/* Charset handling while reading PO files.
   Copyright (C) 2001-2007, 2010, 2019-2021 Free Software Foundation, Inc.
   Written by Bruno Haible <haible@clisp.cons.org>, 2001.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU 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 General Public License for more details.

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


#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <alloca.h>

/* Specification.  */
#include "po-charset.h"

#include <stdlib.h>
#include <string.h>

#include "xmalloca.h"
#include "xvasprintf.h"
#include "po-xerror.h"
#if !IN_LIBGETTEXTPO
# include "basename-lgpl.h"
# include "progname.h"
#endif
#include "c-strstr.h"
#include "c-strcase.h"
#include "gettext.h"

#define _(str) gettext (str)

#define SIZEOF(a) (sizeof(a) / sizeof(a[0]))

static const char ascii[] = "ASCII";

/* The canonicalized encoding name for ASCII.  */
const char *po_charset_ascii = ascii;

static const char utf8[] = "UTF-8";

/* The canonicalized encoding name for UTF-8.  */
const char *po_charset_utf8 = utf8;

/* Canonicalize an encoding name.  */
const char *
po_charset_canonicalize (const char *charset)
{
  /* The list of charsets supported by glibc's iconv() and by the portable
     iconv() across platforms.  Taken from intl/localcharset.h.  */
  static const char *standard_charsets[] =
  {
    ascii, "ANSI_X3.4-1968", "US-ASCII",        /* i = 0..2 */
    "ISO-8859-1", "ISO_8859-1",                 /* i = 3, 4 */
    "ISO-8859-2", "ISO_8859-2",
    "ISO-8859-3", "ISO_8859-3",
    "ISO-8859-4", "ISO_8859-4",
    "ISO-8859-5", "ISO_8859-5",
    "ISO-8859-6", "ISO_8859-6",
    "ISO-8859-7", "ISO_8859-7",
    "ISO-8859-8", "ISO_8859-8",
    "ISO-8859-9", "ISO_8859-9",
    "ISO-8859-13", "ISO_8859-13",
    "ISO-8859-14", "ISO_8859-14",
    "ISO-8859-15", "ISO_8859-15",               /* i = 25, 26 */
    "KOI8-R",
    "KOI8-U",
    "KOI8-T",
    "CP850",
    "CP866",
    "CP874",
    "CP932",
    "CP949",
    "CP950",
    "CP1250",
    "CP1251",
    "CP1252",
    "CP1253",
    "CP1254",
    "CP1255",
    "CP1256",
    "CP1257",
    "GB2312",
    "EUC-JP",
    "EUC-KR",
    "EUC-TW",
    "BIG5",
    "BIG5-HKSCS",
    "GBK",
    "GB18030",
    "SHIFT_JIS",
    "JOHAB",
    "TIS-620",
    "VISCII",
    "GEORGIAN-PS",
    utf8
  };
  size_t i;

  for (i = 0; i < SIZEOF (standard_charsets); i++)
    if (c_strcasecmp (charset, standard_charsets[i]) == 0)
      return standard_charsets[i < 3 ? 0 : i < 27 ? ((i - 3) & ~1) + 3 : i];
  return NULL;
}

/* Test for ASCII compatibility.  */
bool
po_charset_ascii_compatible (const char *canon_charset)
{
  /* There are only a few exceptions to ASCII compatibility.  */
  if (strcmp (canon_charset, "SHIFT_JIS") == 0
      || strcmp (canon_charset, "JOHAB") == 0
      || strcmp (canon_charset, "VISCII") == 0)
    return false;
  else
    return true;
}

/* Test for a weird encoding, i.e. an encoding which has double-byte
   characters ending in 0x5C.  */
bool po_is_charset_weird (const char *canon_charset)
{
  static const char *weird_charsets[] =
  {
    "BIG5",
    "BIG5-HKSCS",
    "GBK",
    "GB18030",
    "SHIFT_JIS",
    "JOHAB"
  };
  size_t i;

  for (i = 0; i < SIZEOF (weird_charsets); i++)
    if (strcmp (canon_charset, weird_charsets[i]) == 0)
      return true;
  return false;
}

