fCraft.BuildingCommands.ParseBlockDBUndoParams C# (CSharp) Method

        private static BlockDBUndoArgs ParseBlockDBUndoParams( Player player, Command cmd, string cmdName, bool not )
        {
            // 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 first and consequent parameters (player names)
            HashSet<PlayerInfo> targets = new HashSet<PlayerInfo>();
            bool allPlayers = false;
            string name = cmd.Next();
            switch (name)
            {
                case null:
                    return null;
                case "*":
                    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;
                    break;
                default:
                {
                    // individual player
                    PlayerInfo target = PlayerDB.FindPlayerInfoOrPrintMatches( player, name );
                    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 );
                }
                    break;
            }

            // parse the 2nd parameter - either numeric or time limit
            string range = cmd.Next();
            if ( range == null ) {
                CdUndoPlayer.PrintUsage( player );
                return null;
            }

            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;
            }

            int countLimit;
            TimeSpan ageLimit = TimeSpan.Zero;
            if ( !Int32.TryParse( range, out countLimit ) && !range.TryParseMiniTimespan( out ageLimit ) ) {
                player.Message( "{0}: Second parameter should be a number or a timespan.", cmdName );
                return null;
            }
            if ( ageLimit > DateTimeUtil.MaxTimeSpan ) {
                player.MessageMaxTimeSpan();
                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
            };
        }