-- Shop Unit of Measurement

CREATE OR REPLACE FUNCTION before_insert_Shop_Unit_Measurement()
RETURNS TRIGGER AS $$
BEGIN
	IF NEW.created_on IS NULL THEN
		NEW.created_on = CURRENT_TIMESTAMP;
	END IF;
    IF NEW.created_by IS NULL THEN
		NEW.created_by = CURRENT_USER;
	END IF;

	RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE TRIGGER tri_before_insert_Shop_Unit_Measurement
BEFORE INSERT ON Shop_Unit_Measurement
FOR EACH ROW
EXECUTE FUNCTION before_insert_Shop_Unit_Measurement();


CREATE OR REPLACE FUNCTION before_update_Shop_Unit_Measurement()
RETURNS TRIGGER AS $$
BEGIN
	IF OLD.id_change_set IS NOT DISTINCT FROM NEW.id_change_set THEN
		RAISE EXCEPTION 'New change Set ID must be provided.'
			USING ERRCODE = '45000';
    END IF;
    
    INSERT INTO Shop_Unit_Measurement_Audit (
		id_unit_measurement,
        name_field,
        value_prev,
        value_new,
        id_change_set
    )
	-- Changed name_singular
	SELECT NEW.id_unit_measurement, 'name_singular', OLD.name_singular, NEW.name_singular, NEW.id_change_set
		WHERE NOT OLD.name_singular <=> NEW.name_singular
    UNION
	-- Changed name_plural
	SELECT NEW.id_unit_measurement, 'name_plural', OLD.name_plural, NEW.name_plural, NEW.id_change_set
		WHERE NOT OLD.name_plural <=> NEW.name_plural
    UNION
	-- Changed symbol
	SELECT NEW.id_unit_measurement, 'symbol', OLD.symbol, NEW.symbol, NEW.id_change_set
		WHERE NOT OLD.symbol <=> NEW.symbol
    UNION
	-- Changed is_base_unit
	SELECT NEW.id_unit_measurement, 'is_base_unit', OLD.is_base_unit, NEW.is_base_unit, NEW.id_change_set
		WHERE NOT OLD.is_base_unit <=> NEW.is_base_unit
    UNION
	-- Changed active
	SELECT NEW.id_unit_measurement, 'active', OLD.active, NEW.active, NEW.id_change_set
		WHERE NOT OLD.active <=> NEW.active
    ;

	RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE TRIGGER tri_before_update_Shop_Unit_Measurement
BEFORE UPDATE ON Shop_Unit_Measurement
FOR EACH ROW
EXECUTE FUNCTION before_update_Shop_Unit_Measurement();