path: root/mail/mail-format.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

/*
 * Author :
 *  Matt Loper <matt@helixcode.com>
 *
 *  Copyright 2000, Helix Code, Inc. (http://www.helixcode.com)
 *
 *  This program 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 program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Street #330, Boston, MA 02111-1307, USA.
 *
 */

#include <config.h>
#include "mail-format.h"
#include "camel/hash-table-utils.h"

#include <libgnome/libgnome.h>
#include <ctype.h>    /* for isprint */
#include <string.h>   /* for strstr  */

/* We shouldn't be doing this, but I don't feel like fixing it right
 * now. (It's for gtk_html_stream_write.) When gtkhtml has nicer
 * interfaces, we can fix it.
 */
#include <gtkhtml/gtkhtml-private.h>

static void handle_text_plain           (CamelDataWrapper *wrapper,
                             GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_text_html            (CamelDataWrapper *wrapper,
                             GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_image                (CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_vcard                (CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_mime_part            (CamelDataWrapper *wrapper,
                             GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_multipart_mixed      (CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_multipart_related    (CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_multipart_alternative(CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);
static void handle_unknown_type         (CamelDataWrapper *wrapper,
                         GtkHTMLStreamHandle *stream,
                     CamelDataWrapper *root);

/* encodes some characters into their 'escaped' version;
 * so '<' turns into '&lt;', and '"' turns into '&quot;' */
static gchar *text_to_html (const guchar *input,
                guint len,
                guint *encoded_len_return,
                gboolean convert_newlines_to_br);

/* writes the header info for a mime message into an html stream */
static void write_header_info_to_stream (CamelMimeMessage* mime_message,
                     GtkHTMLStreamHandle *stream);

/* dispatch html printing via mimetype */
static void call_handler_function (CamelDataWrapper *wrapper,
                   gchar *mimetype_whole, 
                   gchar *mimetype_main,
                   GtkHTMLStreamHandle *stream,
                   CamelDataWrapper *root);

#if 0
/**
 * camel_formatter_wrapper_to_html: 
 * @formatter: the camel formatter object
 * @data_wrapper: the data wrapper
 * @stream: byte stream where data will be written 
 *
 * Writes a CamelDataWrapper out, as html, into a stream passed in as
 * a parameter.
 **/
void camel_formatter_wrapper_to_html (CamelFormatter* formatter,
                      CamelDataWrapper* data_wrapper,
                      CamelStream* stream_out)
{
    CamelFormatterPrivate* fmt = formatter->priv;
    gchar *mimetype_whole =
        g_strdup_printf ("%s/%s",
                 data_wrapper->mime_type->type,
                 data_wrapper->mime_type->subtype);

    debug ("camel_formatter_wrapper_to_html: entered\n");
    g_assert (formatter && data_wrapper && stream_out);

    /* give the root CamelDataWrapper and the stream to the formatter */
    initialize_camel_formatter (formatter, data_wrapper, stream_out);
    
    if (stream_out) {
        
        /* write everything to the stream */
        camel_stream_write_string (
            fmt->stream, "<html><body bgcolor=\"white\">\n");
        call_handler_function (
            formatter,
            data_wrapper,
            mimetype_whole,
            data_wrapper->mime_type->type);
        
        camel_stream_write_string (fmt->stream, "\n</body></html>\n");
    }
    

    g_free (mimetype_whole);
}
#endif

/**
 * mail_format_mime_message: 
 * @mime_message: the input mime message
 * @header_stream: HTML stream to write headers to
 * @body_stream: HTML stream to write data to
 *
 * Writes a CamelMimeMessage out, as html, into streams passed in as
 * a parameter. Either stream may be #NULL.
 **/
void
mail_format_mime_message (CamelMimeMessage *mime_message,
              GtkHTMLStreamHandle *header_stream,
              GtkHTMLStreamHandle *body_stream)
{
    g_return_if_fail (CAMEL_IS_MIME_MESSAGE (mime_message));

