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();

}

}