viem
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JavaScript
import { getBlock, } from '../../actions/public/getBlock.js';
import { getProof, } from '../../actions/public/getProof.js';
import { fromRlp } from '../../utils/encoding/fromRlp.js';
import { toRlp } from '../../utils/encoding/toRlp.js';
import { keccak256 } from '../../utils/hash/keccak256.js';
import { contracts } from '../contracts.js';
import { getWithdrawalHashStorageSlot, } from '../utils/getWithdrawalHashStorageSlot.js';
const outputRootProofVersion = '0x0000000000000000000000000000000000000000000000000000000000000000';
/**
* Builds the transaction that proves a withdrawal was initiated on an L2. Used in the Withdrawal flow.
*
* - Docs: https://viem.sh/op-stack/actions/buildProveWithdrawal
*
* @param client - Client to use
* @param parameters - {@link BuildProveWithdrawalParameters}
* @returns The prove withdraw transaction request. {@link BuildProveWithdrawalReturnType}
*
* @example
* import { createPublicClient, http } from 'viem'
* import { optimism } from 'viem/chains'
* import { buildProveWithdrawal } from 'viem/op-stack'
*
* const publicClientL2 = createPublicClient({
* chain: optimism,
* transport: http(),
* })
*
* const args = await buildProveWithdrawal(publicClientL2, {
* output: { ... },
* withdrawal: { ... },
* })
*/
export async function buildProveWithdrawal(client, args) {
const { account, chain = client.chain, game, output, withdrawal } = args;
const { withdrawalHash } = withdrawal;
const { l2BlockNumber } = game ?? output;
const slot = getWithdrawalHashStorageSlot({ withdrawalHash });
const [proof, block] = await Promise.all([
getProof(client, {
address: contracts.l2ToL1MessagePasser.address,
storageKeys: [slot],
blockNumber: l2BlockNumber,
}),
getBlock(client, {
blockNumber: l2BlockNumber,
}),
]);
return {
account,
l2OutputIndex: game?.index ?? output?.outputIndex,
outputRootProof: {
latestBlockhash: block.hash,
messagePasserStorageRoot: proof.storageHash,
stateRoot: block.stateRoot,
version: outputRootProofVersion,
},
targetChain: chain,
withdrawalProof: maybeAddProofNode(keccak256(slot), proof.storageProof[0].proof),
withdrawal,
};
}
/** @internal */
export function maybeAddProofNode(key, proof) {
const lastProofRlp = proof[proof.length - 1];
const lastProof = fromRlp(lastProofRlp);
if (lastProof.length !== 17)
return proof;
const modifiedProof = [...proof];
for (const item of lastProof) {
// Find any nodes located inside of the branch node.
if (!Array.isArray(item))
continue;
// Check if the key inside the node matches the key we're looking for. We remove the first
// two characters (0x) and then we remove one more character (the first nibble) since this
// is the identifier for the type of node we're looking at. In this case we don't actually
// care what type of node it is because a branch node would only ever be the final proof
// element if (1) it includes the leaf node we're looking for or (2) it stores the value
// within itself. If (1) then this logic will work, if (2) then this won't find anything
// and we won't append any proof elements, which is exactly what we would want.
const suffix = item[0].slice(3);
if (typeof suffix !== 'string' || !key.endsWith(suffix))
continue;
modifiedProof.push(toRlp(item));
}
return modifiedProof;
}
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