Reader + Future Monads Usage

reader_future.js

/**
 * This short program will encrypt the user password
 * and insert a new record into a mock database.
 */
const Reader = require('fantasy-readers');
const Future = require('fluture');
const R = require('ramda');
const crypto = require('crypto');

// our mock database
const database = [
  { email: 'user@example.org', password: 'e0538fd8f022bb3b139d72cf12766cb0e31690ff' },
  { email: 'admin@example.org', password: '42c4fbf6fec201c66b82c97833b08d936d2cd526' }
]

// creates a statefull database connection
const connectTo = (db) => {
  return {
    insert: (doc) => Future.of(db.push(doc)),
    get: (i) => Future.of(db[i]),
    delete: (i) => Future.of(db.splice(i, 1)),
    list: () => Future.of(db)
  }
}

// some utility functions
const encrypt = (i) => crypto.createHash('sha1').update(i).digest('hex');
const encPassword = R.evolve({password: encrypt})


// utility function which makes it easier
// to ask for some dependency
// dependencies should reside in an object { dep: obj }
const inject = R.curry((dep, f, reader) => {
  return reader.chain((v) => {
    return Reader.ask.map((env) => {
      return f(env[dep], v);
    });
  });
});

// this is how you access the cb connection inside the reader
const save = (db, user) => {
  db.insert(user);
  return db.list();
}

// the body of the program
const handler = R.pipe(
  R.map(encPassword),                          // Reader Object
  inject('db', save),                          // Reader Future Error Object
  R.map(R.map(R.map(R.dissoc('password'))))    // Reader Future Error Object
);

// this is our db connection now
const dbCon = connectTo(database);

const request = { email: 'new@example.org', password: 'secret' };

const result = handler(Reader.of(request))
  .run({ 'db': dbCon }) // this is how you pass the db connection in
  .fork(console.error, console.log); // now fork the future