/*-
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 * Copyright 2012 Garrett D'Amore <garrett@damore.org>  All rights reserved.
 * Copyright 2015 John Marino <draco@marino.st>
 *
 * This source code is derived from the illumos localedef command, and
 * provided under BSD-style license terms by Nexenta Systems, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * The functions in this file convert from the standard multibyte forms
 * to the wide character forms used internally by libc.  Unfortunately,
 * this approach means that we need a method for each and every encoding.
 */
#include <sys/cdefs.h>
#include <ctype.h>
#include <stdlib.h>
#include <wchar.h>
#include <string.h>
#include <sys/types.h>
#include "localedef.h"

static int towide_none(wchar_t *, const char *, unsigned);
static int towide_utf8(wchar_t *, const char *, unsigned);
static int towide_big5(wchar_t *, const char *, unsigned);
static int towide_gbk(wchar_t *, const char *, unsigned);
static int towide_gb2312(wchar_t *, const char *, unsigned);
static int towide_gb18030(wchar_t *, const char *, unsigned);
static int towide_mskanji(wchar_t *, const char *, unsigned);
static int towide_euccn(wchar_t *, const char *, unsigned);
static int towide_eucjp(wchar_t *, const char *, unsigned);
static int towide_euckr(wchar_t *, const char *, unsigned);
static int towide_euctw(wchar_t *, const char *, unsigned);

static int tomb_none(char *, wchar_t);
static int tomb_utf8(char *, wchar_t);
static int tomb_mbs(char *, wchar_t);

static int (*_towide)(wchar_t *, const char *, unsigned) = towide_none;
static int (*_tomb)(char *, wchar_t) = tomb_none;
static char _encoding_buffer[20] = {'N','O','N','E'};
static const char *_encoding = _encoding_buffer;
static int _nbits = 7;

/*
 * Table of supported encodings.  We only bother to list the multibyte
 * encodings here, because single byte locales are handed by "NONE".
 */
static struct {
        const char *name;
        /* the name that the underlying libc implemenation uses */
        const char *cname;
        /* the maximum number of bits required for priorities */
        int nbits;
        int (*towide)(wchar_t *, const char *, unsigned);
        int (*tomb)(char *, wchar_t);
} mb_encodings[] = {
        /*
         * UTF8 values max out at 0x1fffff (although in theory there could
         * be later extensions, but it won't happen.)  This means we only need
         * 21 bits to be able to encode the entire range of priorities.
         */
        { "UTF-8",      "UTF-8",        21, towide_utf8, tomb_utf8 },
        { "UTF8",       "UTF-8",        21, towide_utf8, tomb_utf8 },
        { "utf8",       "UTF-8",        21, towide_utf8, tomb_utf8 },
        { "utf-8",      "UTF-8",        21, towide_utf8, tomb_utf8 },

        { "EUC-CN",     "EUC-CN",       16, towide_euccn, tomb_mbs },
        { "eucCN",      "EUC-CN",       16, towide_euccn, tomb_mbs },
        /*
         * Because the 3-byte form of EUC-JP use the same leading byte,
         * only 17 bits required to provide unique priorities.  (The low
         * bit of that first byte is set.)  By setting this value low,
         * we can get by with only 3 bytes in the strxfrm expansion.
         */
        { "EUC-JP",     "EUC-JP",       17, towide_eucjp, tomb_mbs },
        { "eucJP",      "EUC-JP",       17, towide_eucjp, tomb_mbs },

        { "EUC-KR",     "EUC-KR",       16, towide_euckr, tomb_mbs },
        { "eucKR",      "EUC-KR",       16, towide_euckr, tomb_mbs },
        /*
         * EUC-TW uses 2 bytes most of the time, but 4 bytes if the
         * high order byte is 0x8E.  However, with 4 byte encodings,
         * the third byte will be A0-B0.  So we only need to consider
         * the lower order 24 bits for collation.
         */
        { "EUC-TW",     "EUC-TW",       24, towide_euctw, tomb_mbs },
        { "eucTW",      "EUC-TW",       24, towide_euctw, tomb_mbs },

        { "MS_Kanji",   "MSKanji",      16, towide_mskanji, tomb_mbs },
        { "MSKanji",    "MSKanji",      16, towide_mskanji, tomb_mbs },
        { "PCK",        "MSKanji",      16, towide_mskanji, tomb_mbs },
        { "SJIS",       "MSKanji",      16, towide_mskanji, tomb_mbs },
        { "Shift_JIS",  "MSKanji",      16, towide_mskanji, tomb_mbs },

        { "BIG5",       "BIG5",         16, towide_big5, tomb_mbs },
        { "big5",       "BIG5",         16, towide_big5, tomb_mbs },
        { "Big5",       "BIG5",         16, towide_big5, tomb_mbs },

