basic-computer-games/00_Common/dotnet/Games.Common/IO/Token.cs

using System.Text;
using System.Text.RegularExpressions;

namespace Games.Common.IO
{
    internal class Token
    {
        private static readonly Regex _numberPattern = new(@"^[+\-]?\d*(\.\d*)?([eE][+\-]?\d*)?");

        internal Token(string value)
        {
            String = value;

            var match = _numberPattern.Match(String);

            IsNumber = float.TryParse(match.Value, out var number);
            Number = (IsNumber, number) switch
            {
                (false, _) => float.NaN,
                (true, float.PositiveInfinity) => float.MaxValue,
                (true, float.NegativeInfinity) => float.MinValue,
                (true, _) => number
            };
        }

        public string String { get; }
        public bool IsNumber { get; }
        public float Number { get; }

        public override string ToString() => String;

        internal class Builder
        {
            private readonly StringBuilder _builder = new();
            private bool _isQuoted;
            private int _trailingWhiteSpaceCount;

            public Builder Append(char character)
            {
                _builder.Append(character);

                _trailingWhiteSpaceCount = char.IsWhiteSpace(character) ? _trailingWhiteSpaceCount + 1 : 0;

                return this;
            }

            public Builder SetIsQuoted()
            {
                _isQuoted = true;
                return this;
            }

            public Token Build()
            {
                if (!_isQuoted) { _builder.Length -= _trailingWhiteSpaceCount; }
                return new Token(_builder.ToString());
            }
        }
    }
}