using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;
using UnityEngine.Rendering.RenderGraphModule;

/// <summary>
/// 카메라 전환 시 크로스 디졸브 블렌딩을 위한 URP Renderer Feature
/// Unity 6 Render Graph API 사용
/// </summary>
public class CameraBlendRendererFeature : ScriptableRendererFeature
{
    [System.Serializable]
    public class Settings
    {
        // BeforeRenderingPostProcessing으로 변경 - 포스트 프로세싱 전에 블렌딩
        public RenderPassEvent renderPassEvent = RenderPassEvent.BeforeRenderingPostProcessing;
        public Material blendMaterial;
    }

    public Settings settings = new Settings();
    private CameraBlendRenderPass blendPass;

    public override void Create()
    {
        blendPass = new CameraBlendRenderPass(settings);
        blendPass.renderPassEvent = settings.renderPassEvent;
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        if (settings.blendMaterial == null)
            return;

        // 게임 카메라만 처리
        if (renderingData.cameraData.cameraType != CameraType.Game)
            return;

        // 블렌딩이 활성화된 경우에만 패스 추가
        if (CameraBlendController.IsBlending && CameraBlendController.BlendTexture != null)
        {
            renderer.EnqueuePass(blendPass);
        }
    }

    protected override void Dispose(bool disposing)
    {
        blendPass?.Dispose();
    }
}

public class CameraBlendRenderPass : ScriptableRenderPass
{
    private CameraBlendRendererFeature.Settings settings;
    private static readonly int BlendAmountProperty = Shader.PropertyToID("_BlendAmount");
    private static readonly int PrevTexProperty = Shader.PropertyToID("_PrevTex");

    private class PassData
    {
        public Material blendMaterial;
        public float blendAmount;
        public RenderTexture blendTexture;
        public TextureHandle sourceTexture;
        public TextureHandle destinationTexture;
    }

    public CameraBlendRenderPass(CameraBlendRendererFeature.Settings settings)
    {
        this.settings = settings;
        profilingSampler = new ProfilingSampler("Camera Blend Pass");
        ConfigureInput(ScriptableRenderPassInput.Color);
    }

    public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
    {
        if (settings.blendMaterial == null)
            return;

        if (!CameraBlendController.IsBlending || CameraBlendController.BlendTexture == null)
            return;

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

        // 백버퍼인 경우 스킵 (BeforeRenderingPostProcessing에서는 일반적으로 false)
        if (resourceData.isActiveTargetBackBuffer)
        {
            Debug.LogWarning("[CameraBlend] isActiveTargetBackBuffer - skipping");
            return;
        }

        var source = resourceData.activeColorTexture;

        // source가 유효한지 확인
        if (!source.IsValid())
        {
            Debug.LogWarning("[CameraBlend] source texture is not valid");
            return;
        }

        // cameraColorDesc 사용 - 카메라 색상 텍스처 설명자
        var cameraTargetDesc = renderGraph.GetTextureDesc(resourceData.cameraColor);
        cameraTargetDesc.name = "_CameraBlendDestination";
        cameraTargetDesc.clearBuffer = false;
        var destination = renderGraph.CreateTexture(cameraTargetDesc);

        // 블렌딩 패스
        using (var builder = renderGraph.AddRasterRenderPass<PassData>("Camera Blend", out var passData, profilingSampler))
        {
            passData.blendMaterial = settings.blendMaterial;
            passData.blendAmount = CameraBlendController.BlendAmount;
            passData.blendTexture = CameraBlendController.BlendTexture;
            passData.sourceTexture = source;

            builder.UseTexture(source, AccessFlags.Read);
            builder.SetRenderAttachment(destination, 0, AccessFlags.Write);
            builder.AllowPassCulling(false);

            builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
            {
                data.blendMaterial.SetFloat(BlendAmountProperty, data.blendAmount);
                data.blendMaterial.SetTexture(PrevTexProperty, data.blendTexture);
                Blitter.BlitTexture(context.cmd, data.sourceTexture, new Vector4(1, 1, 0, 0), data.blendMaterial, 0);
            });
        }

        // 결과를 source로 복사
        using (var builder = renderGraph.AddRasterRenderPass<PassData>("Camera Blend Copy Back", out var copyData, profilingSampler))
        {
            copyData.sourceTexture = destination;

            builder.UseTexture(destination, AccessFlags.Read);
            builder.SetRenderAttachment(source, 0, AccessFlags.Write);
            builder.AllowPassCulling(false);

            builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
            {
                Blitter.BlitTexture(context.cmd, data.sourceTexture, new Vector4(1, 1, 0, 0), 0, false);
            });
        }
    }

    [System.Obsolete("This rendering path is for compatibility mode only (when Render Graph is disabled). Use Render Graph API instead.", false)]
    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        // Legacy path
    }

    public void Dispose()
    {
    }
}

/// <summary>
/// 카메라 블렌딩을 제어하는 정적 컨트롤러
/// </summary>
public static class CameraBlendController
{
    private static bool isBlending = false;
    private static float blendAmount = 1f;
    private static RenderTexture blendTexture;

    public static bool IsBlending
    {
        get => isBlending;
        set => isBlending = value;
    }

    public static float BlendAmount
    {
        get => blendAmount;
        set => blendAmount = Mathf.Clamp01(value);
    }

    public static RenderTexture BlendTexture
    {
        get => blendTexture;
        set => blendTexture = value;
    }

    public static void StartBlend(RenderTexture texture)
    {
        blendTexture = texture;
        blendAmount = 0f;
        isBlending = true;
    }

    public static void EndBlend()
    {
        isBlending = false;
        blendAmount = 1f;
        blendTexture = null;
    }

    public static void Reset()
    {
        EndBlend();
    }
}