'use strict';

function Mule (obj, ...args) {
  const mule = new Proxy({}, {
    get: function (target, prop, receiver) {
      const topKeys = Object.keys(target);
      if (topKeys.includes(prop)) {
        return target[prop];
      }

      if (!obj.mule) {
        return undefined;
      }

      const muleKeys = Object.keys(obj.mule);
      if (muleKeys.includes(prop)) {
        return obj.mule[prop];
      }

      return undefined;
    }
  });
  obj.apply(mule, args);

  return mule;
};

Mule.inherits = function (child, parent) {
  child.mule = Object.assign({}, parent.mule);
};


const Hello = function () {
  this.hello = function () {
    console.log('hello ');
  };
};

Hello.mule = {};

Hello.mule.world = function () {
  console.log('world');
};

const Foo = function (...args) {
  Hello.apply(this, args);
}
Mule.inherits(Foo, Hello);

Foo.mule.bar = function () {
  console.log('bar');
};

const hello = Mule(Hello);
hello.hello();
hello.world();
console.log(hello.bar);


const foo = Mule(Foo);
foo.hello();
foo.world();
foo.bar();




// Output
/*
hello
world
undefined
hello
world
bar
*/