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

namespace FidelityFX
{
    public static class FfxSpd
    {
        public static void SetupSpdConstants(Vector2Int resolution, ref SpdConstants spdConstants, out Vector2Int dispatchThreadGroupCount, int mips = -1)
        {
            RectInt rectInfo = new RectInt(0, 0, resolution.x, resolution.y);
            SpdSetup(rectInfo, out dispatchThreadGroupCount, out Vector2Int workGroupOffset, out Vector2Int numWorkGroupsAndMips, mips);
            
            spdConstants.numWorkGroups = (uint)numWorkGroupsAndMips.x;
            spdConstants.mips = (uint)numWorkGroupsAndMips.y;
            spdConstants.workGroupOffsetX = (uint)workGroupOffset.x;
            spdConstants.workGroupOffsetY = (uint)workGroupOffset.y;
        }
        
        public static void SpdSetup(RectInt rectInfo, out Vector2Int dispatchThreadGroupCount, out Vector2Int workGroupOffset, out Vector2Int numWorkGroupsAndMips, int mips = -1)
        {
            workGroupOffset = new Vector2Int(rectInfo.x / 64, rectInfo.y / 64);

            int endIndexX = (rectInfo.x + rectInfo.width - 1) / 64;
            int endIndexY = (rectInfo.y + rectInfo.height - 1) / 64;

            dispatchThreadGroupCount = new Vector2Int(endIndexX + 1 - workGroupOffset.x, endIndexY + 1 - workGroupOffset.y);

            numWorkGroupsAndMips = new Vector2Int(dispatchThreadGroupCount.x * dispatchThreadGroupCount.y, mips);
            if (mips < 0)
            {
                float resolution = Math.Max(rectInfo.width, rectInfo.height);
                numWorkGroupsAndMips.y = Math.Min(Mathf.FloorToInt(Mathf.Log(resolution, 2.0f)), 12);
            }
        }
        
        [Serializable, StructLayout(LayoutKind.Sequential)]
        public struct SpdConstants
        {
            public uint mips;
            public uint numWorkGroups;
            public uint workGroupOffsetX;
            public uint workGroupOffsetY;
        }
    }
}