@polkadot/api-provider/coder/json/decodeResponse.ts

// Copyright 2017-2018 @polkadot/api-provider authors & contributors
// This software may be modified and distributed under the terms
// of the ISC license. See the LICENSE file for details.

import { JsonRpcResponse, JsonRpcResponseBase$Error } from '../../types';
import { RpcCoderState } from './types';

import assert from '@polkadot/util/assert';
import isNumber from '@polkadot/util/is/number';
import isUndefined from '@polkadot/util/is/undefined';

function checkError (error?: JsonRpcResponseBase$Error) {
  if (!error) {
    return;
  }

  const { code, message } = error;

  throw new Error(`[${code}]: ${message}`);
}

export default function decodeResponse (self: RpcCoderState, response: JsonRpcResponse): any {
  assert(response, 'Empty response object received');
  assert(response.jsonrpc === '2.0', 'Invalid jsonrpc field in decoded object');

  const isSubscription = !isUndefined(response.params) && !isUndefined(response.method);

  assert(isNumber(response.id) || (isSubscription && isNumber(response.params.subscription)), 'Invalid id field in decoded object');

  checkError(response.error);

  assert(!isUndefined(response.result) || isSubscription, 'No result found in JsonRpc response');

  if (isSubscription) {
    checkError(response.params.error);

    return response.params.result;
  }

  return response.result;
}