osu/osu.Game/Online/SignalRUnionWorkaroundResol...

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// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
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#nullable disable
using System;
using System.Collections.Generic;
using System.Linq;
using MessagePack;
using MessagePack.Formatters;
using MessagePack.Resolvers;
namespace osu.Game.Online
{
/// <summary>
/// Handles SignalR being unable to comprehend [Union] types correctly by redirecting to a known base (union) type.
/// See https://github.com/dotnet/aspnetcore/issues/7298.
/// </summary>
public class SignalRUnionWorkaroundResolver : IFormatterResolver
{
public static readonly MessagePackSerializerOptions OPTIONS =
MessagePackSerializerOptions.Standard.WithResolver(new SignalRUnionWorkaroundResolver());
private static readonly IReadOnlyDictionary<Type, IMessagePackFormatter> formatter_map = createFormatterMap();
private static IReadOnlyDictionary<Type, IMessagePackFormatter> createFormatterMap()
{
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IEnumerable<(Type derivedType, Type baseType)> baseMap = SignalRWorkaroundTypes.BASE_TYPE_MAPPING;
// This should not be required. The fallback should work. But something is weird with the way caching is done.
// For future adventurers, I would not advise looking into this further. It's likely not worth the effort.
baseMap = baseMap.Concat(baseMap.Select(t => (t.baseType, t.baseType)).Distinct());
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return new Dictionary<Type, IMessagePackFormatter>(baseMap.Select(t =>
{
var formatter = (IMessagePackFormatter)Activator.CreateInstance(typeof(TypeRedirectingFormatter<,>).MakeGenericType(t.derivedType, t.baseType));
return new KeyValuePair<Type, IMessagePackFormatter>(t.derivedType, formatter);
}));
}
public IMessagePackFormatter<T> GetFormatter<T>()
{
if (formatter_map.TryGetValue(typeof(T), out var formatter))
return (IMessagePackFormatter<T>)formatter;
return StandardResolver.Instance.GetFormatter<T>();
}
public class TypeRedirectingFormatter<TActual, TBase> : IMessagePackFormatter<TActual>
{
private readonly IMessagePackFormatter<TBase> baseFormatter;
public TypeRedirectingFormatter()
{
baseFormatter = StandardResolver.Instance.GetFormatter<TBase>();
}
public void Serialize(ref MessagePackWriter writer, TActual value, MessagePackSerializerOptions options) =>
baseFormatter.Serialize(ref writer, (TBase)(object)value, StandardResolver.Options);
public TActual Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options) =>
(TActual)(object)baseFormatter.Deserialize(ref reader, StandardResolver.Options);
}
}
}