/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2003, 2005 Ryuichiro Imura
 * 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/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/iconv.h>

#include "iconv_converter_if.h"

/*
 * "UCS" converter
 */

#define KICONV_UCS_COMBINE      0x1
#define KICONV_UCS_FROM_UTF8    0x2
#define KICONV_UCS_TO_UTF8      0x4
#define KICONV_UCS_FROM_LE      0x8
#define KICONV_UCS_TO_LE        0x10
#define KICONV_UCS_FROM_UTF16   0x20
#define KICONV_UCS_TO_UTF16     0x40
#define KICONV_UCS_UCS4         0x80

#define ENCODING_UTF16  "UTF-16BE"
#define ENCODING_UTF8   "UTF-8"

static struct {
        const char *name;
        int from_flag, to_flag;
} unicode_family[] = {
        { "UTF-8",      KICONV_UCS_FROM_UTF8,   KICONV_UCS_TO_UTF8 },
        { "UCS-2LE",    KICONV_UCS_FROM_LE,     KICONV_UCS_TO_LE },
        { "UTF-16BE",   KICONV_UCS_FROM_UTF16,  KICONV_UCS_TO_UTF16 },
        { "UTF-16LE",   KICONV_UCS_FROM_UTF16|KICONV_UCS_FROM_LE,
            KICONV_UCS_TO_UTF16|KICONV_UCS_TO_LE },
        { NULL,         0,      0 }
};

static uint32_t utf8_to_ucs4(const char *src, size_t *utf8width, size_t srclen);
static u_char *ucs4_to_utf8(uint32_t ucs4, char * dst, size_t *utf8width, size_t dstlen);
static uint32_t encode_surrogate(uint32_t code);
static uint32_t decode_surrogate(const u_char *ucs);

#ifdef MODULE_DEPEND
MODULE_DEPEND(iconv_ucs, libiconv, 2, 2, 2);
#endif

/*
 * UCS converter instance
 */
struct iconv_ucs {
        KOBJ_FIELDS;
        int                     convtype;
        struct iconv_cspair *   d_csp;
        struct iconv_cspair *   d_cspf;
        void *                  f_ctp;
        void *                  t_ctp;
        void *                  ctype;
};

static int
iconv_ucs_open(struct iconv_converter_class *dcp,
        struct iconv_cspair *csp, struct iconv_cspair *cspf, void **dpp)
{
        struct iconv_ucs *dp;
        int i;
        const char *from, *to;

        dp = (struct iconv_ucs *)kobj_create((struct kobj_class*)dcp, M_ICONV, M_WAITOK);
        to = csp->cp_to;
        from = cspf ? cspf->cp_from : csp->cp_from;

        dp->convtype = 0;

        if (cspf)
                dp->convtype |= KICONV_UCS_COMBINE;
        for (i = 0; unicode_family[i].name; i++) {
                if (strcasecmp(from, unicode_family[i].name) == 0)
                        dp->convtype |= unicode_family[i].from_flag;
                if (strcasecmp(to, unicode_family[i].name) == 0)
                        dp->convtype |= unicode_family[i].to_flag;
        }
        if (strcmp(ENCODING_UNICODE, ENCODING_UTF16) == 0)
                dp->convtype |= KICONV_UCS_UCS4;
        else
                dp->convtype &= ~KICONV_UCS_UCS4;

        dp->f_ctp = dp->t_ctp = NULL;
        if (dp->convtype & KICONV_UCS_COMBINE) {
                if ((dp->convtype & KICONV_UCS_FROM_UTF8) == 0 &&
                    (dp->convtype & KICONV_UCS_FROM_LE) == 0) {
                        iconv_open(ENCODING_UNICODE, from, &dp->f_ctp);
                }
                if ((dp->convtype & KICONV_UCS_TO_UTF8) == 0 &&
                    (dp->convtype & KICONV_UCS_TO_LE) == 0) {
                        iconv_open(to, ENCODING_UNICODE, &dp->t_ctp);
                }
        }

        dp->ctype = NULL;
        if (dp->convtype & (KICONV_UCS_FROM_UTF8 | KICONV_UCS_TO_UTF8))
                iconv_open(KICONV_WCTYPE_NAME, ENCODING_UTF8, &dp->ctype);

