Telegram Bot for notifying new questions

cms/conf.py

@@ -142,6 +142,8 @@ def __init__(self):
         # necessary to change it.
         # [1] http://freedesktop.org/wiki/Software/shared-mime-info
         self.shared_mime_info_prefix = "/usr"
+        self.telegram_bot_token = None
+        self.telegram_bot_chat_id = None
 
         # AdminWebServer.
         self.admin_listen_address = ""
@@ -202,6 +204,13 @@ def __init__(self):
         # Attempt to load a config file.
         self._load(paths)
 
+        if bool(self.telegram_bot_token) ^ bool(self.telegram_bot_chat_id):
+            raise ConfigError("Both telegram_bot_token and telegram_bot_chat_id "
+                              "should be set or left null")
+        if self.telegram_bot_chat_id:
+            if type(self.telegram_bot_chat_id) != int:
+                raise ConfigError("telegram_bot_chat_id should be an integer")
+
         # If the configuration says to print detailed log on stdout,
         # change the log configuration.
         set_detailed_logs(self.stream_log_detailed)

cms/server/contest/communication.py

@@ -29,6 +29,10 @@
 
 import logging
 
+import gevent
+import requests
+
+from cms import config
 from cms.db import Question, Announcement, Message
 from cmscommon.datetime import make_timestamp
 
@@ -57,6 +61,49 @@ def __init__(self, subject, text, text_params=None):
         self.text_params = text_params
 
 
+def send_telegram_message(content):
+    """Send a message as the Telegram bot with the specified content.
+    """
+    api_url = "https://api.telegram.org/bot{}/sendMessage" \
+        .format(config.telegram_bot_token)
+    body = {"chat_id": config.telegram_bot_chat_id,
+            "text": content,
+            "parse_mode": "HTML"}
+    res = requests.post(api_url, data=body)
+    if res.status_code != 200:
+        logger.warn("Failed to send Telegram notification: %s", res.json())
+    else:
+        logger.debug("Telegram notification sent for the question")
+
+
+def send_telegram_question_notification(question):
+    """Craft and send a Telegram message with the question content.
+
+    This is a no-op if the bot is not configured.
+
+    This also takes care of formatting the message to be sent, escaping
+    it and making sure it doesn't exceed the bot message size limit
+    (4096 bytes).
+
+    The message is sent in a different greenlet, so that it doesn't
+    block the caller if the network is slow.
+    """
+    if not config.telegram_bot_token or not config.telegram_bot_chat_id:
+        return
+    trim = lambda s, n: s[:n] + "…" if len(s) > n else s
+    escape = lambda t: t.replace("<", "&lt;").replace(">", "&gt;")
+    message = """<b>New question</b>
+From: <code>{username}</code>
+Subject: <i>{subject}</i>
+
+{text}
+""".format(
+        username=trim(escape(question.participation.user.username), 50),
+        subject=trim(escape(question.subject), 100),
+        text=trim(escape(question.text), 3000))
+    gevent.spawn(send_telegram_message, message)
+
+
 def accept_question(sql_session, participation, timestamp, subject, text):
     """Add a contestant-submitted question to the database.
 
@@ -100,6 +147,11 @@ def accept_question(sql_session, participation, timestamp, subject, text):
 
     logger.info("Question submitted by user %s.", participation.user.username)
 
+    try:
+        send_telegram_question_notification(question)
+    except Exception as e:
+        logger.exception("Error occurred while sending Telegram notification")
+
     return question
 
 

config/cms.conf.sample

@@ -133,6 +133,13 @@
     "_help": "STL documentation path in the system (exposed in CWS).",
     "stl_path": "/usr/share/cppreference/doc/html/",
 
+    "_help": "Telegram bot configuration for posting notifications for the",
+    "_help": "questions. The token is a string obtained from @BotFather and",
+    "_help": "the chat_id (an int) is the chat id of a conversation where the",
+    "_help": "bot has access to: a chat where the user started the bot or a",
+    "_help": "channel where the bot has been authorized.",
+    "telegram_bot_token": null,
+    "telegram_bot_chat_id": null,
 
 
     "_section": "AdminWebServer",