backward let event indexing scaffolding

Author: Stefan-Ethernal

bridgesync/downloader.go

@@ -52,6 +52,7 @@ var (
 	setClaimEventSignature = crypto.Keccak256Hash([]byte(
 		"SetClaim(bytes32)",
 	))
+	backwardLETEventSignature = crypto.Keccak256Hash([]byte("BackwardLET(uint256,bytes32,uint256,bytes32)"))
 
 	claimAssetEtrogMethodID      = common.Hex2Bytes("ccaa2d11")
 	claimMessageEtrogMethodID    = common.Hex2Bytes("f5efcd79")
@@ -110,6 +111,10 @@ func buildAppender(
 		appender[removeLegacySovereignTokenEventSignature] = buildRemoveLegacyTokenHandler(bridgeDeployment.agglayerBridgeL2)
 		appender[unsetClaimEventSignature] = buildUnsetClaimEventHandler(bridgeDeployment.agglayerBridgeL2)
 		appender[setClaimEventSignature] = buildSetClaimEventHandler(bridgeDeployment.agglayerBridgeL2)
+		appender[backwardLETEventSignature] = buildBackwardLETEventHandler(bridgeDeployment.agglayerBridgeL2)
+
+	default:
+		return nil, fmt.Errorf("unsupported bridge deployment kind: %d", bridgeDeployment.kind)
 	}
 
 	return appender, nil
@@ -419,6 +424,26 @@ func buildSetClaimEventHandler(contract *agglayerbridgel2.Agglayerbridgel2) func
 	}
 }
 
+// buildBackwardLETEventHandler creates a handler for the BackwardLET event log
+func buildBackwardLETEventHandler(contract *agglayerbridgel2.Agglayerbridgel2) func(*sync.EVMBlock, types.Log) error {
+	return func(b *sync.EVMBlock, l types.Log) error {
+		event, err := contract.ParseBackwardLET(l)
+		if err != nil {
+			return fmt.Errorf("error parsing BackwardLET event log %+v: %w", l, err)
+		}
+
+		b.Events = append(b.Events, Event{BackwardLET: &BackwardLET{
+			BlockNum:             b.Num,
+			BlockPos:             uint64(l.Index),
+			PreviousDepositCount: event.PreviousDepositCount,
+			PreviousRoot:         event.PreviousRoot,
+			NewDepositCount:      event.NewDepositCount,
+			NewRoot:              event.NewRoot,
+		}})
+		return nil
+	}
+}
+
 type Call struct {
 	From  common.Address    `json:"from"`
 	To    common.Address    `json:"to"`

bridgesync/processor.go

@@ -484,7 +484,7 @@ func (u *UnsetClaim) String() string {
 }
 
 // SetClaim representation of a SetClaim event,
-// that is emitted by the bridge contract when a claim is set.
+// that is emitted by the L2 bridge contract when a claim is set.
 type SetClaim struct {
 	BlockNum    uint64      `meddler:"block_num"`
 	BlockPos    uint64      `meddler:"block_pos"`
@@ -504,6 +504,17 @@ func (s *SetClaim) String() string {
 		globalIndexStr, s.CreatedAt)
 }
 
+// BackwardLET representation of a BackwardLET event,
+// that is emitted by the L2 bridge contract when a LET is rolled back.
+type BackwardLET struct {
+	BlockNum             uint64      `meddler:"block_num"`
+	BlockPos             uint64      `meddler:"block_pos"`
+	PreviousDepositCount *big.Int    `meddler:"previous_deposit_count,bigint"`
+	PreviousRoot         common.Hash `meddler:"previous_root,hash"`
+	NewDepositCount      *big.Int    `meddler:"new_deposit_count,bigint"`
+	NewRoot              common.Hash `meddler:"new_root,hash"`
+}
+
 // Event combination of bridge, claim, token mapping and legacy token migration events
 type Event struct {
 	Bridge               *Bridge
@@ -513,6 +524,7 @@ type Event struct {
 	RemoveLegacyToken    *RemoveLegacyToken
 	UnsetClaim           *UnsetClaim
 	SetClaim             *SetClaim
+	BackwardLET          *BackwardLET
 }
 
 func (e Event) String() string {