CanonSharp/CanonSharp.Common/LexicalAnalyzer/EmptyChar.cs

namespace CanonSharp.Common.LexicalAnalyzer;

public class EmptyChar : IEquatable<EmptyChar>
{
    public bool IsEmpty { get; }

    public char Char { get; }

    public static EmptyChar Empty => new();

    private EmptyChar()
    {
        IsEmpty = true;
        Char = char.MaxValue;
    }

    public EmptyChar(char c)
    {
        IsEmpty = false;
        Char = c;
    }

    public bool Equals(EmptyChar? other)
    {
        if (other is null)
        {
            return false;
        }

        if (IsEmpty)
        {
            return other.IsEmpty;
        }

        return Char == other.Char;
    }

    public override bool Equals(object? obj) => obj is EmptyChar other && Equals(other);

    public override int GetHashCode()
    {
        return IsEmpty.GetHashCode() ^ Char.GetHashCode();
    }

    public override string ToString()
    {
        return IsEmpty ? "ε" : Char.ToString();
    }
}