using System;
using System.Runtime.InteropServices;
using SharpVk;

using PhysicalDeviceFeaturesNative = SharpVk.Interop.PhysicalDeviceFeatures;

namespace SkiaSharp
{
	public delegate IntPtr GRSharpVkGetProcedureAddressDelegate(string name, Instance instance, Device device);

	public unsafe class GRSharpVkBackendContext : GRVkBackendContext
	{
		private Instance vkInstance;
		private PhysicalDevice vkPhysicalDevice;
		private Device vkDevice;
		private Queue vkQueue;
		private PhysicalDeviceFeatures? vkPhysicalDeviceFeatures;
		private GRSharpVkGetProcedureAddressDelegate getProc;

		private PhysicalDeviceFeaturesNative devFeatures;
		private GCHandle devFeaturesHandle;

		protected override void Dispose(bool disposing)
		{
			base.Dispose(disposing);

			if (disposing)
			{
				if (devFeaturesHandle.IsAllocated)
				{
					devFeaturesHandle.Free();
					devFeaturesHandle = default;
				}
			}
		}

		public new Instance VkInstance
		{
			get => vkInstance;
			set
			{
				vkInstance = value;
				base.VkInstance = (IntPtr)vkInstance?.RawHandle.ToUInt64();
			}
		}

		public new PhysicalDevice VkPhysicalDevice
		{
			get => vkPhysicalDevice;
			set
			{
				vkPhysicalDevice = value;
				base.VkPhysicalDevice = (IntPtr)vkPhysicalDevice?.RawHandle.ToUInt64();
			}
		}

		public new Device VkDevice
		{
			get => vkDevice;
			set
			{
				vkDevice = value;
				base.VkDevice = (IntPtr)vkDevice?.RawHandle.ToUInt64();
			}
		}

		public new Queue VkQueue
		{
			get => vkQueue;
			set
			{
				vkQueue = value;
				base.VkQueue = (IntPtr)vkQueue?.RawHandle.ToUInt64();
			}
		}

		public new PhysicalDeviceFeatures? VkPhysicalDeviceFeatures
		{
			get => vkPhysicalDeviceFeatures;
			set
			{
				vkPhysicalDeviceFeatures = value;

				if (devFeaturesHandle.IsAllocated)
					devFeaturesHandle.Free();

				devFeatures = default;
				devFeaturesHandle = default;
				base.VkPhysicalDeviceFeatures = IntPtr.Zero;

				if (value is PhysicalDeviceFeatures feat)
				{
					devFeatures = feat.ToNative();
					devFeaturesHandle = GCHandle.Alloc(devFeatures, GCHandleType.Pinned);
					base.VkPhysicalDeviceFeatures = devFeaturesHandle.AddrOfPinnedObject();
				}
			}
		}

		public new GRSharpVkGetProcedureAddressDelegate GetProcedureAddress
		{
			get => getProc;
			set
			{
				getProc = value;

				base.GetProcedureAddress = null;

				if (value is GRSharpVkGetProcedureAddressDelegate del)
				{
					base.GetProcedureAddress = (name, instance, device) =>
					{
						if (instance != IntPtr.Zero && vkInstance?.RawHandle.ToUInt64() != (ulong)instance.ToInt64())
							throw new InvalidOperationException("Incorrect object for VkInstance.");
						if (device != IntPtr.Zero && vkDevice?.RawHandle.ToUInt64() != (ulong)device.ToInt64())
							throw new InvalidOperationException("Incorrect object for VkDevice.");

						var i = instance != IntPtr.Zero ? vkInstance : null;
						var d = device != IntPtr.Zero ? vkDevice : null;

						return del?.Invoke(name, i, d) ?? IntPtr.Zero;
					};
				}
			}
		}
	}
}