CREATE FUNCTION _api.post_update()
RETURNS TRIGGER
LANGUAGE plpgsql VOLATILE
AS $BODY$
DECLARE
	_user_id INTEGER;
	_changed BOOLEAN;
BEGIN
	_user_id = _api.get_user_id();
	_changed = FALSE;

	IF OLD.user_id <> _user_id THEN
		PERFORM _api.raise_deny();
	END IF;

	NEW.content = COALESCE(NEW.content, OLD.content);
	NEW.content := _api.trim(NEW.content);
	PERFORM _api.validate_text(
		_text => NEW.content,
		_column => 'content',
		_min => 1,
		_max => 4096
	);

	IF NEW.content IS DISTINCT FROM OLD.content THEN
		_changed = TRUE;
	END IF;

	IF _changed THEN
		UPDATE admin.post
			SET content = NEW.content
			WHERE id = OLD.id;
	END IF;

	RETURN NEW;
END
$BODY$;

GRANT EXECUTE ON FUNCTION _api.post_update()
	TO rest_user;
GRANT UPDATE ON TABLE api.post
	TO rest_user;
GRANT UPDATE ON TABLE admin.post
	TO rest_user;

CREATE TRIGGER api_post_update_trgr
	INSTEAD OF UPDATE
			ON api.post
			FOR EACH ROW
				EXECUTE PROCEDURE _api.post_update();