@ou-imdt/utils/lib/class/mixins/DelegateChangeMixin.js

Utility library for interactive media development

import DelegateChangeModule from '../../modules/DelegateChangeModule.js';
import { defaultState } from '../Base.js';

// defines a prop that holds global value mappings
export const changeMap = Symbol('changeMap');
// defines a prop that holds type options for supported changes
export const changeTargets = Symbol('changeTargets');
// defines a static class field that contains a list of handlers, searches this if null
export const changeHandlers = Symbol('changeHandlers');
// defines a method that computes handler names for a given change and delegates to the handler, if defined

const { map: defaultMap, targets: defaultTargets, handlers: defaultHandlers } = DelegateChangeModule[defaultState];

/**
 * @mixin
 * wraps DelegateChangeModule, exposing overridable defaults to subclasses
 * @member {DelegateChangeModule} - ???
 */
export default (superClass) => class DelegateChangeMixin extends superClass {
  static get [changeMap]() {
    return defaultMap;
  };

  static get [changeTargets]() {
    return defaultTargets;
  };

  static get [changeHandlers]() {
    return defaultHandlers;
  };

  #module;

  constructor() {
    super();

    const { [changeMap]: map, [changeTargets]: targets, [changeHandlers]: handlers } = this.constructor;

    this.#module = new DelegateChangeModule();
    this.#module.state = {
      ...(map === defaultMap) ? null : { map },
      ...(targets === defaultTargets) ? null : { targets },
      ...(handlers === defaultHandlers) ? { handlers: this } : { handlers } // check this!!
    };
  }

  delegateChange(payload, target, thisArg = this) {
    return this.#module.delegateChange(payload, target, thisArg);
  }
}