/* Canonical composition of Unicode characters.
   Copyright (C) 2002, 2006, 2009 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This program is free software: you can redistribute it and/or modify it
   under the terms of the GNU Lesser General Public License as published
   by the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "uninorm.h"

#include <string.h>

struct composition_rule { char codes[4]; unsigned short combined; };

#include "composition-table.h"

ucs4_t
uc_composition (ucs4_t uc1, ucs4_t uc2)
{
  if (uc1 < 0x10000 && uc2 < 0x10000)
    {
      if (uc2 >= 0x1161 && uc2 < 0x1161 + 21
	  && uc1 >= 0x1100 && uc1 < 0x1100 + 19)
	{
	  /* Hangul: Combine single letter L and single letter V to form
	     two-letter syllable LV.  */
	  return 0xAC00 + ((uc1 - 0x1100) * 21 + (uc2 - 0x1161)) * 28;
	}
      else if (uc2 > 0x11A7 && uc2 < 0x11A7 + 28
	       && uc1 >= 0xAC00 && uc1 < 0xD7A4 && ((uc1 - 0xAC00) % 28) == 0)
	{
	  /* Hangul: Combine two-letter syllable LV with single-letter T
	     to form three-letter syllable LVT.  */
	  return uc1 + (uc2 - 0x11A7);
	}
      else
	{
#if 0
	  unsigned int uc = MUL1 * uc1 * MUL2 * uc2;
	  unsigned int index1 = uc >> composition_header_0;
	  if (index1 < composition_header_1)
	    {
	      int lookup1 = u_composition.level1[index1];
	      if (lookup1 >= 0)
		{
		  unsigned int index2 = (uc >> composition_header_2) & composition_header_3;
		  int lookup2 = u_composition.level2[lookup1 + index2];
		  if (lookup2 >= 0)
		    {
		      unsigned int index3 = (uc & composition_header_4);
		      unsigned int lookup3 = u_composition.level3[lookup2 + index3];
		      if ((lookup3 >> 16) == uc2)
			return lookup3 & ((1U << 16) - 1);
		    }
		}
	    }
#else
	  char codes[4];
	  const struct composition_rule *rule;

	  codes[0] = (uc1 >> 8) & 0xff;
	  codes[1] = uc1 & 0xff;
	  codes[2] = (uc2 >> 8) & 0xff;
	  codes[3] = uc2 & 0xff;

	  rule = gl_uninorm_compose_lookup (codes, 4);
	  if (rule != NULL)
	    return rule->combined;
#endif
	}
    }
  return 0;
}