    /* Write the headers fields out as HTML to the header stream. */
    if (header_stream)
        write_header_info_to_stream (mime_message, header_stream);

    /* Write the contents of the MIME message to the body stream. */
    if (body_stream) {
        mail_write_html (body_stream, "<html><body>\n");
        call_handler_function (CAMEL_DATA_WRAPPER (mime_message),
                       "message/rfc822",
                       "message",
                       body_stream,
                       CAMEL_DATA_WRAPPER (mime_message));
        mail_write_html (body_stream, "\n</body></html>\n");
    }
}

/* We're maintaining a hashtable of mimetypes -> functions;
 * Those functions have the following signature...
 */
typedef void (*mime_handler_fn) (CamelDataWrapper *wrapper,
                 GtkHTMLStreamHandle *stream,
                 CamelDataWrapper *root);

static gchar*
lookup_unique_id (CamelDataWrapper *root, CamelDataWrapper *child)
{
    /* ** FIXME : replace this with a string representing
       the location of the objetc in the tree */
    /* TODO: assert our return value != NULL */

    gchar *temp_hack_uid;

    temp_hack_uid = g_strdup_printf ("%p", camel_data_wrapper_get_output_stream (child));

    return temp_hack_uid;
}

static GHashTable *mime_function_table;

/* This tries to create a tag, given a mimetype and the child of a
 * mime message. It can return NULL if it can't match the mimetype to
 * a bonobo object.
 */
static gchar *
get_bonobo_tag_for_object (CamelDataWrapper *wrapper,
               gchar *mimetype, CamelDataWrapper *root)
{
    char *uid = lookup_unique_id (root, wrapper);
    const char *goad_id = gnome_mime_get_value (mimetype,
                            "bonobo-goad-id");

    if (goad_id) {
        return g_strdup_printf ("<object classid=\"%s\"> "
                    "<param name=\"uid\" "
                    "value=\"camel://%s\"> </object>",
                    goad_id, uid);
    } else
        return NULL;
}


/*
 * This takes a mimetype, and tries to map that mimetype to a function
 * or a bonobo object.
 *
 * - If it's mapped to a bonobo object, this function prints a tag
 *   into the stream, designating the bonobo object and a place that
 *   the bonobo object can find data to hydrate from
 *
 * - otherwise, the mimetype is mapped to another function, which can
 *   print into the stream
 */
static void
call_handler_function (CamelDataWrapper *wrapper,
               gchar *mimetype_whole_in, /* ex. "image/jpeg" */
               gchar *mimetype_main_in, /* ex. "image" */
               GtkHTMLStreamHandle *stream,
               CamelDataWrapper *root)
{
    mime_handler_fn handler_function = NULL;
    gchar *mimetype_whole = NULL;
    gchar *mimetype_main = NULL;

    g_return_if_fail (mimetype_whole_in || mimetype_main_in);
    g_return_if_fail (CAMEL_IS_DATA_WRAPPER (wrapper));
    g_return_if_fail (CAMEL_IS_DATA_WRAPPER (root));

    if (mime_function_table == NULL) {
        mime_function_table = g_hash_table_new (g_strcase_hash,
                            g_strcase_equal);

        /* hook up mime types to functions that handle them */
        g_hash_table_insert (mime_function_table, "text/plain",
                     handle_text_plain);
        g_hash_table_insert (mime_function_table, "text/richtext",
                     handle_text_plain);
        g_hash_table_insert (mime_function_table, "text/html",
                     handle_text_html);
        g_hash_table_insert (mime_function_table, "multipart/alternative",
                     handle_multipart_alternative);
        g_hash_table_insert (mime_function_table, "multipart/related",
                     handle_multipart_related);
        g_hash_table_insert (mime_function_table, "multipart/mixed",
                     handle_multipart_mixed);
        g_hash_table_insert (mime_function_table, "message/rfc822",
                     handle_mime_part);
        g_hash_table_insert (mime_function_table, "image",
                     handle_image);
        g_hash_table_insert (mime_function_table, "vcard",
                     handle_vcard);

