private static CommandTreeToken ScanLongOption(CommandTreeTokenizerContext context, TextBuffer reader, int position)
        {
            reader.Consume('-');
            context.AddRemaining('-');

            if (reader.ReachedEnd)
            {
                // Rest of the arguments are remaining ones.
                context.Mode = Mode.Remaining;
                return(new CommandTreeToken(CommandTreeToken.Kind.Remaining, position, "--", "--"));
            }

            var name = ScanString(context, reader, new[] { '=', ':' });

            // Perform validation of the name.
            if (name.Value.Length == 0)
            {
                throw CommandParseException.LongOptionNameIsMissing(reader, position);
            }

            if (name.Value.Length == 1)
            {
                throw CommandParseException.LongOptionNameIsOneCharacter(reader, position, name.Value);
            }

            if (char.IsDigit(name.Value[0]))
            {
                throw CommandParseException.LongOptionNameStartWithDigit(reader, position, name.Value);
            }

            for (var index = 0; index < name.Value.Length; index++)
            {
                if (!char.IsLetterOrDigit(name.Value[index]) && name.Value[index] != '-' && name.Value[index] != '_')
                {
                    throw CommandParseException.LongOptionNameContainSymbol(reader, position + 2 + index, name.Value[index]);
                }
            }

            return(new CommandTreeToken(CommandTreeToken.Kind.LongOption, position, name.Value, $"--{name.Value}"));
        }
        private static IEnumerable <CommandTreeToken> ScanOptions(CommandTreeTokenizerContext context, TextBuffer reader)
        {
            var result = new List <CommandTreeToken>();

            var position = reader.Position;

            reader.Consume('-');
            context.AddRemaining('-');

            if (!reader.TryPeek(out var character))
            {
                var token = new CommandTreeToken(CommandTreeToken.Kind.ShortOption, position, "-", "-");
                throw CommandParseException.OptionHasNoName(reader.Original, token);
            }

            switch (character)
            {
            case '-':
                var option = ScanLongOption(context, reader, position);
                if (option != null)
                {
                    result.Add(option);
                }

                break;

            default:
                result.AddRange(ScanShortOptions(context, reader, position));
                break;
            }

            if (reader.TryPeek(out character))
            {
                // Encountered a separator?
                if (character == '=' || character == ':')
                {
                    reader.Read(); // Consume
                    context.AddRemaining(character);

                    if (!reader.TryPeek(out _))
                    {
                        var token = new CommandTreeToken(CommandTreeToken.Kind.String, reader.Position, "=", "=");
                        throw CommandParseException.OptionValueWasExpected(reader.Original, token);
                    }

                    result.Add(ScanString(context, reader));
                }
            }

            return(result);
        }
        private static IEnumerable <CommandTreeToken> ScanShortOptions(CommandTreeTokenizerContext context, TextBuffer reader, int position)
        {
            var result = new List <CommandTreeToken>();

            while (!reader.ReachedEnd)
            {
                var current = reader.Peek();
                if (char.IsWhiteSpace(current))
                {
                    break;
                }

                // Encountered a separator?
                if (current == '=' || current == ':')
                {
                    break;
                }

                if (char.IsLetter(current))
                {
                    context.AddRemaining(current);
                    reader.Read(); // Consume

                    var value = current.ToString(CultureInfo.InvariantCulture);
                    result.Add(result.Count == 0
                        ? new CommandTreeToken(CommandTreeToken.Kind.ShortOption, position, value, $"-{value}")
                        : new CommandTreeToken(CommandTreeToken.Kind.ShortOption, position + result.Count, value, value));
                }
                else
                {
                    // Create a token representing the short option.
                    var tokenPosition = position + 1 + result.Count;
                    var represntation = current.ToString(CultureInfo.InvariantCulture);
                    var token         = new CommandTreeToken(CommandTreeToken.Kind.ShortOption, tokenPosition, represntation, represntation);
                    throw CommandParseException.InvalidShortOptionName(reader.Original, token);
                }
            }

            if (result.Count > 1)
            {
                foreach (var item in result)
                {
                    item.IsGrouped = true;
                }
            }

            return(result);
        }
        private static CommandTreeToken ScanQuotedString(CommandTreeTokenizerContext context, TextBuffer reader)
        {
            var position = reader.Position;

            context.FlushRemaining();
            reader.Consume('\"');

            var builder    = new StringBuilder();
            var terminated = false;

            while (!reader.ReachedEnd)
            {
                var character = reader.Peek();
                if (character == '\"')
                {
                    terminated = true;
                    reader.Read();
                    break;
                }

                builder.Append(reader.Read());
            }

            if (!terminated)
            {
                var unterminatedQuote = builder.ToString();
                var token             = new CommandTreeToken(CommandTreeToken.Kind.String, position, unterminatedQuote, $"\"{unterminatedQuote}");
                throw CommandParseException.UnterminatedQuote(reader.Original, token);
            }

            var quotedString = builder.ToString();

            // Add to the context
            context.AddRemaining(quotedString);

            return(new CommandTreeToken(
                       CommandTreeToken.Kind.String,
                       position, quotedString,
                       quotedString));
        }