#include "Render/DescentLightPool.h"
#include "Core/Tuning/DescentTune_Look.h"
#include "DescentUnits.h"

#include "Components/PointLightComponent.h"
#include "GameFramework/Actor.h"

namespace LTune = Descent::Tune::Look;

UDescentLightPool::UDescentLightPool()
{
	PrimaryComponentTick.bCanEverTick = false;
}

void UDescentLightPool::BeginPlay()
{
	Super::BeginPlay();
	AActor* Owner = GetOwner();
	if (!Owner || Lights.Num() > 0) { return; }
	for (int32 I = 0; I < LTune::LightPoolSize; ++I)
	{
		UPointLightComponent* L = NewObject<UPointLightComponent>(Owner, NAME_None, RF_Transient);
		L->SetMobility(EComponentMobility::Movable);
		L->bUseInverseSquaredFalloff = false;
		L->SetLightFalloffExponent(LTune::LightFalloffExponent);
		L->SetCastShadows(false);
		L->SetVolumetricScatteringIntensity(static_cast<float>(LTune::LightPoolScatter));
		L->SetVisibility(false);
		L->SetupAttachment(Owner->GetRootComponent());
		L->RegisterComponent();
		Lights.Add(L);
	}
}

void UDescentLightPool::Select(const TArray<FDescentLightRequest>& Reqs, const FVector& Cam, int32 MaxLights, double MaxScore, TArray<int32>& Out)
{
	struct FScored { int32 Index; double Score; };
	TArray<FScored> Scored;
	for (int32 I = 0; I < Reqs.Num(); ++I)
	{
		const double R = FMath::Max(0.01, static_cast<double>(Reqs[I].RadiusM));
		const double D = FVector::Dist(Cam, Reqs[I].PositionUU) / Descent::UUPerMetre;
		const double Score = (D * D) / (R * R) - Reqs[I].Priority;
		if (Score < MaxScore) { Scored.Add({ I, Score }); }
	}
	// Stable on ties: lower index first, so the winners never depend on sort internals.
	Scored.Sort([](const FScored& A, const FScored& B) { return A.Score < B.Score || (A.Score == B.Score && A.Index < B.Index); });
	Out.Reset();
	for (int32 I = 0; I < Scored.Num() && I < MaxLights; ++I) { Out.Add(Scored[I].Index); }
}

void UDescentLightPool::Commit(const FVector& CameraUU)
{
	TArray<int32> Win;
	Select(Requests, CameraUU, Lights.Num(), LTune::LightPoolMaxScore, Win);
	NumRequestsSeen = Requests.Num();
	for (int32 I = 0; I < Lights.Num(); ++I)
	{
		UPointLightComponent* L = Lights[I];
		if (!L) { continue; }
		if (I < Win.Num())
		{
			const FDescentLightRequest& R = Requests[Win[I]];
			L->SetWorldLocation(R.PositionUU);
			L->SetLightColor(R.Color);
			L->SetIntensity(R.Intensity);
			L->SetAttenuationRadius(static_cast<float>(Descent::MetresToUU(R.RadiusM)));
			L->SetVisibility(true);
		}
		else if (L->IsVisible())
		{
			L->SetVisibility(false);
		}
	}
	NumLitLights = Win.Num();
	Requests.Reset();
}