// Copyright Epic Games, Inc. All Rights Reserved.

#include "ThumbnailRendering/MaterialFunctionThumbnailRenderer.h"
#include "Misc/App.h"
#include "ShowFlags.h"
#include "SceneView.h"
#include "Materials/MaterialFunction.h"
#include "Materials/MaterialFunctionInstance.h"
#include "Materials/Material.h"
#include "Materials/MaterialInstanceConstant.h"
#include "ThumbnailHelpers.h"
#include "Settings/ContentBrowserSettings.h"

UMaterialFunctionThumbnailRenderer::UMaterialFunctionThumbnailRenderer(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
{
    ThumbnailScene = nullptr;
}

void UMaterialFunctionThumbnailRenderer::Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget* RenderTarget, FCanvas* Canvas, bool bAdditionalViewFamily)
{
    UMaterialFunctionInterface* MatFunc    = Cast<UMaterialFunctionInterface>(Object);
    UMaterialFunctionInstance* MatFuncInst = Cast<UMaterialFunctionInstance>(Object);
    const bool bIsFunctionInstancePreview  = MatFuncInst && MatFuncInst->GetBaseFunction();

    if (MatFunc || bIsFunctionInstancePreview)
    {
        if (ThumbnailScene == nullptr || ensure(ThumbnailScene->GetWorld() != nullptr) == false)
        {
            if (ThumbnailScene)
            {
                FlushRenderingCommands();
                delete ThumbnailScene;
            }

            ThumbnailScene = new FMaterialThumbnailScene();
        }

        UMaterialInterface* PreviewMaterial  = bIsFunctionInstancePreview ? MatFuncInst->GetPreviewMaterial() : MatFunc->GetPreviewMaterial();
        EMaterialFunctionUsage FunctionUsage = bIsFunctionInstancePreview ? MatFuncInst->GetMaterialFunctionUsage() : MatFunc->GetMaterialFunctionUsage();
        UThumbnailInfo* ThumbnailInfo        = bIsFunctionInstancePreview ? MatFuncInst->ThumbnailInfo : MatFunc->ThumbnailInfo;

        if (PreviewMaterial)
        {
            PreviewMaterial->ThumbnailInfo = ThumbnailInfo;
            if (FunctionUsage == EMaterialFunctionUsage::MaterialLayerBlend)
            {
                PreviewMaterial->SetShouldForcePlanePreview(true);
            }
            ThumbnailScene->SetMaterialInterface(PreviewMaterial);

            FSceneViewFamilyContext ViewFamily(FSceneViewFamily::ConstructionValues(RenderTarget, ThumbnailScene->GetScene(), FEngineShowFlags(ESFIM_Game))
                                                   .SetWorldTimes(FApp::GetCurrentTime() - GStartTime, FApp::GetDeltaTime(), FApp::GetCurrentTime() - GStartTime)
                                                   .SetAdditionalViewFamily(bAdditionalViewFamily));

            ViewFamily.EngineShowFlags.DisableAdvancedFeatures();
            ViewFamily.EngineShowFlags.MotionBlur = 0;

            ThumbnailScene->GetView(&ViewFamily, X, Y, Width, Height);

            if (ViewFamily.Views.Num() > 0)
            {
                RenderViewFamily(Canvas, &ViewFamily);
            }

            ThumbnailScene->SetMaterialInterface(nullptr);
        }
    }
}

bool UMaterialFunctionThumbnailRenderer::CanVisualizeAsset(UObject* Object)
{
    return GetDefault<UContentBrowserSettings>()->bEnableRealtimeMaterialInstanceThumbnails;
}

void UMaterialFunctionThumbnailRenderer::BeginDestroy()
{
    if (ThumbnailScene)
    {
        delete ThumbnailScene;
        ThumbnailScene = nullptr;
    }

    Super::BeginDestroy();
}