using System;

using System.Linq;

using System.Reactive;

using System.Reactive.Linq;

using System.Reactive.Subjects;

using System.Runtime.Serialization;

using ReactiveUI.Serialization;

using ReactiveUI.Xaml;

namespace ReactiveUI.Routing

{

[DataContract]

public class RoutingState : ModelBase

{

[IgnoreDataMember] SerializedCollection<IRoutableViewModel> _NavigationStack;

[DataMember]

public SerializedCollection<IRoutableViewModel> NavigationStack {

get { return _NavigationStack; }

protected set { _NavigationStack = value; }

}

[IgnoreDataMember]

public ReactiveCommand NavigateBack { get; protected set; }

[IgnoreDataMember]

public ReactiveCommand NavigateForward { get; protected set; }

[IgnoreDataMember]

public ReactiveCommand Navigate { get; protected set; }

[IgnoreDataMember]

public IObservable<IRoutableViewModel> CurrentViewModel { get; protected set; }

[DataMember]

string _AutoSaveContract;

public RoutingState() : this(null)

{

}

public RoutingState(string autoSaveContract)

{

_NavigationStack = new SerializedCollection<IRoutableViewModel>();

_AutoSaveContract = autoSaveContract;

setupRx();

}

[OnDeserialized]

void setupRx(StreamingContext sc) { setupRx(); }

void setupRx()

{

NavigateBack = new ReactiveCommand(

NavigationStack.CollectionCountChanged.StartWith(_NavigationStack.Count).Select(x => x > 0));

NavigateBack.Subscribe(_ =>

NavigationStack.RemoveAt(NavigationStack.Count - 1));

NavigateForward = new ReactiveCommand();

NavigateForward.Subscribe(x =>

NavigationStack.Insert(NavigationStack.Count, (IRoutableViewModel)x));

Navigate = new ReactiveCommand();

Navigate.Subscribe(x => {

NavigationStack.Clear();

NavigationStack.Add((IRoutableViewModel) x);

});

if (_AutoSaveContract != null) {

Observable.Merge(Navigate, NavigateForward, NavigateBack)

.Subscribe(_ => RxStorage.Engine.CreateSyncPoint(this, _AutoSaveContract));

}

CurrentViewModel = NavigationStack.CollectionCountChanged

.Select(_ => NavigationStack.LastOrDefault())

.Multicast(new ReplaySubject<IRoutableViewModel>(1)).PermaRef();

}

public T FindViewModelInStack<T>()

where T : IRoutableViewModel

{

return NavigationStack.Reverse().OfType<T>().FirstOrDefault();

}

}

}