-- Create a new task
CREATE OR REPLACE FUNCTION add_task( t_item INT , t_title TEXT , t_description TEXT , t_priority INT , t_user INT )
		RETURNS INT
		STRICT VOLATILE
		SECURITY INVOKER
	AS $add_task$
BEGIN
	INSERT INTO tasks ( item_id , task_title , task_description , task_priority , user_id )
		VALUES ( t_item , t_title , t_description , t_priority , t_user );
	RETURN 0;
EXCEPTION
	WHEN unique_violation THEN
		RETURN 1;
	WHEN foreign_key_violation THEN
		RETURN 2;
END;
$add_task$ LANGUAGE plpgsql;


-- Mark a task as finished
CREATE OR REPLACE FUNCTION finish_task( t_id INT , u_id INT , n_text TEXT )
		RETURNS INT
		STRICT VOLATILE
		SECURITY INVOKER
	AS $finish_task$
BEGIN
	BEGIN
		INSERT INTO completed_tasks ( task_id , user_id )
			VALUES ( t_id , u_id );
	EXCEPTION
		WHEN unique_violation THEN
			RETURN 1;
	END;

	UPDATE tasks SET user_id_assigned = NULL WHERE task_id = t_id;

	INSERT INTO notes ( task_id , user_id , note_text )
		VALUES ( t_id , u_id , n_text );
	RETURN 0;
END;
$finish_task$ LANGUAGE plpgsql;

REVOKE EXECUTE ON FUNCTION finish_task( INT , INT , TEXT ) FROM PUBLIC;
GRANT EXECUTE ON FUNCTION finish_task( INT , INT , TEXT ) TO :webapp_user;


-- Restart a task
CREATE OR REPLACE FUNCTION restart_task( t_id INT , u_id INT , n_text TEXT )
		RETURNS INT
		STRICT VOLATILE
		SECURITY INVOKER
	AS $restart_task$
BEGIN
	DELETE FROM completed_tasks WHERE task_id = t_id;
	IF NOT FOUND THEN
		RETURN 1;
	END IF;
	UPDATE tasks SET user_id_assigned = u_id
		WHERE task_id = t_id;
	INSERT INTO notes ( task_id , user_id , note_text )
		VALUES ( t_id , u_id , n_text );
	RETURN 0;
END;
$restart_task$ LANGUAGE plpgsql;

REVOKE EXECUTE ON FUNCTION restart_task( INT , INT , TEXT ) FROM PUBLIC;
GRANT EXECUTE ON FUNCTION restart_task( INT , INT , TEXT ) TO :webapp_user;


-- Update a task
CREATE OR REPLACE FUNCTION update_task( t_id INT , p_id INT , t_title TEXT , t_description TEXT , t_priority INT , t_assignee INT )
		RETURNS INT
		STRICT VOLATILE
		SECURITY INVOKER
	AS $update_task$
BEGIN
	PERFORM 1
		FROM tasks
			LEFT OUTER JOIN completed_tasks
				USING( task_id )
		WHERE task_id = t_id AND completed_task_time IS NULL
		FOR UPDATE OF tasks;
	IF NOT FOUND THEN
		RETURN 4;
	END IF;

	BEGIN
		IF t_assignee <= 0 THEN
			t_assignee := NULL;
		END IF;
		BEGIN
			UPDATE tasks SET user_id_assigned = t_assignee WHERE task_id = t_id;
		EXCEPTION
			WHEN foreign_key_violation THEN
				RAISE EXCEPTION 'bad user';
		END;
		UPDATE tasks SET item_id = p_id , task_title = t_title ,
				task_description = t_description ,
				task_priority = t_priority
			WHERE task_id = t_id;
	EXCEPTION
		WHEN unique_violation THEN
			RETURN 1;
		WHEN foreign_key_violation THEN
			RETURN 2;
		WHEN raise_exception THEN
			RETURN 3;
	END;

	RETURN 0;
END;
$update_task$ LANGUAGE plpgsql;


REVOKE EXECUTE ON FUNCTION update_task( INT , INT , TEXT , TEXT , INT , INT ) FROM PUBLIC;
GRANT EXECUTE ON FUNCTION update_task( INT , INT , TEXT , TEXT , INT , INT ) TO :webapp_user;