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evals/adaptive-change/fixture/ledger.py

@@ -0,0 +1,17 @@
+class Ledger:
+    def __init__(self) -> None:
+        self._balances: dict[str, int] = {}
+        self._applied: set[str] = set()
+
+    def balance(self, account: str) -> int:
+        return self._balances.get(account, 0)
+
+    def apply(self, operation_id: str, account: str, delta: int) -> int:
+        if operation_id in self._applied:
+            return self.balance(account)
+        self._applied.add(operation_id)
+        updated = self.balance(account) + delta
+        if updated < 0:
+            raise ValueError("insufficient funds")
+        self._balances[account] = updated
+        return updated