import { Stream } from 'stream';

export class Interactor {
  _actions = new Stream();
  _reactions = new Stream();
  _latestReaction;

  constructor(initialReaction = new Reaction()) {
    this._latestReactions = {};
    this._actions.listen((action) => this._interaction(action));
    this._react(initialReaction);
  }

  act(action) {
    if (!(action instanceof Action)) throw 'invalid action';
    this._actions.add(action);
  }

  observe(reactionHandler, provideLatestReaction = true) {
    if (provideLatestReaction) reactionHandler(this._latestReaction);
    let listener = (reaction) => {
      if (!(reaction instanceof Reaction)) throw 'invalid reaction';
      reactionHandler(reaction);
    };
    this._reactions.listen(listener);
    return listener;
  }

  ignore(listener) {
    this._reactions.ignore(listener);
  }

  _interaction(action) {}

  _react(reaction) {
    if (!(reaction instanceof Reaction)) throw 'invalid reaction';
    let latest = this._latestReactions[reaction.constructor.name];
    if (!reaction.equals(latest)) {
      this._latestReaction = reaction;
      this._latestReactions[reaction.constructor.name] = reaction;
      this._reactions.add(reaction);
    }
  }
}

export class Action {}

export class Reaction {
  equals(reaction) {
    return false;
  }
}