// Copyright (c) Microsoft Corporation. All rights reserved.

// Licensed under the MIT license.

using System;

using System.Runtime.CompilerServices;

using Microsoft.ClearScript.Util;

using Microsoft.ClearScript.V8.SplitProxy;

namespace Microsoft.ClearScript.V8.FastProxy

{

internal static class NullableHelpers

{

private static readonly ConditionalWeakTable<Type, Holder<IImpl>> table = new();

public static bool TryGet<TNullable>(Type underlyingType, in V8Value.FastArg arg, object obj, out TNullable value)

{

return GetImpl(underlyingType).TryGet(arg, obj, out value);

}

public static void Set<TNullable>(Type underlyingType, in V8FastResult result, ref TNullable value)

{

GetImpl(underlyingType).Set(result, ref value);

}

private static IImpl GetImpl(Type underlyingType)

{

lock (table)

{

var holder = table.GetOrCreateValue(underlyingType);

return holder.Value ?? (holder.Value = CreateImpl(underlyingType));

}

}

private static IImpl CreateImpl(Type underlyingType)

{

return (IImpl)typeof(Impl<>).MakeGenericType(underlyingType).CreateInstance();

}

#region Nested type: IImpl

private interface IImpl

{

bool TryGet<TNullable>(in V8Value.FastArg arg, object obj, out TNullable value);

void Set<TNullable>(in V8FastResult result, ref TNullable value);

}

#endregion

#region Nested type: Impl<TUnderlying>

private sealed class Impl<TUnderlying> : IImpl where TUnderlying : struct

{

#region IImpl implementation

bool IImpl.TryGet<TNullable>(in V8Value.FastArg arg, object obj, out TNullable value)

{

value = default;

return V8FastArgImpl.TryGet(arg, obj, out Unsafe.As<TNullable, TUnderlying?>(ref value));

}

void IImpl.Set<TNullable>(in V8FastResult result, ref TNullable value)

{

result.SetNullable(Unsafe.As<TNullable, TUnderlying?>(ref value));

}

#endregion

}

#endregion

}

}