/*      $OpenBSD: preconv.c,v 1.9 2018/12/13 11:55:14 schwarze Exp $ */
/*
 * Copyright (c) 2011 Kristaps Dzonsons <kristaps@bsd.lv>
 * Copyright (c) 2014 Ingo Schwarze <schwarze@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <sys/types.h>

#include <assert.h>
#include <stdio.h>
#include <string.h>

#include "mandoc.h"
#include "roff.h"
#include "mandoc_parse.h"
#include "libmandoc.h"

int
preconv_encode(const struct buf *ib, size_t *ii, struct buf *ob, size_t *oi,
    int *filenc)
{
        const unsigned char     *cu;
        int                      nby;
        unsigned int             accum;

        cu = (const unsigned char *)ib->buf + *ii;
        assert(*cu & 0x80);

        if ( ! (*filenc & MPARSE_UTF8))
                goto latin;

        nby = 1;
        while (nby < 5 && *cu & (1 << (7 - nby)))
                nby++;

        switch (nby) {
        case 2:
                accum = *cu & 0x1f;
                if (accum < 0x02)  /* Obfuscated ASCII. */
                        goto latin;
                break;
        case 3:
                accum = *cu & 0x0f;
                break;
        case 4:
                accum = *cu & 0x07;
                if (accum > 0x04) /* Beyond Unicode. */
                        goto latin;
                break;
        default:  /* Bad sequence header. */
                goto latin;
        }

        cu++;
        switch (nby) {
        case 3:
                if ((accum == 0x00 && ! (*cu & 0x20)) ||  /* Use 2-byte. */
                    (accum == 0x0d && *cu & 0x20))  /* Surrogates. */
                        goto latin;
                break;
        case 4:
                if ((accum == 0x00 && ! (*cu & 0x30)) ||  /* Use 3-byte. */
                    (accum == 0x04 && *cu & 0x30))  /* Beyond Unicode. */
                        goto latin;
                break;
        default:
                break;
        }

        while (--nby) {
                if ((*cu & 0xc0) != 0x80)  /* Invalid continuation. */
                        goto latin;
                accum <<= 6;
                accum += *cu & 0x3f;
                cu++;
        }

        assert(accum > 0x7f);
        assert(accum < 0x110000);
        assert(accum < 0xd800 || accum > 0xdfff);

        *oi += snprintf(ob->buf + *oi, 11, "\\[u%.4X]", accum);
        *ii = (const char *)cu - ib->buf;
        *filenc &= ~MPARSE_LATIN1;
        return 1;

latin:
        if ( ! (*filenc & MPARSE_LATIN1))
                return 0;

        *oi += snprintf(ob->buf + *oi, 11,
            "\\[u%.4X]", (unsigned char)ib->buf[(*ii)++]);

        *filenc &= ~MPARSE_UTF8;
        return 1;
}

int
preconv_cue(const struct buf *b, size_t offset)
{
        const char      *ln, *eoln, *eoph;
        size_t           sz, phsz;

        ln = b->buf + offset;
        sz = b->sz - offset;

        /* Look for the end-of-line. */

        if (NULL == (eoln = memchr(ln, '\n', sz)))
                eoln = ln + sz;

        /* Check if we have the correct header/trailer. */

        if ((sz = (size_t)(eoln - ln)) < 10 ||
            memcmp(ln, ".\\\" -*-", 7) || memcmp(eoln - 3, "-*-", 3))
                return MPARSE_UTF8 | MPARSE_LATIN1;

        /* Move after the header and adjust for the trailer. */

        ln += 7;
        sz -= 10;

        while (sz > 0) {
                while (sz > 0 && ' ' == *ln) {
                        ln++;
                        sz--;
                }
                if (0 == sz)
                        break;

                /* Find the end-of-phrase marker (or eoln). */

                if (NULL == (eoph = memchr(ln, ';', sz)))
                        eoph = eoln - 3;
                else
                        eoph++;

                /* Only account for the "coding" phrase. */

                if ((phsz = eoph - ln) < 7 ||
                    strncasecmp(ln, "coding:", 7)) {
                        sz -= phsz;
                        ln += phsz;
                        continue;
                }

                sz -= 7;
                ln += 7;

                while (sz > 0 && ' ' == *ln) {
                        ln++;
                        sz--;
                }
                if (0 == sz)
                        return 0;

                /* Check us against known encodings. */

                if (phsz > 4 && !strncasecmp(ln, "utf-8", 5))
                        return MPARSE_UTF8;
                if (phsz > 10 && !strncasecmp(ln, "iso-latin-1", 11))
                        return MPARSE_LATIN1;
                return 0;
        }
        return MPARSE_UTF8 | MPARSE_LATIN1;
}