// Licensed to the .NET Foundation under one or more agreements.

// The .NET Foundation licenses this file to you under the MS-PL license.

// See the LICENSE file in the project root for more information.

using System;

using System.Linq.Expressions;

using System.Reactive.Linq;

using System.Reflection;

namespace ReactiveUI

{

/// <summary>

/// Generates Observables based on observing Reactive objects

/// </summary>

public class IROObservableForProperty : ICreatesObservableForProperty

{

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

{

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

// tightly than INPCObservableForProperty, so we return 10 here

// instead of one

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

}

public IObservable<IObservedChange<object, object>> GetNotificationForProperty(object sender, Expression expression, bool beforeChanged = false)

{

var iro = sender as IReactiveObject;

if (iro == null) {

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

}

var obs = beforeChanged ? iro.getChangingObservable() : iro.getChangedObservable();

var memberInfo = expression.GetMemberInfo();

if (beforeChanged) {

if (expression.NodeType == ExpressionType.Index) {

return obs.Where(x => x.PropertyName.Equals(memberInfo.Name + "[]"))

.Select(x => new ObservedChange<object, object>(sender, expression));

} else {

return obs.Where(x => x.PropertyName.Equals(memberInfo.Name))

.Select(x => new ObservedChange<object, object>(sender, expression));

}

} else {

if (expression.NodeType == ExpressionType.Index) {

return obs.Where(x => x.PropertyName.Equals(memberInfo.Name + "[]"))

.Select(x => new ObservedChange<object, object>(sender, expression));

} else {

return obs.Where(x => x.PropertyName.Equals(memberInfo.Name))

.Select(x => new ObservedChange<object, object>(sender, expression));

}

}

}

}

}