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 const express = require('express');
const http = require('http');
const WebSocket = require('ws');

const port = 6969;
const server = http.createServer(express);
const wss = new WebSocket.Server({
    server
});

clients = [];
// That array contains the figure positions for all users connected.
// It is array that contains arrays. EXAMPLE:
// Each user has his own userid, username, and the figure position in each array:
// clients {
//   [0] = {'51', 'Diablo', '5'}
//   [1] = {'84', 'Jason', '3'}
//   [2] = {'15', 'Triston', '8'}
// }

// When user makes a move, a data is sent.
wss.on('connection', function connection(ws){
    ws.on('message', function incoming(data){
      // An user with ID 84, is sending his new figure position '13'.
      data = JSON.parse(data);
      // Now we need for loop in the clients array, to find the array index of the player
      // with ID of 84, in order to replace the old figure position in that index with
      // the new figure position.
      change_figure_position(data[0]);
    });
});

function change_figure_position(userid){
  var user_data;
  // looping trough all currently connected users.
  for (var i = 0; i < clients.length; i  ) {
    // Upon each loop, check if the array index of 0 (the user id) matches
    // with the id of the user that send data.
    if(clients[i][0].includes(userid) == true){
      // The user index is found! Change the figure position in that index.
      clients[i][2] = data[2];
    }
  }
}  

 #current status of the clients variable
clients {
 [0] = {'51', 'Diablo', '5'}
 [1] = {'84', 'Jason', '3'}
 [2] = {'15', 'Triston', '8'}
 [3] = {'16', 'Jimmie', '5'}
}

// user Triston moves a figure
// the function finds that his index is [2]

// an user called Jason disconnects AT THE SAME TIME Triston moves a figure
#current status of the clients variable
clients {
 [0] = {'51', 'Diablo', '5'}
 [1] = {'15', 'Triston', '8'}
 [2] = {'16', 'Jimmie', '5'}
}

// remember, Triston disconected before the function FULLY executed itself
// the function still remembers that Triston's index is [2], but now it is [1].
// so what will happen is that Jimmie's figure will be moved instead.