Task 1

CREATE OR REPLACE FUNCTION enclosure_available
    (f_id int, custom_date DATE)
RETURNS BOOLEAN
LANGUAGE plpgsql
AS $$
    DECLARE
        _f_enclosure_id int;
        _c BOOLEAN := TRUE;
    BEGIN

        BEGIN
            SELECT enclosure_id
            INTO STRICT _f_enclosure_id
            FROM bookings
            WHERE enclosure_id =  f_id
            LIMIT 1;
        EXCEPTION
            WHEN NO_DATA_FOUND
            THEN
                RAISE NOTICE 'Не найден вольер с id %', f_id;
                RETURN FALSE;
        END;

    SELECT FALSE
    INTO STRICT _c
    FROM bookings
    WHERE enclosure_id = f_id
        AND
        custom_date BETWEEN date_begin AND date_end
    LIMIT 1;

RETURN _c;

    END;
$$