        { "GBK",        "GBK",          16, towide_gbk, tomb_mbs },

        /*
         * GB18030 can get away with just 31 bits.  This is because the
         * high order bit is always set for 4 byte values, and the
         * at least one of the other bits in that 4 byte value will
         * be non-zero.
         */
        { "GB18030",    "GB18030",      31, towide_gb18030, tomb_mbs },

        /*
         * This should probably be an aliase for euc-cn, or vice versa.
         */
        { "GB2312",     "GB2312",       16, towide_gb2312, tomb_mbs },

        { NULL, NULL, 0, 0, 0 },
};

static char *
show_mb(const char *mb)
{
        static char buf[64];

        /* ASCII stuff we just print */
        if (isascii(*mb) && isgraph(*mb)) {
                buf[0] = *mb;
                buf[1] = 0;
                return (buf);
        }
        buf[0] = 0;
        while (*mb != 0) {
                char scr[8];
                (void) snprintf(scr, sizeof (scr), "\\x%02x", *mb);
                (void) strlcat(buf, scr, sizeof (buf));
                mb++;
        }
        return (buf);
}

static char     *widemsg;

void
werr(const char *fmt, ...)
{
        char    *msg;

        va_list va;
        va_start(va, fmt);
        (void) vasprintf(&msg, fmt, va);
        va_end(va);

        free(widemsg);
        widemsg = msg;
}

/*
 * This is used for 8-bit encodings.
 */
int
towide_none(wchar_t *c, const char *mb, unsigned n __unused)
{
        if (mb_cur_max != 1) {
                werr("invalid or unsupported multibyte locale");
                return (-1);
        }
        *c = (uint8_t)*mb;
        return (1);
}

int
tomb_none(char *mb, wchar_t wc)
{
        if (mb_cur_max != 1) {
                werr("invalid or unsupported multibyte locale");
                return (-1);
        }
        *(uint8_t *)mb = (wc & 0xff);
        mb[1] = 0;
        return (1);
}

/*
 * UTF-8 stores wide characters in UTF-32 form.
 */
int
towide_utf8(wchar_t *wc, const char *mb, unsigned n)
{
        wchar_t c;
        int     nb;
        wchar_t lv;     /* lowest legal value */
        int     i;
        const uint8_t *s = (const uint8_t *)mb;

        c = *s;

        if ((c & 0x80) == 0) {
                /* 7-bit ASCII */
                *wc = c;
                return (1);
        } else if ((c & 0xe0) == 0xc0) {
                /* u80-u7ff - two bytes encoded */
                nb = 2;
                lv = 0x80;
                c &= ~0xe0;
        } else if ((c & 0xf0) == 0xe0) {
                /* u800-uffff - three bytes encoded */
                nb = 3;
                lv = 0x800;
                c &= ~0xf0;
        } else if ((c & 0xf8) == 0xf0) {
                /* u1000-u1fffff - four bytes encoded */
                nb = 4;
                lv = 0x1000;
                c &= ~0xf8;
        } else {
                /* 5 and 6 byte encodings are not legal unicode */
                werr("utf8 encoding too large (%s)", show_mb(mb));
                return (-1);
        }
        if (nb > (int)n) {
                werr("incomplete utf8 sequence (%s)", show_mb(mb));
                return (-1);
        }

        for (i = 1; i < nb; i++) {
                if (((s[i]) & 0xc0) != 0x80) {
                        werr("illegal utf8 byte (%x)", s[i]);
                        return (-1);
                }
                c <<= 6;
                c |= (s[i] & 0x3f);
        }

        if (c < lv) {
                werr("illegal redundant utf8 encoding (%s)", show_mb(mb));
                return (-1);
        }
        *wc = c;
        return (nb);
}

int
tomb_utf8(char *mb, wchar_t wc)
{
        uint8_t *s = (uint8_t *)mb;
        uint8_t msk;
        int cnt;
        int i;

        if (wc <= 0x7f) {
                s[0] = wc & 0x7f;
                s[1] = 0;
                return (1);
        }
        if (wc <= 0x7ff) {
                cnt = 2;
                msk = 0xc0;
        } else if (wc <= 0xffff) {
                cnt = 3;
                msk = 0xe0;
        } else if (wc <= 0x1fffff) {
                cnt = 4;
                msk = 0xf0;
        } else {
                werr("illegal uf8 char (%x)", wc);
                return (-1);
        }
        for (i = cnt - 1; i; i--) {
                s[i] = (wc & 0x3f) | 0x80;
                wc >>= 6;
        }
        s[0] = (msk) | wc;
        s[cnt] = 0;
        return (cnt);
}