/* Test for a weird CJK encoding, i.e. a weird encoding with CJK structure.
   An encoding has CJK structure if every valid character stream is composed
   of single bytes in the range 0x{00..7F} and of byte pairs in the range
   0x{80..FF}{30..FF}.  */
bool po_is_charset_weird_cjk (const char *canon_charset)
{
  static const char *weird_cjk_charsets[] =
  {                     /* single bytes   double bytes       */
    "BIG5",             /* 0x{00..7F},    0x{A1..F9}{40..FE} */
    "BIG5-HKSCS",       /* 0x{00..7F},    0x{88..FE}{40..FE} */
    "GBK",              /* 0x{00..7F},    0x{81..FE}{40..FE} */
    "GB18030",          /* 0x{00..7F},    0x{81..FE}{30..FE} */
    "SHIFT_JIS",        /* 0x{00..7F},    0x{81..F9}{40..FC} */
    "JOHAB"             /* 0x{00..7F},    0x{84..F9}{31..FE} */
  };
  size_t i;

  for (i = 0; i < SIZEOF (weird_cjk_charsets); i++)
    if (strcmp (canon_charset, weird_cjk_charsets[i]) == 0)
      return true;
  return false;
}

/* Hardcoded iterator functions for all kinds of encodings.
   We could also implement a general iterator function with iconv(),
   but we need a fast one.  */

/* Character iterator for 8-bit encodings.  */
static size_t
char_iterator (const char *s)
{
  return 1;
}

/* Character iterator for GB2312.  See libiconv/lib/euc_cn.h.  */
/* Character iterator for EUC-KR.  See libiconv/lib/euc_kr.h.  */
static size_t
euc_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0xa1 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 < 0xff)
        return 2;
    }
  return 1;
}

/* Character iterator for EUC-JP.  See libiconv/lib/euc_jp.h.  */
static size_t
euc_jp_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0xa1 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 < 0xff)
        return 2;
    }
  else if (c == 0x8e)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 < 0xe0)
        return 2;
    }
  else if (c == 0x8f)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 < 0xff)
        {
          unsigned char c3 = s[2];
          if (c3 >= 0xa1 && c3 < 0xff)
            return 3;
        }
    }
  return 1;
}

/* Character iterator for EUC-TW.  See libiconv/lib/euc_tw.h.  */
static size_t
euc_tw_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0xa1 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 < 0xff)
        return 2;
    }
  else if (c == 0x8e)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0xa1 && c2 <= 0xb0)
        {
          unsigned char c3 = s[2];
          if (c3 >= 0xa1 && c3 < 0xff)
            {
              unsigned char c4 = s[3];
              if (c4 >= 0xa1 && c4 < 0xff)
                return 4;
            }
        }
    }
  return 1;
}

/* Character iterator for BIG5.  See libiconv/lib/ces_big5.h.  */
static size_t
big5_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0xa1 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x40 && c2 < 0x7f) || (c2 >= 0xa1 && c2 < 0xff))
        return 2;
    }
  return 1;
}

/* Character iterator for BIG5-HKSCS.  See libiconv/lib/big5hkscs.h.  */
static size_t
big5hkscs_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0x88 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x40 && c2 < 0x7f) || (c2 >= 0xa1 && c2 < 0xff))
        return 2;
    }
  return 1;
}

/* Character iterator for GBK.  See libiconv/lib/ces_gbk.h and
   libiconv/lib/gbk.h.  */
static size_t
gbk_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0x81 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x40 && c2 < 0x7f) || (c2 >= 0x80 && c2 < 0xff))
        return 2;
    }
  return 1;
}

/* Character iterator for GB18030.  See libiconv/lib/gb18030.h.  */
static size_t
gb18030_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0x81 && c < 0xff)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x40 && c2 < 0x7f) || (c2 >= 0x80 && c2 < 0xff))
        return 2;
    }
  if (c >= 0x81 && c <= 0x84)
    {
      unsigned char c2 = s[1];
      if (c2 >= 0x30 && c2 <= 0x39)
        {
          unsigned char c3 = s[2];
          if (c3 >= 0x81 && c3 < 0xff)
            {
              unsigned char c4 = s[3];
              if (c4 >= 0x30 && c4 <= 0x39)
                return 4;
            }
        }
    }
  return 1;
}

