messages_delete_thread( int|array $thread_ids, int $user_id )

function messages_delete_thread( $thread_ids, $user_id = 0 ) {

	if ( empty( $user_id ) ) {
		$user_id =
			bp_displayed_user_id() ?
			bp_displayed_user_id() :
			bp_loggedin_user_id();
	}

	/**
	 * Fires before specified thread IDs have been deleted.
	 *
	 * @since BuddyPress 1.5.0
	 * @since BuddyPress 2.7.0 The $user_id parameter was added.
	 *
	 * @param int|array $thread_ids Thread ID or array of thread IDs to be deleted.
	 * @param int       $user_id    ID of the user the threads are being deleted for.
	 */
	do_action( 'messages_before_delete_thread', $thread_ids, $user_id );

	if ( is_array( $thread_ids ) ) {
		$error = 0;
		for ( $i = 0, $count = count( $thread_ids ); $i < $count; ++$i ) {
			if ( ! BP_Messages_Thread::delete( $thread_ids[$i], $user_id ) ) {
				$error = 1;
			}
		}

		if ( ! empty( $error ) ) {
			return false;
		}

		/**
		 * Fires after specified thread IDs have been deleted.
		 *
		 * @since BuddyPress 1.0.0
		 * @since BuddyPress 2.7.0 The $user_id parameter was added.
		 *
		 * @param int|array Thread ID or array of thread IDs that were deleted.
		 * @param int       ID of the user that the threads were deleted for.
		 */
		do_action( 'messages_delete_thread', $thread_ids, $user_id );

		return true;
	} else {
		if ( ! BP_Messages_Thread::delete( $thread_ids, $user_id ) ) {
			return false;
		}

		/** This action is documented in bp-messages/bp-messages-functions.php */
		do_action( 'messages_delete_thread', $thread_ids, $user_id );

		return true;
	}
}