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

#include "ThumbnailRendering/LevelThumbnailRenderer.h"
#include "EngineDefines.h"
#include "Misc/App.h"
#include "Engine/Level.h"
#include "ShowFlags.h"
#include "SceneView.h"
#include "Engine/LevelBounds.h"

ULevelThumbnailRenderer::ULevelThumbnailRenderer(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
{
}

void ULevelThumbnailRenderer::Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget* RenderTarget, FCanvas* Canvas, bool bAdditionalViewFamily)
{
    ULevel* Level = Cast<ULevel>(Object);
    if (Level != nullptr)
    {
        FSceneViewFamilyContext ViewFamily(FSceneViewFamily::ConstructionValues(RenderTarget, Level->OwningWorld->Scene, FEngineShowFlags(ESFIM_Game))
                                               .SetWorldTimes(FApp::GetCurrentTime() - GStartTime, FApp::GetDeltaTime(), FApp::GetCurrentTime() - GStartTime)
                                               .SetAdditionalViewFamily(bAdditionalViewFamily));

        ViewFamily.EngineShowFlags.DisableAdvancedFeatures();
        ViewFamily.EngineShowFlags.MotionBlur = 0;
        ViewFamily.EngineShowFlags.SetDistanceCulledPrimitives(true);  // show distance culled objects
        ViewFamily.EngineShowFlags.SetPostProcessing(false);

        GetView(Level, &ViewFamily, X, Y, Width, Height);

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

void ULevelThumbnailRenderer::GetView(ULevel* Level, FSceneViewFamily* ViewFamily, int32 X, int32 Y, uint32 SizeX, uint32 SizeY) const
{
    check(ViewFamily);

    FIntRect ViewRect(
        FMath::Max<int32>(X, 0),
        FMath::Max<int32>(Y, 0),
        FMath::Max<int32>(X + SizeX, 0),
        FMath::Max<int32>(Y + SizeY, 0));

    FBox LevelBox(ForceInit);

    if (Level->LevelBoundsActor.IsValid())
    {
        LevelBox = Level->LevelBoundsActor.Get()->GetComponentsBoundingBox();
    }
    else
    {
        LevelBox = ALevelBounds::CalculateLevelBounds(Level);
    }

    if (ViewRect.Width() > 0 && ViewRect.Height() > 0)
    {
        FSceneViewInitOptions ViewInitOptions;

        ViewInitOptions.SetViewRectangle(ViewRect);
        ViewInitOptions.ViewFamily         = ViewFamily;

        const FVector ViewPoint            = LevelBox.GetCenter();
        ViewInitOptions.ViewOrigin         = FVector(ViewPoint.X, ViewPoint.Y, 0);
        ViewInitOptions.ViewRotationMatrix = FMatrix(
            FPlane(1, 0, 0, 0),
            FPlane(0, -1, 0, 0),
            FPlane(0, 0, -1, 0),
            FPlane(0, 0, 0, 1));

        const float ZOffset              = WORLD_MAX;
        ViewInitOptions.ProjectionMatrix = FReversedZOrthoMatrix(
            LevelBox.GetSize().X / 2.f,
            LevelBox.GetSize().Y / 2.f,
            0.5f / ZOffset,
            ZOffset);

        FSceneView* NewView = new FSceneView(ViewInitOptions);

        ViewFamily->Views.Add(NewView);
    }
}