using System;
using XCEngine;
using XCEngine.Rendering;

namespace XCEngine.Rendering.Universal
{
    public abstract class ScriptableRenderPass
    {
        private const string kColorScaleFullscreenPassName =
            "Universal.ColorScaleFullscreen";
        private const string kFinalColorFullscreenPassName =
            "Universal.FinalColorFullscreen";
        private const string kShaderVectorFullscreenPassName =
            "Universal.ShaderVectorFullscreen";
        private readonly CommandBuffer m_lifecycleCommandBuffer =
            new CommandBuffer("ScriptableRenderPass");
        private ScriptableRenderPassInput m_input =
            ScriptableRenderPassInput.None;

        protected ScriptableRenderPass()
        {
        }

        public RenderPassEvent renderPassEvent { get; set; } =
            RenderPassEvent.BeforeRenderingOpaques;

        public ScriptableRenderPassInput input
        {
            get
            {
                return m_input;
            }
        }

        public bool requiresIntermediateTexture
        {
            get
            {
                return m_input != ScriptableRenderPassInput.None;
            }
        }

        protected ProfilingSampler profilingSampler { get; set; } =
            new ProfilingSampler("Unnamed_ScriptableRenderPass");

        public void ConfigureInput(
            ScriptableRenderPassInput passInput)
        {
            m_input = passInput;
        }

        public virtual bool SupportsStage(
            CameraFrameStage stage)
        {
            RendererBlock block;
            return TryResolveRendererBlock(
                renderPassEvent,
                out block) &&
                RendererBlockUtility.GetStage(block) == stage;
        }

        internal bool SupportsRendererBlock(
            RendererBlock block)
        {
            RendererBlock resolvedBlock;
            return TryResolveRendererBlock(
                renderPassEvent,
                out resolvedBlock) &&
                resolvedBlock == block;
        }

        internal bool Record(
            ScriptableRenderContext context,
            RenderingData renderingData)
        {
            RenderingData passRenderingData =
                renderingData;
            OnCameraSetup(
                m_lifecycleCommandBuffer,
                ref passRenderingData);

            try
            {
                return RecordRenderGraph(
                    context,
                    passRenderingData);
            }
            finally
            {
                OnCameraCleanup(
                    m_lifecycleCommandBuffer);
            }
        }

        public virtual void Execute(
            ScriptableRenderContext context,
            ref RenderingData renderingData)
        {
        }

        public virtual void OnCameraSetup(
            CommandBuffer cmd,
            ref RenderingData renderingData)
        {
        }

        public virtual void OnCameraCleanup(
            CommandBuffer cmd)
        {
        }

        public virtual void OnFinishCameraStackRendering(
            CommandBuffer cmd)
        {
        }

        protected virtual bool RecordRenderGraph(
            ScriptableRenderContext context,
            RenderingData renderingData)
        {
            if (context == null ||
                renderingData == null)
            {
                return false;
            }

            Execute(
                context,
                ref renderingData);
            return true;
        }

        public static bool operator >(
            ScriptableRenderPass lhs,
            ScriptableRenderPass rhs)
        {
            return CompareRenderPassEvents(
                       lhs,
                       rhs) > 0;
        }

        public static bool operator <(
            ScriptableRenderPass lhs,
            ScriptableRenderPass rhs)
        {
            return CompareRenderPassEvents(
                       lhs,
                       rhs) < 0;
        }

        protected bool RecordColorScaleFullscreenPass(
            ScriptableRenderContext context,
            Vector4 colorScale)
        {
            RenderGraphTextureHandle sourceColor;
            RenderGraphTextureHandle outputColor;
            return TryResolveDefaultFullscreenTargets(
                       context,
                       out sourceColor,
                       out outputColor) &&
                   RecordColorScaleFullscreenPass(
                       context,
                       sourceColor,
                       outputColor,
                       colorScale);
        }

        protected bool RecordColorScaleFullscreenPass(
            ScriptableRenderContext context,
            RenderGraphTextureHandle sourceColor,
            RenderGraphTextureHandle outputColor,
            Vector4 colorScale,
            string passName = null)
        {
            if (context == null ||
                !outputColor.isValid)
            {
                return false;
            }

            RenderGraphRasterPassBuilder passBuilder =
                context.AddRasterPass(
                    ResolveFullscreenPassName(
                        passName,
                        kColorScaleFullscreenPassName));
            if (sourceColor.isValid)
            {
                passBuilder.UseColorSource(sourceColor);
            }

            return passBuilder
                .SetColorAttachment(outputColor)
                .SetColorScaleFullscreenExecution(colorScale)
                .Commit();
        }

        protected bool RecordShaderVectorFullscreenPass(
            ScriptableRenderContext context,
            string shaderPath,
            Vector4 vectorPayload,
            string passName = null)
        {
            if (string.IsNullOrEmpty(shaderPath))
            {
                throw new ArgumentException(
                    "Fullscreen shader path cannot be null or empty.",
                    nameof(shaderPath));
            }

            RenderGraphTextureHandle sourceColor;
            RenderGraphTextureHandle outputColor;
            return TryResolveDefaultFullscreenTargets(
                       context,
                       out sourceColor,
                       out outputColor) &&
                   RecordShaderVectorFullscreenPass(
                       context,
                       sourceColor,
                       outputColor,
                       shaderPath,
                       vectorPayload,
                       passName: passName);
        }

        protected bool RecordShaderVectorFullscreenPass(
            ScriptableRenderContext context,
            RenderGraphTextureHandle sourceColor,
            RenderGraphTextureHandle outputColor,
            string shaderPath,
            Vector4 vectorPayload,
            string shaderPassName = null,
            string passName = null)
        {
            if (string.IsNullOrEmpty(shaderPath))
            {
                throw new ArgumentException(
                    "Fullscreen shader path cannot be null or empty.",
                    nameof(shaderPath));
            }

            if (context == null ||
                !outputColor.isValid)
            {
                return false;
            }

