#include "hoedown/escape.h"

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


#define likely(x)       __builtin_expect((x),1)
#define unlikely(x)     __builtin_expect((x),0)


/*
 * The following characters will not be escaped:
 *
 *        -_.+!*'(),%#@?=;:/,+&$ alphanum
 *
 * Note that this character set is the addition of:
 *
 *    - The characters which are safe to be in an URL
 *    - The characters which are *not* safe to be in
 *    an URL because they are RESERVED characters.
 *
 * We assume (lazily) that any RESERVED char that
 * appears inside an URL is actually meant to
 * have its native function (i.e. as an URL
 * component/separator) and hence needs no escaping.
 *
 * There are two exceptions: the chacters & (amp)
 * and ' (single quote) do not appear in the table.
 * They are meant to appear in the URL as components,
 * yet they require special HTML-entity escaping
 * to generate valid HTML markup.
 *
 * All other characters will be escaped to %XX.
 *
 */
static const uint8_t HREF_SAFE[UINT8_MAX+1] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

void
hoedown_escape_href(hoedown_buffer *ob, const uint8_t *data, size_t size)
{
    static const char hex_chars[] = "0123456789ABCDEF";
    size_t  i = 0, mark;
    char hex_str[3];

    hex_str[0] = '%';

    while (i < size) {
        mark = i;
        while (i < size && HREF_SAFE[data[i]]) i++;

        /* Optimization for cases where there's nothing to escape */
        if (mark == 0 && i >= size) {
            hoedown_buffer_put(ob, data, size);
            return;
        }

        if (likely(i > mark)) {
            hoedown_buffer_put(ob, data + mark, i - mark);
        }

        /* escaping */
        if (i >= size)
            break;

        switch (data[i]) {
        /* amp appears all the time in URLs, but needs
         * HTML-entity escaping to be inside an href */
        case '&':
            HOEDOWN_BUFPUTSL(ob, "&amp;");
            break;

        /* the single quote is a valid URL character
         * according to the standard; it needs HTML
         * entity escaping too */
        case '\'':
            HOEDOWN_BUFPUTSL(ob, "&#x27;");
            break;

        /* the space can be escaped to %20 or a plus
         * sign. we're going with the generic escape
         * for now. the plus thing is more commonly seen
         * when building GET strings */
#if 0
        case ' ':
            hoedown_buffer_putc(ob, '+');
            break;
#endif

        /* every other character goes with a %XX escaping */
        default:
            hex_str[1] = hex_chars[(data[i] >> 4) & 0xF];
            hex_str[2] = hex_chars[data[i] & 0xF];
            hoedown_buffer_put(ob, (uint8_t *)hex_str, 3);
        }

        i++;
    }
}


/**
 * According to the OWASP rules:
 *
 * & --> &amp;
 * < --> &lt;
 * > --> &gt;
 * " --> &quot;
 * ' --> &#x27;     &apos; is not recommended
 * / --> &#x2F;     forward slash is included as it helps end an HTML entity
 *
 */
static const uint8_t HTML_ESCAPE_TABLE[UINT8_MAX+1] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 1, 0, 0, 0, 2, 3, 0, 0, 0, 0, 0, 0, 0, 4,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 6, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

static const char *HTML_ESCAPES[] = {
        "",
        "&quot;",
        "&amp;",
        "&#39;",
        "&#47;",
        "&lt;",
        "&gt;"
};

void
hoedown_escape_html(hoedown_buffer *ob, const uint8_t *data, size_t size, int secure)
{
    size_t i = 0, mark;

    while (1) {
        mark = i;
        while (i < size && HTML_ESCAPE_TABLE[data[i]] == 0) i++;

        /* Optimization for cases where there's nothing to escape */
        if (mark == 0 && i >= size) {
            hoedown_buffer_put(ob, data, size);
            return;
        }

        if (likely(i > mark))
            hoedown_buffer_put(ob, data + mark, i - mark);

        if (i >= size) break;

        /* The forward slash is only escaped in secure mode */
        if (!secure && data[i] == '/') {
            hoedown_buffer_putc(ob, '/');
        } else {
            hoedown_buffer_puts(ob, HTML_ESCAPES[HTML_ESCAPE_TABLE[data[i]]]);
        }

        i++;
    }
}