        dp->d_csp = csp;
        if (dp->convtype & (KICONV_UCS_FROM_UTF8 | KICONV_UCS_FROM_LE)) {
                if (cspf) {
                        dp->d_cspf = cspf;
                        cspf->cp_refcount++;
                } else
                        csp->cp_refcount++;
        }
        if (dp->convtype & (KICONV_UCS_TO_UTF8 | KICONV_UCS_TO_LE))
                csp->cp_refcount++;
        *dpp = (void*)dp;
        return 0;
}

static int
iconv_ucs_close(void *data)
{
        struct iconv_ucs *dp = data;

        if (dp->f_ctp)
                iconv_close(dp->f_ctp);
        if (dp->t_ctp)
                iconv_close(dp->t_ctp);
        if (dp->ctype)
                iconv_close(dp->ctype);
        if (dp->d_cspf)
                dp->d_cspf->cp_refcount--;
        else if (dp->convtype & (KICONV_UCS_FROM_UTF8 | KICONV_UCS_FROM_LE))
                dp->d_csp->cp_refcount--;
        if (dp->convtype & (KICONV_UCS_TO_UTF8 | KICONV_UCS_TO_LE))
                dp->d_csp->cp_refcount--;
        kobj_delete((struct kobj*)data, M_ICONV);
        return 0;
}

static int
iconv_ucs_conv(void *d2p, const char **inbuf,
        size_t *inbytesleft, char **outbuf, size_t *outbytesleft,
        int convchar, int casetype)
{
        struct iconv_ucs *dp = (struct iconv_ucs*)d2p;
        int ret = 0, i;
        size_t in, on, ir, or, inlen, outlen, ucslen;
        const char *src, *p;
        char *dst;
        u_char ucs[4], *q;
        uint32_t code;

        if (inbuf == NULL || *inbuf == NULL || outbuf == NULL || *outbuf == NULL)
                return 0;
        ir = in = *inbytesleft;
        or = on = *outbytesleft;
        src = *inbuf;
        dst = *outbuf;

        while (ir > 0 && or > 0) {
                /*
                 * The first half of conversion.
                 * (convert any code into ENCODING_UNICODE)
                 */
                code = 0;
                p = src;
                if (dp->convtype & KICONV_UCS_FROM_UTF8) {
                        /* convert UTF-8 to ENCODING_UNICODE */
                        inlen = 0;
                        code = utf8_to_ucs4(p, &inlen, ir);
                        if (code == 0) {
                                ret = -1;
                                break;
                        }

                        if (casetype == KICONV_FROM_LOWER && dp->ctype) {
                                code = towlower(code, dp->ctype);
                        } else if (casetype == KICONV_FROM_UPPER && dp->ctype) {
                                code = towupper(code, dp->ctype);
                        }

                        if ((code >= 0xd800 && code < 0xe000) || code >= 0x110000 ) {
                                /* reserved for utf-16 surrogate pair */
                                /* invalid unicode */
                                ret = -1;
                                break;
                        }

                        if (inlen == 4) {
                                if (dp->convtype & KICONV_UCS_UCS4) {
                                        ucslen = 4;
                                        code = encode_surrogate(code);
                                } else {
                                        /* can't handle with ucs-2 */
                                        ret = -1;
                                        break;
                                }
                        } else {
                                ucslen = 2;
                        }

                        /* save UCS-4 into ucs[] */
                        for (q = ucs, i = ucslen - 1 ; i >= 0 ; i--)
                                *q++ = (code >> (i << 3)) & 0xff;

                } else if (dp->convtype & KICONV_UCS_COMBINE && dp->f_ctp) {
                        /* convert local code to ENCODING_UNICODE */
                        ucslen = 4;
                        inlen = ir;
                        q = ucs;
                        ret = iconv_convchr_case(dp->f_ctp, &p, &inlen, (char **)&q,
                            &ucslen, casetype & (KICONV_FROM_LOWER | KICONV_FROM_UPPER));
                        if (ret)
                                break;
                        inlen = ir - inlen;
                        ucslen = 4 - ucslen;

