Custom post permalink example with %post_id%

add_action('init', 'tribe_events_rewrite');
function tribe_events_rewrite() {
    global $wp_rewrite;
    $queryarg = 'post_type=tribe_events&p=';
    $wp_rewrite->add_rewrite_tag('%tribe_events_id%', '([^/]+)',$queryarg);
    $wp_rewrite->add_permastruct('tribe_events', '/event/%tribe_events_id%', false); }

add_filter('post_type_link', 'tribe_events_permalink', 1, 3);
function tribe_events_permalink($post_link, $id = 0, $leavename) {
    global $wp_rewrite;
    $post = &get_post($id);
    if ( is_wp_error( $post ) )
    return $post;
    $newlink = $wp_rewrite->get_extra_permastruct($post->post_type);
    $newlink = str_replace('%'.$post->post_type.'_id%', $post->ID, $newlink);
    $newlink = home_url(user_trailingslashit($newlink));
    return $newlink;
}