/**
 * Retrieves affiliate id for the given user.
 *
 * @param int $user_id user id.
 *
 * @return string|null
 */
function bdx_get_affiliate_id( $user_id ) {

    global $wpdb;
    $table = $wpdb->prefix . 'uap_referrals';

    return $wpdb->get_var( $wpdb->prepare( "SELECT affiliate_id FROM {$table} WHERE refferal_wp_uid =%d", $user_id ) );
}

/**
 * Make all newly signing user's folllow their sponsor automatically(the affiliate who invited them).
 */
add_action( 'user_register', function ( $user_id ) {

    // 1. check if follow exists.
    if ( ! function_exists( 'bp_follow_is_following' ) ) {
        return;
    }

    global $indeed_db;

    if ( empty( $indeed_db ) || ! method_exists( $indeed_db, 'get_uid_by_affiliate_id' ) ) {
        return;
    }

    // check if wp affiliates pro exists.
    $affiliate_id = bdx_get_affiliate_id( $user_id );
    if ( ! $affiliate_id ) {
        return;
    }

    $affiliate_wp_user_id = $indeed_db->get_uid_by_affiliate_id( $affiliate_id );
    if ( ! $affiliate_wp_user_id ) {
        return;
    }

    $args = array(
        'leader_id'   => absint( $affiliate_wp_user_id ),
        'follower_id' => $user_id,
    );

    if ( ! bp_follow_is_following( $args ) ) {
        bp_follow_start_following( $args );
    }

}, 100 );