/* CharacterBreakIterator.java - Default character BreakIterator.
   Copyright (C) 1999, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package gnu.java.text;

import java.text.BreakIterator;
import java.text.CharacterIterator;

/**
 * @author Tom Tromey <tromey@cygnus.com>
 * @date March 19, 1999
 * Written using The Unicode Standard, Version 2.0.
 */

public class CharacterBreakIterator extends BaseBreakIterator
{
  // Hangul Jamo constants from Unicode book.
  private static final int LBase = 0x1100;
  private static final int VBase = 0x1161;
  private static final int TBase = 0x11a7;
  private static final int LCount = 19;
  private static final int VCount = 21;
  private static final int TCount = 28;

  // Information about surrogates.
  private static final int highSurrogateStart = 0xD800;
  private static final int highSurrogateEnd = 0xDBFF;
  private static final int lowSurrogateStart = 0xDC00;
  private static final int lowSurrogateEnd = 0xDFFF;

  public Object clone ()
  {
    return new CharacterBreakIterator (this);
  }

  public CharacterBreakIterator ()
  {
    iter = null;		// FIXME?
  }

  private CharacterBreakIterator (CharacterBreakIterator other)
  {
    iter = (CharacterIterator) other.iter.clone();
  }

  // Some methods to tell us different properties of characters.
  private final boolean isL (char c)
  {
    return c >= LBase && c <= LBase + LCount;
  }
  private final boolean isV (char c)
  {
    return c >= VBase && c <= VBase + VCount;
  }
  private final boolean isT (char c)
  {
    return c >= TBase && c <= TBase + TCount;
  }
  private final boolean isLVT (char c)
  {
    return isL (c) || isV (c) || isT (c);
  }
  private final boolean isHighSurrogate (char c)
  {
    return c >= highSurrogateStart && c <= highSurrogateEnd;
  }
  private final boolean isLowSurrogate (char c)
  {
    return c >= lowSurrogateStart && c <= lowSurrogateEnd;
  }

  public int next ()
  {
    int end = iter.getEndIndex();
    if (iter.getIndex() == end)
      return DONE;

    char c;
    for (char prev = CharacterIterator.DONE; iter.getIndex() < end; prev = c)
      {
	c = iter.next();
	if (c == CharacterIterator.DONE)
	  break;
	int type = Character.getType(c);

	// Break after paragraph separators.
	if (type == Character.PARAGRAPH_SEPARATOR)
	  break;

	// Now we need some lookahead.
	char ahead = iter.next();
	iter.previous();
	if (ahead == CharacterIterator.DONE)
	  break;
	int aheadType = Character.getType(ahead);

	if (aheadType != Character.NON_SPACING_MARK
	    && ! isLowSurrogate (ahead)
	    && ! isLVT (ahead))
	  break;
	if (! isLVT (c) && isLVT (ahead))
	  break;
	if (isL (c) && ! isLVT (ahead)
	    && aheadType != Character.NON_SPACING_MARK)
	  break;
	if (isV (c) && ! isV (ahead) && !isT (ahead)
	    && aheadType != Character.NON_SPACING_MARK)
	  break;
	if (isT (c) && ! isT (ahead)
	    && aheadType != Character.NON_SPACING_MARK)
	  break;

	if (! isHighSurrogate (c) && isLowSurrogate (ahead))
	  break;
	if (isHighSurrogate (c) && ! isLowSurrogate (ahead))
	  break;
	if (! isHighSurrogate (prev) && isLowSurrogate (c))
	  break;
      }

    return iter.getIndex();
  }

  public int previous ()
  {
    if (iter.getIndex() == iter.getBeginIndex())
      return DONE;

    int start = iter.getBeginIndex();
    while (iter.getIndex() >= iter.getBeginIndex())
      {
	char c = iter.previous();
	if (c == CharacterIterator.DONE)
	  break;
	int type = Character.getType(c);

	if (type != Character.NON_SPACING_MARK
	    && ! isLowSurrogate (c)
	    && ! isLVT (c))
	  break;

	// Now we need some lookahead.
	char ahead = iter.previous();
	if (ahead == CharacterIterator.DONE)
	  {
	    iter.next();
	    break;
	  }
	char ahead2 = iter.previous();
	iter.next();
	iter.next();
	if (ahead2 == CharacterIterator.DONE)
	  break;
	int aheadType = Character.getType(ahead);

	if (aheadType == Character.PARAGRAPH_SEPARATOR)
	  break;

	if (isLVT (c) && ! isLVT (ahead))
	  break;
	if (! isLVT (c) && type != Character.NON_SPACING_MARK
	    && isL (ahead))
	  break;
	if (! isV (c) && ! isT (c) && type != Character.NON_SPACING_MARK
	    && isV (ahead))
	  break;
	if (! isT (c) && type != Character.NON_SPACING_MARK
	    && isT (ahead))
	  break;

	if (isLowSurrogate (c) && ! isHighSurrogate (ahead))
	  break;
	if (! isLowSurrogate (c) && isHighSurrogate (ahead))
	  break;
	if (isLowSurrogate (ahead) && ! isHighSurrogate (ahead2))
	  break;
      }

    return iter.getIndex();
  }
}