#include "Player/DescentInteraction.h"
#include "Core/Tuning/DescentTune_Player.h"
#include "DescentUnits.h"

#include "Engine/World.h"

double IDescentInteractable::GetRangeM() const { return Descent::Tune::Player::DefaultInteractRangeM; }
double IDescentInteractable::GetMinDot() const { return Descent::Tune::Player::DefaultInteractMinDot; }

UDescentInteractionRegistry* UDescentInteractionRegistry::Get(const UWorld* World)
{
	return World ? World->GetSubsystem<UDescentInteractionRegistry>() : nullptr;
}

void UDescentInteractionRegistry::Register(UObject* Interactable)
{
	if (Interactable && Cast<IDescentInteractable>(Interactable))
	{
		Items.AddUnique(Interactable);
	}
}

void UDescentInteractionRegistry::Unregister(UObject* Interactable)
{
	Items.Remove(Interactable);
}

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

void UDescentInteractionComponent::UpdateFocus(const FVector& EyeUU, const FVector& ViewDir)
{
	namespace T = Descent::Tune::Player;
	UDescentInteractionRegistry* Reg = UDescentInteractionRegistry::Get(GetWorld());
	UObject* Best = nullptr;
	double BestScore = 0.0;
	if (Reg)
	{
		for (const TWeakObjectPtr<UObject>& W : Reg->All())
		{
			UObject* O = W.Get();
			const IDescentInteractable* I = O ? Cast<IDescentInteractable>(O) : nullptr;
			if (!I)
			{
				continue;
			}
			const FVector ToTarget = Descent::UUToMetres(I->GetFocusPointUU() - EyeUU);
			const double Dist = ToTarget.Size();
			if (Dist > I->GetRangeM() || Dist < 1e-6)
			{
				continue;
			}
			const double Dot = FVector::DotProduct(ToTarget / Dist, ViewDir);
			if (Dot < I->GetMinDot())
			{
				continue;
			}
			const double Score = Dot - T::InteractDistanceScore * Dist;
			if (!Best || Score > BestScore)
			{
				Best = O;
				BestScore = Score;
			}
		}
	}
	Focus = Best;
	FocusLabel = Best ? Cast<IDescentInteractable>(Best)->GetPrompt() : FString();
}

bool UDescentInteractionComponent::UseFocus(ADescentCharacter* User)
{
	UObject* O = Focus.Get();
	IDescentInteractable* I = O ? Cast<IDescentInteractable>(O) : nullptr;
	if (!I || !I->CanUse(User))
	{
		return false;
	}
	I->Use(User);
	return true;
}