using System;

using System.Reactive.Linq;

using System.Reflection;

namespace ReactiveUI

{

/// <summary>

/// Generates Observables based on observing Reactive objects

/// </summary>

public class IRNPCObservableForProperty : ICreatesObservableForProperty

{

public int GetAffinityForObject(Type type, string propertyName, bool beforeChanged = false)

{

// NB: Since every IRNPC is also an INPC, we need to bind more

// tightly than INPCObservableForProperty, so we return 10 here

// instead of one

return typeof (IReactiveNotifyPropertyChanged).GetTypeInfo().IsAssignableFrom(type.GetTypeInfo()) ? 10 : 0;

}

public IObservable<IObservedChange<object, object>> GetNotificationForProperty(object sender, string propertyName, bool beforeChanged = false)

{

var irnpc = sender as IReactiveNotifyPropertyChanged;

if (irnpc == null) {

throw new ArgumentException("Sender doesn't implement IReactiveNotifyPropertyChanging");

}

return Observable.Create<IObservedChange<object, object>>(subj => {

var obs = (beforeChanged ? irnpc.Changing : irnpc.Changed);

return obs

.Where(x => x.PropertyName == propertyName)

.Subscribe(subj);

});

}

}

}