/*
 * Copyright (C) 2013 by egnite GmbH
 * Copyright (c) 1989, 1993 The Regents of the University of California
 *
 * 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.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 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.
 *
 * For additional information see http://www.ethernut.de/
 */

#include <sys/types.h>
#include <ctype.h>
#include <vis.h>

/*
 * Decode driven by state machine
 */
#define S_GROUND    0   /*!< \brief haven't seen escape char */
#define S_START     1   /*!< \brief start decoding special sequence */
#define S_META      2   /*!< \brief metachar started (M) */
#define S_META1     3   /*!< \brief metachar more, regular char (-) */
#define S_CTRL      4   /*!< \brief control char started (^) */
#define S_OCTAL2    5   /*!< \brief octal digit 2 */
#define S_OCTAL3    6   /*!< \brief octal digit 3 */
#define S_HEX1      7   /*!< \brief hex digit */
#define S_HEX2      8   /*!< \brief hex digit 2 */

#define isoctal(c)  (((unsigned char)(c)) >= '0' && ((unsigned char)(c)) <= '7')
#define xtod(c)     (isdigit(c) ? ((c) - '0') : ((tolower(c) - 'a') + 10))

/*!
 * \brief Decode a visual representation of characters.
 *
 * This function is the inverse function of vis(). It reverts a visual
 * representation of data back to its original form.
 */
int unvis(char *cp, int c, int *astate, int flag)
{

    if (flag & UNVIS_END) {
        if (*astate == S_OCTAL2 || *astate == S_OCTAL3 || *astate == S_HEX2) {
            *astate = S_GROUND;
            return UNVIS_VALID;
        }
        return *astate == S_GROUND ? UNVIS_NOCHAR : UNVIS_SYNBAD;
    }

    switch (*astate) {

    case S_GROUND:
        *cp = 0;
        if (c == '\\') {
            *astate = S_START;
            return 0;
        }
        if ((flag & VIS_HTTPSTYLE) && c == '%') {
            *astate = S_HEX1;
            return 0;
        }
        *cp = c;
        return UNVIS_VALID;

    case S_START:
        switch (c) {
        case '\\':
            *cp = c;
            *astate = S_GROUND;
            return UNVIS_VALID;
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
            *cp = (c - '0');
            *astate = S_OCTAL2;
            return 0;
        case 'M':
            *cp = (char) 0200;
            *astate = S_META;
            return 0;
        case '^':
            *astate = S_CTRL;
            return 0;
        case 'n':
            *cp = '\n';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'r':
            *cp = '\r';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'b':
            *cp = '\b';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'a':
            *cp = '\007';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'v':
            *cp = '\v';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 't':
            *cp = '\t';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'f':
            *cp = '\f';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 's':
            *cp = ' ';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case 'E':
            *cp = '\033';
            *astate = S_GROUND;
            return UNVIS_VALID;
        case '\n':
            /*
             * hidden newline
             */
            *astate = S_GROUND;
            return UNVIS_NOCHAR;
        case '$':
            /*
             * hidden marker
             */
            *astate = S_GROUND;
            return UNVIS_NOCHAR;
        }
        *astate = S_GROUND;
        return UNVIS_SYNBAD;

    case S_META:
        if (c == '-')
            *astate = S_META1;
        else if (c == '^')
            *astate = S_CTRL;
        else {
            *astate = S_GROUND;
            return UNVIS_SYNBAD;
        }
        return 0;

    case S_META1:
        *astate = S_GROUND;
        *cp |= c;
        return UNVIS_VALID;

    case S_CTRL:
        if (c == '?')
            *cp |= 0177;
        else
            *cp |= c & 037;
        *astate = S_GROUND;
        return UNVIS_VALID;

    case S_OCTAL2:             /* second possible octal digit */
        if (isoctal(c)) {
            /*
             * yes - and maybe a third
             */
            *cp = (*cp << 3) + (c - '0');
            *astate = S_OCTAL3;
            return 0;
        }
        /*
         * no - done with current sequence, push back passed char
         */
        *astate = S_GROUND;
        return UNVIS_VALIDPUSH;

    case S_OCTAL3:             /* third possible octal digit */
        *astate = S_GROUND;
        if (isoctal(c)) {
            *cp = (*cp << 3) + (c - '0');
            return UNVIS_VALID;
        }
        /*
         * we were done, push back passed char
         */
        return UNVIS_VALIDPUSH;

    case S_HEX1:
        if (isxdigit(c)) {
            *cp = xtod(c);
            *astate = S_HEX2;
            return 0;
        }
        /*
         * no - done with current sequence, push back passed char
         */
        *astate = S_GROUND;
        return UNVIS_VALIDPUSH;

    case S_HEX2:
        *astate = S_GROUND;
        if (isxdigit(c)) {
            *cp = xtod(c) | (*cp << 4);
            return UNVIS_VALID;
        }
        return UNVIS_VALIDPUSH;

    default:
        /*
         * decoder in unknown state - (probably uninitialized)
         */
        *astate = S_GROUND;
        return UNVIS_SYNBAD;
    }
}

int strunvisx(char *dst, const char *src, int flag)
{
    char c;
    char *start = dst;
    int state = 0;

    while ((c = *src++)) {
      again:
        switch (unvis(dst, c, &state, flag)) {
        case UNVIS_VALID:
            dst++;
            break;
        case UNVIS_VALIDPUSH:
            dst++;
            goto again;
        case 0:
        case UNVIS_NOCHAR:
            break;
        default:
            *dst = '\0';
            return -1;
        }
    }
    if (unvis(dst, c, &state, UNVIS_END) == UNVIS_VALID)
        dst++;
    *dst = '\0';
    return dst - start;
}

/*!
 * \brief Decode a visually encoded string.
 *
 * This function is the inverse function of strvis().
 */
int strunvis(char *dst, const char *src)
{
    return strunvisx(dst, src, 0);
}

/*!
 * \brief Decode a visually encoded string up to a maximum number of characters.
 *
 */
int strnunvis(char *dst, const char *src, size_t sz)
{
    char c, p;
    char *start = dst, *end = dst + sz - 1;
    int state = 0;

    if (sz > 0)
        *end = '\0';
    while ((c = *src++)) {
      again:
        switch (unvis(&p, c, &state, 0)) {
        case UNVIS_VALID:
            if (dst < end)
                *dst = p;
            dst++;
            break;
        case UNVIS_VALIDPUSH:
            if (dst < end)
                *dst = p;
            dst++;
            goto again;
        case 0:
        case UNVIS_NOCHAR:
            break;
        default:
            if (dst <= end)
                *dst = '\0';
            return -1;
        }
    }
    if (unvis(&p, c, &state, UNVIS_END) == UNVIS_VALID) {
        if (dst < end)
            *dst = p;
        dst++;
    }
    if (dst <= end)
        *dst = '\0';
    return dst - start;
}