text: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  /**
   * websocket module
   */
  /*global WebSocket*/
  export default (function () {
    const registerListeners = ['onopen', 'onmessage', 'onerror', 'onclose']
    const ws = {
      INSTANCE: null,
      WebSocket: function (url, protocol) {
        if (!url) {
          ws.INSTANCE = null
          return
        }
        if (!protocol) {
          ws.INSTANCE = new WebSocket(url)
        }
        else {
          ws.INSTANCE = new WebSocket(url, protocol)
        }
        return ws.INSTANCE
      },
      send: function (messages) {
        ws.INSTANCE && ws.INSTANCE.send(messages)
      },
      close: function () {
        ws.INSTANCE && ws.INSTANCE.close()
      }
    }
    for (const i in registerListeners) {
      if (registerListeners.hasOwnProperty(i)) {
        Object.defineProperty(ws, registerListeners[i], {
          get: function () {
            return ws.INSTANCE && ws.INSTANCE[registerListeners[i]]
          },
          set: function (fn) {
            if (ws.INSTANCE) {
              ws.INSTANCE[registerListeners[i]] = fn
            }
          }
        })
      }
    }
    return ws
  })()
  