using System;
using XCEngine;
using XCEngine.Rendering;

namespace XCEngine.Rendering.Universal
{
    public abstract class ScriptableRenderPass
    {
        private const string kColorScaleFullscreenPassName =
            "Universal.ColorScaleFullscreen";
        private const string kShaderVectorFullscreenPassName =
            "Universal.ShaderVectorFullscreen";

        protected ScriptableRenderPass()
        {
        }

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

        public virtual bool SupportsStage(
            CameraFrameStage stage)
        {
            CameraFrameStage resolvedStage;
            return TryResolveStage(
                renderPassEvent,
                out resolvedStage) &&
                resolvedStage == stage;
        }

        internal bool Record(
            ScriptableRenderContext context,
            RenderingData renderingData)
        {
            return RecordRenderGraph(
                context,
                renderingData);
        }

        protected abstract bool RecordRenderGraph(
            ScriptableRenderContext context,
            RenderingData renderingData);

        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();
        }

        internal static bool TryResolveStage(
            RenderPassEvent passEvent,
            out CameraFrameStage stage)
        {
            switch (passEvent)
            {
                case RenderPassEvent.BeforeRenderingOpaques:
                case RenderPassEvent.RenderOpaques:
                case RenderPassEvent.AfterRenderingOpaques:
                case RenderPassEvent.BeforeRenderingSkybox:
                case RenderPassEvent.RenderSkybox:
                case RenderPassEvent.AfterRenderingSkybox:
                case RenderPassEvent.BeforeRenderingTransparents:
                case RenderPassEvent.RenderTransparents:
                case RenderPassEvent.AfterRenderingTransparents:
                    stage = CameraFrameStage.MainScene;
                    return true;
                case RenderPassEvent.BeforeRenderingPostProcessing:
                case RenderPassEvent.AfterRenderingPostProcessing:
                    stage = CameraFrameStage.PostProcess;
                    return true;
                case RenderPassEvent.BeforeRenderingFinalOutput:
                case RenderPassEvent.AfterRenderingFinalOutput:
                    stage = CameraFrameStage.FinalOutput;
                    return true;
                default:
                    stage = CameraFrameStage.MainScene;
                    return false;
            }
        }

        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;
        }
    }
}