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src/crypto.ts

import * as Account from 'eth-lib/lib/account'
import * as Hash from 'eth-lib/lib/hash'
import * as web3Utils from 'web3-utils'

/**
 * Like web3.eth.accounts.hashMessage without the envelope.
 *
 * @param {*} data
 *  A message to hash - if it is hex it'll be UTF8 decoded.
 *
 * @returns {*}
 *  The hashed message (using keccak256)
 */
export const hashMsgRaw = (data: string | number[]): string => {
  const msg = web3Utils.isHexStrict(data) ? web3Utils.hexToBytes(data) : data
  const msgBuffer = Buffer.from(msg)
  return Hash.keccak256s(msgBuffer)
}

/**
 * Sign a message such that it can be verified with `ecrecover`.
 * Similar to `web3.eth.accounts.sign` except that we sign the hash directly.
 *
 * @param {*} messageHash
 *  Hash of a message, as returned by `web3.utils.soliditySha3` or similar.
 * @param {*} privateKey
 *  Privkey to sign with.
 *
 * @returns {{messageHash: string, r: string, s: string, v: string}}
 */
export const ethSignHash = (messageHash: string, privateKey: string) => {
  // near identical to web3-eth-accounts (web3 v1)
  // the main difference is we don't envelop the data.
  const signature = Account.sign(messageHash, privateKey)
  const vrs = Account.decodeSignature(signature)
  return {
    messageHash,
    v: vrs[0],
    r: vrs[1],
    s: vrs[2],
    signature
  }
}

export /**
 *
 * Operates `ecrecover` over the provided signature
 *
 * @param {string} messageHash This should be an Ethereum HexString
 * @param {string[]} [v, r, s] Components for the secp256k1 signature
 * @returns {{verified: bool, address: EthAddress}}
 */
const ethVerifySig = (messageHash: string, [v, r, s]: string[]) => {
  const address = Account.recover(
    messageHash,
    Account.encodeSignature([v, r, s])
  )
  return {
    verified: true,
    address
  }
}