overhaul voting to support smart single voting protections and enforcing, new exceptions, vote clearing functions inside models, persistence updating

bot/exceptions.py

@@ -1,3 +1,32 @@
-class FinishedPeriod(Exception):
-    """A inactive period, or a period in it's final state cannot be advanced or further modified."""
+class ContestException(Exception):
+    """A exception directly related to the Contest Assistant bot."""
     pass
+
+
+class FinishedPeriodException(ContestException):
+    """A inactive period, or a period in it's final state cannot be advanced or further modified."""
+
+    def __repr__(self) -> str:
+        return 'Period is inactive.'
+
+
+class DatabaseDoubleVoteException(ContestException):
+    """
+    The database was asked to increment a vote for a submission with a user ID that was already added.
+
+    Companion to `DatabaseNoVoteException`
+    """
+
+    def __repr__(self) -> str:
+        return 'You can\'t vote for a submission twice.'
+
+
+class DatabaseNoVoteException(ContestException):
+    """
+    The database was asked to decrement a vote for a submission with a user ID that did not or no longer exists for the given submission.
+
+    Companion to `DatabaseDoubleVoteException`
+    """
+
+    def __repr__(self) -> str:
+        return 'You can\'t remove a vote that never or no longer exists'