import { autorun, toJS } from 'mobx';
import { props } from 'skatejs';

export const withObserver = (Base = HTMLElement) =>
  class extends Base {
    constructor() {
      super();
      const { stores } = this;

      // This dynamically adds props post construction, so this happens for every instance that is created. One way to
      // make this more efficient is to allow for this as an edge case, but to use staticially defined stores on the
      // class instead.
      Component.props = Object.keys(stores).reduce((prev, curr) => {
        prev[curr] = props.array;
        return prev;
      }, {});

      // Define an updater for each store. Doing this separately for each store ensures that if one store is updated,
      // the others aren't triggered.
      Object.keys(stores).forEach(key => {
        autorun(() => (this[key] = toJS(stores[key].items)));
      });
    }
  };