using Ryujinx.Common;
using Ryujinx.Graphics.GAL;
using Ryujinx.Graphics.Shader;
using Ryujinx.Graphics.Shader.Translation;
using SharpMetal.Metal;
using System;
using System.Collections.Generic;
using System.Runtime.Versioning;

namespace Ryujinx.Graphics.Metal
{
    [SupportedOSPlatform("macos")]
    public class HelperShader : IDisposable
    {
        private const int ConvertElementsPerWorkgroup = 32 * 100; // Work group size of 32 times 100 elements.
        private const string ShadersSourcePath = "/Ryujinx.Graphics.Metal/Shaders";
        private readonly MetalRenderer _renderer;
        private readonly Pipeline _pipeline;
        private MTLDevice _device;

        private readonly ISampler _samplerLinear;
        private readonly ISampler _samplerNearest;
        private readonly IProgram _programColorBlit;
        private readonly List<IProgram> _programsColorClear = new();
        private readonly IProgram _programDepthStencilClear;
        private readonly IProgram _programStrideChange;

        public HelperShader(MTLDevice device, MetalRenderer renderer, Pipeline pipeline)
        {
            _device = device;
            _renderer = renderer;
            _pipeline = pipeline;

            _samplerNearest = new Sampler(_device, SamplerCreateInfo.Create(MinFilter.Nearest, MagFilter.Nearest));
            _samplerLinear = new Sampler(_device, SamplerCreateInfo.Create(MinFilter.Linear, MagFilter.Linear));

            var blitSource = ReadMsl("Blit.metal");
            _programColorBlit = new Program(
            [
                new ShaderSource(blitSource, ShaderStage.Fragment, TargetLanguage.Msl),
                new ShaderSource(blitSource, ShaderStage.Vertex, TargetLanguage.Msl)
            ], device);

            var colorClearSource = ReadMsl("ColorClear.metal");
            for (int i = 0; i < Constants.MaxColorAttachments; i++)
            {
                var crntSource = colorClearSource.Replace("COLOR_ATTACHMENT_INDEX", i.ToString());
                _programsColorClear.Add(new Program(
                [
                    new ShaderSource(crntSource, ShaderStage.Fragment, TargetLanguage.Msl),
                    new ShaderSource(crntSource, ShaderStage.Vertex, TargetLanguage.Msl)
                ], device));
            }

            var depthStencilClearSource = ReadMsl("DepthStencilClear.metal");
            _programDepthStencilClear = new Program(
            [
                new ShaderSource(depthStencilClearSource, ShaderStage.Fragment, TargetLanguage.Msl),
                new ShaderSource(depthStencilClearSource, ShaderStage.Vertex, TargetLanguage.Msl)
            ], device);

            var strideChangeSource = ReadMsl("ChangeBufferStride.metal");
            _programStrideChange = new Program(
            [
                new ShaderSource(strideChangeSource, ShaderStage.Compute, TargetLanguage.Msl)
            ], device);
        }

        private static string ReadMsl(string fileName)
        {
            return EmbeddedResources.ReadAllText(string.Join('/', ShadersSourcePath, fileName));
        }

        public unsafe void BlitColor(
            CommandBufferScoped cbs,
            ITexture src,
            ITexture dst,
            Extents2D srcRegion,
            Extents2D dstRegion,
            bool linearFilter)
        {
            // Save current state
            _pipeline.SaveAndResetState();

            const int RegionBufferSize = 16;

            var sampler = linearFilter ? _samplerLinear : _samplerNearest;

            _pipeline.SetTextureAndSampler(ShaderStage.Fragment, 0, src, sampler);

            Span<float> region = stackalloc float[RegionBufferSize / sizeof(float)];

            region[0] = srcRegion.X1 / (float)src.Width;
            region[1] = srcRegion.X2 / (float)src.Width;
            region[2] = srcRegion.Y1 / (float)src.Height;
            region[3] = srcRegion.Y2 / (float)src.Height;

            if (dstRegion.X1 > dstRegion.X2)
            {
                (region[0], region[1]) = (region[1], region[0]);
            }

            if (dstRegion.Y1 > dstRegion.Y2)
            {
                (region[2], region[3]) = (region[3], region[2]);
            }

            using var buffer = _renderer.BufferManager.ReserveOrCreate(cbs, RegionBufferSize);
            buffer.Holder.SetDataUnchecked<float>(buffer.Offset, region);
            _pipeline.SetUniformBuffers([new BufferAssignment(0, buffer.Range)]);

            var rect = new Rectangle<float>(
                MathF.Min(dstRegion.X1, dstRegion.X2),
                MathF.Min(dstRegion.Y1, dstRegion.Y2),
                MathF.Abs(dstRegion.X2 - dstRegion.X1),
                MathF.Abs(dstRegion.Y2 - dstRegion.Y1));

