import {Promise, PromiseWrapper, EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
import {Map, MapWrapper, List, ListWrapper} from 'angular2/src/facade/collection';
import {isBlank, isPresent, Type} from 'angular2/src/facade/lang';

import {RouteRegistry} from './route_registry';
import {Pipeline} from './pipeline';
import {Instruction} from './instruction';
import {RouterOutlet} from './router_outlet';
import {Location} from './location';

/**
 * # Router
 * The router is responsible for mapping URLs to components.
 *
 * You can see the state of the router by inspecting the read-only field `router.navigating`.
 * This may be useful for showing a spinner, for instance.
 *
 * ## Concepts
 * Routers and component instances have a 1:1 correspondence.
 *
 * The router holds reference to a number of "outlets." An outlet is a placeholder that the
 * router dynamically fills in depending on the current URL.
 *
 * When the router navigates from a URL, it must first recognizes it and serialize it into an `Instruction`.
 * The router uses the `RouteRegistry` to get an `Instruction`.
 *
 * @exportedAs angular2/router
 */
export class Router {
  hostComponent:any;
  parent:Router;
  navigating:boolean;
  lastNavigationAttempt: string;
  previousUrl:string;

  _currentInstruction:Instruction;

  _pipeline:Pipeline;
  _registry:RouteRegistry;
  _outlets:Map<any, Outlet>;
  _subject:EventEmitter;


  constructor(registry:RouteRegistry, pipeline:Pipeline, parent:Router, hostComponent:any) {
    this.hostComponent = hostComponent;
    this.navigating = false;
    this.parent = parent;
    this.previousUrl = null;
    this._outlets = MapWrapper.create();
    this._registry = registry;
    this._pipeline = pipeline;
    this._subject = new EventEmitter();
    this._currentInstruction = null;
  }


  /**
   * Constructs a child router. You probably don't need to use this unless you're writing a reusable component.
   */
  childRouter(hostComponent:any): Router {
    return new ChildRouter(this, hostComponent);
  }


  /**
   * Register an object to notify of route changes. You probably don't need to use this unless you're writing a reusable component.
   */
  registerOutlet(outlet:RouterOutlet, name: string = 'default'): Promise {
    MapWrapper.set(this._outlets, name, outlet);
    if (isPresent(this._currentInstruction)) {
      var childInstruction = this._currentInstruction.getChild(name);
      return outlet.activate(childInstruction);
    }
    return PromiseWrapper.resolve(true);
  }


  /**
   * Dynamically update the routing configuration and trigger a navigation.
   *
   * # Usage
   *
   * ```
   * router.config({ 'path': '/', 'component': IndexCmp});
   * ```
   *
   * Or:
   *
   * ```
   * router.config([
   *   { 'path': '/', 'component': IndexComp },
   *   { 'path': '/user/:id', 'component': UserComp },
   * ]);
   * ```
   *
   */
  config(config:any): Promise {
    if (config instanceof List) {
      config.forEach((configObject) => {
        this._registry.config(this.hostComponent, configObject);
      });
    } else {
      this._registry.config(this.hostComponent, config);
    }
    return this.renavigate();
  }


  /**
   * Navigate to a URL. Returns a promise that resolves to the canonical URL for the route.
   *
   * If the given URL begins with a `/`, router will navigate absolutely.
   * If the given URL does not begin with `/`, the router will navigate relative to this component.
   */
  navigate(url:string):Promise {
    if (this.navigating) {
      return PromiseWrapper.resolve(true);
    }

    this.lastNavigationAttempt = url;

    var matchedInstruction = this.recognize(url);

    if (isBlank(matchedInstruction)) {
      return PromiseWrapper.resolve(false);
    }

    if (isPresent(this._currentInstruction)) {
      matchedInstruction.reuseComponentsFrom(this._currentInstruction);
    }

    this._startNavigating();

    var result = this.commit(matchedInstruction)
        .then((_) => {
          ObservableWrapper.callNext(this._subject, matchedInstruction.accumulatedUrl);
          this._finishNavigating();
        });

    PromiseWrapper.catchError(result, (_) => this._finishNavigating());

    return result;
  }

  _startNavigating(): void {
    this.navigating = true;
  }

  _finishNavigating(): void {
    this.navigating = false;
  }


  /**
   * Subscribe to URL updates from the router
   */
  subscribe(onNext): void {
    ObservableWrapper.subscribe(this._subject, onNext);
  }


  /**
   *
   */
  commit(instruction:Instruction):Promise {
    this._currentInstruction = instruction;

    // collect all outlets that do not have a corresponding child instruction
    // and remove them from the internal map of child outlets
    var toDeactivate = ListWrapper.create();
    MapWrapper.forEach(this._outlets, (outlet, outletName) => {
      if (!instruction.hasChild(outletName)) {
        MapWrapper.delete(this._outlets, outletName);
        ListWrapper.push(toDeactivate, outlet);
      }
    });

    return PromiseWrapper.all(ListWrapper.map(toDeactivate, (outlet) => outlet.deactivate()))
        .then((_) => this.activate(instruction));
  }


  /**
   * Recursively remove all components contained by this router's outlets.
   * Calls deactivate hooks on all descendant components
   */
  deactivate():Promise {
    return this._eachOutletAsync((outlet) => outlet.deactivate);
  }


  /**
   * Recursively activate.
   * Calls the "activate" hook on descendant components.
   */
  activate(instruction:Instruction):Promise {
    return this._eachOutletAsync((outlet, name) => outlet.activate(instruction.getChild(name)));
  }


  _eachOutletAsync(fn):Promise {
    return mapObjAsync(this._outlets, fn);
  }


  /**
   * Given a URL, returns an instruction representing the component graph
   */
  recognize(url:string): Instruction {
    return this._registry.recognize(url, this.hostComponent);
  }


  /**
   * Navigates to either the last URL successfully navigated to, or the last URL requested if the router has yet to successfully navigate.
   */
  renavigate():Promise {
    var destination = isBlank(this.previousUrl) ? this.lastNavigationAttempt : this.previousUrl;
    if (this.navigating || isBlank(destination)) {
      return PromiseWrapper.resolve(false);
    }
    return this.navigate(destination);
  }


  /**
   * Generate a URL from a component name and optional map of parameters. The URL is relative to the app's base href.
   */
  generate(name:string, params:StringMap<string, string>): string {
    return this._registry.generate(name, params, this.hostComponent);
  }
}

export class RootRouter extends Router {
  _location:Location;

  constructor(registry:RouteRegistry, pipeline:Pipeline, location:Location, hostComponent:Type) {
    super(registry, pipeline, null, hostComponent);
    this._location = location;
    this._location.subscribe((change) => this.navigate(change['url']));
    this._registry.configFromComponent(hostComponent);
    this.navigate(location.path());
  }

  commit(instruction):Promise {
    return super.commit(instruction).then((_) => {
      this._location.go(instruction.accumulatedUrl);
    });
  }
}

class ChildRouter extends Router {
  constructor(parent:Router, hostComponent) {
    super(parent._registry, parent._pipeline, parent, hostComponent);
    this.parent = parent;
  }
}

function mapObjAsync(obj:Map, fn): Promise {
  return PromiseWrapper.all(mapObj(obj, fn));
}

function mapObj(obj:Map, fn):List {
  var result = ListWrapper.create();
  MapWrapper.forEach(obj, (value, key) => ListWrapper.push(result, fn(value, key)));
  return result;
}