Context

app.ts

import { curry, flowRight as compose } from 'lodash';
const Task = require('folktale/concurrency/task');


/* example code, pieces from application */
/* Imagine a functional-progrmaming style Forgot Password workflow */

usernameOrEmailExists = (input: {/*...*/}) => isValid(input)
  ? Task.of(input.username)
  : Task.rejected('Invalid');

// compChain and compMap take whatever and call map or chain on them (a la folktale map/chain on Task or Result, or whatever)

// excutes the task and returns a promise - so Feathers (or express, or microservice framework, or whatever)
//  can handle it appropriately
const runAndReturn = (t: Task) => t.run().promise();

// compose from right to left (or in this case, bottom up)
let processRequest = compose(
  runAndReturn,
  compChain(saveUserToken(persistUser, getExpiration)),
  compChain(getUsernameAndToken(getUserData, getKey)),
  compMap(buildFindUserQuery),
  usernameOrEmailExists);


// alternatively, I can declare my own function which does this:
let app = (input) =>
  usernameOrEmailExists(input)
    .map(buildFindUserQuery)
    .chain(getUsernameAndToken(getUserData, getKey))
    .chain(saveUserToken(persistUser, getExpiration));

// then pass this as service handler, request handler, or whatever larger context we're in
let processedReq = compose(runAndReturn, app);


// expose processRequest as a service call, or whatever. Express route, Feathers service, microservice call, whatever