proper-signature.ts

import Web3 from 'web3'
import util from 'ethereumjs-util'

export function toSolSig(sig: string): string {
  const {r, s, v} = util.fromRpcSig(sig)

  // NOTE: with potential introduction of chainId this might need to be updated
  if (v !== 27 && v !== 28) {
    throw new Error('Invalid recovery id');
  }

  const parts = [util.setLengthLeft(r, 32) as Buffer, util.setLengthLeft(s, 32) as Buffer, util.toBuffer(v)]
  return util.bufferToHex(Buffer.concat(parts));
}

export async function properSignature(web3: Web3, account: string, data: string): Promise<string> {
  const improperSig = await web3.eth.sign(data, account)
  return toSolSig(improperSig)
}