Check board validity for fromPosition challenges

Author: Torom

challenge_validator.py

@@ -1,5 +1,7 @@
 from typing import Any
 
+import chess
+
 from config import Config
 from enums import DeclineReason
 from game_manager import GameManager
@@ -38,6 +40,13 @@ def get_decline_reason(self, challenge_event: dict[str, Any]) -> DeclineReason |
             print(f'Variant "{challenge_event["variant"]["key"]}" is not allowed according to config.')
             return DeclineReason.VARIANT
 
+        if (
+            challenge_event["variant"]["key"] == "fromPosition"
+            and not chess.Board(challenge_event["initialFen"]).is_valid()
+        ):
+            print("Invalid start position.")
+            return DeclineReason.VARIANT
+
         if (
             len(self.game_manager.tournaments) + len(self.game_manager.tournaments_to_join)
         ) >= self.config.challenge.concurrency: