using UnityEngine.Experimental.Rendering;
using UnityEngine.Rendering.RenderGraphModule;

namespace UnityEngine.Rendering.HighDefinition
{
    public partial class HDRenderPipeline
    {
        class AlphaUpscalePassData
        {
            public ComputeShader alphaUpscaleCS;
            public int alphaUpscaleKernel;

            public int width, height;
            public int viewCount;

            public TextureHandle source;
            public TextureHandle depth;
            public TextureHandle motionVectors;
            public TextureHandle output;

            public bool resetHistory;
            public TextureHandle prevAlpha;
            public TextureHandle nextAlpha;
        }

        TextureHandle UpscaleAlpha(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle source, TextureHandle depth, TextureHandle motionVectors, TextureHandle output)
        {
            using (var builder = renderGraph.AddRenderPass<AlphaUpscalePassData>("Alpha Upscale", out var passData, ProfilingSampler.Get(HDProfileId.AlphaCopy)))
            {
                Vector2Int finalViewport = DynamicResolutionHandler.instance.finalViewport;

                passData.alphaUpscaleCS = runtimeShaders.upscaleAlphaCS;
                passData.alphaUpscaleKernel = passData.alphaUpscaleCS.FindKernel("KMain");
                passData.width = finalViewport.x;
                passData.height = finalViewport.y;
                passData.viewCount = hdCamera.viewCount;
                passData.source = builder.ReadTexture(source);
                passData.depth = builder.ReadTexture(depth);
                passData.motionVectors = builder.ReadTexture(motionVectors);
                passData.output = builder.ReadWriteTexture(output);

                bool validHistory = GrabPostProcessHistoryTextures(hdCamera, HDCameraFrameHistoryType.AlphaUpscale, "Alpha History", GraphicsFormat.R8_UNorm, finalViewport, out RTHandle previous, out RTHandle next);
                passData.resetHistory = !validHistory;
                passData.prevAlpha = validHistory ? builder.ReadTexture(renderGraph.ImportTexture(previous)) : builder.ReadWriteTexture(renderGraph.ImportTexture(previous));
                passData.nextAlpha = builder.WriteTexture(renderGraph.ImportTexture(next));

                builder.SetRenderFunc((AlphaUpscalePassData data, RenderGraphContext ctx) =>
                {
                    if (data.resetHistory)
                    {
                        ctx.cmd.SetRenderTarget(data.prevAlpha);
                        ctx.cmd.ClearRenderTarget(false, true, Color.clear);
                    }

                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._InputTexture, data.source);
                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._CameraDepthTexture, data.depth);
                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._CameraMotionVectorsTexture, data.motionVectors);
                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._OutputTexture, data.output);
                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._InputHistoryTexture, data.prevAlpha);
                    ctx.cmd.SetComputeTextureParam(data.alphaUpscaleCS, data.alphaUpscaleKernel, HDShaderIDs._OutputHistoryTexture, data.nextAlpha);
                    ctx.cmd.DispatchCompute(data.alphaUpscaleCS, data.alphaUpscaleKernel, (data.width + 7) / 8, (data.height + 7) / 8, data.viewCount);
                });

                return passData.output;
            }
        }

        public bool GrabPostProcessHistoryTextures(
            HDCamera camera, HDCameraFrameHistoryType historyType, string name, GraphicsFormat format, in Vector2Int viewportSize, out RTHandle previous, out RTHandle next, bool useMips = false)
        {
            bool validHistory = true;
            next = camera.GetCurrentFrameRT((int)historyType);
            if (next == null || (useMips == true && next.rt.mipmapCount == 1) || next.rt.width != viewportSize.x || next.rt.height != viewportSize.y)
            {
                validHistory = false;
                var textureAllocator = new PostProcessHistoryTextureAllocator(name, viewportSize, format, useMips);

                if (next != null)
                    camera.ReleaseHistoryFrameRT((int)historyType);
                next = camera.AllocHistoryFrameRT((int)historyType, textureAllocator.Allocator, 2);
            }
            previous = camera.GetPreviousFrameRT((int)historyType);
            return validHistory;
        }
    }
}