/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {APP_BASE_HREF, HashLocationStrategy, LOCATION_INITIALIZED, Location, LocationStrategy, PathLocationStrategy, PlatformLocation} from '@angular/common';
import {ANALYZE_FOR_ENTRY_COMPONENTS, APP_BOOTSTRAP_LISTENER, APP_INITIALIZER, ApplicationRef, Compiler, ComponentRef, Inject, Injectable, InjectionToken, Injector, ModuleWithProviders, NgModule, NgModuleFactoryLoader, NgProbeToken, Optional, Provider, SkipSelf, SystemJsNgModuleLoader} from '@angular/core';
import {ɵgetDOM as getDOM} from '@angular/platform-browser';
import {Subject} from 'rxjs/Subject';
import {of } from 'rxjs/observable/of';

import {Route, Routes} from './config';
import {RouterLink, RouterLinkWithHref} from './directives/router_link';
import {RouterLinkActive} from './directives/router_link_active';
import {RouterOutlet} from './directives/router_outlet';
import {RouteReuseStrategy} from './route_reuse_strategy';
import {ErrorHandler, Router} from './router';
import {ROUTES} from './router_config_loader';
import {ChildrenOutletContexts} from './router_outlet_context';
import {NoPreloading, PreloadAllModules, PreloadingStrategy, RouterPreloader} from './router_preloader';
import {ActivatedRoute} from './router_state';
import {UrlHandlingStrategy} from './url_handling_strategy';
import {DefaultUrlSerializer, UrlSerializer} from './url_tree';
import {flatten} from './utils/collection';


/**
 * @whatItDoes Contains a list of directives
 * @stable
 */
const ROUTER_DIRECTIVES = [RouterOutlet, RouterLink, RouterLinkWithHref, RouterLinkActive];

/**
 * @whatItDoes Is used in DI to configure the router.
 * @stable
 */
export const ROUTER_CONFIGURATION = new InjectionToken<ExtraOptions>('ROUTER_CONFIGURATION');

/**
 * @docsNotRequired
 */
export const ROUTER_FORROOT_GUARD = new InjectionToken<void>('ROUTER_FORROOT_GUARD');

export const ROUTER_PROVIDERS: Provider[] = [
  Location,
  {provide: UrlSerializer, useClass: DefaultUrlSerializer},
  {
    provide: Router,
    useFactory: setupRouter,
    deps: [
      ApplicationRef, UrlSerializer, ChildrenOutletContexts, Location, Injector,
      NgModuleFactoryLoader, Compiler, ROUTES, ROUTER_CONFIGURATION,
      [UrlHandlingStrategy, new Optional()], [RouteReuseStrategy, new Optional()]
    ]
  },
  ChildrenOutletContexts,
  {provide: ActivatedRoute, useFactory: rootRoute, deps: [Router]},
  {provide: NgModuleFactoryLoader, useClass: SystemJsNgModuleLoader},
  RouterPreloader,
  NoPreloading,
  PreloadAllModules,
  {provide: ROUTER_CONFIGURATION, useValue: {enableTracing: false}},
];

export function routerNgProbeToken() {
  return new NgProbeToken('Router', Router);
}

/**
 * @whatItDoes Adds router directives and providers.
 *
 * @howToUse
 *
 * RouterModule can be imported multiple times: once per lazily-loaded bundle.
 * Since the router deals with a global shared resource--location, we cannot have
 * more than one router service active.
 *
 * That is why there are two ways to create the module: `RouterModule.forRoot` and
 * `RouterModule.forChild`.
 *
 * * `forRoot` creates a module that contains all the directives, the given routes, and the router
 *   service itself.
 * * `forChild` creates a module that contains all the directives and the given routes, but does not
 *   include the router service.
 *
 * When registered at the root, the module should be used as follows
 *
 * ```
 * @NgModule({
 *   imports: [RouterModule.forRoot(ROUTES)]
 * })
 * class MyNgModule {}
 * ```
 *
 * For submodules and lazy loaded submodules the module should be used as follows:
 *
 * ```
 * @NgModule({
 *   imports: [RouterModule.forChild(ROUTES)]
 * })
 * class MyNgModule {}
 * ```
 *
 * @description
 *
 * Managing state transitions is one of the hardest parts of building applications. This is
 * especially true on the web, where you also need to ensure that the state is reflected in the URL.
 * In addition, we often want to split applications into multiple bundles and load them on demand.
 * Doing this transparently is not trivial.
 *
 * The Angular router solves these problems. Using the router, you can declaratively specify
 * application states, manage state transitions while taking care of the URL, and load bundles on
 * demand.
 *
 * [Read this developer guide](https://angular.io/docs/ts/latest/guide/router.html) to get an
 * overview of how the router should be used.
 *
 * @stable
 */
@NgModule({declarations: ROUTER_DIRECTIVES, exports: ROUTER_DIRECTIVES})
export class RouterModule {
  // Note: We are injecting the Router so it gets created eagerly...
  constructor(@Optional() @Inject(ROUTER_FORROOT_GUARD) guard: any, @Optional() router: Router) {}

