/*

 * Copyright © 2014 Canonical Limited

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library 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 library 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 library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Ryan Lortie <desrt@desrt.ca>

 */

#include <config.h>

#include "gstrfuncs.h"

#include <glib.h>

#include <locale.h>

#include <stdlib.h>

#include <string.h>

struct mapping_entry

{

  guint16 src;

  guint16 ascii;

};

struct mapping_range

{

  guint16 start;

  guint16 length;

};

struct locale_entry

{

  guint8 name_offset;

  guint8 item_id;

};

#include "gtranslit-data.h"

#define get_src_char(array, encoded, index) ((encoded & 0x8000) ? (array)[((encoded) & 0xfff) + index] : encoded)

#define get_length(encoded)                 ((encoded & 0x8000) ? ((encoded & 0x7000) >> 12) : 1)

#if G_BYTE_ORDER == G_BIG_ENDIAN

#define get_ascii_item(array, encoded)      ((encoded & 0x8000) ? &(array)[(encoded) & 0xfff] : (gpointer) (((char *) &(encoded)) + 1))

#else

#define get_ascii_item(array, encoded)      ((encoded & 0x8000) ? &(array)[(encoded) & 0xfff] : (gpointer) &(encoded))

#endif

static const gchar * lookup_in_item (guint           item_id,

                                     const gunichar *key,

                                     gint           *result_len,

                                     gint           *key_consumed);

static gint

compare_mapping_entry (gconstpointer user_data,

                       gconstpointer data)

{

  const struct mapping_entry *entry = data;

  const gunichar *key = user_data;

  gunichar src_0;

  G_STATIC_ASSERT(MAX_KEY_SIZE == 2);

  src_0 = get_src_char (src_table, entry->src, 0);

  if (key[0] > src_0)

    return 1;

  else if (key[0] < src_0)

    return -1;

  if (get_length (entry->src) > 1)

    {

      gunichar src_1;

      src_1 = get_src_char (src_table, entry->src, 1);

      if (key[1] > src_1)

        return 1;

      else if (key[1] < src_1)

        return -1;

    }

  else if (key[1])

    return 1;

  return 0;

}

static const gchar *

lookup_in_mapping (const struct mapping_entry *mapping,

                   gint                        mapping_size,

                   const gunichar             *key,

                   gint                       *result_len,

                   gint                       *key_consumed)

{

  const struct mapping_entry *hit;

  hit = bsearch (key, mapping, mapping_size, sizeof (struct mapping_entry), compare_mapping_entry);

  if (hit == NULL)

    return NULL;

  *key_consumed = get_length (hit->src);

  *result_len = get_length (hit->ascii);

  return get_ascii_item(ascii_table, hit->ascii);

}

static const gchar *

lookup_in_chain (const guint8   *chain,

                 const gunichar *key,

                 gint           *result_len,

                 gint           *key_consumed)

{

  const gchar *result;

  while (*chain != 0xff)

    {

      result = lookup_in_item (*chain, key, result_len, key_consumed);

      if (result)

        return result;

      chain++;

    }

  return NULL;

}

static const gchar *

lookup_in_item (guint           item_id,

                const gunichar *key,

                gint           *result_len,

                gint           *key_consumed)

{

  if (item_id & 0x80)

    {

      const guint8 *chain = chains_table + chain_starts[item_id & 0x7f];

      return lookup_in_chain (chain, key, result_len, key_consumed);

    }

  else

    {

      const struct mapping_range *range = &mapping_ranges[item_id];

      return lookup_in_mapping (mappings_table + range->start, range->length, key, result_len, key_consumed);

    }

}

static gint

compare_locale_entry (gconstpointer user_data,

                      gconstpointer data)

{

  const struct locale_entry *entry = data;

  const gchar *key = user_data;

  return strcmp (key, &locale_names[entry->name_offset]);

}

static gboolean

lookup_item_id_for_one_locale (const gchar *key,

                               guint       *item_id)

{

  const struct locale_entry *hit;

  hit = bsearch (key, locale_index, G_N_ELEMENTS (locale_index), sizeof (struct locale_entry), compare_locale_entry);

  if (hit == NULL)

    return FALSE;

  *item_id = hit->item_id;

  return TRUE;

}

static guint

lookup_item_id_for_locale (const gchar *locale)

{

  gchar key[MAX_LOCALE_NAME + 1];

  const gchar *language;

  guint language_len;

  const gchar *territory = NULL;

  guint territory_len = 0;

  const gchar *modifier = NULL;

  guint modifier_len = 0;

  const gchar *next_char;

  guint id;

  /* As per POSIX, a valid locale looks like:

   *

   *   language[_territory][.codeset][@modifier]

   */

  language = locale;

  language_len = strcspn (language, "_.@");

  next_char = language + language_len;

  if (*next_char == '_')

    {

      territory = next_char;

      territory_len = strcspn (territory + 1, "_.@") + 1;

      next_char = territory + territory_len;

    }

  if (*next_char == '.')

