/* Case mapping for UTF-8/UTF-16/UTF-32 strings (locale dependent).
   Copyright (C) 2009-2025 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This file is free software.
   It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+".
   You can redistribute it and/or modify it under either
     - the terms of the GNU Lesser General Public License as published
       by the Free Software Foundation, either version 3, or (at your
       option) any later version, or
     - 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, or
     - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+".

   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 and the GNU General Public License
   for more details.

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

UNIT *
FUNC (const UNIT *s, size_t n,
      casing_prefix_context_t prefix_context,
      casing_suffix_context_t suffix_context,
      const char *iso639_language,
      ucs4_t (*single_character_map) (ucs4_t),
      size_t offset_in_rule, /* offset in 'struct special_casing_rule' */
      uninorm_t nf,
      UNIT *resultbuf, size_t *lengthp)
{
  /* The result being accumulated.  */
  UNIT *result;
  size_t length;
  size_t allocated;

  /* Initialize the accumulator.  */
  if (nf != NULL || resultbuf == NULL)
    {
      result = NULL;
      allocated = 0;
    }
  else
    {
      result = resultbuf;
      allocated = *lengthp;
    }
  length = 0;

  {
    const UNIT *s_end = s + n;

    /* Helper for evaluating the FINAL_SIGMA condition:
       Last character that was not case-ignorable.  */
    ucs4_t last_char_except_ignorable =
      prefix_context.last_char_except_ignorable;

    /* Helper for evaluating the AFTER_SOFT_DOTTED and AFTER_I conditions:
       Last character that was of combining class 230 ("Above") or 0.  */
    ucs4_t last_char_normal_or_above =
      prefix_context.last_char_normal_or_above;

    while (s < s_end)
      {
        ucs4_t uc;
        int count = U_MBTOUC_UNSAFE (&uc, s, s_end - s);

        ucs4_t mapped_uc[3];
        unsigned int mapped_count;

        if (uc < 0x10000)
          {
            /* Look first in the special-casing table.  */
            char code[3];

            code[0] = (uc >> 8) & 0xff;
            code[1] = uc & 0xff;

            for (code[2] = 0; ; code[2]++)
              {
                const struct special_casing_rule *rule =
                  gl_unicase_special_lookup (code, 3);

                if (rule == NULL)
                  break;

                /* Test if the condition applies.  */
                /* Does the language apply?  */
                if (rule->language[0] == '\0'
                    || (iso639_language != NULL
                        && iso639_language[0] == rule->language[0]
                        && iso639_language[1] == rule->language[1]))
                  {
                    /* Does the context apply?  */
                    int context = rule->context;
                    bool applies;

                    if (context < 0)
                      context = - context;
                    switch (context)
                      {
                      case SCC_ALWAYS:
                        applies = true;
                        break;

                      case SCC_FINAL_SIGMA:
                        /* "Before" condition: preceded by a sequence
                           consisting of a cased letter and a case-ignorable
                           sequence.
                           "After" condition: not followed by a sequence
                           consisting of a case-ignorable sequence and then a
                           cased letter.  */
                        /* Test the "before" condition.  */
                        applies = uc_is_cased (last_char_except_ignorable);
                        /* Test the "after" condition.  */
                        if (applies)
                          {
                            const UNIT *s2 = s + count;
                            for (;;)
                              {
                                if (s2 < s_end)
                                  {
                                    ucs4_t uc2;
                                    int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                    /* Our uc_is_case_ignorable function is
                                       known to return false for all cased
                                       characters.  So we can call
                                       uc_is_case_ignorable first.  */
                                    if (!uc_is_case_ignorable (uc2))
                                      {
                                        applies = ! uc_is_cased (uc2);
                                        break;
                                      }
                                    s2 += count2;
                                  }
                                else
                                  {
                                    applies = ! uc_is_cased (suffix_context.first_char_except_ignorable);
                                    break;
                                  }
                              }
                          }
                        break;

                      case SCC_AFTER_SOFT_DOTTED:
                        /* "Before" condition: There is a Soft_Dotted character
                           before it, with no intervening character of
                           combining class 0 or 230 (Above).  */
                        /* Test the "before" condition.  */
                        applies = uc_is_property_soft_dotted (last_char_normal_or_above);
                        break;

                      case SCC_MORE_ABOVE:
                        /* "After" condition: followed by a character of
                           combining class 230 (Above) with no intervening
                           character of combining class 0 or 230 (Above).  */
                        /* Test the "after" condition.  */
                        {
                          const UNIT *s2 = s + count;
                          applies = false;
                          for (;;)
                            {
                              if (s2 < s_end)
                                {
                                  ucs4_t uc2;
                                  int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                  int ccc = uc_combining_class (uc2);
                                  if (ccc == UC_CCC_A)
                                    {
                                      applies = true;
                                      break;
                                    }
                                  if (ccc == UC_CCC_NR)
                                    break;
                                  s2 += count2;
                                }
                              else
                                {
                                  applies = ((suffix_context.bits & SCC_MORE_ABOVE_MASK) != 0);
                                  break;
                                }
                            }
                        }
                        break;