            RenderGraphRasterPassBuilder passBuilder =
                context.AddRasterPass(
                    ResolveFullscreenPassName(
                        passName,
                        kShaderVectorFullscreenPassName));
            if (sourceColor.isValid)
            {
                passBuilder.UseColorSource(sourceColor);
            }

            return passBuilder
                .SetColorAttachment(outputColor)
                .SetShaderVectorFullscreenExecution(
                    shaderPath,
                    vectorPayload,
                    shaderPassName)
                .Commit();
        }

        protected bool RecordFinalColorFullscreenPass(
            ScriptableRenderContext context,
            FinalColorSettings settings,
            string passName = null)
        {
            RenderGraphTextureHandle sourceColor;
            RenderGraphTextureHandle outputColor;
            return TryResolveDefaultFullscreenTargets(
                       context,
                       out sourceColor,
                       out outputColor) &&
                   RecordFinalColorFullscreenPass(
                       context,
                       sourceColor,
                       outputColor,
                       settings,
                       passName);
        }

        protected bool RecordFinalColorFullscreenPass(
            ScriptableRenderContext context,
            RenderGraphTextureHandle sourceColor,
            RenderGraphTextureHandle outputColor,
            FinalColorSettings settings,
            string passName = null)
        {
            if (context == null ||
                !outputColor.isValid)
            {
                return false;
            }

            RenderGraphRasterPassBuilder passBuilder =
                context.AddRasterPass(
                    ResolveFullscreenPassName(
                        passName,
                        kFinalColorFullscreenPassName));
            if (sourceColor.isValid)
            {
                passBuilder.UseColorSource(sourceColor);
            }

            return passBuilder
                .SetColorAttachment(outputColor)
                .SetFinalColorFullscreenExecution(settings)
                .Commit();
        }

        internal static bool TryResolveStage(
            RenderPassEvent passEvent,
            out CameraFrameStage stage)
        {
            RendererBlock block;
            if (TryResolveRendererBlock(
                    passEvent,
                    out block))
            {
                stage =
                    RendererBlockUtility.GetStage(block);
                return true;
            }

            stage = CameraFrameStage.MainScene;
            return false;
        }

        internal static bool TryResolveRendererBlock(
            RenderPassEvent passEvent,
            out RendererBlock block)
        {
            switch (passEvent)
            {
                case RenderPassEvent.BeforeRenderingShadows:
                case RenderPassEvent.AfterRenderingShadows:
                    block = RendererBlock.ShadowCaster;
                    return true;
                case RenderPassEvent.BeforeRenderingPrePasses:
                case RenderPassEvent.AfterRenderingPrePasses:
                    block = RendererBlock.DepthPrepass;
                    return true;
                case RenderPassEvent.BeforeRenderingGbuffer:
                case RenderPassEvent.AfterRenderingGbuffer:
                case RenderPassEvent.BeforeRenderingDeferredLights:
                case RenderPassEvent.AfterRenderingDeferredLights:
                case RenderPassEvent.BeforeRenderingOpaques:
                case RenderPassEvent.RenderOpaques:
                case RenderPassEvent.AfterRenderingOpaques:
                    block = RendererBlock.MainOpaque;
                    return true;
                case RenderPassEvent.BeforeRenderingSkybox:
                case RenderPassEvent.RenderSkybox:
                case RenderPassEvent.AfterRenderingSkybox:
                    block = RendererBlock.MainSkybox;
                    return true;
                case RenderPassEvent.BeforeRenderingTransparents:
                case RenderPassEvent.RenderTransparents:
                case RenderPassEvent.AfterRenderingTransparents:
                    block = RendererBlock.MainTransparent;
                    return true;
                case RenderPassEvent.BeforeRenderingPostProcessing:
                case RenderPassEvent.AfterRenderingPostProcessing:
                    block = RendererBlock.PostProcess;
                    return true;
                case RenderPassEvent.BeforeRenderingFinalOutput:
                case RenderPassEvent.AfterRendering:
                case RenderPassEvent.AfterRenderingFinalOutput:
                    block = RendererBlock.FinalOutput;
                    return true;
                default:
                    block = RendererBlock.MainOpaque;
                    return false;
            }
        }

        private static int CompareRenderPassEvents(
            ScriptableRenderPass lhs,
            ScriptableRenderPass rhs)
        {
            if (ReferenceEquals(
                    lhs,
                    rhs))
            {
                return 0;
            }

            if (lhs == null)
            {
                return -1;
            }

            if (rhs == null)
            {
                return 1;
            }

            return lhs.renderPassEvent.CompareTo(
                rhs.renderPassEvent);
        }

        private static bool TryResolveDefaultFullscreenTargets(
            ScriptableRenderContext context,
            out RenderGraphTextureHandle sourceColor,
            out RenderGraphTextureHandle outputColor)
        {
            sourceColor = new RenderGraphTextureHandle();
            outputColor = new RenderGraphTextureHandle();
            if (context == null)
            {
                return false;
            }

            sourceColor = context.sourceColorTexture;
            outputColor = context.primaryColorTarget;
            return sourceColor.isValid &&
                   outputColor.isValid;
        }

        private static string ResolveFullscreenPassName(
            string passName,
            string defaultPassName)
        {
            return string.IsNullOrEmpty(passName)
                ? defaultPassName
                : passName;
        }
    }
}