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// Copyright (c) 2022-2023 Magic Leap, Inc. All Rights Reserved.
// Use of this file is governed by the Magic Leap 2 Software License Agreement, located here: https://www.magicleap.com/software-license-agreement-ml2  
// Terms and conditions applicable to third-party materials accompanying this distribution may also be found in the top-level NOTICE file appearing herein.
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using UnityEngine;
using UnityEngine.Rendering.Universal;
using UnityEngine.Rendering;
using System;

namespace MagicLeap
{
    public class MLSpectatorPreview : IDisposable
    {
        #region Private classes

        private class PreviewRenderPass : ScriptableRenderPass
        {
            public RenderTexture preview { get; set; } = null;

            public PreviewRenderPass(RenderTexture preview)
            {
                this.preview = preview;
            }

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

                var renderer = renderingData.cameraData.renderer;
                var colorTarget = renderer.cameraColorTargetHandle.rt;

                CommandBuffer cmd = CommandBufferPool.Get();

                cmd.Blit(preview, colorTarget);
                context.ExecuteCommandBuffer(cmd);
                cmd.Clear();

                CommandBufferPool.Release(cmd);
            }
        }

        #endregion

        #region Private variables

        private Camera mainCam = null;
        private UniversalAdditionalCameraData cameraData = null;
        private PreviewRenderPass previewPass = null;

        #endregion

        #region Constructor / Destructor

        public MLSpectatorPreview(RenderTexture preview)
        {
            mainCam = Camera.main;
            cameraData = mainCam.GetUniversalAdditionalCameraData();

            previewPass = new PreviewRenderPass(preview);
            previewPass.renderPassEvent = RenderPassEvent.AfterRendering;
            RenderPipelineManager.beginCameraRendering += RenderPreview;
        }

        ~MLSpectatorPreview()
        {
            Dispose();
        }

        #endregion

        #region Public methods

        public void SetPreview(RenderTexture preview)
        {
            previewPass.preview = preview;
        }

        public void Dispose()
        {
            if (previewPass == null) return;
            RenderPipelineManager.beginCameraRendering -= RenderPreview;
            previewPass.preview = null;
            previewPass = null;
        }

        #endregion

        #region Private methods

        private void RenderPreview(ScriptableRenderContext context, Camera camera)
        {
            if (previewPass == null || camera != mainCam) return;
            cameraData.scriptableRenderer.EnqueuePass(previewPass);
        }

        #endregion
    }
}