/* Canonical decomposition of Unicode characters.
   Copyright (C) 2009-2020 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 either:

     * 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.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   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 <https://www.gnu.org/licenses/>.  */

#include <config.h>

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

#include <stdlib.h>

#include "uninorm/decomposition-table.h"

int
uc_canonical_decomposition (ucs4_t uc, ucs4_t *decomposition)
{
  if (uc >= 0xAC00 && uc < 0xD7A4)
    {
      /* Hangul syllable.  See Unicode standard, chapter 3, section
         "Hangul Syllable Decomposition",  See also the clarification at
         <https://www.unicode.org/versions/Unicode5.1.0/>, section
         "Clarification of Hangul Jamo Handling".  */
      unsigned int t;

      uc -= 0xAC00;
      t = uc % 28;

      if (t == 0)
        {
          unsigned int v, l;

          uc = uc / 28;
          v = uc % 21;
          l = uc / 21;

          decomposition[0] = 0x1100 + l;
          decomposition[1] = 0x1161 + v;
          return 2;
        }
      else
        {
#if 1 /* Return the pairwise decomposition, not the full decomposition.  */
          decomposition[0] = 0xAC00 + uc - t; /* = 0xAC00 + (l * 21 + v) * 28; */
          decomposition[1] = 0x11A7 + t;
          return 2;
#else
          unsigned int v, l;

          uc = uc / 28;
          v = uc % 21;
          l = uc / 21;

          decomposition[0] = 0x1100 + l;
          decomposition[1] = 0x1161 + v;
          decomposition[2] = 0x11A7 + t;
          return 3;
#endif
        }
    }
  else if (uc < 0x110000)
    {
      unsigned short entry = decomp_index (uc);
      /* An entry of (unsigned short)(-1) denotes an absent entry.
         Otherwise, bit 15 of the entry tells whether the decomposition
         is a canonical one.  */
      if (entry < 0x8000)
        {
          const unsigned char *p;
          unsigned int element;
          unsigned int length;

          p = &gl_uninorm_decomp_chars_table[3 * entry];
          element = (p[0] << 16) | (p[1] << 8) | p[2];
          /* The first element has 5 bits for the decomposition type.  */
          if (((element >> 18) & 0x1f) != UC_DECOMP_CANONICAL)
            abort ();
          length = 1;
          for (;;)
            {
              /* Every element has an 18 bits wide Unicode code point.  */
              *decomposition = element & 0x3ffff;
              /* Bit 23 tells whether there are more elements,  */
              if ((element & (1 << 23)) == 0)
                break;
              p += 3;
              element = (p[0] << 16) | (p[1] << 8) | p[2];
              decomposition++;
              length++;
            }
          return length;
        }
    }
  return -1;
}