/* Character iterator for SHIFT_JIS.  See libiconv/lib/sjis.h.  */
static size_t
shift_jis_character_iterator (const char *s)
{
  unsigned char c = *s;
  if ((c >= 0x81 && c <= 0x9f) || (c >= 0xe0 && c <= 0xf9))
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x40 && c2 <= 0x7e) || (c2 >= 0x80 && c2 <= 0xfc))
        return 2;
    }
  return 1;
}

/* Character iterator for JOHAB.  See libiconv/lib/johab.h and
   libiconv/lib/johab_hangul.h.  */
static size_t
johab_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0x84 && c <= 0xd3)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x41 && c2 < 0x7f) || (c2 >= 0x81 && c2 < 0xff))
        return 2;
    }
  else if (c >= 0xd9 && c <= 0xf9)
    {
      unsigned char c2 = s[1];
      if ((c2 >= 0x31 && c2 <= 0x7e) || (c2 >= 0x91 && c2 <= 0xfe))
        return 2;
    }
  return 1;
}

/* Character iterator for UTF-8.  See libiconv/lib/utf8.h.  */
static size_t
utf8_character_iterator (const char *s)
{
  unsigned char c = *s;
  if (c >= 0xc2)
    {
      if (c < 0xe0)
        {
          unsigned char c2 = s[1];
          if (c2 >= 0x80 && c2 < 0xc0)
            return 2;
        }
      else if (c < 0xf0)
        {
          unsigned char c2 = s[1];
          if (c2 >= 0x80 && c2 < 0xc0)
            {
              unsigned char c3 = s[2];
              if (c3 >= 0x80 && c3 < 0xc0)
                return 3;
            }
        }
      else if (c < 0xf8)
        {
          unsigned char c2 = s[1];
          if (c2 >= 0x80 && c2 < 0xc0)
            {
              unsigned char c3 = s[2];
              if (c3 >= 0x80 && c3 < 0xc0)
                {
                  unsigned char c4 = s[3];
                  if (c4 >= 0x80 && c4 < 0xc0)
                    return 4;
                }
            }
        }
    }
  return 1;
}

/* Returns a character iterator for a given encoding.
   Given a pointer into a string, it returns the number occupied by the next
   single character.  If the piece of string is not valid or if the *s == '\0',
   it returns 1.  */
character_iterator_t
po_charset_character_iterator (const char *canon_charset)
{
  if (canon_charset == utf8)
    return utf8_character_iterator;
  if (strcmp (canon_charset, "GB2312") == 0
      || strcmp (canon_charset, "EUC-KR") == 0)
    return euc_character_iterator;
  if (strcmp (canon_charset, "EUC-JP") == 0)
    return euc_jp_character_iterator;
  if (strcmp (canon_charset, "EUC-TW") == 0)
    return euc_tw_character_iterator;
  if (strcmp (canon_charset, "BIG5") == 0)
    return big5_character_iterator;
  if (strcmp (canon_charset, "BIG5-HKSCS") == 0)
    return big5hkscs_character_iterator;
  if (strcmp (canon_charset, "GBK") == 0)
    return gbk_character_iterator;
  if (strcmp (canon_charset, "GB18030") == 0)
    return gb18030_character_iterator;
  if (strcmp (canon_charset, "SHIFT_JIS") == 0)
    return shift_jis_character_iterator;
  if (strcmp (canon_charset, "JOHAB") == 0)
    return johab_character_iterator;
  return char_iterator;
}


/* The PO file's encoding, as specified in the header entry.  */
const char *po_lex_charset;

/* Representation of U+2068 FIRST STRONG ISOLATE (FSI) in the PO file's
   encoding, or NULL if not available.  */
const char *po_lex_isolate_start;
/* Representation of U+2069 POP DIRECTIONAL ISOLATE (PDI) in the PO file's
   encoding, or NULL if not available.  */
const char *po_lex_isolate_end;

