<?php
/*
Plugin Name: Trackback and CC RSS/ATOM module
Version: 0.1
Plugin URI: http://www.fabriziotarizzo.org/
Description: Adds trackback and Creative Commons License info in RSS and ATOM feeds
Author: Fabrizio Tarizzo
Author URI: http://www.fabriziotarizzo.org/
*/

/* Trackback functions */
function trackback_feed_namespace ($feedtype) {
    if ($feedtype != 'commentsrss2')
        echo 'xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/"' . "\n";
}
function trackback_feed_item ($feedtype, $post_ID) {
    if ($feedtype == 'rdf') {
        echo '<trackback:ping rdf:resource="';
        trackback_url();
        echo '" />' . "\n";
    } elseif ($feedtype == 'rss2' || $feedtype == 'atom') {
        echo '<trackback:ping>';
        trackback_url();
        echo "</trackback:ping>\n";
    }
}

/* CC Functions */
function cc_feed_namespace ($feedtype) {
    if ($feedtype == 'rss2' || $feedtype == 'atom')
        echo 'xmlns:creativeCommons="http://backend.userland.com/creativeCommonsRssModule"' . "\n";
    elseif ($feedtype == 'rdf')
        echo 'xmlns:cc="http://web.resource.org/cc/"' . "\n";
}
function cc_feed_channel ($feedtype) {
    if ($feedtype == 'rdf') {
        echo '<cc:license rdf:resource="http://creativecommons.org/licenses/by-sa/2.0/" />' . "\n";
    } elseif ($feedtype == 'rss2' || $feedtype == 'atom') {
        echo "<creativeCommons:license>http://creativecommons.org/licenses/by-sa/2.0/</creativeCommons:license>\n";
    }
}
function cc_feed_rdf () {
    echo '
<cc:License rdf:about="http://creativecommons.org/licenses/by-sa/2.0/">
    <cc:permits rdf:resource="http://web.resource.org/cc/Reproduction" />
    <cc:permits rdf:resource="http://web.resource.org/cc/Distribution" />
    <cc:requires rdf:resource="http://web.resource.org/cc/Notice" />
    <cc:requires rdf:resource="http://web.resource.org/cc/Attribution" />
    <cc:permits rdf:resource="http://web.resource.org/cc/DerivativeWorks" />
    <cc:requires rdf:resource="http://web.resource.org/cc/ShareAlike" />
</cc:License>
';
}

/* Declare hooks functions */
add_action ('wp_feed_namespace', 'trackback_feed_namespace');
add_action ('wp_feed_item', 'trackback_feed_item');

add_action ('wp_feed_namespace', 'cc_feed_namespace');
add_action ('wp_feed_channel', 'cc_feed_channel');
add_action ('wp_feed_rdf', 'cc_feed_rdf');
?>