using System;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;

namespace ln.parse.tokenizer
{
    public class RegularExpressionMatcher : TokenMatcher
    {
        Regex regex;
        Func<SourceBuffer, int, int, Token> createTokenDelegate;

        public RegularExpressionMatcher(string pattern,Func<SourceBuffer,int,int,Token> createTokenDelegate)
            :this(pattern)
        {
            this.createTokenDelegate = createTokenDelegate;
        }
        protected RegularExpressionMatcher(string pattern)
        {
            regex = new Regex(pattern);
        }

        public virtual Token CreateToken(SourceBuffer sourceBuffer, int start, int length) => createTokenDelegate(sourceBuffer, start, length);

        public override bool Match(SourceBuffer sourceBuffer,out Token token)
        {
            Match match = regex.Match(sourceBuffer.GetCurrentText());
            if ((match != null) && match.Success && (match.Index == 0))
            {
                token = CreateToken(sourceBuffer, sourceBuffer.LinearPosition, match.Length);
                return true;
            }
            token = null;
            return false;
        }
    }
}