using Microsoft.Extensions.DependencyInjection;

using System;

namespace Jering.Javascript.NodeJS

{

/// <summary>

/// A class that provides static access to an instance of the default <see cref="INodeJSService"/> implementation's public methods.

/// </summary>

public static partial class StaticNodeJSService

{

private static volatile ServiceProvider? _serviceProvider;

private static volatile IServiceCollection? _services;

private static volatile INodeJSService? _nodeJSService;

private static readonly object _createLock = new();

private static INodeJSService GetOrCreateNodeJSService()

{

if (_nodeJSService == null || _services != null)

{

lock (_createLock)

{

if (_nodeJSService == null || _services != null)

{

// Dispose of service provider

_serviceProvider?.Dispose();

// Create new service provider

_services ??= new ServiceCollection().AddNodeJS();

_serviceProvider = _services.BuildServiceProvider();

_nodeJSService = _serviceProvider.GetRequiredService<INodeJSService>();

_services = null;

}

}

}

// NodeJSService already exists and no configuration pending

return _nodeJSService;

}

/// <summary>

/// <para>Disposes the underlying <see cref="IServiceProvider"/> used to resolve <see cref="INodeJSService"/>.</para>

/// <para>This method is not thread safe.</para>

/// </summary>

public static void DisposeServiceProvider()

{

_serviceProvider?.Dispose();

_serviceProvider = null;

_nodeJSService = null;

}

/// <summary>

/// <para>Configures options.</para>

/// <para>This method is not thread safe.</para>

/// </summary>

/// <typeparam name="T">The type of options to configure.</typeparam>

/// <param name="configureOptions">The action that configures the options.</param>

public static void Configure<T>(Action<T> configureOptions) where T : class

{

_services = (_services ?? new ServiceCollection().AddNodeJS()).Configure(configureOptions);

}

/// <summary>

/// <para>Sets the <see cref="ServiceCollection"/> used to create an <see cref="INodeJSService"/>.</para>

/// <para>This method is not thread safe.</para>

/// </summary>

/// <param name="services">

/// <para>The <see cref="ServiceCollection"/> used to create an <see cref="INodeJSService"/>.</para>

/// <para>If this value doesn't contain a valid service for <see cref="INodeJSService"/>, <see cref="InvalidOperationException"/>s are

/// thrown on subsequent invocations.</para>

/// </param>

public static void SetServices(ServiceCollection services)

{

_services = services;

}

}

}