    {

      const gchar *codeset;

      guint codeset_len;

      codeset = next_char;

      codeset_len = strcspn (codeset + 1, "_.@") + 1;

      next_char = codeset + codeset_len;

    }

  if (*next_char == '@')

    {

      modifier = next_char;

      modifier_len = strcspn (modifier + 1, "_.@") + 1;

      next_char = modifier + modifier_len;

    }

  /* What madness is this? */

  if (language_len == 0 || *next_char)

    return default_item_id;

  /* We are not interested in codeset.

   *

   * For this locale:

   *

   *  aa_BB@cc

   *

   * try in this order:

   *

   * Note: we have no locales of the form aa_BB@cc in the database.

   *

   *  1. aa@cc

   *  2. aa_BB

   *  3. aa

   */

  /* 1. */

  if (modifier_len && language_len + modifier_len <= MAX_LOCALE_NAME)

    {

      memcpy (key, language, language_len);

      memcpy (key + language_len, modifier, modifier_len);

      key[language_len + modifier_len] = '\0';

      if (lookup_item_id_for_one_locale (key, &id))

        return id;

    }

  /* 2. */

  if (territory_len && language_len + territory_len <= MAX_LOCALE_NAME)

    {

      memcpy (key, language, language_len);

      memcpy (key + language_len, territory, territory_len);

      key[language_len + territory_len] = '\0';

      if (lookup_item_id_for_one_locale (key, &id))

        return id;

    }

  /* 3. */

  if (language_len <= MAX_LOCALE_NAME)

    {

      memcpy (key, language, language_len);

      key[language_len] = '\0';

      if (lookup_item_id_for_one_locale (key, &id))

        return id;

    }

  return default_item_id;

}

static guint

get_default_item_id (void)

{

  static guint item_id;

  static gboolean done;

  /* Doesn't need to be locked -- no harm in doing it twice. */

  if (!done)

    {

      const gchar *locale;

      locale = setlocale (LC_CTYPE, NULL);

      item_id = lookup_item_id_for_locale (locale);

      done = TRUE;

    }

  return item_id;

}

/**

 * g_str_to_ascii:

 * @str: a string, in UTF-8

 * @from_locale: (nullable): the source locale, if known

 *

 * Transliterate @str to plain ASCII.

 *

 * For best results, @str should be in composed normalised form.

 *

 * This function performs a reasonably good set of character

 * replacements.  The particular set of replacements that is done may

 * change by version or even by runtime environment.

 *

 * If the source language of @str is known, it can used to improve the

 * accuracy of the translation by passing it as @from_locale.  It should

 * be a valid POSIX locale string (of the form

 * `language[_territory][.codeset][@modifier]`).

 *

 * If @from_locale is %NULL then the current locale is used.

 *

 * If you want to do translation for no specific locale, and you want it

 * to be done independently of the currently locale, specify `"C"` for

 * @from_locale.

 *

 * Returns: a string in plain ASCII

 *

 * Since: 2.40

 **/

gchar *

g_str_to_ascii (const gchar *str,

                const gchar *from_locale)

{

  GString *result;

  guint item_id;

  g_return_val_if_fail (str != NULL, NULL);

  if (g_str_is_ascii (str))

    return g_strdup (str);

  if (from_locale)

    item_id = lookup_item_id_for_locale (from_locale);

  else

    item_id = get_default_item_id ();

  result = g_string_sized_new (strlen (str));

  while (*str)

    {

      /* We only need to transliterate non-ASCII values... */

      if (*str & 0x80)

        {

          gunichar key[MAX_KEY_SIZE];

          const gchar *r;

          gint consumed;

          gint r_len;

          gunichar c;

          G_STATIC_ASSERT(MAX_KEY_SIZE == 2);

          c = g_utf8_get_char (str);

          /* This is where it gets evil...

           *

           * We know that MAX_KEY_SIZE is 2.  We also know that we

           * only want to try another character if it's non-ascii.

           */

          str = g_utf8_next_char (str);

          key[0] = c;

          if (*str & 0x80)

            key[1] = g_utf8_get_char (str);

          else

            key[1] = 0;

          r = lookup_in_item (item_id, key, &r_len, &consumed);

          /* If we failed to map two characters, try again with one.

           *

           * gconv behaviour is a bit weird here -- it seems to

           * depend in the randomness of the binary search and the

           * size of the input buffer as to what result we get here.

           *

           * Doing it this way is more work, but should be

           * more-correct.

           */

          if (r == NULL && key[1])

            {

              key[1] = 0;

              r = lookup_in_item (item_id, key, &r_len, &consumed);

            }

          if (r != NULL)

            {

              g_string_append_len (result, r, r_len);

              if (consumed == 2)

                /* If it took both then skip again */

                str = g_utf8_next_char (str);

            }

          else /* no match found */

            g_string_append_c (result, '?');

        }

      else /* ASCII case */

        g_string_append_c (result, *str++);

    }

  return g_string_free (result, FALSE);

}