/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright 2013 Garrett D'Amore <garrett@damore.org>
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 2002-2004 Tim J. Robbins
 * All rights reserved.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 *
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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 AUTHOR 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 AUTHOR 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.
 */

#include <sys/param.h>
#include <errno.h>
#include <limits.h>
#include <runetype.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include "mblocal.h"

extern int __mb_sb_limit;

static size_t   _UTF8_mbrtowc(wchar_t * __restrict, const char * __restrict,
                    size_t, mbstate_t * __restrict);
static int      _UTF8_mbsinit(const mbstate_t *);
static size_t   _UTF8_mbsnrtowcs(wchar_t * __restrict,
                    const char ** __restrict, size_t, size_t,
                    mbstate_t * __restrict);
static size_t   _UTF8_wcrtomb(char * __restrict, wchar_t,
                    mbstate_t * __restrict);
static size_t   _UTF8_wcsnrtombs(char * __restrict, const wchar_t ** __restrict,
                    size_t, size_t, mbstate_t * __restrict);

typedef struct {
        wchar_t ch;
        int     want;
        wchar_t lbound;
} _UTF8State;

int
_UTF8_init(struct xlocale_ctype *l, _RuneLocale *rl)
{

        l->__mbrtowc = _UTF8_mbrtowc;
        l->__wcrtomb = _UTF8_wcrtomb;
        l->__mbsinit = _UTF8_mbsinit;
        l->__mbsnrtowcs = _UTF8_mbsnrtowcs;
        l->__wcsnrtombs = _UTF8_wcsnrtombs;
        l->runes = rl;
        l->__mb_cur_max = 4;
        /*
         * UCS-4 encoding used as the internal representation, so
         * slots 0x0080-0x00FF are occuped and must be excluded
         * from the single byte ctype by setting the limit.
         */
        l->__mb_sb_limit = 128;

        return (0);
}

static int
_UTF8_mbsinit(const mbstate_t *ps)
{

        return (ps == NULL || ((const _UTF8State *)ps)->want == 0);
}

static size_t
_UTF8_mbrtowc(wchar_t * __restrict pwc, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps)
{
        _UTF8State *us;
        int ch, i, mask, want;
        wchar_t lbound, wch;

        us = (_UTF8State *)ps;

        if (us->want < 0 || us->want > 6) {
                errno = EINVAL;
                return ((size_t)-1);
        }

        if (s == NULL) {
                s = "";
                n = 1;
                pwc = NULL;
        }

        if (n == 0)
                /* Incomplete multibyte sequence */
                return ((size_t)-2);

        if (us->want == 0) {
                /*
                 * Determine the number of octets that make up this character
                 * from the first octet, and a mask that extracts the
                 * interesting bits of the first octet. We already know
                 * the character is at least two bytes long.
                 *
                 * We also specify a lower bound for the character code to
                 * detect redundant, non-"shortest form" encodings. For
                 * example, the sequence C0 80 is _not_ a legal representation
                 * of the null character. This enforces a 1-to-1 mapping
                 * between character codes and their multibyte representations.
                 */
                ch = (unsigned char)*s;
                if ((ch & 0x80) == 0) {
                        /* Fast path for plain ASCII characters. */
                        if (pwc != NULL)
                                *pwc = ch;
                        return (ch != '\0' ? 1 : 0);
                }
                if ((ch & 0xe0) == 0xc0) {
                        mask = 0x1f;
                        want = 2;
                        lbound = 0x80;
                } else if ((ch & 0xf0) == 0xe0) {
                        mask = 0x0f;
                        want = 3;
                        lbound = 0x800;
                } else if ((ch & 0xf8) == 0xf0) {
                        mask = 0x07;
                        want = 4;
                        lbound = 0x10000;
                } else {
                        /*
                         * Malformed input; input is not UTF-8.
                         */
                        errno = EILSEQ;
                        return ((size_t)-1);
                }
        } else {
                want = us->want;
                lbound = us->lbound;
        }

        /*
         * Decode the octet sequence representing the character in chunks
         * of 6 bits, most significant first.
         */
        if (us->want == 0)
                wch = (unsigned char)*s++ & mask;
        else
                wch = us->ch;

        for (i = (us->want == 0) ? 1 : 0; i < MIN(want, n); i++) {
                if ((*s & 0xc0) != 0x80) {
                        /*
                         * Malformed input; bad characters in the middle
                         * of a character.
                         */
                        errno = EILSEQ;
                        return ((size_t)-1);
                }
                wch <<= 6;
                wch |= *s++ & 0x3f;
        }
        if (i < want) {
                /* Incomplete multibyte sequence. */
                us->want = want - i;
                us->lbound = lbound;
                us->ch = wch;
                return ((size_t)-2);
        }
        if (wch < lbound) {
                /*
                 * Malformed input; redundant encoding.
                 */
                errno = EILSEQ;
                return ((size_t)-1);
        }
        if ((wch >= 0xd800 && wch <= 0xdfff) || wch > 0x10ffff) {
                /*
                 * Malformed input; invalid code points.
                 */
                errno = EILSEQ;
                return ((size_t)-1);
        }
        if (pwc != NULL)
                *pwc = wch;
        us->want = 0;
        return (wch == L'\0' ? 0 : want);
}

static size_t
_UTF8_mbsnrtowcs(wchar_t * __restrict dst, const char ** __restrict src,
    size_t nms, size_t len, mbstate_t * __restrict ps)
{
        _UTF8State *us;
        const char *s;
        size_t nchr;
        wchar_t wc;
        size_t nb;

        us = (_UTF8State *)ps;

        s = *src;
        nchr = 0;

