import { DEFAULT_ADAPTER } from './constants';

/*

  Remove a token from an array of subscriptions

  @param subscriptions Array (of tokens)
  @param token Array ([action, callback])

*/

const removeSubscription = (subscriptions, token, adapter) => {
  const idx = subscriptions.indexOf(token);
  if (idx < 0) {
    console.log('PubSub cannot unregister an unrecognized token');
  } else {
    subscriptions.splice(idx, 1);
    adapter.unsubscribe(token);
  }
};

/*

  Creates the subscription object

  @param component function the React component
  @param autoUnmount boolean defaults to true, if it has to remove all subscriptions on cwunmount
  @param adapter object the pubsub adapter
  @return the subscription object

*/

const createSubscription = function(component, autoUnmount = true, adapter) {
  let sub = {
    componentWillUnmount: component.componentWillUnmount,
    subscriptions: [],
    add(action, cb) {
      const token = adapter.subscribe(action, cb);
      sub.subscriptions.push(token);
      return () => removeSubscription(sub.subscriptions, token);
    },
    removeAll() {
      sub.subscriptions.forEach( token => adapter.unsubscribe(token) );
      sub.subscriptions = [];
    },
    publish(action, params) {
      adapter.publish(action, params);
    }
  };

  if (autoUnmount) {
    component.componentWillUnmount = () => {
      const { componentWillUnmount, removeAll } = sub;
      componentWillUnmount && componentWillUnmount.apply(component, arguments);
      removeAll();
      sub = void 0;
    };
  }

  return sub;
};


/*

  PubSubAdapter function

  @param Object adapter being used
  @returns an object wrapping publish/subscribe/unsubscribe from given adapter

*/

const PubSubAdapter = (adapter) => {
  const { publish, subscribe, unsubscribe } = adapter;
  return {
    publish,
    subsribe,
    unsubscribe
  }
};


/*

  createPubSub function

  @param subscribersMap Object, default to empty object, subscribers that will be populated
         like so:
         subscribersMap[MyReactComponent] = {...}
  @param adapter Object, default to default adapter specified
  @returns an object wrapping register/unregister for a particular component

*/

const createPubSub = (subscribersMap = {}, adapter = DEFAULT_ADAPTER) => {
  return {
    register(component, autoUnmount = true) {
      let registeredComponent = subscribersMap[component];
      registeredComponent = registeredComponent || createSubscription(component, autoUnmount, PubSubAdapter(adapter));
      return registeredComponent;
    },
    unregister(component) {
      if (subscribersMap[component]) {
        subscribersMap[component].removeAll() && delete subscribersMap[component];
      } else {
        console.log(`${component.displayName} is NOT registerd to PubSub`);
      }
    },
  };
};