CREATE OR REPLACE FUNCTION trigf() RETURNS trigger AS
$$

DECLARE num_of_buys integer;

BEGIN

    IF (TG_OP = 'INSERT') --checks if insert or update
        THEN

        num_of_buys := (select count(*) from buys where new.cid = cid AND new.rno = rno and new.iname = iname);
        IF num_of_buys >= 5 --do if client bought item 5 times, no matter the quantity
            THEN
            IF NOT EXISTS( select * from likes where new.iname = iname AND new.cid = cid)
                THEN --do if likes table doesn't have item yet

                INSERT INTO likes (cid,iname) values (new.cid, new.iname); -- insert the item and the related cid
                RETURN new;
            ELSE
                RAISE NOTICE 'client no. % likes % product ' , new.cid , new.iname;
                RETURN NULL;
            END IF;
        ELSE IF EXISTS( select * from likes where new.iname = iname AND new.cid = cid )
            THEN
            DELETE from likes where cid = new.cid AND iname = new.iname;
            RETURN new;

        ELSE IF (TG_OP = 'UPDATE') ----checks if insert or update
            THEN
            num_of_buys := (select count(*) from buys where new.cid = cid AND new.rno = rno AND new.iname);
            IF num_of_buys >= 5
                THEN
                IF NOT EXISTS( select * from likes where old.iname = iname AND old.cid = cid)
                    THEN
                    INSERT INTO likes (cid,iname) values (old.cid, old.iname);
                    RETURN new;
                ELSE
                    DELETE FROM likes where cid = old.cid AND iname = old.iname;
                    INSERT INTO likes (cid,iname) values (new.cid, new.iname);
                    RETURN new;
                END IF;
            ELSE
                IF EXISTS( select * from likes where old.iname = iname AND old.cid = cid )
                    THEN
                    DELETE from likes where cid = old.cid AND iname = old.iname;
                    RETURN new;
                END IF;
            END IF;
        END IF;
    END IF;
END IF;
END IF;
END;
$$ LANGUAGE 'plpgsql';


CREATE TRIGGER T BEFORE INSERT OR UPDATE ON buys
FOR EACH ROW EXECUTE PROCEDURE trigf();