        /* RFC 2046 says unrecognized multipart subtypes should
         * be treated like multipart/mixed.
         */
        g_hash_table_insert (mime_function_table, "multipart",
                     handle_multipart_mixed);

        /* Body parts don't have mime parts per se, so Camel
         * sticks on the following one.
         */
        g_hash_table_insert (mime_function_table, "mime/body-part",
                     handle_mime_part);
    }

    /* Try to find a handler function in our own lookup table */
    if (mimetype_whole_in) {
        mimetype_whole = g_strdup (mimetype_whole_in);
        g_strdown (mimetype_whole);

        handler_function = g_hash_table_lookup (mime_function_table,
                            mimetype_whole);
    }

    if (mimetype_main_in && !handler_function) {
        mimetype_main = g_strdup (mimetype_main_in);
        g_strdown (mimetype_main);

        handler_function = g_hash_table_lookup (mime_function_table,
                            mimetype_main);
    }

    /* Upon failure, try to find a bonobo object to show the object */
    if (!handler_function) {
        gchar *bonobo_tag = NULL;

        if (mimetype_whole)
            bonobo_tag = get_bonobo_tag_for_object (
                wrapper, mimetype_whole, root);

        if (mimetype_main && !bonobo_tag)
            bonobo_tag = get_bonobo_tag_for_object (
                wrapper, mimetype_main, root);

        if (bonobo_tag) {
            /* We can print a tag, and return! */

            mail_write_html (stream, bonobo_tag);
            g_free (bonobo_tag);
            if (mimetype_whole)
                g_free (mimetype_whole);
            if (mimetype_main)
                g_free (mimetype_main);

            return; 
        }
    }

    /* Use either a handler function we've found, or a default handler. */
    if (handler_function)
        (*handler_function) (wrapper, stream, root);
    else
        handle_unknown_type (wrapper, stream, root);
    if (mimetype_whole)
        g_free (mimetype_whole);
    if (mimetype_main)
        g_free (mimetype_main);
}


/* Convert plain text in equivalent-looking valid HTML. */
static gchar *
text_to_html (const guchar *input, guint len,
          guint *encoded_len_return,
          gboolean convert_newlines_to_br)
{
    const guchar *cur = input;
    guchar *buffer = NULL;
    guchar *out = NULL;
    gint buffer_size = 0;
    guint count;

    /* Allocate a translation buffer.  */
    buffer_size = len * 2;
    buffer = g_malloc (buffer_size);

    out = buffer;
    count = 0;

    while (len--) {
        if (out - buffer > buffer_size - 100) {
            gint index = out - buffer;

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

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

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

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

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

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

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

        cur++;
    }

    *out = '\0';
    if (encoded_len_return)
        *encoded_len_return = out - buffer;

    return buffer;
}


static void
write_field_to_stream (const gchar *description, const gchar *value,
               gboolean bold, GtkHTMLStreamHandle *stream)
{
    gchar *s;
    gchar *encoded_value;

    if (value) {
        unsigned char *p;

        encoded_value = text_to_html (value, strlen(value),
                          NULL, TRUE);
        for (p = (unsigned char *)encoded_value; *p; p++) {
            if (!isprint (*p))
                *p = '?';
        }
    } else
        encoded_value = g_strdup ("");

    s = g_strdup_printf ("<tr valign=top><%s align=right>%s</%s>"
                 "<td>%s</td></tr>", bold ? "th" : "td",
                 description, bold ? "th" : "td",
                 encoded_value);
    mail_write_html (stream, s);
    g_free (encoded_value);
    g_free (s);
}

static void
write_recipients_to_stream (const gchar *recipient_type,
                const GList *recipients, gboolean bold,
                GtkHTMLStreamHandle *stream)
{
    gchar *recipients_string = NULL;

    while (recipients) {
        gchar *old_string = recipients_string;
        recipients_string =
            g_strdup_printf ("%s%s%s",
                     old_string ? old_string : "",
                     old_string ? "; " : "",
                     (gchar *)recipients->data);
        g_free (old_string);

        recipients = recipients->next;
    }

    write_field_to_stream (recipient_type, recipients_string,
                   bold, stream);
    g_free (recipients_string);
}



static void
write_header_info_to_stream (CamelMimeMessage *mime_message,
                 GtkHTMLStreamHandle *stream)
{
    const GList *recipients;

    mail_write_html (stream, "<table>");

