index.js

require ('./globals')(global); // Mixed in Ramda to global here
var Task = require ('data.future'),
    M    = require ('control.monads'),
    State = require ('fantasy-states'),
    Reader = require ('fantasy-readers'),
    Tuple2 = require ('fantasy-tuples').Tuple2,
    Maybe = require ('data.maybe'),

    ST  = State.StateT (Task),
    App = Reader.ReaderT (ST);
    App.liftT = function (t) {
      return App.liftR (ST (function (s) {
        return new Task (function (reject, resolve) {
          t.fork (reject, function (data) {
            return resolve (Tuple2 (data, s));
          });
        });
      }));
    };
    App.liftR = App.lift;
    App.lift  = compose (App.liftR, ST.lift);

    App.prototype.map = function (f) { return this.chain (compose (App.of, f)); };

    // For inserting custom lift function
    App.prototype.mapLift = curry (function (lift, f) {
      return this.chain (compose (lift, f));
    });

    var
//  getPathFromRequest :: Request -> String
    getPathFromRequest = compose (get ('path'), get ('file'), get ('files')),

//  savePath :: App -> App
    savePath = App.ask.chain (function (r) {
      var path = getPathFromRequest (r);
      return App.liftR (ST.modify ( mixin ({ path: path }) ));
    }),

//  getPath :: App -> App
    getPath = App.liftR (ST.get).map (get ('path')),

//  getFileHash :: Path -> Task Hash
    getFileHash = function (path) {
      return new Task (function (reject, resolve) {
        require ('child_process').exec ('md5sum '+ path, function (err, stdout, stderr) {
          if (err) { return reject (err); }
          return compose (resolve, head, split (/\s/)) (stdout);
        });
      });
    },

//  saveHash :: Hash -> App
    saveHash = function (hash) {
      return App.liftR (ST.modify ( mixin ({ hash: hash }) ));
    },

    getFileHash = M.sequence (App, [ savePath, getPath .chain (compose ( App.liftT, getFileHash )) ]),

    nil = null;

//==============================================================================
// Impure
//==============================================================================
var express      = require ('express'),
    bodyParser   = require ('body-parser'),
    cookieParser = require ('cookie-parser'),
    multer       = require ('multer'),
    app          = express (),

    errJson     = curry (function (code, res, data) { res.send (code, data); }),
    succJson    = curry (function (res, data) { res.json (data || {}); }),

    appResponse = curry (function (app, req, res) {
      var defaultState = {};
      app.run (req)
        .evalState (defaultState)
        .fork (
          errJson (401, res),
          succJson (res)
        );
    }),

    ask = App.ask,
    nil = null;

app.use (express.static (__dirname + '/public'));
app.use (bodyParser.urlencoded ({ extended: true }));
app.use (bodyParser.json ());
app.use (multer ({ dest: './uploads/' }));

app.get ('/', function (req, res) {
  res.send (compose (toString, add (2))(4));
});

app.post ('/upload', appResponse (getFileHash));

app.listen (7171);