feat: add WithdrawalTransaction entity to L2 subgraph

Signed-off-by: Tomás Migone <tomas@edgeandnode.com>

schema.graphql

@@ -283,6 +283,7 @@ type GraphAccount @entity {
   # Transactions / activity feed
   "Name signal transactions created by this GraphAccount"
   nameSignalTransactions: [NameSignalTransaction!]! @derivedFrom(field: "signer")
+  bridgeWithdrawalTransactions: [BridgeWithdrawalTransaction!]! @derivedFrom(field: "signer")
 
   # Token Lock Wallets that this account is associated with
   tokenLockWallets: [TokenLockWallet!]!
@@ -1146,13 +1147,41 @@ type SignalTransaction implements Transaction @entity {
   withdrawalFees: BigInt!
 }
 
+"""
+All relevant data for a bridge withdrawal Transaction in The Graph Network
+"""
+type BridgeWithdrawalTransaction implements Transaction @entity {
+  id: ID!
+  blockNumber: Int!
+  timestamp: Int!
+  signer: GraphAccount!
+  type: TransactionType!
+
+  "On both subgraphs"
+  txHash: Bytes!
+  from: Bytes
+  to: Bytes
+  """
+  transactionIndex is the unique value that allows matching an L2 transaction with its L1 counterpart
+  - On L1, Arbitrum's Outbox contract emits OutBoxTransactionExecuted event with a transactionIndex property
+  - On L2, the Graph gateway emits WithdrawalInitiated with the transaction index as l2ToL1Id
+  """
+  transactionIndex: Int!
+
+  "Only on L2 subgraph"
+  exitNum: Int
+  amount: BigInt
+  l1Token: Bytes
+}
+
 enum TransactionType {
   Stake
   Unstake
   MintSignal
   BurnSignal
   MintNSignal
   BurnNSignal
+  BridgeWithdrawal
 }
 
 """

src/mappings/l1Gateway.ts

@@ -1,5 +1,4 @@
 import { DepositInitiated } from '../types/L1GraphTokenGateway/L1GraphTokenGateway'
-import { GraphNetwork } from '../types/schema'
 import { createOrLoadGraphNetwork } from './helpers'
 
 export function handleDepositInitiated(event: DepositInitiated): void {

src/mappings/l2Gateway.ts

@@ -1,9 +1,30 @@
 import { WithdrawalInitiated } from '../types/L2GraphTokenGateway/L2GraphTokenGateway'
-import { GraphNetwork } from '../types/schema'
 import { createOrLoadGraphNetwork } from './helpers'
+import { BridgeWithdrawalTransaction } from '../types/schema'
 
 export function handleWithdrawalInitiated(event: WithdrawalInitiated): void {
   let graphNetwork = createOrLoadGraphNetwork(event.block.number, event.address)
+
+  // Save the withdrawal transaction
+  let withdrawalTransaction = new BridgeWithdrawalTransaction(
+    event.transaction.hash.toHexString().concat('-').concat(event.logIndex.toString()),
+  )
+
+  // Note that this only runs on L2, so we can fix block number to the current L1 estimate
+  withdrawalTransaction.blockNumber = graphNetwork.currentL1BlockNumber!.toI32()
+  withdrawalTransaction.timestamp = event.block.timestamp.toI32()
+  withdrawalTransaction.signer = event.params.from.toHexString()
+  withdrawalTransaction.type = 'BridgeWithdrawal'
+  withdrawalTransaction.txHash = event.transaction.hash
+  withdrawalTransaction.from = event.params.from
+  withdrawalTransaction.to = event.params.to
+  withdrawalTransaction.transactionIndex = event.params.l2ToL1Id
+  withdrawalTransaction.exitNum = event.params.exitNum
+  withdrawalTransaction.amount = event.params.amount
+  withdrawalTransaction.l1Token = event.params.l1Token
+  withdrawalTransaction.save()
+
+  // Update total GRT withdrawn
   graphNetwork.totalGRTWithdrawn = graphNetwork.totalGRTWithdrawn.plus(event.params.amount)
   graphNetwork.save()
 }