How to use the rfc4648.base64.stringify function in rfc4648

emit(ai.props.output.context.api, 'loginStart', {
    username: stashTree.username
  })

  // Find the appropriate child:
  const child = searchTree(stashTree, stash => stash.appId === appId)
  if (child == null) {
    throw new Error(`Cannot find requested appId: "${appId}"`)
  }

  // The Airbitz mobile will sometimes send the pin2Key in base58
  // instead of base64 due to an unfortunate bug. Fix that:
  if (child.pin2Key != null && child.pin2Key.slice(-1) !== '=') {
    io.console.warn('Fixing base58 pin2Key')
    child.pin2Key = base64.stringify(base58.parse(child.pin2Key))
  }
  await saveStash(ai, stashTree)

  // This is almost guaranteed to blow up spectacularly:
  const loginKey = base64.parse(reply.loginKey)
  const loginTree = makeLoginTree(stashTree, loginKey, appId)
  const login = searchTree(loginTree, login => login.appId === appId)
  if (login == null) {
    throw new Error(`Cannot find requested appId: "${appId}"`)
  }
  const newLoginTree = await syncLogin(ai, loginTree, login)
  const account = await makeAccount(ai, appId, newLoginTree, 'edgeLogin', opts)
  emit(ai.props.output.context.api, 'login', account)
}

if (mnemonicBox != null && rootKeyBox != null) {
    const rootKey = decrypt(rootKeyBox, loginKey)
    const infoKey = hmacSha256(rootKey, utf8.parse('infoKey'))
    const keys = {
      mnemonic: utf8.stringify(decrypt(mnemonicBox, infoKey)),
      rootKey: base64.stringify(rootKey)
    }
    legacyKeys.push(makeKeyInfo('wallet:bitid', keys, rootKey))
  }

  // Account settings:
  if (stash.syncKeyBox != null) {
    const syncKey = decrypt(stash.syncKeyBox, loginKey)
    const type = makeAccountType(login.appId)
    const keys = {
      syncKey: base64.stringify(syncKey),
      dataKey: base64.stringify(loginKey)
    }
    legacyKeys.push(makeKeyInfo(type, keys, loginKey))
  }

  // Keys:
  const stashKeyBoxes = stash.keyBoxes != null ? stash.keyBoxes : []
  const keyInfos = stashKeyBoxes.map(box =>
    JSON.parse(utf8.stringify(decrypt(box, loginKey)))
  )

  login.keyInfos = mergeKeyInfos([...legacyKeys, ...keyInfos]).map(walletInfo =>
    fixWalletInfo(walletInfo)
  )

  // Recurse into children:

const rootKey = decrypt(rootKeyBox, loginKey)
    const infoKey = hmacSha256(rootKey, utf8.parse('infoKey'))
    const keys = {
      mnemonic: utf8.stringify(decrypt(mnemonicBox, infoKey)),
      rootKey: base64.stringify(rootKey)
    }
    legacyKeys.push(makeKeyInfo('wallet:bitid', keys, rootKey))
  }

  // Account settings:
  if (stash.syncKeyBox != null) {
    const syncKey = decrypt(stash.syncKeyBox, loginKey)
    const type = makeAccountType(login.appId)
    const keys = {
      syncKey: base64.stringify(syncKey),
      dataKey: base64.stringify(loginKey)
    }
    legacyKeys.push(makeKeyInfo(type, keys, loginKey))
  }

  // Keys:
  const stashKeyBoxes = stash.keyBoxes != null ? stash.keyBoxes : []
  const keyInfos = stashKeyBoxes.map(box =>
    JSON.parse(utf8.stringify(decrypt(box, loginKey)))
  )

  login.keyInfos = mergeKeyInfos([...legacyKeys, ...keyInfos]).map(walletInfo =>
    fixWalletInfo(walletInfo)
  )