                } else {
                        /* src code is a proper subset of ENCODING_UNICODE */
                        q = ucs;
                        if (dp->convtype & KICONV_UCS_FROM_LE) {
                                *q = *(p + 1);
                                *(q + 1) = *p;
                                p += 2;
                        } else {
                                *q = *p++;
                                *(q + 1) = *p++;
                        }
                        if ((*q & 0xfc) == 0xd8) {
                                if (dp->convtype & KICONV_UCS_UCS4 &&
                                    dp->convtype & KICONV_UCS_FROM_UTF16) {
                                        inlen = ucslen = 4;
                                } else {
                                        /* invalid unicode */
                                        ret = -1;
                                        break;
                                }
                        } else {
                                inlen = ucslen = 2;
                        }
                        if (ir < inlen) {
                                ret = -1;
                                break;
                        }
                        if (ucslen == 4) {
                                q += 2;
                                if (dp->convtype & KICONV_UCS_FROM_LE) {
                                        *q = *(p + 1);
                                        *(q + 1) = *p;
                                } else {
                                        *q = *p++;
                                        *(q + 1) = *p;
                                }
                                if ((*q & 0xfc) != 0xdc) {
                                        /* invalid unicode */
                                        ret = -1;
                                        break;
                                }
                        }
                }

                /*
                 * The second half of conversion.
                 * (convert ENCODING_UNICODE into any code)
                 */
                p = ucs;
                if (dp->convtype & KICONV_UCS_TO_UTF8) {
                        q = (u_char *)dst;
                        if (ucslen == 4 && dp->convtype & KICONV_UCS_UCS4) {
                                /* decode surrogate pair */
                                code = decode_surrogate(p);
                        } else {
                                code = (ucs[0] << 8) | ucs[1];
                        }

                        if (casetype == KICONV_LOWER && dp->ctype) {
                                code = towlower(code, dp->ctype);
                        } else if (casetype == KICONV_UPPER && dp->ctype) {
                                code = towupper(code, dp->ctype);
                        }

                        outlen = 0;
                        if (ucs4_to_utf8(code, q, &outlen, or) == NULL) {
                                ret = -1;
                                break;
                        }

                        src += inlen;
                        ir -= inlen;
                        dst += outlen;
                        or -= outlen;

                } else if (dp->convtype & KICONV_UCS_COMBINE && dp->t_ctp) {
                        ret = iconv_convchr_case(dp->t_ctp, &p, &ucslen, &dst,
                            &or, casetype & (KICONV_LOWER | KICONV_UPPER));
                        if (ret)
                                break;

                        src += inlen;
                        ir -= inlen;

                } else {
                        /* dst code is a proper subset of ENCODING_UNICODE */
                        if (or < ucslen) {
                                ret = -1;
                                break;
                        }
                        src += inlen;
                        ir -= inlen;
                        or -= ucslen;
                        if (dp->convtype & KICONV_UCS_TO_LE) {
                                *dst++ = *(p + 1);
                                *dst++ = *p;
                                p += 2;
                        } else {
                                *dst++ = *p++;
                                *dst++ = *p++;
                        }
                        if (ucslen == 4) {
                                if ((dp->convtype & KICONV_UCS_UCS4) == 0 ||
                                    (dp->convtype & KICONV_UCS_TO_UTF16) == 0) {
                                        ret = -1;
                                        break;
                                }
                                if (dp->convtype & KICONV_UCS_TO_LE) {
                                        *dst++ = *(p + 1);
                                        *dst++ = *p;
                                } else {
                                        *dst++ = *p++;
                                        *dst++ = *p;
                                }
                        }
                }

                if (convchar == 1)
                        break;
        }

        *inbuf += in - ir;
        *outbuf += on - or;
        *inbytesleft -= in - ir;
        *outbytesleft -= on - or;
        return (ret);
}

static int
iconv_ucs_init(struct iconv_converter_class *dcp)
{
        int error;

        error = iconv_add(ENCODING_UNICODE, ENCODING_UNICODE, ENCODING_UTF8);
        if (error)
                return (error);
        error = iconv_add(ENCODING_UNICODE, ENCODING_UTF8, ENCODING_UNICODE);
        if (error)
                return (error);
        return (0);
}

static int
iconv_ucs_done(struct iconv_converter_class *dcp)
{
        return (0);
}

static const char *
iconv_ucs_name(struct iconv_converter_class *dcp)
{
        return (ENCODING_UNICODE);
}

static kobj_method_t iconv_ucs_methods[] = {
        KOBJMETHOD(iconv_converter_open,        iconv_ucs_open),
        KOBJMETHOD(iconv_converter_close,       iconv_ucs_close),
        KOBJMETHOD(iconv_converter_conv,        iconv_ucs_conv),
        KOBJMETHOD(iconv_converter_init,        iconv_ucs_init),
        KOBJMETHOD(iconv_converter_done,        iconv_ucs_done),
        KOBJMETHOD(iconv_converter_name,        iconv_ucs_name),
        {0, 0}
};

