BP_Friends_Friendship::search_friends( string $filter, int $user_id, int|null $limit = null, int|null $page = null )

	public static function search_friends( $filter, $user_id, $limit = null, $page = null ) {
		global $wpdb;

		/*
		 * TODO: Optimize this function.
		 */

		if ( empty( $user_id ) )
			$user_id = bp_loggedin_user_id();

		// Only search for matching strings at the beginning of the
		// name (@todo - figure out why this restriction).
		$search_terms_like = bp_esc_like( $filter ) . '%';

		$pag_sql = '';
		if ( !empty( $limit ) && !empty( $page ) )
			$pag_sql = $wpdb->prepare( " LIMIT %d, %d", intval( ( $page - 1 ) * $limit), intval( $limit ) );

		if ( !$friend_ids = BP_Friends_Friendship::get_friend_user_ids( $user_id ) )
			return false;

		// Get all the user ids for the current user's friends.
		$fids = implode( ',', wp_parse_id_list( $friend_ids ) );

		if ( empty( $fids ) )
			return false;

		$bp = buddypress();

		// Filter the user_ids based on the search criteria.
		if ( bp_is_active( 'xprofile' ) ) {
			$sql       = $wpdb->prepare( "SELECT DISTINCT user_id FROM {$bp->profile->table_name_data} WHERE user_id IN ({$fids}) AND value LIKE %s {$pag_sql}", $search_terms_like );
			$total_sql = $wpdb->prepare( "SELECT COUNT(DISTINCT user_id) FROM {$bp->profile->table_name_data} WHERE user_id IN ({$fids}) AND value LIKE %s", $search_terms_like );
		} else {
			$sql       = $wpdb->prepare( "SELECT DISTINCT user_id FROM {$wpdb->usermeta} WHERE user_id IN ({$fids}) AND meta_key = 'nickname' AND meta_value LIKE %s {$pag_sql}", $search_terms_like );
			$total_sql = $wpdb->prepare( "SELECT COUNT(DISTINCT user_id) FROM {$wpdb->usermeta} WHERE user_id IN ({$fids}) AND meta_key = 'nickname' AND meta_value LIKE %s", $search_terms_like );
		}

		$filtered_friend_ids = $wpdb->get_col( $sql );
		$total_friend_ids    = $wpdb->get_var( $total_sql );

		if ( empty( $filtered_friend_ids ) )
			return false;

		return array( 'friends' => array_map( 'intval', $filtered_friend_ids ), 'total' => (int) $total_friend_ids );
	}