module.exports = function patchGunWithCancel(Gun) {
  Gun.chain.onWithCancel = (function() {
    function cancelCallback(data,key,msg,ev) {
      if (ev && typeof ev.off === 'function') {
        ev.off();
      }
    }

    return function(tag, arg, eas, as) {
      if (typeof tag === 'function') {
        let callback = tag;
        const cancelEv = function() {
          callback = cancelCallback;
        };
        const wrapper = function() {
          return callback.apply(this, arguments);
        };
        this.on(wrapper, arg, eas, as);
        return cancelEv;
      } else {
        this.on(tag, arg, eas, as);
        return null;
      }
    };
  })();
};