From 427b8199d7573afe7f505d026a52fc60c2c185dc Mon Sep 17 00:00:00 2001
From: gzeon <95478735+gzeoneth@users.noreply.github.com>
Date: Fri, 24 Jun 2022 23:29:58 +0800
Subject: [PATCH 1/2] feat: expose isSpent in Outbox

---
 contracts/src/bridge/Outbox.sol | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/contracts/src/bridge/Outbox.sol b/contracts/src/bridge/Outbox.sol
index 9dee5fab0f..329db58339 100644
--- a/contracts/src/bridge/Outbox.sol
+++ b/contracts/src/bridge/Outbox.sol
@@ -207,6 +207,30 @@ contract Outbox is DelegateCallAware, IOutbox {
         context = prevContext;
     }
 
+    function _calcSpentIndexOffset(uint256 index)
+        internal
+        view
+        returns (
+            uint256,
+            uint256,
+            bytes32
+        )
+    {
+        uint256 spentIndex = index / 255; // Note: Reserves the MSB.
+        uint256 bitOffset = index % 255;
+        bytes32 replay = spent[spentIndex];
+        return (spentIndex, bitOffset, replay);
+    }
+
+    function _isSpent(uint256 bitOffset, bytes32 replay) internal pure returns (bool) {
+        return ((replay >> bitOffset) & bytes32(uint256(1))) != bytes32(0);
+    }
+
+    function isSpent(uint256 index) public view returns (bool) {
+        (, uint256 bitOffset, bytes32 replay) = _calcSpentIndexOffset(index);
+        return _isSpent(bitOffset, replay);
+    }
+
     function recordOutputAsSpent(
         bytes32[] memory proof,
         uint256 index,
@@ -219,11 +243,9 @@ contract Outbox is DelegateCallAware, IOutbox {
         bytes32 calcRoot = calculateMerkleRoot(proof, index, item);
         if (roots[calcRoot] == bytes32(0)) revert UnknownRoot(calcRoot);
 
-        uint256 spentIndex = index / 255; // Note: Reserves the MSB.
-        uint256 bitOffset = index % 255;
+        (uint256 spentIndex, uint256 bitOffset, bytes32 replay) = _calcSpentIndexOffset(index);
 
-        bytes32 replay = spent[spentIndex];
-        if (((replay >> bitOffset) & bytes32(uint256(1))) != bytes32(0)) revert AlreadySpent(index);
+        if (_isSpent(bitOffset, replay)) revert AlreadySpent(index);
         spent[spentIndex] = (replay | bytes32(1 << bitOffset));
     }
 

From f0aeeb93233b592104aa9a98b8333c486ba82568 Mon Sep 17 00:00:00 2001
From: gzeon <95478735+gzeoneth@users.noreply.github.com>
Date: Sat, 25 Jun 2022 00:04:58 +0800
Subject: [PATCH 2/2] fix: change isSpent to external

---
 contracts/src/bridge/Outbox.sol | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/src/bridge/Outbox.sol b/contracts/src/bridge/Outbox.sol
index 329db58339..8ff52afa3c 100644
--- a/contracts/src/bridge/Outbox.sol
+++ b/contracts/src/bridge/Outbox.sol
@@ -226,7 +226,7 @@ contract Outbox is DelegateCallAware, IOutbox {
         return ((replay >> bitOffset) & bytes32(uint256(1))) != bytes32(0);
     }
 
-    function isSpent(uint256 index) public view returns (bool) {
+    function isSpent(uint256 index) external view returns (bool) {
         (, uint256 bitOffset, bytes32 replay) = _calcSpentIndexOffset(index);
         return _isSpent(bitOffset, replay);
     }