+
+
+@patch.object(http_server, "run")
+@patch("webbrowser.open_new")
+def test_successful_authorization(
+    webbrowser_open_new,
+    http_server_run,
+    oauth_helper_config,
+    reddit,
+):
+    """Test successful OAuth authorization."""
+    http_server_run.return_value = OAUTH_CODE
+
+    oauth_helper = OAuthHelper(oauth_helper_config, reddit)
+
+    oauth_helper.authorize()
+
+    assert webbrowser_open_new.call_count == 1
+    assert reddit.auth.authorize.call_args == call(OAUTH_CODE)
+
+
+@patch.object(http_server, "run")
+@patch("webbrowser.open_new")
+def test_failed_authorization(
+    webbrowser_open_new,
+    http_server_run,
+    oauth_helper_config,
+    reddit,
+):
+    """Test an error during OAuth authorization."""
+    http_server_run.side_effect = AuthorizationError("Tsundere response")
+
+    oauth_helper = OAuthHelper(oauth_helper_config, reddit)
+
+    with pytest.raises(AuthorizationError):
+        oauth_helper.authorize()
+
+
+@patch.object(http_server, "run")
+@patch("webbrowser.open_new")
+def test_failed_token_retrieval(
+    webbrowser_open_new,
+    http_server_run,
+    oauth_helper_config,
+    reddit,
+):
+    """Test errors during the refresh token retrieval."""
+    http_server_run.return_value = OAUTH_CODE
+    reddit.auth.authorize.side_effect = [
+        PrawcoreException,
+        None,
+    ]
+
+    oauth_helper = OAuthHelper(oauth_helper_config, reddit)
+
+    with pytest.raises(RedditError):
+        oauth_helper.authorize()
+
+    with pytest.raises(AuthorizationError):
+        oauth_helper.authorize()
+
+
+@pytest.fixture()
+def oauth_helper_config():
+    """Return mock Config for testing OAuthHelper."""
+    return MockConfig({
+        "reddit": {"oauth_scope": ["headpat", "hug"]},
+        "http_server": {
+            "hostname": HTTP_SERVER_HOSTNAME,
+            "port": HTTP_SERVER_PORT,
+        },
+    })