import {
  ClassProvider,
  FactoryProvider,
  InjectionToken,
  PLATFORM_ID,
  Injectable
} from '@angular/core';
import { isPlatformBrowser } from '@angular/common';

/* Create a new injection token for injecting the window into a component. */
export const WINDOW = new InjectionToken('WindowToken');

/* Define abstract class for obtaining reference to the global window object. */
export abstract class WindowRef {
  get nativeWindow(): Window | Object {
    throw new Error('Not implemented.');
  }
}

/* Define class that implements the abstract class and returns the native window object. */
@Injectable()
export class BrowserWindowRef extends WindowRef {
  constructor() {
    super();
  }

  get nativeWindow(): Window | Object {
    return window;
  }
}

/* Create an factory function that returns the native window object. */
export function windowFactory(
  browserWindowRef: BrowserWindowRef,
  platformId: Object
): Window | Object {
  if (isPlatformBrowser(platformId)) {
    return browserWindowRef.nativeWindow;
  }
  return new Object();
}

/* Create a injectable provider for the WindowRef token that uses the BrowserWindowRef class. */
const browserWindowProvider: ClassProvider = {
  provide: WindowRef,
  useClass: BrowserWindowRef
};

/* Create an injectable provider that uses the windowFactory function for returning the native window object. */
const windowProvider: FactoryProvider = {
  provide: WINDOW,
  useFactory: windowFactory,
  deps: [WindowRef, PLATFORM_ID]
};

/* Create an array of providers. */
export const WINDOW_PROVIDERS = [browserWindowProvider, windowProvider];