/*
 * Several encodings share a simplistic dual byte encoding.  In these
 * forms, they all indicate that a two byte sequence is to be used if
 * the first byte has its high bit set.  They all store this simple
 * encoding as a 16-bit value, although a great many of the possible
 * code points are not used in most character sets.  This gives a possible
 * set of just over 32,000 valid code points.
 *
 * 0x00 - 0x7f          - 1 byte encoding
 * 0x80 - 0x7fff        - illegal
 * 0x8000 - 0xffff      - 2 byte encoding
 */

static int
towide_dbcs(wchar_t *wc, const char *mb, unsigned n)
{
        wchar_t c;

        c = *(const uint8_t *)mb;

        if ((c & 0x80) == 0) {
                /* 7-bit */
                *wc = c;
                return (1);
        }
        if (n < 2) {
                werr("incomplete character sequence (%s)", show_mb(mb));
                return (-1);
        }

        /* Store both bytes as a single 16-bit wide. */
        c <<= 8;
        c |= (uint8_t)(mb[1]);
        *wc = c;
        return (2);
}

/*
 * Most multibyte locales just convert the wide character to the multibyte
 * form by stripping leading null bytes, and writing the 32-bit quantity
 * in big-endian order.
 */
int
tomb_mbs(char *mb, wchar_t wc)
{
        uint8_t *s = (uint8_t *)mb;
        int     n = 0, c;

        if ((wc & 0xff000000U) != 0) {
                n = 4;
        } else if ((wc & 0x00ff0000U) != 0) {
                n = 3;
        } else if ((wc & 0x0000ff00U) != 0) {
                n = 2;
        } else {
                n = 1;
        }
        c = n;
        while (n) {
                n--;
                s[n] = wc & 0xff;
                wc >>= 8;
        }
        /* ensure null termination */
        s[c] = 0;
        return (c);
}


/*
 * big5 is a simple dual byte character set.
 */
int
towide_big5(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_dbcs(wc, mb, n));
}

/*
 * GBK encodes wides in the same way that big5 does, the high order
 * bit of the first byte indicates a double byte character.
 */
int
towide_gbk(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_dbcs(wc, mb, n));
}

/*
 * GB2312 is another DBCS.  Its cleaner than others in that the second
 * byte does not encode ASCII, but it supports characters.
 */
int
towide_gb2312(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_dbcs(wc, mb, n));
}

/*
 * GB18030.  This encodes as 8, 16, or 32-bits.
 * 7-bit values are in 1 byte,  4 byte sequences are used when
 * the second byte encodes 0x30-39 and all other sequences are 2 bytes.
 */
int
towide_gb18030(wchar_t *wc, const char *mb, unsigned n)
{
        wchar_t c;

        c = *(const uint8_t *)mb;

        if ((c & 0x80) == 0) {
                /* 7-bit */
                *wc = c;
                return (1);
        }
        if (n < 2) {
                werr("incomplete character sequence (%s)", show_mb(mb));
                return (-1);
        }

        /* pull in the second byte */
        c <<= 8;
        c |= (uint8_t)(mb[1]);

        if (((c & 0xff) >= 0x30) && ((c & 0xff) <= 0x39)) {
                if (n < 4) {
                        werr("incomplete 4-byte character sequence (%s)",
                            show_mb(mb));
                        return (-1);
                }
                c <<= 8;
                c |= (uint8_t)(mb[2]);
                c <<= 8;
                c |= (uint8_t)(mb[3]);
                *wc = c;
                return (4);
        }

        *wc = c;
        return (2);
}

/*
 * MS-Kanji (aka SJIS) is almost a clean DBCS like the others, but it
 * also has a range of single byte characters above 0x80.  (0xa1-0xdf).
 */
int
towide_mskanji(wchar_t *wc, const char *mb, unsigned n)
{
        wchar_t c;

        c = *(const uint8_t *)mb;

        if ((c < 0x80) || ((c > 0xa0) && (c < 0xe0))) {
                /* 7-bit */
                *wc = c;
                return (1);
        }

        if (n < 2) {
                werr("incomplete character sequence (%s)", show_mb(mb));
                return (-1);
        }

        /* Store both bytes as a single 16-bit wide. */
        c <<= 8;
        c |= (uint8_t)(mb[1]);
        *wc = c;
        return (2);
}

/*
 * EUC forms.  EUC encodings are "variable".  FreeBSD carries some additional
 * variable data to encode these, but we're going to treat each as independent
 * instead.  Its the only way we can sensibly move forward.
 *
 * Note that the way in which the different EUC forms vary is how wide
 * CS2 and CS3 are and what the first byte of them is.
 */
static int
towide_euc_impl(wchar_t *wc, const char *mb, unsigned n,
    uint8_t cs2, uint8_t cs2width, uint8_t cs3, uint8_t cs3width)
{
        int i;
        int width = 2;
        wchar_t c;

        c = *(const uint8_t *)mb;

