// This shows that Lichess's frontend discards illegal moves. Run this script in Tampermonkey and set a breakpoint to the '// outcoming websockets' line. Try to make an illegal move. The line won't be reached, because Lichess discards illegal moves. Try to make a legal move, and the line will be reached.

// ==UserScript==
// @name         Check WebSockets
// @namespace    http://tampermonkey.net/
// @version      0.1
// @match        https://lichess.org/*
// @icon         https://www.google.com/s2/favicons?domain=lichess.org
// @grant        none
// @run-at       document-start
// ==/UserScript==

console.log('script to check websockets');

(function () {
      //to get the move that has been sent by the client, https://stackoverflow.com/a/31182643/10364842
      var OrigWebSocket = window.WebSocket;
      var callWebSocket = OrigWebSocket.apply.bind(OrigWebSocket);
      var wsAddListener = OrigWebSocket.prototype.addEventListener;
      wsAddListener = wsAddListener.call.bind(wsAddListener);
      window.WebSocket = function WebSocket(url, protocols) {
        var ws;
        if (!(this instanceof WebSocket)) {
          // Called without 'new' (browsers will throw an error).
          ws = callWebSocket(this, arguments);
        } else if (arguments.length === 1) {
          ws = new OrigWebSocket(url);
        } else if (arguments.length >= 2) {
          ws = new OrigWebSocket(url, protocols);
        } else {
          // No arguments (browsers will throw an error)
          ws = new OrigWebSocket();
        }
        wsAddListener(ws, 'message', function (event) {
          // TODO: Do something with event.data (received data) if you wish.
          console.log(event)
        });
        return ws;
      }.bind();
      window.WebSocket.prototype = OrigWebSocket.prototype;
      window.WebSocket.prototype.constructor = window.WebSocket;

      var wsSend = OrigWebSocket.prototype.send;
      wsSend = wsSend.apply.bind(wsSend);
      OrigWebSocket.prototype.send = function (data) {
        // TODO: Do something with the sent data if you wish.
        if (data !== null && data !== 'null') {
          // outcoming websockets
          console.log(data);
          debugger;
        }
        return wsSend(this, arguments);
      };
    })();