zulip_bots/github_detail: Reply with contents of file when URL is given.

zulip_bots/zulip_bots/bots/github_detail/github_detail.py

@@ -15,19 +15,29 @@ class GithubHandler(object):
     '''
 
     GITHUB_ISSUE_URL_TEMPLATE = 'https://api.github.com/repos/{owner}/{repo}/issues/{id}'
-    HANDLE_MESSAGE_REGEX = re.compile("(?:([\w-]+)\/)?([\w-]+)?#(\d+)")
+    ISSUE_PR_NUMBER_REGEX = re.compile("(?:([\w-]+)\/)?([\w-]+)?#(\d+)")
+
+    GITHUB_RAW_FILE_CONTENT_URL_TEMPLATE = 'https://raw.githubusercontent.com/{owner}/{repo}/{path}'
+    GITHUB_REPO_URL_REGEX = re.compile('^(http|https|git)://(www\.|)github.com/(?P<owner>([^/]+))/'
+                                       '(?P<repository>([^/]+))/(?P<type>([^/]+))/'
+                                       '(?P<path>([^#]+))(?P<lines>(|#.*))$')
 
     def initialize(self, bot_handler: Any) -> None:
         self.config_info = bot_handler.get_config_info('github_detail', optional=True)
         self.owner = self.config_info.get("owner", False)
         self.repo = self.config_info.get("repo", False)
 
     def usage(self) -> str:
-        return ("This plugin displays details on github issues and pull requests. "
+        return ("* **Get PR/issue details:**This plugin displays details on github issues and pull requests. "
                 "To reference an issue or pull request usename mention the bot then "
                 "anytime in the message type its id, for example:\n"
                 "@**Github detail** #3212 zulip#3212 zulip/zulip#3212\n"
-                "The default owner is {} and the default repo is {}.".format(self.owner, self.repo))
+                "The default owner is {} and the default repo is {}."
+                "\n* **Get a file's contents:**Give a full url to get the line contents"
+                "\nSend an valid  URL to a GitHub file to get its contents."
+                "\nUse the line numbers to get only the specific lines from the file.\n"
+                "Example: `@**Github detail**` https://github.com/zulip/zulip/blob/"
+                "master/zerver/apps.py#L10-L12".format(self.owner, self.repo))
 
     def format_message(self, details: Dict[str, Any]) -> str:
         number = details['number']
@@ -72,16 +82,31 @@ def handle_message(self, message: Dict[str, str], bot_handler: Any) -> None:
         if message['content'] == 'help':
             bot_handler.send_reply(message, self.usage())
             return
+        reply = ''
+        try:
+            # Try and match if a GitHub URL is present in the message
+            url_details = self.get_file_url_match(message['content'])
+            if url_details and url_details['type'] == 'blob':
+                reply = self.get_file_contents(**url_details)
+            else:
+                # Try and match the `owner/repo#123` type issue or PR number
+                reply = self.match_pr_and_get_reply(message['content'])
 
+            bot_handler.send_reply(message, reply or 'I couldn\'t process that message.'
+                                                     'Try replying `help` to know what I can do.')
+        except Exception as e:
+            logging.exception(str(e))
+            bot_handler.send_reply(message, ':dizzy:  Something unexpected happened!')
+
+    def match_pr_and_get_reply(self, message_content):
         # Capture owner, repo, id
         issue_prs = list(re.finditer(
-            self.HANDLE_MESSAGE_REGEX, message['content']))
+            self.ISSUE_PR_NUMBER_REGEX, message_content))
         bot_messages = []
         if len(issue_prs) > 5:
             # We limit to 5 requests to prevent denial-of-service
             bot_message = 'Please ask for <=5 links in any one request'
-            bot_handler.send_reply(message, bot_message)
-            return
+            return bot_message
 
         for issue_pr in issue_prs:
             owner, repo = self.get_owner_and_repo(issue_pr)
@@ -97,8 +122,42 @@ def handle_message(self, message: Dict[str, str], bot_handler: Any) -> None:
             else:
                 bot_messages.append("Failed to detect owner and repository name.")
         if len(bot_messages) == 0:
-            bot_messages.append("Failed to find any issue or PR.")
+            return None
         bot_message = '\n'.join(bot_messages)
-        bot_handler.send_reply(message, bot_message)
+        return bot_message
+
+    def get_file_url_match(self, message_content):
+            details = re.match(self.GITHUB_REPO_URL_REGEX, message_content)
+            return details.groupdict() if details is not None else None
+
+    def get_file_contents(self, owner, repository, path, lines, **kwargs):
+        url = self.GITHUB_RAW_FILE_CONTENT_URL_TEMPLATE.format(owner=owner,
+                                                               repo=repository,
+                                                               path=path)
+        try:
+            raw_file = requests.get(url)
+            raw_file.raise_for_status()
+        except requests.exceptions.RequestException as e:
+            return 'An error occurred while trying to fetch the contents of the file :oh_no: \n' \
+                'Are you sure the URL is correct ?'
+
+        if lines:
+            line_number_regex = re.compile('^#L(?P<start>(\d+))(|-L(?P<end>(\d+)))$')
+            line_number_match = re.match(line_number_regex, lines)
+            if line_number_match:
+                # Decrementing to select the index in a list
+                start = int(line_number_match.group('start'))-1
+
+                # Sometimes, the ending line number might be missing(i.e only one line has been selected)
+                # In that case we set it to start+1 (so the list can be sliced correctly)
+                end = line_number_match.group('end') or start+1
+                end = int(end)
+                lines_as_list = raw_file.text.split('\n')
+                reply = '\n'.join(lines_as_list[start:end])
+                return '**[{}](https://www.github.com/blob/{}):** *{} - {}*\n' \
+                       '```\n\n{}\n```'.format(path, path, start+1, end, reply)
+        else:
+            return '**[{}](https://www.github.com/blob/{}):**\n' \
+                   '```\n{}\n```'.format(path, path, raw_file.text)
 
 handler_class = GithubHandler