feat: add docstrings to createRollupFetchTransactionHash

Author: anegg0

src/createRollupFetchTransactionHash.ts

@@ -1,4 +1,5 @@
 import { Address, PublicClient } from 'viem';
+-
 import { AbiEvent } from 'abitype';
 
 import { validateParentChain } from './types/ParentChain';
@@ -14,9 +15,86 @@ import {
 } from './chains';
 
 export type CreateRollupFetchTransactionHashParams = {
-  params: CreateRollupFetchTransactionHashParams;
   rollup: Address;
   publicClient: PublicClient;
 };
 
-const RollupIni...
+const RollupInitializedEventAbi: AbiEvent = {
+  anonymous: false,
+  inputs: [
+    {
+      indexed: false,
+      internalType: 'bytes32',
+      name: 'machineHash',
+      type: 'bytes32',
+    },
+    {
+      indexed: false,
+      internalType: 'uint256',
+      name: 'chainId',
+      type: 'uint256',
+    },
+  ],
+  name: 'RollupInitialized',
+  type: 'event',
+};
+
+const earliestRollupCreatorDeploymentBlockNumber = {
+  // mainnet
+  [mainnet.id]: 18736164n,
+  [arbitrumOne.id]: 150599584n,
+  [arbitrumNova.id]: 47798739n,
+  // testnet
+  [sepolia.id]: 4741823n,
+  [holesky.id]: 1083992n,
+  [arbitrumSepolia.id]: 654628n,
+  // local nitro-testnode
+  [nitroTestnodeL1.id]: 0n,
+  [nitroTestnodeL2.id]: 0n,
+};
+
+/**
+ * createRollupFetchTransactionHash retrieves the transaction hash of the
+ * RollupInitialized event for a specified rollup contract on a given chain. It
+ * takes in the rollup contract address and a PublicClient, validates the parent
+ * chain, and then fetches the RollupInitialized event logs to extract the
+ * transaction hash. This function ensures that only one RollupInitialized event
+ * is found for the specified rollup address before returning the transaction
+ * hash.
+ */
+export async function createRollupFetchTransactionHash({
+  rollup,
+  publicClient,
+}: CreateRollupFetchTransactionHashParams) {
+  const chainId = validateParentChain(publicClient);
+
+  const fromBlock =
+    chainId in earliestRollupCreatorDeploymentBlockNumber
+      ? earliestRollupCreatorDeploymentBlockNumber[chainId]
+      : 'earliest';
+
+  // Find the RollupInitialized event from that Rollup contract
+  const rollupInitializedEvents = await publicClient.getLogs({
+    address: rollup,
+    event: RollupInitializedEventAbi,
+    fromBlock,
+    toBlock: 'latest',
+  });
+
+  if (rollupInitializedEvents.length !== 1) {
+    throw new Error(
+      `Expected to find 1 RollupInitialized event for rollup address ${rollup} but found ${rollupInitializedEvents.length}`,
+    );
+  }
+
+  // Get the transaction hash that emitted that event
+  const transactionHash = rollupInitializedEvents[0].transactionHash;
+
+  if (!transactionHash) {
+    throw new Error(
+      `No transactionHash found in RollupInitialized event for rollup address ${rollup}`,
+    );
+  }
+
+  return transactionHash;
+}