// SPDX-License-Identifier: MIT
#if GS_ENABLE_URP

using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;
#if UNITY_6000_0_OR_NEWER
using UnityEngine.Rendering.RenderGraphModule;
#endif

namespace GaussianSplatting.Runtime
{
    // Note: I have no idea what is the purpose of ScriptableRendererFeature vs ScriptableRenderPass, which one of those
    // is supposed to do resource management vs logic, etc. etc. Code below "seems to work" but I'm just fumbling along,
    // without understanding any of it.
    //
    // ReSharper disable once InconsistentNaming
    class GaussianSplatURPFeature : ScriptableRendererFeature
    {
        class GSRenderPass : ScriptableRenderPass
        {
            const string GaussianSplatRTName = "_GaussianSplatRT";
#if !UNITY_6000_0_OR_NEWER
            RTHandle m_RenderTarget;
            internal ScriptableRenderer m_Renderer;
            internal CommandBuffer m_Cmb;
#endif

            public void Dispose()
            {
#if !UNITY_6000_0_OR_NEWER
                m_RenderTarget?.Release();
#endif
            }

#if UNITY_6000_0_OR_NEWER
            const string ProfilerTag = "GaussianSplatRenderGraph";
            static readonly ProfilingSampler s_profilingSampler = new(ProfilerTag);
            static readonly int s_gaussianSplatRT = Shader.PropertyToID(GaussianSplatRTName);

            class PassData
            {
                internal UniversalCameraData CameraData;
                internal TextureHandle SourceTexture;
                internal TextureHandle SourceDepth;
                internal TextureHandle GaussianSplatRT;
            }

            public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
            {
                using var builder = renderGraph.AddUnsafePass(ProfilerTag, out PassData passData);

                var cameraData = frameData.Get<UniversalCameraData>();
                var resourceData = frameData.Get<UniversalResourceData>();

                RenderTextureDescriptor rtDesc = cameraData.cameraTargetDescriptor;
                rtDesc.depthBufferBits = 0;
                rtDesc.msaaSamples = 1;
                rtDesc.graphicsFormat = GraphicsFormat.R16G16B16A16_SFloat;
                var textureHandle = UniversalRenderer.CreateRenderGraphTexture(renderGraph, rtDesc, GaussianSplatRTName, true);

                passData.CameraData = cameraData;
                passData.SourceTexture = resourceData.activeColorTexture;
                passData.SourceDepth = resourceData.activeDepthTexture;
                passData.GaussianSplatRT = textureHandle;

                builder.UseTexture(resourceData.activeColorTexture, AccessFlags.ReadWrite);
                builder.UseTexture(resourceData.activeDepthTexture);
                builder.UseTexture(textureHandle, AccessFlags.Write);
                builder.AllowPassCulling(false);
                builder.SetRenderFunc(static (PassData data, UnsafeGraphContext context) =>
                {
                    var commandBuffer = CommandBufferHelpers.GetNativeCommandBuffer(context.cmd);
                    using var _ = new ProfilingScope(commandBuffer, s_profilingSampler);
                    commandBuffer.SetGlobalTexture(s_gaussianSplatRT, data.GaussianSplatRT);
                    CoreUtils.SetRenderTarget(commandBuffer, data.GaussianSplatRT, data.SourceDepth, ClearFlag.Color, Color.clear);
                    Material matComposite = GaussianSplatRenderSystem.instance.SortAndRenderSplats(data.CameraData.camera, commandBuffer);
                    commandBuffer.BeginSample(GaussianSplatRenderSystem.s_ProfCompose);
                    Blitter.BlitCameraTexture(commandBuffer, data.GaussianSplatRT, data.SourceTexture, matComposite, 0);
                    commandBuffer.EndSample(GaussianSplatRenderSystem.s_ProfCompose);
                });
            }
#else
            public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
            {
                RenderTextureDescriptor rtDesc = renderingData.cameraData.cameraTargetDescriptor;
                rtDesc.depthBufferBits = 0;
                rtDesc.msaaSamples = 1;
                rtDesc.graphicsFormat = GraphicsFormat.R16G16B16A16_SFloat;
                RenderingUtils.ReAllocateIfNeeded(ref m_RenderTarget, rtDesc, FilterMode.Point, TextureWrapMode.Clamp, name: GaussianSplatRTName);
                cmd.SetGlobalTexture(m_RenderTarget.name, m_RenderTarget.nameID);

                ConfigureTarget(m_RenderTarget, m_Renderer.cameraDepthTargetHandle);
                ConfigureClear(ClearFlag.Color, new Color(0,0,0,0));
            }

            public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
            {
                if (m_Cmb == null)
                    return;

                // add sorting, view calc and drawing commands for each splat object
                Material matComposite = GaussianSplatRenderSystem.instance.SortAndRenderSplats(renderingData.cameraData.camera, m_Cmb);

                // compose
                m_Cmb.BeginSample(GaussianSplatRenderSystem.s_ProfCompose);
                Blitter.BlitCameraTexture(m_Cmb, m_RenderTarget, m_Renderer.cameraColorTargetHandle, RenderBufferLoadAction.Load, RenderBufferStoreAction.Store, matComposite, 0);
                m_Cmb.EndSample(GaussianSplatRenderSystem.s_ProfCompose);
                context.ExecuteCommandBuffer(m_Cmb);
            }
#endif
        }

        GSRenderPass m_Pass;
        bool m_HasCamera;

        public override void Create()
        {
            m_Pass = new GSRenderPass
            {
                renderPassEvent = RenderPassEvent.BeforeRenderingTransparents
            };
        }

        public override void OnCameraPreCull(ScriptableRenderer renderer, in CameraData cameraData)
        {
            m_HasCamera = false;
            var system = GaussianSplatRenderSystem.instance;
            if (!system.GatherSplatsForCamera(cameraData.camera))
                return;

#if !UNITY_6000_0_OR_NEWER
            CommandBuffer cmb = system.InitialClearCmdBuffer(cameraData.camera);
            m_Pass.m_Cmb = cmb;
#endif
            m_HasCamera = true;
        }

        public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
        {
            if (!m_HasCamera)
                return;
#if !UNITY_6000_0_OR_NEWER
            m_Pass.m_Renderer = renderer;
#endif
            renderer.EnqueuePass(m_Pass);
        }

        protected override void Dispose(bool disposing)
        {
            m_Pass?.Dispose();
            m_Pass = null;
        }
    }
}

#endif // #if GS_ENABLE_URP