Flee/Parsing/CombineElement.cs

namespace Flee.Parsing
{
    internal class CombineElement : Element
    {
        private readonly Element _elem1;
        private readonly Element _elem2;

        public CombineElement(Element first, Element second)
        {
            _elem1 = first;
            _elem2 = second;
        }

        public override object Clone()
        {
            return new CombineElement(_elem1, _elem2);
        }

        public override int Match(Matcher m,
                                  ReaderBuffer buffer,
                                  int start,
                                  int skip)
        {
            int length1 = -1;
            int length2 = 0;
            int skip1 = 0;
            int skip2 = 0;

            while (skip >= 0)
            {
                length1 = _elem1.Match(m, buffer, start, skip1);
                if (length1 < 0)
                {
                    return -1;
                }
                length2 = _elem2.Match(m, buffer, start + length1, skip2);
                if (length2 < 0)
                {
                    skip1++;
                    skip2 = 0;
                }
                else
                {
                    skip2++;
                    skip--;
                }
            }

            return length1 + length2;
        }

        public override void PrintTo(TextWriter output, string indent)
        {
            _elem1.PrintTo(output, indent);
            _elem2.PrintTo(output, indent);
        }
    }
}