using System;
using System.Linq;
using System.Reflection;

namespace ScreenConnect;

public class Singleton<T> where T : class
{
	private static T instance;

	public static T Instance
	{
		get
		{
			if (instance == null)
			{
				lock (typeof(Singleton<T>))
				{
					if (instance == null)
					{
						instance = CreateInstance();
					}
				}
			}
			return instance;
		}
	}

	private static T CreateInstance()
	{
		AssemblyName thisTypeAssemblyName = typeof(T).GetAssemblyX().GetName();
		Exception lastException = null;
		foreach (Type type in (from singletonTypeAttribute in typeof(T).GetCustomAttributes<SingletonTypeAttribute>()
			where singletonTypeAttribute.EnvironmentFlags == (EnvironmentInfo.Current & ((singletonTypeAttribute.EnvironmentFlagsMask == EnvironmentFlags.UnknownRuntime) ? singletonTypeAttribute.EnvironmentFlags : singletonTypeAttribute.EnvironmentFlagsMask))
			select Extensions.TryGet(() => string.Format(singletonTypeAttribute.AssemblyName, thisTypeAssemblyName.Version, thisTypeAssemblyName.GetPublicKeyToken().ToHexString()).Pipe((string it) => new AssemblyName(it)).Pipe(Assembly.Load)
				.Pipe((Assembly it) => it.GetType(singletonTypeAttribute.TypeName).AssertNonNull()), out Type value2, out lastException, shouldTraceException: false).Pipe((bool _) => value2)).WhereNotNull().AppendIf<Type>(typeof(T), !typeof(T).IsAbstractX()))
		{
			if (Extensions.TryGet(() => (T)Activator.CreateInstance(type), out T value, out lastException))
			{
				return value;
			}
		}
		throw new InvalidOperationException($"Cannot create singleton instance of {typeof(T)}", lastException);
	}
}