using System;
using System.Runtime.InteropServices;
using UnityEngine;
using UnityEngine.Rendering;

namespace FidelityFX
{
    public abstract class FfxContextBase
    {
        protected static void DestroyPass<TPass>(ref TPass pass)
            where TPass: class, IDisposable
        {
            if (pass == null)
                return;
            
            pass.Dispose();
            pass = null;
        }

        /// <summary>
        /// Convenience class for handling a constants buffer containing a single struct item.
        /// This wraps the compute buffer and the value array, as well as providing easy access to both.
        /// </summary>
        protected class ConstantsBuffer<TConst>
            where TConst: struct
        {
            private ComputeBuffer _computeBuffer;
            
            private readonly TConst[] _constArray = { new TConst() };
            public ref TConst Value => ref _constArray[0];

            public void Create()
            {
                _computeBuffer = new ComputeBuffer(1, Marshal.SizeOf<TConst>(), ComputeBufferType.Constant);
            }

            public void UpdateBufferData(CommandBuffer commandBuffer)
            {
                commandBuffer.SetBufferData(_computeBuffer, _constArray);
            }
            
            public void Destroy()
            {
                if (_computeBuffer == null)
                    return;
                
                _computeBuffer.Release();
                _computeBuffer = null;
            }

            public static implicit operator ComputeBuffer(ConstantsBuffer<TConst> constants)
            {
                return constants._computeBuffer;
            }
        }
    }
}