  /**
   * Creates a module with all the router providers and directives. It also optionally sets up an
   * application listener to perform an initial navigation.
   *
   * Options:
   * * `enableTracing` makes the router log all its internal events to the console.
   * * `useHash` enables the location strategy that uses the URL fragment instead of the history
   * API.
   * * `initialNavigation` disables the initial navigation.
   * * `errorHandler` provides a custom error handler.
   */
  static forRoot(routes: Routes, config?: ExtraOptions): ModuleWithProviders {
    return {
      ngModule: RouterModule,
      providers: [
        ROUTER_PROVIDERS,
        provideRoutes(routes),
        {
          provide: ROUTER_FORROOT_GUARD,
          useFactory: provideForRootGuard,
          deps: [[Router, new Optional(), new SkipSelf()]]
        },
        {provide: ROUTER_CONFIGURATION, useValue: config ? config : {}},
        {
          provide: LocationStrategy,
          useFactory: provideLocationStrategy,
          deps: [
            PlatformLocation, [new Inject(APP_BASE_HREF), new Optional()], ROUTER_CONFIGURATION
          ]
        },
        {
          provide: PreloadingStrategy,
          useExisting: config && config.preloadingStrategy ? config.preloadingStrategy :
                                                             NoPreloading
        },
        {provide: NgProbeToken, multi: true, useFactory: routerNgProbeToken},
        provideRouterInitializer(),
      ],
    };
  }

  /**
   * Creates a module with all the router directives and a provider registering routes.
   */
  static forChild(routes: Routes): ModuleWithProviders {
    return {ngModule: RouterModule, providers: [provideRoutes(routes)]};
  }
}

export function provideLocationStrategy(
    platformLocationStrategy: PlatformLocation, baseHref: string, options: ExtraOptions = {}) {
  return options.useHash ? new HashLocationStrategy(platformLocationStrategy, baseHref) :
                           new PathLocationStrategy(platformLocationStrategy, baseHref);
}

export function provideForRootGuard(router: Router): any {
  if (router) {
    throw new Error(
        `RouterModule.forRoot() called twice. Lazy loaded modules should use RouterModule.forChild() instead.`);
  }
  return 'guarded';
}

/**
 * @whatItDoes Registers routes.
 *
 * @howToUse
 *
 * ```
 * @NgModule({
 *   imports: [RouterModule.forChild(ROUTES)],
 *   providers: [provideRoutes(EXTRA_ROUTES)]
 * })
 * class MyNgModule {}
 * ```
 *
 * @stable
 */
export function provideRoutes(routes: Routes): any {
  return [
    {provide: ANALYZE_FOR_ENTRY_COMPONENTS, multi: true, useValue: routes},
    {provide: ROUTES, multi: true, useValue: routes},
  ];
}

/**
 * @whatItDoes Represents an option to configure when the initial navigation is performed.
 *
 * @description
 * * 'enabled' - the initial navigation starts before the root component is created.
 * The bootstrap is blocked until the initial navigation is complete.
 * * 'disabled' - the initial navigation is not performed. The location listener is set up before
 * the root component gets created.
 * * 'legacy_enabled'- the initial navigation starts after the root component has been created.
 * The bootstrap is not blocked until the initial navigation is complete. @deprecated
 * * 'legacy_disabled'- the initial navigation is not performed. The location listener is set up
 * after @deprecated
 * the root component gets created.
 * * `true` - same as 'legacy_enabled'. @deprecated since v4
 * * `false` - same as 'legacy_disabled'. @deprecated since v4
 *
 * The 'enabled' option should be used for applications unless there is a reason to have
 * more control over when the router starts its initial navigation due to some complex
 * initialization logic. In this case, 'disabled' should be used.
 *
 * The 'legacy_enabled' and 'legacy_disabled' should not be used for new applications.
 *
 * @experimental
 */
export type InitialNavigation =
    true | false | 'enabled' | 'disabled' | 'legacy_enabled' | 'legacy_disabled';

/**
 * @whatItDoes Represents options to configure the router.
 *
 * @stable
 */
export interface ExtraOptions {
  /**
   * Makes the router log all its internal events to the console.
   */
  enableTracing?: boolean;

  /**
   * Enables the location strategy that uses the URL fragment instead of the history API.
   */
  useHash?: boolean;

  /**
   * Disables the initial navigation.
   */
  initialNavigation?: InitialNavigation;

  /**
   * A custom error handler.
   */
  errorHandler?: ErrorHandler;