#if HAVE_ICONV
/* Converter from the PO file's encoding to UTF-8.  */
iconv_t po_lex_iconv;
#endif
/* If no converter is available, some information about the structure of the
   PO file's encoding.  */
bool po_lex_weird_cjk;

void
po_lex_charset_init ()
{
  po_lex_charset = NULL;
  po_lex_isolate_start = NULL;
  po_lex_isolate_end = NULL;
#if HAVE_ICONV
  po_lex_iconv = (iconv_t)(-1);
#endif
  po_lex_weird_cjk = false;
}

void
po_lex_charset_set (const char *header_entry, const char *filename)
{
  /* Verify the validity of CHARSET.  It is necessary
     1. for the correct treatment of multibyte characters containing
        0x5C bytes in the PO lexer,
     2. so that at run time, gettext() can call iconv() to convert
        msgstr.  */
  const char *charsetstr = c_strstr (header_entry, "charset=");

  if (charsetstr != NULL)
    {
      size_t len;
      char *charset;
      const char *canon_charset;

      charsetstr += strlen ("charset=");
      len = strcspn (charsetstr, " \t\n");
      charset = (char *) xmalloca (len + 1);
      memcpy (charset, charsetstr, len);
      charset[len] = '\0';

      canon_charset = po_charset_canonicalize (charset);
      if (canon_charset == NULL)
        {
          /* Don't warn for POT files, because POT files usually contain
             only ASCII msgids.  */
          size_t filenamelen = strlen (filename);

          if (!(filenamelen >= 4
                && memcmp (filename + filenamelen - 4, ".pot", 4) == 0
                && strcmp (charset, "CHARSET") == 0))
            {
              char *warning_message =
                xasprintf (_("\
Charset \"%s\" is not a portable encoding name.\n\
Message conversion to user's charset might not work.\n"),
                           charset);
              po_xerror (PO_SEVERITY_WARNING, NULL,
                         filename, (size_t)(-1), (size_t)(-1), true,
                         warning_message);
              free (warning_message);
            }
        }
      else
        {
          const char *envval;

          po_lex_charset = canon_charset;

          if (strcmp (canon_charset, "UTF-8") == 0)
            {
              po_lex_isolate_start = "\xE2\x81\xA8";
              po_lex_isolate_end = "\xE2\x81\xA9";
            }
          else if (strcmp (canon_charset, "GB18030") == 0)
            {
              po_lex_isolate_start = "\x81\x36\xAC\x34";
              po_lex_isolate_end = "\x81\x36\xAC\x35";
            }
          else
            {
              /* The other encodings don't contain U+2068, U+2069.  */
              po_lex_isolate_start = NULL;
              po_lex_isolate_end = NULL;
            }

#if HAVE_ICONV
          if (po_lex_iconv != (iconv_t)(-1))
            iconv_close (po_lex_iconv);
#endif

          /* The old Solaris/openwin msgfmt and GNU msgfmt <= 0.10.35
             don't know about multibyte encodings, and require a spurious
             backslash after every multibyte character whose last byte is
             0x5C.  Some programs, like vim, distribute PO files in this
             broken format.  GNU msgfmt must continue to support this old
             PO file format when the Makefile requests it.  */
          envval = getenv ("OLD_PO_FILE_INPUT");
          if (envval != NULL && *envval != '\0')
            {
              /* Assume the PO file is in old format, with extraneous
                 backslashes.  */
#if HAVE_ICONV
              po_lex_iconv = (iconv_t)(-1);
#endif
              po_lex_weird_cjk = false;
            }
          else
            {
              /* Use iconv() to parse multibyte characters.  */
#if HAVE_ICONV
              /* Avoid glibc-2.1 bug with EUC-KR.  */
# if ((__GLIBC__ == 2 && __GLIBC_MINOR__ <= 1) && !defined __UCLIBC__) \
     && !defined _LIBICONV_VERSION
              if (strcmp (po_lex_charset, "EUC-KR") == 0)
                po_lex_iconv = (iconv_t)(-1);
              else
# endif
              /* Avoid Solaris 2.9 bug with GB2312, EUC-TW, BIG5, BIG5-HKSCS,
                 GBK, GB18030.  */
# if defined __sun && !defined _LIBICONV_VERSION
              if (   strcmp (po_lex_charset, "GB2312") == 0
                  || strcmp (po_lex_charset, "EUC-TW") == 0
                  || strcmp (po_lex_charset, "BIG5") == 0
                  || strcmp (po_lex_charset, "BIG5-HKSCS") == 0
                  || strcmp (po_lex_charset, "GBK") == 0
                  || strcmp (po_lex_charset, "GB18030") == 0)
                po_lex_iconv = (iconv_t)(-1);
              else
# endif
              po_lex_iconv = iconv_open ("UTF-8", po_lex_charset);
              if (po_lex_iconv == (iconv_t)(-1))
                {
                  const char *progname;
                  char *warning_message;
                  const char *recommendation;
                  const char *note;
                  char *whole_message;

