-- Special node such as orphaned and deleted nodes.
ALTER TABLE public.node ADD special bool DEFAULT false NOT NULL;


-- Needs to be dropped in order to drop the index on UUID.
ALTER TABLE public.node DROP CONSTRAINT node_node_fk;

-- Index was missing user ID.
DROP INDEX public.node_uuid_idx;
CREATE UNIQUE INDEX node_user_uuid_idx ON public.node (user_id,"uuid");

-- Restore the "foreign" key of parent UUID back to UUID.
ALTER TABLE public.node ADD CONSTRAINT node_node_fk FOREIGN KEY (user_id,parent_uuid) REFERENCES public.node(user_id,"uuid") ON DELETE RESTRICT ON UPDATE RESTRICT;


-- Auto-create the special nodes for each user.
CREATE OR REPLACE FUNCTION create_user_nodes()
RETURNS TRIGGER AS $$
BEGIN
	-- NEW holds the row being created.
	-- No semi-colons omitted here, PL/pgSQL requires them.
	INSERT INTO public.node (user_id, uuid, parent_uuid, special, name)
	VALUES
		(NEW.id, '00000000-0000-0000-0000-000000000000'::uuid, null, true, 'Start'),
		(NEW.id, '00000000-0000-0000-0000-000000000001'::uuid, null, true, 'Orphaned nodes'),
		(NEW.id, '00000000-0000-0000-0000-000000000002'::uuid, null, true, 'Deleted nodes');

	RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER trg_after_user_insert
AFTER INSERT ON public.user
FOR EACH ROW
EXECUTE FUNCTION create_user_nodes();