  /**
   * Configures a preloading strategy. See {@link PreloadAllModules}.
   */
  preloadingStrategy?: any;
}

export function setupRouter(
    ref: ApplicationRef, urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts,
    location: Location, injector: Injector, loader: NgModuleFactoryLoader, compiler: Compiler,
    config: Route[][], opts: ExtraOptions = {}, urlHandlingStrategy?: UrlHandlingStrategy,
    routeReuseStrategy?: RouteReuseStrategy) {
  const router = new Router(
      null, urlSerializer, contexts, location, injector, loader, compiler, flatten(config));

  if (urlHandlingStrategy) {
    router.urlHandlingStrategy = urlHandlingStrategy;
  }

  if (routeReuseStrategy) {
    router.routeReuseStrategy = routeReuseStrategy;
  }

  if (opts.errorHandler) {
    router.errorHandler = opts.errorHandler;
  }

  if (opts.enableTracing) {
    const dom = getDOM();
    router.events.subscribe(e => {
      dom.logGroup(`Router Event: ${(<any>e.constructor).name}`);
      dom.log(e.toString());
      dom.log(e);
      dom.logGroupEnd();
    });
  }

  return router;
}

export function rootRoute(router: Router): ActivatedRoute {
  return router.routerState.root;
}

/**
 * To initialize the router properly we need to do in two steps:
 *
 * We need to start the navigation in a APP_INITIALIZER to block the bootstrap if
 * a resolver or a guards executes asynchronously. Second, we need to actually run
 * activation in a BOOTSTRAP_LISTENER. We utilize the afterPreactivation
 * hook provided by the router to do that.
 *
 * The router navigation starts, reaches the point when preactivation is done, and then
 * pauses. It waits for the hook to be resolved. We then resolve it only in a bootstrap listener.
 */
@Injectable()
export class RouterInitializer {
  private initNavigation: boolean = false;
  private resultOfPreactivationDone = new Subject<void>();

  constructor(private injector: Injector) {}

  appInitializer(): Promise<any> {
    const p: Promise<any> = this.injector.get(LOCATION_INITIALIZED, Promise.resolve(null));
    return p.then(() => {
      let resolve: Function = null !;
      const res = new Promise(r => resolve = r);
      const router = this.injector.get(Router);
      const opts = this.injector.get(ROUTER_CONFIGURATION);

      if (this.isLegacyDisabled(opts) || this.isLegacyEnabled(opts)) {
        resolve(true);

      } else if (opts.initialNavigation === 'disabled') {
        router.setUpLocationChangeListener();
        resolve(true);

      } else if (opts.initialNavigation === 'enabled') {
        router.hooks.afterPreactivation = () => {
          // only the initial navigation should be delayed
          if (!this.initNavigation) {
            this.initNavigation = true;
            resolve(true);
            return this.resultOfPreactivationDone;

            // subsequent navigations should not be delayed
          } else {
            return of (null) as any;
          }
        };
        router.initialNavigation();

      } else {
        throw new Error(`Invalid initialNavigation options: '${opts.initialNavigation}'`);
      }

      return res;
    });
  }

  bootstrapListener(bootstrappedComponentRef: ComponentRef<any>): void {
    const opts = this.injector.get(ROUTER_CONFIGURATION);
    const preloader = this.injector.get(RouterPreloader);
    const router = this.injector.get(Router);
    const ref = this.injector.get(ApplicationRef);

    if (bootstrappedComponentRef !== ref.components[0]) {
      return;
    }

    if (this.isLegacyEnabled(opts)) {
      router.initialNavigation();
    } else if (this.isLegacyDisabled(opts)) {
      router.setUpLocationChangeListener();
    }

    preloader.setUpPreloading();
    router.resetRootComponentType(ref.componentTypes[0]);
    this.resultOfPreactivationDone.next(null !);
    this.resultOfPreactivationDone.complete();
  }

  private isLegacyEnabled(opts: ExtraOptions): boolean {
    return opts.initialNavigation === 'legacy_enabled' || opts.initialNavigation === true ||
        opts.initialNavigation === undefined;
  }

  private isLegacyDisabled(opts: ExtraOptions): boolean {
    return opts.initialNavigation === 'legacy_disabled' || opts.initialNavigation === false;
  }
}

export function getAppInitializer(r: RouterInitializer) {
  return r.appInitializer.bind(r);
}

export function getBootstrapListener(r: RouterInitializer) {
  return r.bootstrapListener.bind(r);
}

/**
 * A token for the router initializer that will be called after the app is bootstrapped.
 *
 * @experimental
 */
export const ROUTER_INITIALIZER =
    new InjectionToken<(compRef: ComponentRef<any>) => void>('Router Initializer');

export function provideRouterInitializer() {
  return [
    RouterInitializer,
    {
      provide: APP_INITIALIZER,
      multi: true,
      useFactory: getAppInitializer,
      deps: [RouterInitializer]
    },
    {provide: ROUTER_INITIALIZER, useFactory: getBootstrapListener, deps: [RouterInitializer]},
    {provide: APP_BOOTSTRAP_LISTENER, multi: true, useExisting: ROUTER_INITIALIZER},
  ];
}