add problem upload flag

migrations/20240727123308_initial.sql

@@ -18,6 +18,7 @@ CREATE TABLE IF NOT EXISTS languages
 CREATE TABLE IF NOT EXISTS problems
 (
     id           serial       NOT NULL,
+    is_uploaded  BOOLEAN      NOT NULL,
     name         VARCHAR(300) NOT NULL,
     description  TEXT         NOT NULL,
     time_limit   INT          NOT NULL,
@@ -65,6 +66,16 @@ CREATE INDEX ON tasks USING BTREE (id);
 CREATE INDEX ON tasks USING BTREE (contest_id);
 CREATE INDEX ON tasks USING BTREE (problem_id);
 
+CREATE FUNCTION check_problem_uploaded() RETURNS TRIGGER
+LANGUAGE plpgsql AS $$ BEGIN
+    IF NOT EXISTS (SELECT (id) FROM problems WHERE id=NEW.problem_id AND is_uploaded=TRUE) THEN
+        RAISE EXCEPTION 'trying to add not uploaded problem';
+    END IF;
+    RETURN NEW;
+END;$$;
+
+CREATE TRIGGER check_problem_uploaded_trg BEFORE INSERT ON tasks FOR EACH ROW EXECUTE FUNCTION check_problem_uploaded();
+