/* Canonical composition of Unicode characters.
   Copyright (C) 2002, 2006, 2009, 2011-2022 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This file 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 2.1 of the
   License, or (at your option) any later version.

   This file 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 <https://www.gnu.org/licenses/>.  */

#include <config.h>

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

#include <string.h>

struct composition_rule { char codes[6]; unsigned int combined; };

#include "composition-table.h"

ucs4_t
uc_composition (ucs4_t uc1, ucs4_t uc2)
{
  if (uc1 < 0x12000 && uc2 < 0x12000)
    {
      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[6];
          const struct composition_rule *rule;

          codes[0] = (uc1 >> 16) & 0xff;
          codes[1] = (uc1 >> 8) & 0xff;
          codes[2] = uc1 & 0xff;
          codes[3] = (uc2 >> 16) & 0xff;
          codes[4] = (uc2 >> 8) & 0xff;
          codes[5] = uc2 & 0xff;

          rule = gl_uninorm_compose_lookup (codes, 6);
          if (rule != NULL)
            return rule->combined;
#endif
        }
    }
  return 0;
}