  // Recurse into children:
  const stashChildren = stash.children != null ? stash.children : []

pin: string,
  enableLogin: boolean
): LoginKit {
  const { io } = ai.props
  const pin2TextBox = encrypt(io, utf8.parse(pin), login.loginKey)

  if (enableLogin) {
    const pin2Key = login.pin2Key || io.random(32)
    const pin2Box = encrypt(io, login.loginKey, pin2Key)
    const pin2KeyBox = encrypt(io, pin2Key, login.loginKey)

    return {
      serverPath: '/v2/login/pin2',
      server: {
        pin2Id: base64.stringify(pin2Id(pin2Key, username)),
        pin2Auth: base64.stringify(pin2Auth(pin2Key, pin)),
        pin2Box,
        pin2KeyBox,
        pin2TextBox
      },
      stash: {
        pin2Key: base64.stringify(pin2Key),
        pin2TextBox
      },
      login: {
        pin2Key,
        pin
      },
      loginId: login.loginId
    }
  } else {
    return {

username: string,
  pin: string,
  enableLogin: boolean
): LoginKit {
  const { io } = ai.props
  const pin2TextBox = encrypt(io, utf8.parse(pin), login.loginKey)

  if (enableLogin) {
    const pin2Key = login.pin2Key || io.random(32)
    const pin2Box = encrypt(io, login.loginKey, pin2Key)
    const pin2KeyBox = encrypt(io, pin2Key, login.loginKey)

    return {
      serverPath: '/v2/login/pin2',
      server: {
        pin2Id: base64.stringify(pin2Id(pin2Key, username)),
        pin2Auth: base64.stringify(pin2Auth(pin2Key, pin)),
        pin2Box,
        pin2KeyBox,
        pin2TextBox
      },
      stash: {
        pin2Key: base64.stringify(pin2Key),
        pin2TextBox
      },
      login: {
        pin2Key,
        pin
      },
      loginId: login.loginId
    }
  } else {

async function fetchLoginKey(
  ai: ApiInput,
  username: string,
  password: string,
  otp: string | void
) {
  const up = makeHashInput(username, password)

  const [userId, passwordAuth] = await Promise.all([
    hashUsername(ai, username),
    scrypt(ai, up, passwordAuthSnrp)
  ])
  const request = {
    userId: base64.stringify(userId),
    passwordAuth: base64.stringify(passwordAuth),
    otp
  }
  const reply = await authRequest(ai, 'POST', '/v2/login', request)
  if (reply.passwordBox == null || reply.passwordKeySnrp == null) {
    throw new Error('Missing data for online password login')
  }
  const passwordKey = await scrypt(ai, up, reply.passwordKeySnrp)
  return {
    loginKey: decrypt(reply.passwordBox, passwordKey),
    loginReply: reply
  }
}

async function fetchLoginKey(
  ai: ApiInput,
  pin2Key: Uint8Array,
  username: string,
  pin: string,
  otp: string | void
) {
  const request = {
    pin2Id: base64.stringify(pin2Id(pin2Key, username)),
    pin2Auth: base64.stringify(pin2Auth(pin2Key, pin)),
    otp
  }
  const reply = await authRequest(ai, 'POST', '/v2/login', request)
  if (reply.pin2Box == null) {
    throw new Error('Missing data for PIN v2 login')
  }
  return {
    loginKey: decrypt(reply.pin2Box, pin2Key),
    loginReply: reply
  }
}

recovery2Key
  )
  const recovery2Box = encrypt(io, login.loginKey, recovery2Key)
  const recovery2KeyBox = encrypt(io, recovery2Key, login.loginKey)

  return {
    serverPath: '/v2/login/recovery2',
    server: {
      recovery2Id: base64.stringify(recovery2Id(recovery2Key, username)),
      recovery2Auth: recovery2Auth(recovery2Key, answers),
      recovery2Box,
      recovery2KeyBox,
      question2Box
    },
    stash: {
      recovery2Key: base64.stringify(recovery2Key)
    },
    login: {
      recovery2Key
    },
    loginId: login.loginId
  }
}

export function makeStorageKeyInfo(
  ai: ApiInput,
  type: string,
  keys: StorageKeys = {}
) {
  const { io } = ai.props
  if (keys.dataKey == null) keys.dataKey = base64.stringify(io.random(32))
  if (keys.syncKey == null) keys.syncKey = base64.stringify(io.random(20))

  return makeKeyInfo(type, keys, base64.parse(keys.dataKey))
}