package cart

import (
	"fmt"

	messages "git.k6n.net/go-cart-actor/proto/cart"
)

// SetLineItemCustomFields sets/merges user-supplied custom input fields on an
// existing cart line. It is the dict equivalent of LineItemMarking: keys in the
// request are upserted; existing keys not present in the request are left
// untouched. (Send an empty value to clear a single field at the API layer if
// desired.)
func SetLineItemCustomFields(grain *CartGrain, req *messages.SetLineItemCustomFields) error {
	for _, item := range grain.Items {
		if item.Id != req.Id {
			continue
		}
		if len(req.CustomFields) == 0 {
			return nil
		}
		if item.CustomFields == nil {
			item.CustomFields = make(map[string]string, len(req.CustomFields))
		}
		for k, v := range req.CustomFields {
			item.CustomFields[k] = v
		}
		return nil
	}
	return fmt.Errorf("item with ID %d not found", req.Id)
}