/*
 * Copyright (c) 2009-2016 Petri Lehtinen <petri@digip.org>
 *
 * Jansson is free software; you can redistribute it and/or modify
 * it under the terms of the MIT license.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
 */

/*escaping from https://github.com/akheron/jansson dump.c */

#include "string_escape.h"


size_t utf8_check_first(char byte)
{
    unsigned char u = (unsigned char)byte;

    if(u < 0x80)
        return 1;

    if(0x80 <= u && u <= 0xBF) {
        /* second, third or fourth byte of a multi-byte
           sequence, i.e. a "continuation byte" */
        return 0;
    }
    else if(u == 0xC0 || u == 0xC1) {
        /* overlong encoding of an ASCII byte */
        return 0;
    }
    else if(0xC2 <= u && u <= 0xDF) {
        /* 2-byte sequence */
        return 2;
    }

    else if(0xE0 <= u && u <= 0xEF) {
        /* 3-byte sequence */
        return 3;
    }
    else if(0xF0 <= u && u <= 0xF4) {
        /* 4-byte sequence */
        return 4;
    }
    else { /* u >= 0xF5 */
        /* Restricted (start of 4-, 5- or 6-byte sequence) or invalid
           UTF-8 */
        return 0;
    }
}

size_t utf8_check_full(const char *buffer, size_t size, int32_t *codepoint)
{
    size_t i;
    int32_t value = 0;
    unsigned char u = (unsigned char)buffer[0];

    if(size == 2)
    {
        value = u & 0x1F;
    }
    else if(size == 3)
    {
        value = u & 0xF;
    }
    else if(size == 4)
    {
        value = u & 0x7;
    }
    else
        return 0;

    for(i = 1; i < size; i++)
    {
        u = (unsigned char)buffer[i];

        if(u < 0x80 || u > 0xBF) {
            /* not a continuation byte */
            return 0;
        }

        value = (value << 6) + (u & 0x3F);
    }

    if(value > 0x10FFFF) {
        /* not in Unicode range */
        return 0;
    }

    else if(0xD800 <= value && value <= 0xDFFF) {
        /* invalid code point (UTF-16 surrogate halves) */
        return 0;
    }

    else if((size == 2 && value < 0x80) ||
            (size == 3 && value < 0x800) ||
            (size == 4 && value < 0x10000)) {
        /* overlong encoding */
        return 0;
    }

    if(codepoint)
        *codepoint = value;

    return 1;
}

const char *utf8_iterate(const char *buffer, size_t bufsize, int32_t *codepoint)
{
    size_t count;
    int32_t value;

    if(!bufsize)
        return buffer;

    count = utf8_check_first(buffer[0]);
    if(count <= 0)
        return NULL;

    if(count == 1)
        value = (unsigned char)buffer[0];
    else
    {
        if(count > bufsize || !utf8_check_full(buffer, count, &value))
            return NULL;
    }

    if(codepoint)
        *codepoint = value;

    return buffer + count;
}

/* String unescape functions */
int utf8_encode(int32_t codepoint, char *buffer, size_t *size)
{
    if(codepoint < 0)
        return -1;
    else if(codepoint < 0x80)
    {
        buffer[0] = (char)codepoint;
        *size = 1;
    }
    else if(codepoint < 0x800)
    {
        buffer[0] = (char)(0xC0 + ((codepoint & 0x7C0) >> 6));
        buffer[1] = (char)(0x80 + ((codepoint & 0x03F)));
        *size = 2;
    }
    else if(codepoint < 0x10000)
    {
        buffer[0] = (char)(0xE0 + ((codepoint & 0xF000) >> 12));
        buffer[1] = (char)(0x80 + ((codepoint & 0x0FC0) >> 6));
        buffer[2] = (char)(0x80 + ((codepoint & 0x003F)));
        *size = 3;
    }
    else if(codepoint <= 0x10FFFF)
    {
        buffer[0] = (char)(0xF0 + ((codepoint & 0x1C0000) >> 18));
        buffer[1] = (char)(0x80 + ((codepoint & 0x03F000) >> 12));
        buffer[2] = (char)(0x80 + ((codepoint & 0x000FC0) >> 6));
        buffer[3] = (char)(0x80 + ((codepoint & 0x00003F)));
        *size = 4;
    }
    else
        return -1;

    return 0;
}

/* assumes that str points to 'u' plus at least 4 valid hex digits */
int32_t decode_unicode_escape(const char *str) {
    int i;
    int32_t value = 0;

    for(i = 1; i <= 4; i++) {
        char c = str[i];
        value <<= 4;
        if(l_isdigit(c))
            value += c - '0';
        else if(l_islower(c))
            value += c - 'a' + 10;
        else if(l_isupper(c))
            value += c - 'A' + 10;
        else
            return -1;
    }

    return value;
}