How to programmatically create a connection with [Plugin: Posts 2 Posts] on cpt publish?

How can I programmatically create a connection between one custom post type, cpt, (with post id known) to another on cpt on publish?

I am using VoodooPress’s front-end posting method to publish a post type called post-type-A. One input field in the post-type-A form is the public inventory number, which through some wp_query love gives me the post id of the post-type-B that I wish to create a relationship with.

I know that I can use this function to create a one-way connection from post-type-A to post-type-B using a custom field.

add_action('publish_page', 'add_custom_field_automatically');
add_action('publish_post', 'add_custom_field_automatically');
function add_custom_field_automatically($post_ID) {
    global $wpdb;
    if(!wp_is_post_revision($post_ID)) {
        add_post_meta($post_ID, 'field-name', 'custom value', true);
    }
}

But how do I programmatically create a connection using @Scribu’s Posts 2 Posts plugin? A two-way relationship would reduce a lot of hassle and programming time. 🙂

For reference, the snippet below is the connect api reference for the plugin…

/**
 * Connect a post to another one
 *
 * @param int $post_a The first end of the connection
 * @param int $post_b The second end of the connection
 * @param bool $bydirectional Wether the connection should be bydirectional
 */
function p2p_connect( $post_a, $post_b, $bydirectional = false ) {
        add_post_meta( $post_a, P2P_META_KEY, $post_b );

        if ( $bydirectional )
                add_post_meta( $post_b, P2P_META_KEY, $post_a );
}