//
// This software is now distributed according to
// the Lesser Gnu Public License.  Please see
// http://www.gnu.org/copyleft/lesser.txt for
// the details.
//    -- Happy Computing!
//
package com.stevesoft.pat;

import java.util.*;

/**
 * Provides the ability to match a backreference from within a Pattern.
 */
class BackMatch extends Pattern
{
  int id;

  BackMatch(int id)
  {
    this.id = id;
  }

  public String toString()
  {
    return "\\" + (id) + nextString();
  }

  public int matchInternal(int pos, Pthings p)
  {
    int i1 = p.marks[id];
    int i2 = p.marks[id + p.nMarks];
    int imax = i2 - i1;
    if (i1 < 0 || imax < 0 || pos + imax > p.src.length())
    {
      return -1;
    }
    int ns = p.src.length() - pos;
    if (imax < ns)
    {
      ns = imax;
    }
    for (int i = 0; i < ns; i++)
    {
      if (p.src.charAt(i + i1) != p.src.charAt(pos + i))
      {
        return -1;
      }
    }
    return nextMatch(pos + imax, p);
  }

  Pattern clone1(Hashtable h)
  {
    return new BackMatch(id);
  }
}