How to use the fluture.encaseN2 function in fluture

'use strict';

const fs            = require ('fs');

const Future        = require ('fluture');

const exit0         = require ('./common/exit0');
const exit1         = require ('./common/exit1');
const join          = require ('./common/join');
const S             = require ('./common/sanctuary');


//    readFile :: String -> Future Error String
const readFile = S.flip (Future.encaseN2 (fs.readFile)) ({encoding: 'utf8'});

//    readFilePar :: String -> ConcurrentFuture Error String
const readFilePar = S.compose (Future.Par) (readFile);

//    concatFiles :: (String -> String) -> Future Error String
const concatFiles = path =>
  S.pipe ([path,                                            // :: String
           readFile,                                        // :: Future Error String
           S.map (S.lines),                                 // :: Future Error (Array String)
           S.map (S.map (path)),                            // :: Future Error (Array String)
           S.map (S.traverse (Future.Par) (readFilePar)),   // :: Future Error (ConcurrentFuture Error (Array String))
           S.chain (Future.seq),                            // :: Future Error (Array String)
           S.map (S.joinWith (''))])                        // :: Future Error String
         ('index.txt');

return function (path, options = {}) {
    options.version = options.version || this.version
    const encased = Future.encaseN2(method.bind(this))
    return encased(path, options)
  }
}

'use strict';

const {Stream} = require ('../..');
const Future = require ('fluture');
const fs = require ('fs');
const path = require ('path');

const access = Future.encaseN2 (fs.access);

module.exports = req => Future.do (function* () {
  const file = path.resolve (__dirname, '..', path.basename (req.query.file));

  if (path.extname (req.query.file) !== '.jpeg') {
    yield Future.reject (new Error ('You can only load JPEGs'));
  }

  yield (access (file, fs.constants.R_OK)).mapRej (
    _ => new Error ('No read access to the requested file')
  );

  return Stream (200,
                 path.extname (req.query.file),
                 fs.createReadStream (file));
});