TODO

- Is http.MarketDepth {bids, ask} or {bids, asks}?

/**
 * Provides the API for creating and managing a WebSocket connection to
 * a server, as well as for sending and receiving data on the connection.
 */
export class Connection extends WebSocket {
  /** To recieve response to a request. */
  recievers: Reciever[] = []

  setup() {
    var ping = setInterval(() => {
      if (this.readyState !== WebSocket.OPEN) return;
      this.send("ping");
    }, PING_INTERVAL);
    this.binaryType = "arraybuffer";
    this.onerror = e => {
      for (var r of this.recievers)
        r.reject(e.error);
      clearInterval(ping);
      reject(e.error);
    };
    this.onopen = () => resolve(this);
    this.onmessage = e => {
      if (typeof e.data !== "string") return;
      if (e.data === "pong") return;
      var x = JSON.parse(e.data); fn(x);
      if (!x.hasOwnProperty("d") && this.recievers.length > 0) this.recievers.shift().resolve(x);
    };
  }

  /**
   * Send a request through connection.
   * @param data request data
   * @returns response {s, code, message}
   */
  sendRequest(data: any): Promise<Response> {
    var r: Reciever = null;
    this.send(JSON.stringify(data), err => {
      if (r == null) return;
      var i = this.recievers.indexOf(r);
      this.recievers.splice(i, 1);
      r.reject(err);
    });
    return new Promise((resolve, reject) => {
      r = {resolve, reject};
      this.recievers.push(r);
    });
  }
}