            Span<Viewport> viewports = stackalloc Viewport[1];

            viewports[0] = new Viewport(
                rect,
                ViewportSwizzle.PositiveX,
                ViewportSwizzle.PositiveY,
                ViewportSwizzle.PositiveZ,
                ViewportSwizzle.PositiveW,
                0f,
                1f);

            _pipeline.SetProgram(_programColorBlit);

            int dstWidth = dst.Width;
            int dstHeight = dst.Height;

            _pipeline.SetRenderTargets([dst], null);
            _pipeline.SetScissors(stackalloc Rectangle<int>[] { new Rectangle<int>(0, 0, dstWidth, dstHeight) });

            _pipeline.SetClearLoadAction(true);

            _pipeline.SetViewports(viewports);
            _pipeline.SetPrimitiveTopology(PrimitiveTopology.TriangleStrip);
            _pipeline.Draw(4, 1, 0, 0);

            // Restore previous state
            _pipeline.RestoreState();
        }

        public unsafe void DrawTexture(
            ITexture src,
            ISampler srcSampler,
            Extents2DF srcRegion,
            Extents2DF dstRegion)
        {
            // Save current state
            _pipeline.SaveState();

            const int RegionBufferSize = 16;

            _pipeline.SetTextureAndSampler(ShaderStage.Fragment, 0, src, srcSampler);

            Span<float> region = stackalloc float[RegionBufferSize / sizeof(float)];

            region[0] = srcRegion.X1 / src.Width;
            region[1] = srcRegion.X2 / src.Width;
            region[2] = srcRegion.Y1 / src.Height;
            region[3] = srcRegion.Y2 / src.Height;

            if (dstRegion.X1 > dstRegion.X2)
            {
                (region[0], region[1]) = (region[1], region[0]);
            }

            if (dstRegion.Y1 > dstRegion.Y2)
            {
                (region[2], region[3]) = (region[3], region[2]);
            }

            var bufferHandle = _renderer.BufferManager.CreateWithHandle(RegionBufferSize);
            _renderer.BufferManager.SetData<float>(bufferHandle, 0, region);
            _pipeline.SetUniformBuffers([new BufferAssignment(0, new BufferRange(bufferHandle, 0, RegionBufferSize))]);

            Span<Viewport> viewports = stackalloc Viewport[1];

            var rect = new Rectangle<float>(
                MathF.Min(dstRegion.X1, dstRegion.X2),
                MathF.Min(dstRegion.Y1, dstRegion.Y2),
                MathF.Abs(dstRegion.X2 - dstRegion.X1),
                MathF.Abs(dstRegion.Y2 - dstRegion.Y1));

            viewports[0] = new Viewport(
                rect,
                ViewportSwizzle.PositiveX,
                ViewportSwizzle.PositiveY,
                ViewportSwizzle.PositiveZ,
                ViewportSwizzle.PositiveW,
                0f,
                1f);

            _pipeline.SetProgram(_programColorBlit);
            _pipeline.SetViewports(viewports);
            _pipeline.SetPrimitiveTopology(PrimitiveTopology.TriangleStrip);
            _pipeline.Draw(4, 1, 0, 0);

            _renderer.BufferManager.Delete(bufferHandle);

            // Restore previous state
            _pipeline.RestoreState();
        }

        public void ConvertI8ToI16(CommandBufferScoped cbs, BufferHolder src, BufferHolder dst, int srcOffset, int size)
        {
            ChangeStride(cbs, src, dst, srcOffset, size, 1, 2);
        }

        public unsafe void ChangeStride(
            CommandBufferScoped cbs,
            BufferHolder src,
            BufferHolder dst,
            int srcOffset,
            int size,
            int stride,
            int newStride)
        {
            int elems = size / stride;

            var srcBuffer = src.GetBuffer();
            var dstBuffer = dst.GetBuffer();

            const int ParamsBufferSize = 16;

            // Save current state
            _pipeline.SaveAndResetState();

            Span<int> shaderParams = stackalloc int[ParamsBufferSize / sizeof(int)];

            shaderParams[0] = stride;
            shaderParams[1] = newStride;
            shaderParams[2] = size;
            shaderParams[3] = srcOffset;

            using var buffer = _renderer.BufferManager.ReserveOrCreate(cbs, ParamsBufferSize);
            buffer.Holder.SetDataUnchecked<int>(buffer.Offset, shaderParams);
            _pipeline.SetUniformBuffers([new BufferAssignment(0, buffer.Range)]);

            Span<Auto<DisposableBuffer>> sbRanges = new Auto<DisposableBuffer>[2];

            sbRanges[0] = srcBuffer;
            sbRanges[1] = dstBuffer;
            _pipeline.SetStorageBuffers(1, sbRanges);