                      case SCC_BEFORE_DOT:
                        /* "After" condition: followed by COMBINING DOT ABOVE
                           (U+0307). Any sequence of characters with a
                           combining class that is neither 0 nor 230 may
                           intervene between the current character and the
                           combining dot above.  */
                        /* Test the "after" condition.  */
                        {
                          const UNIT *s2 = s + count;
                          applies = false;
                          for (;;)
                            {
                              if (s2 < s_end)
                                {
                                  ucs4_t uc2;
                                  int count2 = U_MBTOUC_UNSAFE (&uc2, s2, s_end - s2);
                                  if (uc2 == 0x0307) /* COMBINING DOT ABOVE */
                                    {
                                      applies = true;
                                      break;
                                    }
                                  {
                                    int ccc = uc_combining_class (uc2);
                                    if (ccc == UC_CCC_A || ccc == UC_CCC_NR)
                                      break;
                                  }
                                  s2 += count2;
                                }
                              else
                                {
                                  applies = ((suffix_context.bits & SCC_BEFORE_DOT_MASK) != 0);
                                  break;
                                }
                            }
                        }
                        break;

                      case SCC_AFTER_I:
                        /* "Before" condition: There is an uppercase I before
                           it, and there is no intervening character of
                           combining class 0 or 230 (Above).  */
                        /* Test the "before" condition.  */
                        applies = (last_char_normal_or_above == 'I');
                        break;

                      default:
                        abort ();
                      }
                    if (rule->context < 0)
                      applies = !applies;

                    if (applies)
                      {
                        /* The rule applies.
                           Look up the mapping (0 to 3 characters).  */
                        const unsigned short *mapped_in_rule =
                          (const unsigned short *)((const char *)rule + offset_in_rule);

                        if (mapped_in_rule[0] == 0)
                          mapped_count = 0;
                        else
                          {
                            mapped_uc[0] = mapped_in_rule[0];
                            if (mapped_in_rule[1] == 0)
                              mapped_count = 1;
                            else
                              {
                                mapped_uc[1] = mapped_in_rule[1];
                                if (mapped_in_rule[2] == 0)
                                  mapped_count = 2;
                                else
                                  {
                                    mapped_uc[2] = mapped_in_rule[2];
                                    mapped_count = 3;
                                  }
                              }
                          }
                        goto found_mapping;
                      }
                  }

                /* Optimization: Save a hash table lookup in the next round.  */
                if (!rule->has_next)
                  break;
              }
          }

        /* No special-cased mapping.  So use the locale and context independent
           mapping.  */
        mapped_uc[0] = single_character_map (uc);
        mapped_count = 1;

       found_mapping:
        /* Found the mapping: uc maps to mapped_uc[0..mapped_count-1].  */
        {
          unsigned int i;

          for (i = 0; i < mapped_count; i++)
            {
              ucs4_t muc = mapped_uc[i];

              /* Append muc to the result accumulator.  */
              if (length < allocated)
                {
                  int ret = U_UCTOMB (result + length, muc, allocated - length);
                  if (ret == -1)
                    {
                      errno = EINVAL;
                      goto fail;
                    }
                  if (ret >= 0)
                    {
                      length += ret;
                      goto done_appending;
                    }
                }
              {
                size_t old_allocated = allocated;
                size_t new_allocated = 2 * old_allocated;
                if (new_allocated < 64)
                  new_allocated = 64;
                if (new_allocated < old_allocated) /* integer overflow? */
                  abort ();
                {
                  UNIT *larger_result;
                  if (result == NULL)
                    {
                      larger_result = (UNIT *) malloc (new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                    }
                  else if (result == resultbuf)
                    {
                      larger_result = (UNIT *) malloc (new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                      U_CPY (larger_result, resultbuf, length);
                    }
                  else
                    {
                      larger_result =
                        (UNIT *) realloc (result, new_allocated * sizeof (UNIT));
                      if (larger_result == NULL)
                        {
                          errno = ENOMEM;
                          goto fail;
                        }
                    }
                  result = larger_result;
                  allocated = new_allocated;
                  {
                    int ret = U_UCTOMB (result + length, muc, allocated - length);
                    if (ret == -1)
                      {
                        errno = EINVAL;
                        goto fail;
                      }
                    if (ret < 0)
                      abort ();
                    length += ret;
                    goto done_appending;
                  }
                }
              }
             done_appending: ;
            }
        }

        if (!uc_is_case_ignorable (uc))
          last_char_except_ignorable = uc;

        {
          int ccc = uc_combining_class (uc);
          if (ccc == UC_CCC_A || ccc == UC_CCC_NR)
            last_char_normal_or_above = uc;
        }

        s += count;
      }
  }

  if (nf != NULL)
    {
      /* Finally, normalize the result.  */
      UNIT *normalized_result;

      normalized_result = U_NORMALIZE (nf, result, length, resultbuf, lengthp);
      if (normalized_result == NULL)
        goto fail;

      free (result);
      return normalized_result;
    }

  if (length == 0)
    {
      if (result == NULL)
        {
          /* Return a non-NULL value.  NULL means error.  */
          result = (UNIT *) malloc (1);
          if (result == NULL)
            {
              errno = ENOMEM;
              goto fail;
            }
        }
    }
  else if (result != resultbuf && length < allocated)
    {
      /* Shrink the allocated memory if possible.  */
      UNIT *memory;

      memory = (UNIT *) realloc (result, length * sizeof (UNIT));
      if (memory != NULL)
        result = memory;
    }

  *lengthp = length;
  return result;

 fail:
  if (result != resultbuf)
    {
      int saved_errno = errno;
      free (result);
      errno = saved_errno;
    }
  return NULL;
}
