Dashboard/Dashboard.Drawing.OpenGL/ContextResourcePool.cs

namespace Dashboard.Drawing.OpenGL
{
    public class ContextResourcePoolManager
    {
        private readonly Dictionary<IGLContext, ContextResourcePool> _unique = new Dictionary<IGLContext, ContextResourcePool>();
        private readonly Dictionary<int, ContextResourcePool> _shared = new Dictionary<int, ContextResourcePool>();

        public ContextResourcePool Get(IGLContext context)
        {
            if (context.ContextGroup == -1)
            {
                if (!_unique.TryGetValue(context, out ContextResourcePool? pool))
                {
                    pool = new ContextResourcePool(this, context);
                    _unique.Add(context, pool);
                }

                return pool;
            }
            else
            {
                if (!_shared.TryGetValue(context.ContextGroup, out ContextResourcePool? pool))
                {
                    pool = new ContextResourcePool(this, context.ContextGroup);
                    _shared.Add(context.ContextGroup, pool);
                }

                return pool;
            }
        }

        internal void Disposed(ContextResourcePool pool)
        {
            // TODO:
        }
    }

    public class ContextResourcePool : IGLDisposable, IArc
    {
        private int _references = 0;
        private bool _isDisposed = false;
        private readonly Dictionary<int, IResourceManager> _managers = new Dictionary<int, IResourceManager>();

        public ContextResourcePoolManager Manager { get; }
        public IGLContext? Context { get; private set; } = null;
        public int ContextGroup { get; private set; } = -1;
        public int References => _references;
        public ContextCollector Collector { get; } = new ContextCollector();

        internal ContextResourcePool(ContextResourcePoolManager manager, int contextGroup)
        {
            Manager = manager;
            ContextGroup = contextGroup;
        }

        internal ContextResourcePool(ContextResourcePoolManager manager, IGLContext context)
        {
            Manager = manager;
            Context = context;
        }

        public T GetResourceManager<T>(bool init = true) where T : IResourceManager, new()
        {
            int index = ManagerAtom<T>.Atom;

            if (!_managers.TryGetValue(index, out IResourceManager? resourceClass))
            {
                _managers[index] = resourceClass = new T();
            }

            if (init && resourceClass is IInitializer initializer)
            {
                initializer.Initialize();
            }

            return (T)resourceClass;
        }

        ~ContextResourcePool()
        {
            Dispose(true, false);
        }

        public void Dispose() => Dispose(true, false);

        public void Dispose(bool safeExit) => Dispose(safeExit, true);

        private void Dispose(bool safeExit, bool disposing)
        {
            if (_isDisposed)
                return;
            _isDisposed = true;

            Manager.Disposed(this);

            if (disposing)
            {
                foreach ((int _, IResourceManager manager) in _managers)
                {
                    if (manager is IGLDisposable glDisposable)
                        glDisposable.Dispose(safeExit);
                    else if (manager is IDisposable disposable)
                        disposable.Dispose();
                }
                GC.SuppressFinalize(this);
            }
        }

        public void IncrementReference()
        {
            Interlocked.Increment(ref _references);
        }

        public bool DecrementReference()
        {
            return Interlocked.Decrement(ref _references) == 0;
        }


        private class ManagerAtom
        {
            private static int _counter = -1;

            protected static int Acquire() => Interlocked.Increment(ref _counter);
        }
        private class ManagerAtom<T> : ManagerAtom where T : IResourceManager
        {
            public static int Atom { get; } = Acquire();
        }
    }
}