console.clear();

function logMethods({ log }) {
  return target => {
    const proto = target.prototype;
    Object.getOwnPropertyNames(proto)
      .filter(n => n !== 'constructor')
      .map(n => ({
        key: n,
        pd: Object.getOwnPropertyDescriptor(proto, n)
      }))
      .filter(({ pd }) => typeof pd.value === 'function')
      .forEach(({ key, pd }) => {
        const orig = pd.value;
        pd.value = function() {
          setTimeout(() => log({ key, className: target.name }), 0);
          return orig.apply(this, arguments);
        };
        Object.defineProperty(proto, key, pd);
      });
  };
}

function logTime({ logTo }) {
  return (target, key, pd: PropertyDescriptor) => {
    const origMeth = pd.value;
    pd.value = function() {
      const startTime = Date.now(),
        result = origMeth.apply(this, arguments),
        duration = Date.now() - startTime,
        logf = d =>
          logTo.call(this, {
            duration: d,
            method: key,
            class: target.constructor.name
          });

      if (
        result &&
        (result instanceof Promise || result.constructor.name === 'Promise')
      )
        Promise.all([result]).then(r => logf(Date.now() - startTime));
      else logf(duration);
      return result;
    };
  };
}

@logMethods({
  log: ({ key, className }) =>
    console.log(`call the '${key}' method of class '${className}'`)
})
class MyClass {
  static options = {
    logTo: MyClass.prototype.log
  };

  @logTime(MyClass.options)
  async test(...args) {
    await this.delay(1000);
    return 'ok';
  }

  @logTime(MyClass.options)
  async delay(ms) {
    await new Promise(res => setTimeout(res, ms));
  }

  @logTime(MyClass.options)
  log(...o) {
    console.log(...o);
  }
}

(async () => {
  let m = new MyClass();
  await m.test();
  m.log('decorators are awesome!');
})();


/*
console out:
call the 'test' method of class 'MyClass'
call the 'delay' method of class 'MyClass'
{ duration: 1006, method: 'delay', class: 'MyClass' }
{ duration: 1010, method: 'test', class: 'MyClass' }
decorators are awesome!
{ duration: 0, method: 'log', class: 'MyClass' }
call the 'log' method of class 'MyClass'
*/