        if (dst == NULL) {
                /*
                 * The fast path in the loop below is not safe if an ASCII
                 * character appears as anything but the first byte of a
                 * multibyte sequence. Check now to avoid doing it in the loop.
                 */
                if (nms > 0 && us->want > 0 && (signed char)*s > 0) {
                        errno = EILSEQ;
                        return ((size_t)-1);
                }
                for (;;) {
                        if (nms > 0 && (signed char)*s > 0)
                                /*
                                 * Fast path for plain ASCII characters
                                 * excluding NUL.
                                 */
                                nb = 1;
                        else if ((nb = _UTF8_mbrtowc(&wc, s, nms, ps)) ==
                            (size_t)-1)
                                /* Invalid sequence - mbrtowc() sets errno. */
                                return ((size_t)-1);
                        else if (nb == 0 || nb == (size_t)-2)
                                return (nchr);
                        s += nb;
                        nms -= nb;
                        nchr++;
                }
                /*NOTREACHED*/
        }

        /*
         * The fast path in the loop below is not safe if an ASCII
         * character appears as anything but the first byte of a
         * multibyte sequence. Check now to avoid doing it in the loop.
         */
        if (nms > 0 && len > 0 && us->want > 0 && (signed char)*s > 0) {
                errno = EILSEQ;
                return ((size_t)-1);
        }
        while (len-- > 0) {
                if (nms > 0 && (signed char)*s > 0) {
                        /*
                         * Fast path for plain ASCII characters
                         * excluding NUL.
                         */
                        *dst = (wchar_t)*s;
                        nb = 1;
                } else if ((nb = _UTF8_mbrtowc(dst, s, nms, ps)) ==
                    (size_t)-1) {
                        *src = s;
                        return ((size_t)-1);
                } else if (nb == (size_t)-2) {
                        *src = s + nms;
                        return (nchr);
                } else if (nb == 0) {
                        *src = NULL;
                        return (nchr);
                }
                s += nb;
                nms -= nb;
                nchr++;
                dst++;
        }
        *src = s;
        return (nchr);
}

static size_t
_UTF8_wcrtomb(char * __restrict s, wchar_t wc, mbstate_t * __restrict ps)
{
        _UTF8State *us;
        unsigned char lead;
        int i, len;

        us = (_UTF8State *)ps;

        if (us->want != 0) {
                errno = EINVAL;
                return ((size_t)-1);
        }

        if (s == NULL)
                /* Reset to initial shift state (no-op) */
                return (1);

        /*
         * Determine the number of octets needed to represent this character.
         * We always output the shortest sequence possible. Also specify the
         * first few bits of the first octet, which contains the information
         * about the sequence length.
         */
        if ((wc & ~0x7f) == 0) {
                /* Fast path for plain ASCII characters. */
                *s = (char)wc;
                return (1);
        } else if ((wc & ~0x7ff) == 0) {
                lead = 0xc0;
                len = 2;
        } else if ((wc & ~0xffff) == 0) {
                if (wc >= 0xd800 && wc <= 0xdfff) {
                        errno = EILSEQ;
                        return ((size_t)-1);
                }
                lead = 0xe0;
                len = 3;
        } else if (wc >= 0 && wc <= 0x10ffff) {
                lead = 0xf0;
                len = 4;
        } else {
                errno = EILSEQ;
                return ((size_t)-1);
        }

        /*
         * Output the octets representing the character in chunks
         * of 6 bits, least significant last. The first octet is
         * a special case because it contains the sequence length
         * information.
         */
        for (i = len - 1; i > 0; i--) {
                s[i] = (wc & 0x3f) | 0x80;
                wc >>= 6;
        }
        *s = (wc & 0xff) | lead;

        return (len);
}

static size_t
_UTF8_wcsnrtombs(char * __restrict dst, const wchar_t ** __restrict src,
    size_t nwc, size_t len, mbstate_t * __restrict ps)
{
        _UTF8State *us;
        char buf[MB_LEN_MAX];
        const wchar_t *s;
        size_t nbytes;
        size_t nb;

        us = (_UTF8State *)ps;

        if (us->want != 0) {
                errno = EINVAL;
                return ((size_t)-1);
        }

        s = *src;
        nbytes = 0;

        if (dst == NULL) {
                while (nwc-- > 0) {
                        if (0 <= *s && *s < 0x80)
                                /* Fast path for plain ASCII characters. */
                                nb = 1;
                        else if ((nb = _UTF8_wcrtomb(buf, *s, ps)) ==
                            (size_t)-1)
                                /* Invalid character - wcrtomb() sets errno. */
                                return ((size_t)-1);
                        if (*s == L'\0')
                                return (nbytes + nb - 1);
                        s++;
                        nbytes += nb;
                }
                return (nbytes);
        }

        while (len > 0 && nwc-- > 0) {
                if (0 <= *s && *s < 0x80) {
                        /* Fast path for plain ASCII characters. */
                        nb = 1;
                        *dst = *s;
                } else if (len > (size_t)MB_CUR_MAX) {
                        /* Enough space to translate in-place. */
                        if ((nb = _UTF8_wcrtomb(dst, *s, ps)) == (size_t)-1) {
                                *src = s;
                                return ((size_t)-1);
                        }
                } else {
                        /*
                         * May not be enough space; use temp. buffer.
                         */
                        if ((nb = _UTF8_wcrtomb(buf, *s, ps)) == (size_t)-1) {
                                *src = s;
                                return ((size_t)-1);
                        }
                        if (nb > (int)len)
                                /* MB sequence for character won't fit. */
                                break;
                        memcpy(dst, buf, nb);
                }
                if (*s == L'\0') {
                        *src = NULL;
                        return (nbytes + nb - 1);
                }
                s++;
                dst += nb;
                len -= nb;
                nbytes += nb;
        }
        *src = s;
        return (nbytes);
}