gui-cs.Terminal.Gui/Terminal.Gui/Drivers/AnsiHandling/Keyboard/EscAsAltPattern.cs

using System.Text.RegularExpressions;

namespace Terminal.Gui.Drivers;

internal class EscAsAltPattern : AnsiKeyboardParserPattern
{
    public EscAsAltPattern () { IsLastMinute = true; }

#pragma warning disable IDE1006 // Naming Styles
    private static readonly Regex _pattern = new (@"^\u001b([\u0001-\u001a\u001fa-zA-Z0-9_])$");
#pragma warning restore IDE1006 // Naming Styles

    public override bool IsMatch (string? input) { return _pattern.IsMatch (input!); }

    protected override Key? GetKeyImpl (string? input)
    {
        Match match = _pattern.Match (input!);

        if (!match.Success)
        {
            return null;
        }

        char ch = match.Groups [1].Value [0];

        Key key = ch switch
                  {
                      >= '\u0001' and <= '\u001a' => ((Key)(ch + 96)).WithCtrl,
                      '\u001f' => Key.D7.WithCtrl.WithShift,
                      _ => ch
                  };

        return new Key (key).WithAlt;
    }
}