import {TickingPromise} from '@avocado/core';

import {Collection} from './collection';
import {Traversal} from './traversal';

export class Traversals extends Collection('traversal') {

  parallel(context) {
    const results = this.traversals.map((traversal) => {
      return traversal.traverse(context);
    });
    // Early out if no promises.
    if (!results.reduce((has, result) => {
      return has || result instanceof Promise;
    }, false)) {
      return results;
    }
    // Proxy any tickers.
    const tickableResults = results.filter((result) => {
      if (!(result instanceof TickingPromise)) {
        return false;
      }
      return true;
    });
    // If none, just promise.
    if (0 === tickableResults.length) {
      return Promise.all(results);
    }
    // Otherwise, tick all tickers and resolve.
    return new TickingPromise(
      (resolve) => {
        resolve(Promise.all(results));
      },
      (elapsed) => {
        tickableResults.forEach((result) => result.tick(elapsed));
      },
    );
  }

}