KICONV_CONVERTER(ucs, sizeof(struct iconv_ucs));

static uint32_t
utf8_to_ucs4(const char *src, size_t *utf8width, size_t srclen)
{
        size_t i, w = 0;
        uint32_t ucs4 = 0;

        /*
         * get leading 1 byte from utf-8
         */
        if ((*src & 0x80) == 0) {
                /*
                 * leading 1 bit is "0"
                 *  utf-8: 0xxxxxxx
                 *  ucs-4: 00000000 00000000 00000000 0xxxxxxx
                 */
                w = 1;
                /* get trailing 7 bits */
                ucs4 = *src & 0x7f;
        } else if ((*src & 0xe0) == 0xc0) {
                /*
                 * leading 3 bits are "110"
                 *  utf-8: 110xxxxx 10yyyyyy
                 *  ucs-4: 00000000 00000000 00000xxx xxyyyyyy
                 */
                w = 2;
                /* get trailing 5 bits */
                ucs4 = *src & 0x1f;
        } else if ((*src & 0xf0) == 0xe0) {
                /*
                 * leading 4 bits are "1110"
                 *  utf-8: 1110xxxx 10yyyyyy 10zzzzzz
                 *  ucs-4: 00000000 00000000 xxxxyyyy yyzzzzzz
                 */
                w = 3;
                /* get trailing 4 bits */
                ucs4 = *src & 0x0f;
        } else if ((*src & 0xf8) == 0xf0) {
                /*
                 * leading 5 bits are "11110"
                 *  utf-8: 11110www 10xxxxxx 10yyyyyy 10zzzzzz
                 *  ucs-4: 00000000 000wwwxx xxxxyyyy yyzzzzzz
                 */
                w = 4;
                /* get trailing 3 bits */
                ucs4 = *src & 0x07;
        } else {
                /* out of utf-16 range or having illegal bits */
                return (0);
        }

        if (srclen < w)
                return (0);

        /*
         * get left parts from utf-8
         */
        for (i = 1 ; i < w ; i++) {
                if ((*(src + i) & 0xc0) != 0x80) {
                        /* invalid: leading 2 bits are not "10" */
                        return (0);
                }
                /* concatenate trailing 6 bits into ucs4 */
                ucs4 <<= 6;
                ucs4 |= *(src + i) & 0x3f;
        }

        *utf8width = w;
        return (ucs4);
}

static u_char *
ucs4_to_utf8(uint32_t ucs4, char *dst, size_t *utf8width, size_t dstlen)
{
        u_char lead, *p;
        size_t i, w;

        /*
         * determine utf-8 width and leading bits
         */
        if (ucs4 < 0x80) {
                w = 1;
                lead = 0;       /* "0" */
        } else if (ucs4 < 0x800) {
                w = 2;
                lead = 0xc0;    /* "11" */
        } else if (ucs4 < 0x10000) {
                w = 3;
                lead = 0xe0;    /* "111" */
        } else if (ucs4 < 0x200000) {
                w = 4;
                lead = 0xf0;    /* "1111" */
        } else {
                return (NULL);
        }

        if (dstlen < w)
                return (NULL);

        /*
         * construct utf-8
         */
        p = dst;
        for (i = w - 1 ; i >= 1 ; i--) {
                /* get trailing 6 bits and put it with leading bit as "1" */
                *(p + i) = (ucs4 & 0x3f) | 0x80;
                ucs4 >>= 6;
        }
        *p = ucs4 | lead;

        *utf8width = w;

        return (p);
}

static uint32_t
encode_surrogate(uint32_t code)
{
        return ((((code - 0x10000) << 6) & 0x3ff0000) |
            ((code - 0x10000) & 0x3ff) | 0xd800dc00);
}

static uint32_t
decode_surrogate(const u_char *ucs)
{
        return ((((ucs[0] & 0x3) << 18) | (ucs[1] << 10) |
            ((ucs[2] & 0x3) << 8) | ucs[3]) + 0x10000);
}