/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2013 Ed Schouten <ed@FreeBSD.org>
 * All rights reserved.
 *
 * 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/queue.h>

#include <assert.h>
#include <errno.h>
#include <langinfo.h>
#include <limits.h>
#include <string.h>
#include <uchar.h>

#include "../iconv/citrus_hash.h"
#include "../iconv/citrus_module.h"
#include "../iconv/citrus_iconv.h"
#include "mblocal.h"

typedef struct {
        bool                    initialized;
        struct _citrus_iconv    iconv;
        char                    srcbuf[MB_LEN_MAX];
        size_t                  srcbuf_len;
        union {
                charXX_t        widechar[DSTBUF_LEN];
                char            bytes[sizeof(charXX_t) * DSTBUF_LEN];
        } dstbuf;
        size_t                  dstbuf_len;
} _ConversionState;
_Static_assert(sizeof(_ConversionState) <= sizeof(mbstate_t),
    "Size of _ConversionState must not exceed mbstate_t's size.");

size_t
mbrtocXX_l(charXX_t * __restrict pc, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps, locale_t locale)
{
        _ConversionState *cs;
        struct _citrus_iconv *handle;
        size_t i, retval;
        charXX_t retchar;

        FIX_LOCALE(locale);
        if (ps == NULL)
                ps = &(XLOCALE_CTYPE(locale)->mbrtocXX);
        cs = (_ConversionState *)ps;
        handle = &cs->iconv;

        /* Reinitialize mbstate_t. */
        if (s == NULL || !cs->initialized) {
                if (_citrus_iconv_open(&handle,
                    nl_langinfo_l(CODESET, locale), UTF_XX_INTERNAL) != 0) {
                        cs->initialized = false;
                        errno = EINVAL;
                        return (-1);
                }
                cs->srcbuf_len = cs->dstbuf_len = 0;
                cs->initialized = true;
                if (s == NULL)
                        return (0);
        }

        /* See if we still have characters left from the previous invocation. */
        if (cs->dstbuf_len > 0) {
                retval = (size_t)-3;
                goto return_char;
        }

        /* Fill up the read buffer as far as possible. */
        if (n > sizeof(cs->srcbuf) - cs->srcbuf_len)
                n = sizeof(cs->srcbuf) - cs->srcbuf_len;
        memcpy(cs->srcbuf + cs->srcbuf_len, s, n);

        /* Convert as few characters to the dst buffer as possible. */
        for (i = 0; ; i++) {
                char *src, *dst;
                size_t srcleft, dstleft, invlen;
                int err;

                src = cs->srcbuf;
                srcleft = cs->srcbuf_len + n;
                dst = cs->dstbuf.bytes;
                dstleft = i * sizeof(charXX_t);
                assert(srcleft <= sizeof(cs->srcbuf) &&
                    dstleft <= sizeof(cs->dstbuf.bytes));
                err = _citrus_iconv_convert(handle, &src, &srcleft,
                    &dst, &dstleft, _CITRUS_ICONV_F_HIDE_INVALID, &invlen);
                cs->dstbuf_len = (dst - cs->dstbuf.bytes) / sizeof(charXX_t);

                /* Got new character(s). Return the first. */
                if (cs->dstbuf_len > 0) {
                        assert(src - cs->srcbuf > cs->srcbuf_len);
                        retval = src - cs->srcbuf - cs->srcbuf_len;
                        cs->srcbuf_len = 0;
                        goto return_char;
                }

                /* Increase dst buffer size, to obtain the surrogate pair. */
                if (err == E2BIG)
                        continue;

                /* Illegal sequence. */
                if (invlen > 0) {
                        cs->srcbuf_len = 0;
                        errno = EILSEQ;
                        return ((size_t)-1);
                }

                /* Save unprocessed remainder for the next invocation. */
                memmove(cs->srcbuf, src, srcleft);
                cs->srcbuf_len = srcleft;
                return ((size_t)-2);
        }

return_char:
        retchar = cs->dstbuf.widechar[0];
        memmove(&cs->dstbuf.widechar[0], &cs->dstbuf.widechar[1],
            --cs->dstbuf_len * sizeof(charXX_t));
        if (pc != NULL)
                *pc = retchar;
        if (retchar == 0)
                return (0);
        return (retval);
}

size_t
mbrtocXX(charXX_t * __restrict pc, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps)
{

        return (mbrtocXX_l(pc, s, n, ps, __get_locale()));
}