fCraft.DrawCommands.ParseBlockDBUndoParams C# (CSharp) Method

        static BlockDBUndoArgs ParseBlockDBUndoParams([NotNull] Player player, [NotNull] CommandReader cmd,
                                                      [NotNull] string cmdName, bool not) {
            if (player == null) throw new ArgumentNullException("player");
            if (cmd == null) throw new ArgumentNullException("cmd");
            if (cmdName == null) throw new ArgumentNullException("cmdName");

            // check if command's being called by a worldless player (e.g. console)
            World playerWorld = player.World;
            if (playerWorld == null) PlayerOpException.ThrowNoWorld(player);

            // ensure that BlockDB is enabled
            if (!BlockDB.IsEnabledGlobally) {
                player.Message("&W{0}: BlockDB is disabled on this server.", cmdName);
                return null;
            }
            if (!playerWorld.BlockDB.IsEnabled) {
                player.Message("&W{0}: BlockDB is disabled in this world.", cmdName);
                return null;
            }

            // parse the first parameter - either numeric or time limit
            string range = cmd.Next();
            if (range == null) {
                CdUndoPlayer.PrintUsage(player);
                return null;
            }
            int countLimit;
            TimeSpan ageLimit = TimeSpan.Zero;
            if (!Int32.TryParse(range, out countLimit) && !range.TryParseMiniTimeSpan(out ageLimit)) {
                player.Message("{0}: First parameter should be a number or a timespan.", cmdName);
                return null;
            }
            if (ageLimit > DateTimeUtil.MaxTimeSpan) {
                player.MessageMaxTimeSpan();
                return null;
            }

            // parse second and consequent parameters (player names)
            HashSet<PlayerInfo> targets = new HashSet<PlayerInfo>();
            bool allPlayers = false;
            while (true) {
                string name = cmd.Next();
                if (name == null) {
                    break;
                } else if (name == "*") {
                    // all players
                    if (not) {
                        player.Message("{0}: \"*\" not allowed (cannot undo \"everyone except everyone\")", cmdName);
                        return null;
                    }
                    if (allPlayers) {
                        player.Message("{0}: \"*\" was listed twice.", cmdName);
                        return null;
                    }
                    allPlayers = true;
                } else {
                    // individual player
                    PlayerInfo target = PlayerDB.FindPlayerInfoOrPrintMatches(player, name, SearchOptions.IncludeSelf);
                    if (target == null) {
                        return null;
                    }
                    if (targets.Contains(target)) {
                        player.Message("{0}: Player {1}&S was listed twice.",
                                       target.ClassyName,
                                       cmdName);
                        return null;
                    }
                    // make sure player has the permission
                    if (!not &&
                        player.Info != target && !player.Can(Permission.UndoAll) &&
                        !player.Can(Permission.UndoOthersActions, target.Rank)) {
                        player.Message("&W{0}: You may only undo actions of players ranked {1}&S or lower.",
                                       cmdName,
                                       player.Info.Rank.GetLimit(Permission.UndoOthersActions).ClassyName);
                        player.Message("Player {0}&S is ranked {1}",
                                       target.ClassyName,
                                       target.Rank.ClassyName);
                        return null;
                    }
                    targets.Add(target);
                }
            }
            if (targets.Count == 0 && !allPlayers) {
                player.Message("{0}: Specify at least one player name, or \"*\" to undo everyone.", cmdName);
                return null;
            }
            if (targets.Count > 0 && allPlayers) {
                player.Message("{0}: Cannot mix player names and \"*\".", cmdName);
                return null;
            }

            // undoing everyone ('*' in place of player name) requires UndoAll permission
            if ((not || allPlayers) && !player.Can(Permission.UndoAll)) {
                player.MessageNoAccess(Permission.UndoAll);
                return null;
            }

            // Queue UndoPlayerCallback to run
            return new BlockDBUndoArgs {
                Player = player,
                AgeLimit = ageLimit,
                CountLimit = countLimit,
                Area = player.WorldMap.Bounds,
                World = playerWorld,
                Targets = targets.ToArray(),
                Not = not
            };
        }