const keccak = require('keccak')

export const checksumAddress = (address, chainId = null) => {
  if (typeof address !== 'string') {
    return ''
  }

  if (!/^(0x)?[0-9a-f]{40}$/i.test(address)) {
    return ''
  }

  const stripAddress = stripHexPrefix(address).toLowerCase()
  const prefix = chainId != null ? chainId.toString() + '0x' : ''
  const keccakHash = keccak('keccak256')
    .update(prefix + stripAddress)
    .digest('hex')
  let checksumAddress = '0x'

  for (let i = 0; i < stripAddress.length; i++) {
    checksumAddress +=
      parseInt(keccakHash[i], 16) >= 8
        ? stripAddress[i].toUpperCase()
        : stripAddress[i]
  }
  return checksumAddress
}

export const checkAddressChecksum = (address) => {
  const stripAddress = stripHexPrefix(address).toLowerCase()
  const prefix = '0x'
  const keccakHash = keccak('keccak256')
    .update(prefix + stripAddress)
    .digest('hex')

  for (let i = 0; i < stripAddress.length; i++) {
    const output =
      parseInt(keccakHash[i], 16) >= 8
        ? stripAddress[i].toUpperCase()
        : stripAddress[i]
    if (stripHexPrefix(address)[i] !== output) {
      return false
    }
  }
  return true
}

const stripHexPrefix = (value) => {
  return value.slice(0, 2) === '0x' ? value.slice(2) : value
}