    /* A few fields will probably be available from the mime_message;
     * for each one that's available, write it to the output stream
     * with a helper function, 'write_field_to_stream'.
     */

    write_field_to_stream ("From:",
                   camel_mime_message_get_from (mime_message),
                   TRUE, stream);

    if (camel_mime_message_get_reply_to (mime_message)) {
        write_field_to_stream ("Reply-To:",
                       camel_mime_message_get_reply_to (mime_message),
                       FALSE, stream);
    }

    write_recipients_to_stream ("To:",
                    camel_mime_message_get_recipients (mime_message, CAMEL_RECIPIENT_TYPE_TO),
                    TRUE, stream);

    recipients = camel_mime_message_get_recipients (mime_message, CAMEL_RECIPIENT_TYPE_CC);
    if (recipients)
        write_recipients_to_stream ("Cc:", recipients, TRUE, stream);
    write_field_to_stream ("Subject:",
                   camel_mime_message_get_subject (mime_message),
                   TRUE, stream);

    mail_write_html (stream, "</table>");   
}

#define MIME_TYPE_WHOLE(a)  (gmime_content_field_get_mime_type ( \
                                      camel_mime_part_get_content_type (CAMEL_MIME_PART (a))))
#define MIME_TYPE_MAIN(a)  ((camel_mime_part_get_content_type (CAMEL_MIME_PART (a)))->type)
#define MIME_TYPE_SUB(a)   ((camel_mime_part_get_content_type (CAMEL_MIME_PART (a)))->subtype)


/*----------------------------------------------------------------------*
 *                     Mime handling functions
 *----------------------------------------------------------------------*/

static void
handle_text_plain (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
           CamelDataWrapper *root)
{
    gchar *text;
    CamelStream *wrapper_output_stream;
    gchar tmp_buffer[4096];
    gint nb_bytes_read;
    gboolean empty_text = TRUE;

    
    mail_write_html (stream, "\n<!-- text/plain below -->\n");
    mail_write_html (stream, "<pre>\n");

    /* FIXME: text/richtext is not difficult to translate into HTML */
    if (strcmp (wrapper->mime_type->subtype, "richtext") == 0) {
        mail_write_html (stream, "<center><b>"
                 "<table bgcolor=\"b0b0ff\" cellpadding=3>"
                 "<tr><td>Warning: the following "
                 "richtext may not be formatted correctly. "
                 "</b></td></tr></table></center><br>");
    }

    /* Get the output stream of the data wrapper. */
    wrapper_output_stream = camel_data_wrapper_get_output_stream (wrapper);
    camel_stream_reset (wrapper_output_stream);

    do {
        /* Read next chunk of text. */
        nb_bytes_read = camel_stream_read (wrapper_output_stream,
                           tmp_buffer, 4096);

        /* If there's any text, write it to the stream. */
        if (nb_bytes_read > 0) {
            int returned_strlen;

            empty_text = FALSE;

            /* replace '<' with '&lt;', etc. */
            text = text_to_html (tmp_buffer,
                         nb_bytes_read,
                         &returned_strlen,
                         FALSE);
            mail_write_html (stream, text);
            g_free (text);
        }
    } while (!camel_stream_eos (wrapper_output_stream));

    if (empty_text)
        mail_write_html (stream, "<b>(empty)</b>");

    mail_write_html (stream, "</pre>\n");   
}

static void
handle_text_html (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
          CamelDataWrapper *root)
{
    CamelStream *wrapper_output_stream;
    gchar tmp_buffer[4096];
    gint nb_bytes_read;
    gboolean empty_text = TRUE;

