Displaying bbpress link after return

I found this plugin that takes all the usernames that are commented on a post and makes the link go to a different page. I’m trying to make it call the bbp_user_profile_url. This way, when the link of a user is clicked on from the comments it goes to the users bbpress profile.

My PHP is a little rusty, so I deliberately coded this wrong hoping someone can see what I’m trying to accomplish. My code modifications are at the very end.

if ( ! function_exists( 't5_comment_uri_to_author_archive' ) )
{
    add_filter( 'get_comment_author_url', 't5_comment_uri_to_author_archive' );

    function t5_comment_uri_to_author_archive( $uri )
    {
        global $comment;

        // We do not get the real comment with this filter.
        if ( empty ( $comment )
            or ! is_object( $comment )
            or empty ( $comment->comment_author_email )
            or ! $user = get_user_by( 'email', $comment->comment_author_email )
        )
        {
            return $uri;
        }

        return <a href="<?php bbp_user_profile_url( bbp_get_current_user_id() ); ?>" ></a>( $user->ID );
    }
}