function findDelegateTarget(event, selector) {
  let currentNode = event.target;
  while (currentNode) {
    if (currentNode.matches(selector)) {
      return currentNode;
    }

    if (currentNode == event.currentTarget) {
      break;
    }
    currentNode = currentNode.parentElement;
  }
  return null;
}

// delegate(table, 'th', click, handler)
// table
//   thead
//     th         ^*
//       code  <--
function delegate(topElement, selector, eventName, handler, context) {
  /* jshint -W040 */
  topElement.addEventListener(eventName, function(event) {
    let found = findDelegateTarget(event, selector);

    // .currentTarget is read only, I can not overwrite it to the "found" element
    // Object.create wrapper would break event.preventDefault()
    // so, keep in mind:
    // --> event.currentTarget is always the top-level (delegating) element!
    // use "this" to get the found target

    event.delegateTarget = found; // use instead of "this" in object methods

    if (found) {
      // if in context of object, use object as this,
      handler.call(context || this, event);
    }
  });
}

delegate.delegateMixin = function(obj) {
  obj.delegate = function(selector, eventName, handler) {
    delegate(this.elem, selector, eventName, handler, this);
  };
};

module.exports = delegate;