    /* Get the output stream of the data wrapper. */
    wrapper_output_stream = camel_data_wrapper_get_output_stream (wrapper);
    camel_stream_reset (wrapper_output_stream);

    /* Write the header. */
    mail_write_html (stream, "\n<!-- text/html below -->\n");

    do {
        /* Read next chunk of text. */
        nb_bytes_read = camel_stream_read (wrapper_output_stream,
                           tmp_buffer, 4096);

        /* If there's any text, write it to the stream */
        if (nb_bytes_read > 0) {
            empty_text = FALSE;
            
            /* Write the buffer to the html stream */
            gtk_html_stream_write (stream, tmp_buffer,
                           nb_bytes_read);
        }
    } while (!camel_stream_eos (wrapper_output_stream));

    if (empty_text)
        mail_write_html (stream, "<b>(empty)</b>");
}

static void
handle_image (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
          CamelDataWrapper *root)
{
    gchar *uuid;
    gchar *tag;

    uuid = lookup_unique_id (root, wrapper);

    mail_write_html (stream, "\n<!-- image below -->\n");
    tag = g_strdup_printf ("<img src=\"camel://%s\">\n", uuid);
    mail_write_html (stream, tag);
    g_free (uuid);
    g_free (tag);       
}

static void
handle_vcard (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
          CamelDataWrapper *root)
{
    mail_write_html (stream, "\n<!-- vcard below -->\n");

    /* FIXME: do something here. */
}

static void
handle_mime_part (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
          CamelDataWrapper *root)
{
    CamelMimePart *mime_part; 
    CamelDataWrapper *message_contents; 
    gchar *whole_mime_type;

    g_return_if_fail (CAMEL_IS_MIME_PART (wrapper));

    mime_part = CAMEL_MIME_PART (wrapper);
    message_contents =
        camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));

    g_assert (message_contents);

    mail_write_html (stream, "\n<!-- mime message below -->\n");

//  mail_write_html (stream,
//                 "<table width=95% border=1><tr><td>\n\n");       

    /* dispatch the correct handler function for the mime type */
    whole_mime_type = MIME_TYPE_WHOLE (mime_part);
    call_handler_function (message_contents,
                   whole_mime_type,
                   MIME_TYPE_MAIN (mime_part),
                   stream, root);
    g_free (whole_mime_type);

    /* close up the table we opened */
//  mail_write_html (stream,
//                 "\n\n</td></tr></table>\n\n");
}


/* called for each body part in a multipart/mixed */
static void
display_camel_body_part (CamelMimeBodyPart *body_part,
             GtkHTMLStreamHandle *stream,
             CamelDataWrapper *root)
{
    gchar *whole_mime_type;

    CamelDataWrapper* contents =
        camel_medium_get_content_object (CAMEL_MEDIUM (body_part));

    whole_mime_type = MIME_TYPE_WHOLE (body_part);
    call_handler_function (contents, whole_mime_type,
                   MIME_TYPE_MAIN (body_part),
                   stream, root);
    g_free (whole_mime_type);

    mail_write_html (stream, "\n<hr>\n");
}


/* Our policy here is this:
   (1) print text/(plain|html) parts found
   (2) print vcards and images inline
   (3) treat all other parts as attachments */
static void
handle_multipart_mixed (CamelDataWrapper *wrapper,
            GtkHTMLStreamHandle *stream, CamelDataWrapper *root)
{
    CamelMultipart *mp;
    int i, nparts;

    g_return_if_fail (CAMEL_IS_MULTIPART (wrapper));

    mp = CAMEL_MULTIPART (wrapper);

    nparts = camel_multipart_get_number (mp);   
    for (i = 0; i < nparts; i++) {
        CamelMimeBodyPart *body_part =
            camel_multipart_get_part (mp, i);

        display_camel_body_part (body_part, stream, root);
    }
}

/* As seen in RFC 2387! */
/* FIXME: camel doesn't currently set CamelMultipart::parent, so we
 * can use it here.
 */
static void
handle_multipart_related (CamelDataWrapper *wrapper,
              GtkHTMLStreamHandle *stream,
              CamelDataWrapper *root)
{
    CamelMultipart *mp;
    CamelMimeBodyPart *body_part;
#if 0
    GMimeContentField *parent_content_type;
    const char *start, *cid;
    int i, nparts;
#endif

