// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using Microsoft.Extensions.DependencyInjection;

namespace Microsoft.AspNetCore.SignalR.Internal;

internal sealed class DefaultHubActivator<[DynamicallyAccessedMembers(Hub.DynamicallyAccessedMembers)] THub> : IHubActivator<THub> where THub : Hub
{
    // Object factory for THub instances
    private static readonly Lazy<ObjectFactory> _objectFactory = new Lazy<ObjectFactory>(() => ActivatorUtilities.CreateFactory(typeof(THub), Type.EmptyTypes));
    private readonly IServiceProvider _serviceProvider;
    private bool? _created;

    public DefaultHubActivator(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    public THub Create()
    {
        Debug.Assert(!_created.HasValue, "hub activators must not be reused.");

        _created = false;
        var hub = _serviceProvider.GetService<THub>();
        if (hub == null)
        {
            hub = (THub)_objectFactory.Value(_serviceProvider, Array.Empty<object>());
            _created = true;
        }

        return hub;
    }

    public void Release(THub hub)
    {
        ArgumentNullException.ThrowIfNull(hub);

        Debug.Assert(_created.HasValue, "hubs must be released with the hub activator they were created");

        if (_created.Value)
        {
            hub.Dispose();
        }
    }
}