Medium: M2M in GraphQL context (Factory function for creating the binding)

index.ts

import { readFile } from "fs";
import { join as joinPath } from "path";
import { promisify } from "util";

import fetch from "node-fetch";
import { makeRemoteExecutableSchema } from "graphql-tools";
import { createHttpLink } from "apollo-link-http";

import { Binding as TelemetryBinding } from "./telemetry";

/**
 * Factory function for instantiating the Telemetry binding.
 *
 * @param endpoint {string} The endpoint of the Telemetry API
 * @returns {Binding}
 *
 */
const createTelemetryBinding = async (
  endpoint: string
): Promise<TelemetryBinding> => {
  // 1. Read the type defs from our downloaded remote schema.
  const readTypeDefs = promisify(readFile);
  const typeDefsPath = joinPath(__dirname, "telemetry.graphql");

  const typeDefs = await readTypeDefs(typeDefsPath, {
    encoding: "utf8"
  });

  // 2. Create a HTTP link. This component is responsible for
  // perfoming the actual HTTP communication. We use `node-fetch`
  // as the underlying transport mechanism.
  const link = createHttpLink({ uri: endpoint, fetch });

  // 3. Combine the type definitions with the HTTP link
  // and make the schema "executable".
  const schema = makeRemoteExecutableSchema({
    schema: typeDefs,
    link
  });

  // 4. Instantiate the generated binding by passing
  // the executable remote schema.
  return new TelemetryBinding({
    schema
  });
};

export { createTelemetryBinding };