Functional wrapHandler

test.wrapHandler.js

'use strict';

function wrapHandler (handler, callback) {
  var name = arguments[0].name || 'clone';
  return function (err) {
    if (err) return callback(err);
    console.log(name, 'called with', arguments);
    var args = Array.prototype.slice.call(arguments, 1);
    args.push(callback);
    handler.apply(this, args);
  };
}

describe('Functional', function () {

  it('passes 1 method', function (done) {
    // methods
    function fn1 (msg, callback) {
      callback();
    }
    // wrap
    var w1 = wrapHandler(fn1, done);
    // call
    w1(null, 'hello');
  });

  it('passes 2 methods', function (done) {
    // methods
    function fn1 (msg, callback) {
      callback();
    }
    function fn2 (callback) {
      callback();
    }
    // wrap
    var w1 = wrapHandler(fn1, wrapHandler(fn2, done));
    // call
    w1(null, 'hello');
  });

  it('passes 3 methods', function (done) {
    // methods
    function fn1 (msg, callback) {
      callback(null, msg + '.');
    }
    var fn2 = fn1.bind({});
    function fn3 (msg, callback) {
      callback(null, msg);
    }
    // wrap
    var w1 = wrapHandler(fn1, wrapHandler(fn2, wrapHandler(fn3, function (err, msg) {
      (!err).should.be.true;
      msg.should.equal('hello..');
      done(err);
    })));
    // call
    w1(null, 'hello');
  });

  it('passes err to 2nd, thus skips 2nd and 3rd method', function (done) {
    // methods
    function fn1 (msg, callback) {
      callback('bad msg');
    }
    var fn2 = fn1.bind({});
    function fn3 (msg, callback) {
      console.log('please do not call me');
      callback();
    }
    // wrap
    var w1 = wrapHandler(fn1, wrapHandler(fn2, wrapHandler(fn3, function (err) {
      (!!err).should.be.true;
      done();
    })));
    // call
    w1(null, 'hello');
  });

});