import { types } from "mobx-state-tree";
import { isDefined } from "../../utils/utilities";

/**
 * This mixin is created as a definition of the interface of object-tags that should be able to work with valueList parameter
 * The first entity of it is Multi-Image Segmentation case
 */
const MultiItemObjectBase = types
  .model({
    valuelist: types.maybeNull(types.string),
  })
  .extend((self) => {
    /* Validation */
    if (self.isObjectTag !== true) {
      throw new Error("The MultiItemObjectBase mixin should be used only for object-tags");
    }
    return {};
  })
  .views((self) => ({
    get isMultiItem() {
      return isDefined(self.valuelist);
    },
    /**
     * An index of the last item for multi-items object-tag
     */
    get maxItemIndex() {
      throw new Error("MultiItemMixin needs to implement maxItemIndex getter in views");
    },
    /**
     * An index of currently selected object-tag item
     */
    get currentItemIndex() {
      throw new Error("MultiItemMixin needs to implement currentItemIndex getter in views");
    },
    /**
     * A list of regions related to the current object item
     */
    get regs() {
      if (self.isMultiItem) {
        return self.allRegs.filter((r) => (r.item_index ?? 0) === self.currentItemIndex);
      }
      return self.allRegs;
    },
  }));

export default MultiItemObjectBase;