        /*
         * All variations of EUC encode 7-bit ASCII as one byte, and use
         * additional bytes for more than that.
         */
        if ((c & 0x80) == 0) {
                /* 7-bit */
                *wc = c;
                return (1);
        }

        /*
         * All EUC variants reserve 0xa1-0xff to identify CS1, which
         * is always two bytes wide.  Note that unused CS will be zero,
         * and that cannot be true because we know that the high order
         * bit must be set.
         */
        if (c >= 0xa1) {
                width = 2;
        } else if (c == cs2) {
                width = cs2width;
        } else if (c == cs3) {
                width = cs3width;
        }

        if ((int)n < width) {
                werr("incomplete character sequence (%s)", show_mb(mb));
                return (-1);
        }

        for (i = 1; i < width; i++) {
                /* pull in the next byte */
                c <<= 8;
                c |= (uint8_t)(mb[i]);
        }

        *wc = c;
        return (width);
}

/*
 * EUC-CN encodes as follows:
 *
 * Code set 0 (ASCII):                          0x21-0x7E
 * Code set 1 (CNS 11643-1992 Plane 1):         0xA1A1-0xFEFE
 * Code set 2:                                  unused
 * Code set 3:                                  unused
 */
int
towide_euccn(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_euc_impl(wc, mb, n, 0x8e, 4, 0, 0));
}

/*
 * EUC-JP encodes as follows:
 *
 * Code set 0 (ASCII or JIS X 0201-1976 Roman): 0x21-0x7E
 * Code set 1 (JIS X 0208):                     0xA1A1-0xFEFE
 * Code set 2 (half-width katakana):            0x8EA1-0x8EDF
 * Code set 3 (JIS X 0212-1990):                0x8FA1A1-0x8FFEFE
 */
int
towide_eucjp(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_euc_impl(wc, mb, n, 0x8e, 2, 0x8f, 3));
}

/*
 * EUC-KR encodes as follows:
 *
 * Code set 0 (ASCII or KS C 5636-1993):        0x21-0x7E
 * Code set 1 (KS C 5601-1992):                 0xA1A1-0xFEFE
 * Code set 2:                                  unused
 * Code set 3:                                  unused
 */
int
towide_euckr(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_euc_impl(wc, mb, n, 0, 0, 0, 0));
}

/*
 * EUC-TW encodes as follows:
 *
 * Code set 0 (ASCII):                          0x21-0x7E
 * Code set 1 (CNS 11643-1992 Plane 1):         0xA1A1-0xFEFE
 * Code set 2 (CNS 11643-1992 Planes 1-16):     0x8EA1A1A1-0x8EB0FEFE
 * Code set 3:                                  unused
 */
int
towide_euctw(wchar_t *wc, const char *mb, unsigned n)
{
        return (towide_euc_impl(wc, mb, n, 0x8e, 4, 0, 0));
}

/*
 * Public entry points.
 */

int
to_wide(wchar_t *wc, const char *mb)
{
        /* this won't fail hard */
        return (_towide(wc, mb, strlen(mb)));
}

int
to_mb(char *mb, wchar_t wc)
{
        int     rv;

        if ((rv = _tomb(mb, wc)) < 0) {
                warn("%s", widemsg);
                free(widemsg);
                widemsg = NULL;
        }
        return (rv);
}

char *
to_mb_string(const wchar_t *wcs)
{
        char    *mbs;
        char    *ptr;
        int     len;

        mbs = malloc((wcslen(wcs) * mb_cur_max) + 1);
        if (mbs == NULL) {
                warn("out of memory");
                return (NULL);
        }
        ptr = mbs;
        while (*wcs) {
                if ((len = to_mb(ptr, *wcs)) < 0) {
                        INTERR;
                        free(mbs);
                        return (NULL);
                }
                wcs++;
                ptr += len;
        }
        *ptr = 0;
        return (mbs);
}

void
set_wide_encoding(const char *encoding)
{
        int i;

        _towide = towide_none;
        _tomb = tomb_none;
        _nbits = 8;

        snprintf(_encoding_buffer, sizeof(_encoding_buffer), "NONE:%s",
            encoding);
        for (i = 0; mb_encodings[i].name; i++) {
                if (strcasecmp(encoding, mb_encodings[i].name) == 0) {
                        _towide = mb_encodings[i].towide;
                        _tomb = mb_encodings[i].tomb;
                        _encoding = mb_encodings[i].cname;
                        _nbits = mb_encodings[i].nbits;
                        break;
                }
        }
}

const char *
get_wide_encoding(void)
{
        return (_encoding);
}

int
max_wide(void)
{
        return ((int)((1U << _nbits) - 1));
}