RegexFC.cs

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using System.Globalization;
 
namespace System.Text.RegularExpressions;
 
internal sealed class RegexFC
{
    private readonly RegexCharClass _cc;
 
    public bool _nullable;
 
    public bool CaseInsensitive { get; private set; }
 
    public RegexFC(bool nullable)
    {
        _cc = new RegexCharClass();
        _nullable = nullable;
    }
 
    public RegexFC(char ch, bool not, bool nullable, bool caseInsensitive)
    {
        _cc = new RegexCharClass();
        if (not)
        {
            if (ch > '\0')
            {
                _cc.AddRange('\0', (char)(ch - 1));
            }
            if (ch < '\uffff')
            {
                _cc.AddRange((char)(ch + 1), '\uffff');
            }
        }
        else
        {
            _cc.AddRange(ch, ch);
        }
        CaseInsensitive = caseInsensitive;
        _nullable = nullable;
    }
 
    public RegexFC(string charClass, bool nullable, bool caseInsensitive)
    {
        _cc = RegexCharClass.Parse(charClass);
        _nullable = nullable;
        CaseInsensitive = caseInsensitive;
    }
 
    public bool AddFC(RegexFC fc, bool concatenate)
    {
        if (!_cc.CanMerge || !fc._cc.CanMerge)
        {
            return false;
        }
        if (concatenate)
        {
            if (!_nullable)
            {
                return true;
            }
            if (!fc._nullable)
            {
                _nullable = false;
            }
        }
        else if (fc._nullable)
        {
            _nullable = true;
        }
        CaseInsensitive |= fc.CaseInsensitive;
        _cc.AddCharClass(fc._cc);
        return true;
    }
 
    public void AddLowercase(CultureInfo culture)
    {
        _cc.AddLowercase(culture);
    }
 
    public string GetFirstChars()
    {
        return _cc.ToStringClass();
    }
}