path: root/e-util/e-html-utils.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/* e-html-utils.c
 * Copyright (C) 2000  Helix Code, Inc.
 * Author: Dan Winship <danw@helixcode.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <glib.h>
#include <unicode.h>

#include "e-html-utils.h"

static char *
check_size (char **buffer, int *buffer_size, char *out, int len)
{
    if (out + len > *buffer + *buffer_size) {
        int index = out - *buffer;

        *buffer_size *= 2;
        *buffer = g_realloc (*buffer, *buffer_size);
        out = *buffer + index;
    }
    return out;
}

static char *
url_extract (const unsigned char **text, gboolean check)
{
    const unsigned char *end = *text, *p;
    char *out;

    while (*end && !isspace (*end) && (*end != '"') && (*end < 0x80))
        end++;

    /* Back up if we probably went too far. */
    while (end > *text && strchr (",.!?;:>)]}", *(end - 1)))
        end--;

    if (check) {
        /* Make sure we weren't fooled. */
        p = memchr (*text, ':', end - *text);
        if (!p || end - p < 4)
            return NULL;
    }

    out = g_strndup (*text, end - *text);
    *text = end;
    return out;
}

static gboolean
is_citation (const unsigned char *c)
{
    unicode_char_t u;
    gint i;

    for (i = 0; c && *c && i < 10; i ++, c = unicode_next_utf8 (c)) {
        unicode_get_utf8 (c, &u);
        if (u == '>')
            return TRUE;
        if (!unicode_isalnum (u))
            return FALSE;
    }
    return FALSE;
}

/**
 * e_text_to_html_full:
 * @input: a NUL-terminated input buffer
 * @flags: some combination of the E_TEXT_TO_HTML_* flags defined
 * in e-html-utils.h
 * @color: color for citation highlighting
 *
 * This takes a buffer of text as input and produces a buffer of
 * "equivalent" HTML, subject to certain transformation rules.
 *
 * The set of possible flags is:
 *
 *   - E_TEXT_TO_HTML_PRE: wrap the output HTML in <PRE> and </PRE>.
 *     Should only be used if @input is the entire buffer to be
 *     converted. If e_text_to_html is being called with small pieces
 *     of data, you should wrap the entire result in <PRE> yourself.
 *
 *   - E_TEXT_TO_HTML_CONVERT_NL: convert "\n" to "<BR>\n" on output.
 *     (should not be used with E_TEXT_TO_HTML_PRE, since that would
 *     result in double-newlines).
 *
 *   - E_TEXT_TO_HTML_CONVERT_SPACES: convert a block of N spaces
 *     into N-1 non-breaking spaces and one normal space. A space
 *     at the start of the buffer is always converted to a
 *     non-breaking space, regardless of the following character,
 *     which probably means you don't want to use this flag on
 *     pieces of data that aren't delimited by at least line breaks.
 *
 *     If E_TEXT_TO_HTML_CONVERT_NL and E_TEXT_TO_HTML_CONVERT_SPACES
 *     are both defined, then TABs will also be converted to spaces.
 *
 *   - E_TEXT_TO_HTML_CONVERT_URLS: wrap <a href="..."> </a> around
 *     strings that look like URLs.
 *
 *   - E_TEXT_TO_HTML_MARK_CITATION: wrap <font color="blue"> </font> around
 *     citations (lines beginning with "> ").
 **/
char *
e_text_to_html_full (const char *input, unsigned int flags, guint32 color)
{
    const unsigned char *cur = input;
    char *buffer = NULL;
    char *out = NULL;
    int buffer_size = 0, col;
    gboolean colored = FALSE;

    /* Allocate a translation buffer.  */
    buffer_size = strlen (input) * 2 + 5;
    buffer = g_malloc (buffer_size);

    out = buffer;
    if (flags & E_TEXT_TO_HTML_PRE)
        out += sprintf (out, "<PRE>\n");

    col = 0;

    for (cur = input; cur && *cur; cur = unicode_next_utf8 (cur)) {
        unicode_char_t u;

        unicode_get_utf8 (cur, &u);
        if (flags & E_TEXT_TO_HTML_MARK_CITATION && col == 0) {
            if (is_citation (cur)) {
                if (!colored) {
                    gchar font [25];

                    g_snprintf (font, 25, "<FONT COLOR=\"#%06x\">", color);