            _pipeline.SetProgram(_programStrideChange);
            _pipeline.DispatchCompute(1 + elems / ConvertElementsPerWorkgroup, 1, 1, 64, 1, 1);

            // Restore previous state
            _pipeline.RestoreState();
        }

        public unsafe void ClearColor(
            int index,
            ReadOnlySpan<float> clearColor,
            uint componentMask,
            int dstWidth,
            int dstHeight)
        {
            // Save current state
            _pipeline.SaveState();

            const int ClearColorBufferSize = 16;

            // TODO: Flush

            using var buffer = _renderer.BufferManager.ReserveOrCreate(_pipeline.CurrentCommandBuffer, ClearColorBufferSize);
            buffer.Holder.SetDataUnchecked(buffer.Offset, clearColor);
            _pipeline.SetUniformBuffers([new BufferAssignment(0, buffer.Range)]);

            Span<Viewport> viewports = stackalloc Viewport[1];

            // TODO: Set exact viewport!
            viewports[0] = new Viewport(
                new Rectangle<float>(0, 0, dstWidth, dstHeight),
                ViewportSwizzle.PositiveX,
                ViewportSwizzle.PositiveY,
                ViewportSwizzle.PositiveZ,
                ViewportSwizzle.PositiveW,
                0f,
                1f);

            _pipeline.SetProgram(_programsColorClear[index]);
            _pipeline.SetBlendState(index, new BlendDescriptor(false, new ColorF(0f, 0f, 0f, 1f), BlendOp.Add, BlendFactor.One, BlendFactor.Zero, BlendOp.Add, BlendFactor.One, BlendFactor.Zero));
            _pipeline.SetFaceCulling(false, Face.Front);
            _pipeline.SetDepthTest(new DepthTestDescriptor(false, false, CompareOp.Always));
            _pipeline.SetRenderTargetColorMasks([componentMask]);
            _pipeline.SetViewports(viewports);
            _pipeline.SetPrimitiveTopology(PrimitiveTopology.TriangleStrip);
            _pipeline.Draw(4, 1, 0, 0);

            // Restore previous state
            _pipeline.RestoreState();
        }

        public unsafe void ClearDepthStencil(
            float depthValue,
            bool depthMask,
            int stencilValue,
            int stencilMask,
            int dstWidth,
            int dstHeight)
        {
            const int ClearDepthBufferSize = 4;

            IntPtr ptr = new(&depthValue);

            // Save current state
            _pipeline.SaveState();

            Span<Viewport> viewports = stackalloc Viewport[1];

            viewports[0] = new Viewport(
                new Rectangle<float>(0, 0, dstWidth, dstHeight),
                ViewportSwizzle.PositiveX,
                ViewportSwizzle.PositiveY,
                ViewportSwizzle.PositiveZ,
                ViewportSwizzle.PositiveW,
                0f,
                1f);

            _pipeline.SetProgram(_programDepthStencilClear);
            _pipeline.SetFaceCulling(false, Face.Front);
            _pipeline.SetDepthTest(new DepthTestDescriptor(false, false, CompareOp.Always));
            _pipeline.SetPrimitiveTopology(PrimitiveTopology.TriangleStrip);
            _pipeline.SetViewports(viewports);
            _pipeline.SetDepthTest(new DepthTestDescriptor(true, depthMask, CompareOp.Always));
            _pipeline.SetStencilTest(CreateStencilTestDescriptor(stencilMask != 0, stencilValue, 0xFF, stencilMask));
            _pipeline.GetOrCreateRenderEncoder(true).SetFragmentBytes(ptr, ClearDepthBufferSize, 0);
            _pipeline.Draw(4, 1, 0, 0);

            // Restore previous state
            _pipeline.RestoreState();
        }

        private static StencilTestDescriptor CreateStencilTestDescriptor(
            bool enabled,
            int refValue = 0,
            int compareMask = 0xff,
            int writeMask = 0xff)
        {
            return new StencilTestDescriptor(
                enabled,
                CompareOp.Always,
                StencilOp.Replace,
                StencilOp.Replace,
                StencilOp.Replace,
                refValue,
                compareMask,
                writeMask,
                CompareOp.Always,
                StencilOp.Replace,
                StencilOp.Replace,
                StencilOp.Replace,
                refValue,
                compareMask,
                writeMask);
        }

        public void Dispose()
        {
            _programColorBlit.Dispose();
            foreach (var programColorClear in _programsColorClear)
            {
                programColorClear.Dispose();
            }
            _programDepthStencilClear.Dispose();
            _pipeline.Dispose();
            _samplerLinear.Dispose();
            _samplerNearest.Dispose();
        }
    }
}