using System;
using SharpDX.D3DCompiler;
using SharpDX.Direct3D;
using SharpDX.Direct3D11;
using SharpDX.Mathematics.Interop;

namespace Intromat.Pipelines
{
    public class DisplayMeshPipeline
    {
        private readonly VertexShader _vs;
        private readonly PixelShader _ps;
        private readonly DeviceContext _context;
        private readonly SamplerState _sampler;
        private ShaderResourceView? _srv;
        private readonly RasterizerState _rs;
        private readonly DepthStencilState _dss;
        private const string _vertexShader = "void main(in uint i : SV_VertexID, out float2 uv : TEXCOORD, out float4 pos : SV_Position) { uv = float2(i % 2, i / 2); pos = float4(uv * 2 - 1, 0.5, 1); }";
        private const string _pixelShader = "Texture2D t; SamplerState s; float4 main(in float2 uv : TEXCOORD) : SV_Target0 { return float4(t.Sample(s, uv).xyz, 1); }";

        public DisplayMeshPipeline(Device device, DeviceContext context)
        {
            var flags = ShaderFlags.None;
#if DEBUG
            flags |= ShaderFlags.Debug;
#endif
            _vs = new VertexShader(device, ShaderBytecode.Compile(_vertexShader, "main", "vs_5_0", flags).Bytecode.Data);
            _ps = new PixelShader(device, ShaderBytecode.Compile(_pixelShader, "main", "ps_5_0", flags).Bytecode.Data);
            _context = context;
            var samplerDesc = new SamplerStateDescription
            {
                Filter = Filter.MinMagMipLinear,
                AddressU = TextureAddressMode.Clamp,
                AddressV = TextureAddressMode.Clamp,
                AddressW = TextureAddressMode.Clamp
            };
            _sampler = new SamplerState(device, samplerDesc);
            var rasterizerDesc = RasterizerStateDescription.Default();
            rasterizerDesc.CullMode = CullMode.None;
            rasterizerDesc.IsDepthClipEnabled = false;
            _rs = new RasterizerState(device, rasterizerDesc);
            var depthStencilStateDesc = DepthStencilStateDescription.Default();
            depthStencilStateDesc.IsDepthEnabled = false;
            _dss = new DepthStencilState(device, depthStencilStateDesc);
        }

        public void Apply()
        {
            var viewport = _context.Rasterizer.GetViewports<RawViewportF>()[0];
            var dim = Math.Min(viewport.Width, viewport.Height);
            var offsetX = dim < viewport.Width ? (viewport.Width - dim) / 2 : 0;
            var offsetY = dim < viewport.Height ? (viewport.Height - dim) / 2 : 0;
            _context.Rasterizer.SetViewport(offsetX, offsetY, dim, dim);
            _context.InputAssembler.PrimitiveTopology = PrimitiveTopology.TriangleStrip;
            _context.VertexShader.Set(_vs);
            _context.PixelShader.Set(_ps);
            _context.PixelShader.SetShaderResources(0, _srv);
            _context.PixelShader.SetSampler(0, _sampler);
            _context.Rasterizer.State = _rs;
            _context.OutputMerger.DepthStencilState = _dss;
            _context.Draw(4, 0);
            _context.PixelShader.SetShaderResources(0, (ShaderResourceView?)null);
        }

        public ShaderResourceView? ShaderResourceView
        {
            get => _srv;
            set => _srv = value;
        }
    }
}