angular/modules/angular2/src/router/pipeline.js

import {Promise, PromiseWrapper} from 'angular2/src/facade/async';
import {List, ListWrapper} from 'angular2/src/facade/collection';
import {Instruction} from './instruction';

/**
 * Responsible for performing each step of navigation.
 * "Steps" are conceptually similar to "middleware"
 */
export class Pipeline {
  steps:List<Function>;

  constructor() {
    this.steps = [
      instruction => instruction.router.activateOutlets(instruction)
    ];
  }

  process(instruction:Instruction):Promise {
    var steps = this.steps,
        currentStep = 0;

    function processOne(result:any = true):Promise {
      if (currentStep >= steps.length) {
        return PromiseWrapper.resolve(result);
      }
      var step = steps[currentStep];
      currentStep += 1;
      return PromiseWrapper.resolve(step(instruction)).then(processOne);
    }

    return processOne();
  }
}