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MaxBy.cs
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MaxBy.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information.
using System.Collections.Generic;
namespace System.Reactive.Linq.ObservableImpl
{
internal sealed class MaxBy<TSource, TKey> : Producer<IList<TSource>, MaxBy<TSource, TKey>._>
{
private readonly IObservable<TSource> _source;
private readonly Func<TSource, TKey> _keySelector;
private readonly IComparer<TKey> _comparer;
public MaxBy(IObservable<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
{
_source = source;
_keySelector = keySelector;
_comparer = comparer;
}
protected override _ CreateSink(IObserver<IList<TSource>> observer) => new _(this, observer);
protected override void Run(_ sink) => sink.Run(_source);
internal sealed class _ : Sink<TSource, IList<TSource>>
{
private readonly Func<TSource, TKey> _keySelector;
private readonly IComparer<TKey> _comparer;
private bool _hasValue;
private TKey _lastKey;
private List<TSource> _list;
public _(MaxBy<TSource, TKey> parent, IObserver<IList<TSource>> observer)
: base(observer)
{
_keySelector = parent._keySelector;
_comparer = parent._comparer;
_list = new List<TSource>();
}
public override void OnNext(TSource value)
{
TKey key;
try
{
key = _keySelector(value);
}
catch (Exception ex)
{
_list = null;
_lastKey = default;
ForwardOnError(ex);
return;
}
var comparison = 0;
if (!_hasValue)
{
_hasValue = true;
_lastKey = key;
}
else
{
try
{
comparison = _comparer.Compare(key, _lastKey);
}
catch (Exception ex)
{
_list = null;
_lastKey = default;
ForwardOnError(ex);
return;
}
}
if (comparison > 0)
{
_lastKey = key;
_list.Clear();
}
if (comparison >= 0)
{
_list.Add(value);
}
}
public override void OnError(Exception error)
{
_lastKey = default;
_list = null;
base.OnError(error);
}
public override void OnCompleted()
{
var list = _list;
_list = null;
_lastKey = default;
ForwardOnNext(list);
ForwardOnCompleted();
}
}
}
}