    g_return_if_fail (CAMEL_IS_MULTIPART (wrapper));

    mp = CAMEL_MULTIPART (wrapper);
#if 0
    parent_content_type =
        camel_mime_part_get_content_type (
            camel_multipart_get_parent (mp));

    start = gmime_content_field_get_parameter (parent_content_type,
                           "start");
    if (start) {
        nparts = camel_multipart_get_number (mp);   
        for (i = 0; i < nparts; i++) {
            CamelMimeBodyPart *body_part =
                camel_multipart_get_part (mp, i);

            cid = camel_mime_part_get_content_id (
                CAMEL_MIME_PART (body_part));

            if (!strcmp (cid, start)) {
                display_camel_body_part (body_part, stream,
                             root);
                return;
            }
        }

        /* Oops. Hrmph. */
        handle_multipart_mixed (wrapper, stream, root);
    }
#endif

    /* No start parameter, so it defaults to the first part. */
    body_part = camel_multipart_get_part (mp, 0);
    display_camel_body_part (body_part, stream, root);
}

/* multipart/alternative helper function --
 * Returns NULL if no displayable msg is found
 */
static CamelMimePart *
find_preferred_alternative (CamelMultipart *multipart)
{
    int i, nparts;
    CamelMimePart* html_part = NULL;
    CamelMimePart* plain_part = NULL;   

    /* Find out out many parts are in it. */
    nparts = camel_multipart_get_number (multipart);

    /* FIXME: DO LEAF-LOOKUP HERE FOR OTHER MIME-TYPES!!! */

    for (i = 0; i < nparts; i++) {
        CamelMimeBodyPart *body_part =
            camel_multipart_get_part (multipart, i);

        if (strcasecmp (MIME_TYPE_MAIN (body_part), "text") != 0)
            continue;

        if (strcasecmp (MIME_TYPE_SUB (body_part), "plain") == 0)
            plain_part = CAMEL_MIME_PART (body_part);
        else if (strcasecmp (MIME_TYPE_SUB (body_part), "html") == 0)
            html_part = CAMEL_MIME_PART (body_part);
    }

    if (html_part)
        return html_part;
    if (plain_part)
        return plain_part;
    return NULL;
}

/* The current policy for multipart/alternative is this: 
 *
 * if (we find a text/html body part)
 *     we print it
 * else if (we find a text/plain body part)
 *     we print it
 * else
 *     we print nothing
 */
static void
handle_multipart_alternative (CamelDataWrapper *wrapper,
                  GtkHTMLStreamHandle *stream,
                  CamelDataWrapper *root)
{
    CamelMultipart *multipart = CAMEL_MULTIPART (wrapper);
    CamelMimePart *mime_part;
    gchar *whole_mime_type;

    mime_part = find_preferred_alternative (multipart); 
    if (mime_part) {
        CamelDataWrapper *contents =
            camel_medium_get_content_object (
                CAMEL_MEDIUM (mime_part));

        whole_mime_type = MIME_TYPE_WHOLE (mime_part);
        call_handler_function (contents, whole_mime_type,
                       MIME_TYPE_MAIN (mime_part),
                       stream, root);
        g_free (whole_mime_type);
    }
}

static void
handle_unknown_type (CamelDataWrapper *wrapper,
             GtkHTMLStreamHandle *stream,
             CamelDataWrapper *root)
{
    gchar *tag;
    char *uid = lookup_unique_id (root, wrapper);   

    tag = g_strdup_printf ("<a href=\"camel://%s\">click-me-to-save</a>\n",
                   uid);

    mail_write_html (stream, tag);
}


void
mail_write_html (GtkHTMLStreamHandle *stream, const char *data)
{
    gtk_html_stream_write (stream, data, strlen (data));
}