import 'dart:async' show Stream, StreamController;
import 'dart:html' show AnchorElement, window;
import 'angel_route.dart';

final RegExp _hash = new RegExp(r'^#/');

/// A variation of the [Router] support both hash routing and push state.
abstract class BrowserRouter extends Router {
  /// Fires whenever the active route changes. Fires `null` if none is selected (404).
  Stream<RoutingResult> get onResolve;

  /// Fires whenever the active route changes. Fires `null` if none is selected (404).
  Stream<Route> get onRoute;

  /// Set `hash` to true to use hash routing instead of push state.
  /// `listen` as `true` will call `listen` after initialization.
  factory BrowserRouter({bool hash: false, bool listen: true}) {
    return hash
        ? new _HashRouter(listen: listen)
        : new _PushStateRouter(listen: listen);
  }

  BrowserRouter._() : super();

  void _goTo(String path);

  /// Navigates to the path generated by calling
  /// [navigate] with the given [linkParams].
  ///
  /// This always navigates to an absolute path.
  void go(List linkParams);

  /// Begins listen for location changes.
  void listen();

  /// Identical to [all].
  Route on(Pattern path, handler, {List middleware}) =>
      all(path, handler, middleware: middleware);
}

class _BrowserRouterImpl extends Router implements BrowserRouter {
  Route _current;
  StreamController<RoutingResult> _onResolve =
      new StreamController<RoutingResult>();
  StreamController<Route> _onRoute = new StreamController<Route>();
  Route get currentRoute => _current;

  @override
  Stream<RoutingResult> get onResolve => _onResolve.stream;

  @override
  Stream<Route> get onRoute => _onRoute.stream;

  _BrowserRouterImpl({bool listen}) : super() {
    if (listen != false) this.listen();
    prepareAnchors();
  }

  @override
  void go(Iterable linkParams) => _goTo(navigate(linkParams));

  void prepareAnchors() {
    final anchors = window.document.querySelectorAll('a:not([dynamic])');

    for (final AnchorElement $a in anchors) {
      if ($a.attributes.containsKey('href') &&
          !$a.attributes.containsKey('download') &&
          !$a.attributes.containsKey('target') &&
          $a.attributes['rel'] != 'external') {
        $a.onClick.listen((e) {
          e.preventDefault();
          go($a.attributes['href'].split('/').where((str) => str.isNotEmpty));
        });
      }

      $a.attributes['dynamic'] = 'true';
    }
  }
}

class _HashRouter extends _BrowserRouterImpl {
  _HashRouter({bool listen}) : super(listen: listen) {
    if (listen) this.listen();
  }

  @override
  void _goTo(String uri) {
    window.location.hash = '#$uri';
  }

  @override
  void listen() {
    window.onHashChange.listen((_) {
      final path = window.location.hash.replaceAll(_hash, '');
      final resolved = resolveAbsolute(path);

      if (resolved == null) {
        _onResolve.add(null);
        _onRoute.add(_current = null);
      } else if (resolved != null && resolved.route != _current) {
        _onResolve.add(resolved);
        _onRoute.add(_current = resolved.route);
      }
    });
  }
}

class _PushStateRouter extends _BrowserRouterImpl {
  _PushStateRouter({bool listen, Route root}) : super(listen: listen) {
    if (listen) this.listen();
  }

  @override
  void _goTo(String uri) {
    final resolved = resolveAbsolute(uri);

    if (resolved == null) {
      _onResolve.add(null);
      _onRoute.add(_current = null);
    } else {
      final route = resolved.route;
      window.history.pushState(
          {'path': route.path, 'params': {}, 'properties': properties},
          route.name ?? route.path,
          uri);
      _onResolve.add(resolved);
      _onRoute.add(_current = route);
    }
  }

  @override
  void listen() {
    window.onPopState.listen((e) {
      if (e.state is Map && e.state.containsKey('path')) {
        final resolved = resolveAbsolute(e.state['path']);

        if (resolved != null && resolved.route != _current) {
          properties.addAll(e.state['properties'] ?? {});
          _onResolve.add(resolved);
          _onRoute.add(_current = resolved.route
            ..state.properties.addAll(e.state['params'] ?? {}));
        }
      } else {
        _onResolve.add(null);
        _onRoute.add(_current = null);
      }
    });
  }
}