Support a fallback session cookie in constants

To mitigate problems due to expiring session cookies, I'm currently in
the process of adding support for a fallback cookie. Basically, my
Advent of Code account is a member of *all* leaderboards, which means
that my cookie can be used to fetch all leaderboards as well.

As my session cookie should not expire until after the event, it should
not give us any issues. However, to avoid issues with issuing too many
requests from one session, we should still make sure to set individual
session values regardless of the mitigation.

1 files changed, 20 insertions, 2 deletions

diff --git a/bot/constants.py b/bot/constants.py
index e313e086..9e6db7a6 100644
--- a/bot/constants.py
+++ b/bot/constants.py
@@ -1,3 +1,4 @@
+import dataclasses
 import enum
 import logging
 from datetime import datetime
@@ -29,11 +30,27 @@ __all__ = (
 log = logging.getLogger(__name__)
 
 
-class AdventOfCodeLeaderboard(NamedTuple):
[email protected]
+class AdventOfCodeLeaderboard:
     id: str
-    session: str
+    _session: str
     join_code: str
 
+    # If we notice that the session for this board expired, we set
+    # this attribute to `True`. We will emit a Sentry error so we
+    # can handle it, but, in the meantime, we'll try using the
+    # fallback session to make sure the commands still work.
+    use_fallback_session: bool = False
+
+    @property
+    def session(self) -> str:
+        """Return either the actual `session` cookie or the fallback cookie."""
+        if self.use_fallback_session:
+            log.info(f"Returning fallback cookie for board `{self.id}`.")
+            return AdventOfCode.fallback_session
+
+        return self._session
+
 
 def _parse_aoc_leaderboard_env() -> Dict[str, AdventOfCodeLeaderboard]:
     """
@@ -61,6 +78,7 @@ class AdventOfCode:
     # Information for the several leaderboards we have
     leaderboards = _parse_aoc_leaderboard_env()
     staff_leaderboard_id = environ.get("AOC_STAFF_LEADERBOARD_ID", "")
+    fallback_session = environ.get("AOC_FALLBACK_SESSION", "")
 
     # Other Advent of Code constants
     ignored_days = [day for day in environ.get("AOC_IGNORED_DAYS", "").split(",")]