(function () {
  'use strict';

  /* eslint-env browser */

  class Event {

    constructor(type, data) {
      this.type = type;
      this.data = data;
    }

  }

  class Observable {

    constructor() {
      this.listeners = {};
    }

    addEventListener(type, callback) {
      if (this.listeners[type] === undefined) {
        this.listeners[type] = [];
      }
      this.listeners[type].push(callback);
    }

    notifyAll(event) {
      let listeners = this.listeners[event.type];
      if (listeners) {
        for (let i = 0; i < listeners.length; i++) {
          listeners[i](event);
        }
      }
    }

  }

  /* eslint-env browser */

  class GazeDataEvent extends Event {
    constructor(data) {
      super("gazeDataAvailable", data);
    }
  }

  class ConnectionEvent extends Event {
    constructor() {
      super("connected");
    }
  }

  class WebSocketClient extends Observable {

    constructor() {
      super();
    }

    connect(url) {

      this.ws = new WebSocket(url);
      this.ws.onopen = onOpen.bind(this);
      this.ws.onmessage = onMessage.bind(this);
    }

  }

  function onOpen() {
    let connectionEvent = new ConnectionEvent();
    this.notifyAll(connectionEvent);
  }

  function onMessage(event) {
    let gazeEvent = new GazeDataEvent(event.data);
    this.notifyAll(gazeEvent);
  }

  /* eslint-env browser */

  class GazeClient extends Observable {

    constructor() {
      super();
    }

    connect(url) {
      this.url = url;
      this.client = new WebSocketClient();
      this.client.addEventListener("connected", this.onConnected.bind(this));
      this.client.addEventListener("gazeDataAvailable", this.onGazeDataAvailable
        .bind(this));
      this.client.connect(url);
    }

    onOpen() {
      this.client.send("hello server");
    }

    onConnected(event) {
      // TODO: Implement event broadcasting
    }

    onGazeDataAvailable(event) {
      this.notifyAll(event);
    }

  }

  window.GazeClient = GazeClient;

}());