# if IN_LIBGETTEXTPO
                  progname = "libgettextpo";
# else
                  progname = last_component (program_name);
# endif

                  warning_message =
                    xasprintf (_("\
Charset \"%s\" is not supported. %s relies on iconv(),\n\
and iconv() does not support \"%s\".\n"),
                               po_lex_charset, progname, po_lex_charset);

# if !defined _LIBICONV_VERSION
                  recommendation = _("\
Installing GNU libiconv and then reinstalling GNU gettext\n\
would fix this problem.\n");
# else
                  recommendation = "";
# endif

                  /* Test for a charset which has double-byte characters
                     ending in 0x5C.  For these encodings, the string parser
                     is likely to be confused if it can't see the character
                     boundaries.  */
                  po_lex_weird_cjk = po_is_charset_weird_cjk (po_lex_charset);
                  if (po_is_charset_weird (po_lex_charset)
                      && !po_lex_weird_cjk)
                    note = _("Continuing anyway, expect parse errors.");
                  else
                    note = _("Continuing anyway.");

                  whole_message =
                    xasprintf ("%s%s%s\n",
                               warning_message, recommendation, note);

                  po_xerror (PO_SEVERITY_WARNING, NULL,
                             filename, (size_t)(-1), (size_t)(-1), true,
                             whole_message);

                  free (whole_message);
                  free (warning_message);
                }
#else
              /* Test for a charset which has double-byte characters
                 ending in 0x5C.  For these encodings, the string parser
                 is likely to be confused if it can't see the character
                 boundaries.  */
              po_lex_weird_cjk = po_is_charset_weird_cjk (po_lex_charset);
              if (po_is_charset_weird (po_lex_charset) && !po_lex_weird_cjk)
                {
                  const char *progname;
                  char *warning_message;
                  const char *recommendation;
                  const char *note;
                  char *whole_message;

# if IN_LIBGETTEXTPO
                  progname = "libgettextpo";
# else
                  progname = last_component (program_name);
# endif

                  warning_message =
                    xasprintf (_("\
Charset \"%s\" is not supported. %s relies on iconv().\n\
This version was built without iconv().\n"),
                               po_lex_charset, progname);

                  recommendation = _("\
Installing GNU libiconv and then reinstalling GNU gettext\n\
would fix this problem.\n");

                  note = _("Continuing anyway, expect parse errors.");

                  whole_message =
                    xasprintf ("%s%s%s\n",
                               warning_message, recommendation, note);

                  po_xerror (PO_SEVERITY_WARNING, NULL,
                             filename, (size_t)(-1), (size_t)(-1), true,
                             whole_message);

                  free (whole_message);
                  free (warning_message);
                }
#endif
            }
        }
      freea (charset);
    }
  else
    {
      /* Don't warn for POT files, because POT files usually contain
         only ASCII msgids.  */
      size_t filenamelen = strlen (filename);

      if (!(filenamelen >= 4
            && memcmp (filename + filenamelen - 4, ".pot", 4) == 0))
        po_xerror (PO_SEVERITY_WARNING,
                   NULL, filename, (size_t)(-1), (size_t)(-1), true,
                   _("\
Charset missing in header.\n\
Message conversion to user's charset will not work.\n"));
    }
}

void
po_lex_charset_close ()
{
  po_lex_charset = NULL;
  po_lex_isolate_start = NULL;
  po_lex_isolate_end = NULL;
#if HAVE_ICONV
  if (po_lex_iconv != (iconv_t)(-1))
    {
      iconv_close (po_lex_iconv);
      po_lex_iconv = (iconv_t)(-1);
    }
#endif
  po_lex_weird_cjk = false;
}