/// Spart License (zlib/png)
/// 
/// 
/// Copyright (c) 2003 Jonathan de Halleux
/// 
/// This software is provided 'as-is', without any express or implied warranty. 
/// In no event will the authors be held liable for any damages arising from 
/// the use of this software.
/// 
/// Permission is granted to anyone to use this software for any purpose, 
/// including commercial applications, and to alter it and redistribute it 
/// freely, subject to the following restrictions:
/// 
/// 1. The origin of this software must not be misrepresented; you must not 
/// claim that you wrote the original software. If you use this software in a 
/// product, an acknowledgment in the product documentation would be 
/// appreciated but is not required.
/// 
/// 2. Altered source versions must be plainly marked as such, and must not be 
/// misrepresented as being the original software.
/// 
/// 3. This notice may not be removed or altered from any source distribution.
/// 
/// Author: Jonathan de Halleuxusing System;

namespace Spart.Parsers.Composite
{
	/// <summary>
	/// Summary description for DifferenceParser.
	/// </summary>
	public class DifferenceParser : BinaryTerminalParser
	{
		public DifferenceParser(Parser left, Parser right)
			:base(left,right)
		{}

		public override ParserMatch ParseMain(Spart.Scanners.IScanner scan)
		{
			long offset = scan.Offset;

			ParserMatch m = FirstParser.Parse(scan);
			long goodOffset= scan.Offset;

			if (!m.Success)
			{
				scan.Seek(offset);
				return scan.NoMatch;
			}

			// doing difference
			scan.Seek(offset);
			ParserMatch d = SecondParser.Parse(scan);
			if (d.Success)
			{
				scan.Seek(offset);
				return scan.NoMatch;
			}

			// ok
			scan.Seek(goodOffset);
			return m;
		}

        public override Parser Clone()
        {
            return base.Clone();
        }
	}
}