Set up a TypeScript project

EVM_PRIVATE_KEY=0x…
EVM_RPC_URL=https://mainnet.base.org

import 'dotenv/config';
import { createClient, type BuildStep } from '@kernlog/brdg-sdk';
import { createPublicClient, createWalletClient, http, type Hex } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { base } from 'viem/chains';

export const brdg = createClient();
export const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as Hex);

const wallet = createWalletClient({ account, chain: base, transport: http(process.env.EVM_RPC_URL) });
const chain = createPublicClient({ chain: base, transport: http(process.env.EVM_RPC_URL) });

/** Sign one EVM step from a build and wait for it to be mined. */
export async function signEvmStep(step: BuildStep): Promise<Hex> {
  if (step.vm !== 'evm') throw new Error(`expected an EVM step, got ${step.vm}`);
  if (step.chainId !== base.id) throw new Error(`this signer is set up for Base, not chain ${step.chainId}`);
  const hash = await wallet.sendTransaction({
    to: step.to as Hex,
    data: step.data as Hex,
    value: BigInt(step.value),
  });
  await chain.waitForTransactionReceipt({ hash });
  return hash;
}