import {PromiseWrapper, Promise} from 'angular2/src/facade/async';
import {BaseException} from 'angular2/src/facade/lang';

import {Template, ProtoView} from '../../api';
import {CompilePipeline} from './compile_pipeline';
import {TemplateLoader} from 'angular2/src/render/dom/compiler/template_loader';
import {CompileStepFactory} from './compile_step_factory';

/**
 * The compiler loads and translates the html templates of components into
 * nested ProtoViews. To decompose its functionality it uses
 * the CompilePipeline and the CompileSteps.
 */
export class Compiler {
  _templateLoader: TemplateLoader;
  _stepFactory: CompileStepFactory;

  constructor(stepFactory: CompileStepFactory, templateLoader: TemplateLoader) {
    this._templateLoader = templateLoader;
    this._stepFactory = stepFactory;
  }

  compile(template: Template):Promise<ProtoView> {
    var tplPromise = this._templateLoader.load(template);
    return PromiseWrapper.then(tplPromise,
      (el) => this._compileTemplate(template, el),
      (_) => { throw new BaseException(`Failed to load the template "${template.componentId}"`); }
    );
  }

  _compileTemplate(template: Template, tplElement):Promise<ProtoView> {
    var subTaskPromises = [];
    var pipeline = new CompilePipeline(this._stepFactory.createSteps(template, subTaskPromises));
    var compileElements;

    compileElements = pipeline.process(tplElement, template.componentId);

    var protoView = compileElements[0].inheritedProtoView.build();

    if (subTaskPromises.length > 0) {
      return PromiseWrapper.all(subTaskPromises).then((_) => protoView);
    } else {
      return PromiseWrapper.resolve(protoView);
    }
  }
}