jbielick/faktory_worker_node

import compose, { ComposedMiddleware } from "koa-compose";
import { Middleware, MiddlewareContext, Registry } from "./worker";

/**
 * Builds a koa-compose stack of the middleware functions in addition to
 * two worker-added middleware functions for pulling the job function from the
 * registry and calling the job function and/or thunk
 *
 * @private
 * @return {function} entrypoint function to the middleware stack
 */

export default function createExecutionChain(
  middleware: Middleware[],
  registry: Registry
): ComposedMiddleware<MiddlewareContext> {
  return compose([
    ...middleware,
    function getJobFnFromRegistry(ctx, next) {
      const {
        job: { jobtype },
      } = ctx;
      ctx.fn = registry[jobtype];
      return next();
    },
    async function callJobFn(ctx, next) {
      const {
        fn,
        job: { jobtype, args },
      } = ctx;
      if (!fn) throw new Error(`No jobtype registered: ${jobtype}`);
      const thunkOrPromise = await fn(...args);
      if (typeof thunkOrPromise === "function") {
        await thunkOrPromise(ctx);
      } else {
        await thunkOrPromise;
      }
      return next();
    },
  ]);
}