source: TFP-WebServer/WebServer/src/UserRegistrationTokens.cs@ 439

using System;
using System.Collections.Generic;
using HarmonyLib;
using JetBrains.Annotations;

namespace Webserver {
        public static class UserRegistrationTokens {
                private const float tokenExpirationMinutes = 3;

                public class RegistrationData {
                        public readonly string PlayerName;
                        public readonly DateTime ExpiryTime;
                        public readonly PlatformUserIdentifierAbs PlatformUserId;
                        public readonly PlatformUserIdentifierAbs CrossPlatformUserId;

                        public RegistrationData (string _playerName, PlatformUserIdentifierAbs _platformUserId, PlatformUserIdentifierAbs _crossPlatformUserId) {
                                PlayerName = _playerName;
                                ExpiryTime = DateTime.Now + TimeSpan.FromMinutes (tokenExpirationMinutes);
                                PlatformUserId = _platformUserId;
                                CrossPlatformUserId = _crossPlatformUserId;
                        }
                }

                public static bool TryValidate (string _token, out RegistrationData _data) {
                        return activeTokens.TryGetValue (_token, out _data) && _data.ExpiryTime > DateTime.Now;
                }

                private static readonly Dictionary<string, RegistrationData> activeTokens = new Dictionary<string, RegistrationData> ();

                [HarmonyPatch(typeof(ConsoleCmdCreateWebUser))]
                [HarmonyPatch("createToken")]
                private class CommandPatch {
                        [UsedImplicitly]
                        private static bool Prefix (ref string __result, string _playerName, PlatformUserIdentifierAbs _platformUserId, PlatformUserIdentifierAbs _crossPlatformUserId) {
                                string token = Utils.GenerateGuid ();

                                bool hasCrossplatformId = _crossPlatformUserId != null;
                                DateTime currentTime = DateTime.Now;
                                
                                // Check if the user already has a registration attempt running and if so delete the old one
                                // Also clear out any expired tokens
                                activeTokens.RemoveAll (_data => _data.ExpiryTime < currentTime || _platformUserId.Equals (_data.PlatformUserId) ||
                                                                 (hasCrossplatformId && _crossPlatformUserId.Equals (_data.CrossPlatformUserId)));
                                
                                RegistrationData data = new RegistrationData (_playerName, _platformUserId, _crossPlatformUserId);
                                activeTokens [token] = data;
                                
                                __result = token;
                                return false;
                        }
                }
                
        }
}