                    check_size (&buffer, &buffer_size, out, 25);
                    out += sprintf (out, "%s", font);
                    colored = TRUE;
                }
            } else if (colored) {
                gchar *no_font = "</FONT>";

                check_size (&buffer, &buffer_size, out, 9);
                out += sprintf (out, "%s", no_font);
                colored = FALSE;
            }
        }

        if (unicode_isalpha (u) &&
            (flags & E_TEXT_TO_HTML_CONVERT_URLS)) {
            char *tmpurl = NULL, *refurl = NULL, *dispurl = NULL;

            if (!strncasecmp (cur, "http://", 7) ||
                !strncasecmp (cur, "https://", 8) ||
                !strncasecmp (cur, "ftp://", 6) ||
                !strncasecmp (cur, "nntp://", 7) ||
                !strncasecmp (cur, "mailto:", 7) ||
                !strncasecmp (cur, "news:", 5)) {
                tmpurl = url_extract (&cur, TRUE);
                if (tmpurl) {
                    refurl = e_text_to_html (tmpurl, 0);
                    dispurl = g_strdup (refurl);
                }
            } else if (!strncasecmp (cur, "www.", 4) &&
                   (*(cur + 4) < 0x80) &&
                   unicode_isalnum (*(cur + 4))) {
                tmpurl = url_extract (&cur, FALSE);
                dispurl = e_text_to_html (tmpurl, 0);
                refurl = g_strdup_printf ("http://%s",
                              dispurl);
            }

            if (tmpurl) {
                out = check_size (&buffer, &buffer_size, out,
                          strlen (refurl) +
                          strlen (dispurl) + 15);
                out += sprintf (out,
                        "<a href=\"%s\">%s</a>",
                        refurl, dispurl);
                col += strlen (tmpurl);
                g_free (tmpurl);
                g_free (refurl);
                g_free (dispurl);
            }

            if (!*cur)
                break;
            unicode_get_utf8 (cur, &u);
        }
        if (u == (unicode_char_t)-1) {
            /* Sigh. Someone sent undeclared 8-bit data.
             * Assume it's iso-8859-1.
             */
            u = *cur;
        }

        out = check_size (&buffer, &buffer_size, out, 10);

        switch (u) {
        case '<':
            strcpy (out, "&lt;");
            out += 4;
            col++;
            break;

        case '>':
            strcpy (out, "&gt;");
            out += 4;
            col++;
            break;

        case '&':
            strcpy (out, "&amp;");
            out += 5;
            col++;
            break;

        case '"':
            strcpy (out, "&quot;");
            out += 6;
            col++;
            break;

        case '\n':
            if (flags & E_TEXT_TO_HTML_CONVERT_NL) {
                strcpy (out, "<br>");
                out += 4;
            }
            *out++ = *cur;
            col = 0;
            break;

        case '\t':
            if (flags & (E_TEXT_TO_HTML_CONVERT_SPACES |
                     E_TEXT_TO_HTML_CONVERT_NL)) {
                do {
                    out = check_size (&buffer, &buffer_size,
                            out, 7);
                    strcpy (out, "&nbsp;");
                    out += 6;
                    col++;
                } while (col % 8);
                break;
            }
            /* otherwise, FALL THROUGH */

        case ' ':
            if (flags & E_TEXT_TO_HTML_CONVERT_SPACES) {
                if (cur == (const unsigned char *)input ||
                    *(cur + 1) == ' ' || *(cur + 1) == '\t') {
                    strcpy (out, "&nbsp;");
                    out += 6;
                    col++;
                    break;
                }
            }
            /* otherwise, FALL THROUGH */

        default:
            if ((u >= 0x20 && u < 0x80) ||
                (u == '\r' || u == '\t')) {
                /* Default case, just copy. */
                *out++ = u;
            } else {
                out += g_snprintf(out, 9, "&#%d;", u);
            }
            col++;
            break;
        }
    }

    out = check_size (&buffer, &buffer_size, out, 7);
    if (flags & E_TEXT_TO_HTML_PRE)
        strcpy (out, "</PRE>");
    else
        *out = '\0';

    return buffer;
}

char *
e_text_to_html (const char *input, unsigned int flags)
{
    return e_text_to_html_full (input, flags, 0);
}