-- complete_order: transisi delivering -> completed secara atomik & idempotent.
-- Idempotensi: partial unique index stock_movements_order_out_unique_idx
-- ON (reference_type, reference_id) WHERE type='order_out' AND reference_type='order'
-- membuat insert mutasi ganda otomatis dilewati (ON CONFLICT DO NOTHING).
CREATE OR REPLACE FUNCTION public.complete_order(p_order_id uuid, p_actor uuid DEFAULT NULL)
RETURNS void
LANGUAGE plpgsql
SECURITY DEFINER
SET search_path = public
AS $fn$
DECLARE
    v_order       public.orders%ROWTYPE;
    v_item        record;
    v_new_balance integer;
BEGIN
    SELECT * INTO v_order FROM public.orders WHERE id = p_order_id FOR UPDATE;

    IF NOT FOUND THEN
        RAISE EXCEPTION 'ORDER_NOT_FOUND';
    END IF;

    -- Sudah selesai: anggap sukses (idempotent), tanpa efek stok.
    IF v_order.order_status = 'completed' THEN
        RETURN;
    END IF;

    IF v_order.deleted_at IS NOT NULL THEN
        RAISE EXCEPTION 'ORDER_DELETED';
    END IF;

    IF v_order.order_status <> 'delivering' THEN
        RAISE EXCEPTION 'INVALID_TRANSITION:%_TO_COMPLETED', v_order.order_status;
    END IF;

    FOR v_item IN
        SELECT oi.product_id, oi.quantity
        FROM public.order_items oi
        WHERE oi.order_id = p_order_id
        ORDER BY oi.product_id
        FOR UPDATE OF oi
    LOOP
        SELECT s.quantity
        INTO v_new_balance
        FROM public.stocks s
        WHERE s.product_id = v_item.product_id
        FOR UPDATE;

        v_new_balance := COALESCE(v_new_balance, 0) - v_item.quantity;

        IF v_new_balance < 0 THEN
            RAISE EXCEPTION 'INSUFFICIENT_STOCK:%', v_item.product_id;
        END IF;

        INSERT INTO public.stock_movements
            (product_id, type, quantity, reference_type, reference_id, notes, created_by)
        VALUES
            (v_item.product_id, 'order_out', -v_item.quantity, 'order', p_order_id, NULL, p_actor)
        ON CONFLICT DO NOTHING;

        UPDATE public.stocks s
           SET quantity = v_new_balance,
               updated_at = now()
         WHERE s.product_id = v_item.product_id;

    END LOOP;

    UPDATE public.orders
       SET order_status = 'completed',
           completed_at = now(),
           updated_at = now()
     WHERE id = p_order_id;

    INSERT INTO public.order_status_histories
        (order_id, old_status, new_status, changed_by)
    VALUES
        (p_order_id, v_order.order_status, 'completed', COALESCE(p_actor, v_order.created_by));
END;
$fn$;