appsync invoke

invoke.ts

import * as https from 'https';
import { URL } from 'url';

const AWS = require('aws-sdk');

export function assertEnv(key: string): string {
  if (process.env[key] !== undefined) {
    return process.env[key]!;
  }
  throw new Error(`expected environment variable ${key}`);
}  

const aws_appsync_graphqlEndpointP = assertEnv('aws_appsync_graphqlEndpoint');
const aws_appsync_regionP = assertEnv('aws_appsync_region');

const invoke = async (body): Promise<any> => {
  const [aws_appsync_graphqlEndpoint, aws_appsync_region] = await Promise.all([
    aws_appsync_graphqlEndpointP,
    aws_appsync_regionP,
  ]);

  const req = new AWS.HttpRequest(aws_appsync_graphqlEndpoint, aws_appsync_region);
  const endpoint = new URL(aws_appsync_graphqlEndpoint).hostname.toString();

  req.method = 'POST';
  req.path = '/graphql';
  req.headers.host = endpoint;
  req.headers['Content-Type'] = 'application/json';
  req.body = JSON.stringify(body);
  const signer = new AWS.Signers.V4(req, 'appsync', true);
  signer.addAuthorization(AWS.config.credentials, AWS.util.date.getDate());

  return new Promise((resolve, reject) => {
    const httpRequest = https.request({ ...req, host: endpoint }, (result) => {
      let data = '';

      result.on('data', (chunk) => {
        data += chunk;
      });
      result.on('error', (e) => {
        reject(e);
      });

      result.on('end', () => {
        try {
          if (typeof result.statusCode === 'number' && (result.statusCode < 200 || result.statusCode >= 400)) {
            throw new Error(`unexpected response code ${result.statusCode}: ${data.toString()}`);
          }
          const respBody = JSON.parse(data.toString());
          resolve(respBody);
        } catch (e) {
          reject(e);
        }
      });
    });

    httpRequest.write(req.body);
    httpRequest.end();
  });
};