#pragma once

#include "CoreMinimal.h"
#include "Containers/BitArray.h"
#include "Core/DescentHandle.h"
#include "Core/DescentWorldSubsystem.h"
#include "DescentSonar.generated.h"

/** Sonar and survey map (M9, requirement V2; DESIGN_UE.md sections 8.1, 8.2): the numbers and the pure parts. */
namespace Descent::Sonar
{
	constexpr double RevealMps = 170.0, PointLifeSec = 20.0, ContactLifeSec = 16.0, GhostLifeSec = 2.2;
	constexpr int32 RaysPerStep = 420, MaxPoints = 30000;
	constexpr double TenderRangeM = 160.0, TenderModuleRangeM = 260.0, HandRangeM = 90.0, HelmRangeM = 420.0;
	constexpr int32 TenderRays = 2200, HandRays = 900, HelmRays = 4200;
	constexpr double TenderCooldownSec = 2.5, HandCooldownSec = 3.0, HelmCooldownSec = 4.0;
	/** Direction I of N on a Fibonacci sphere. */
	THEDESCENT_API FVector FibonacciDir(int32 I, int32 N);

	// the survey map: cells 4 x 4 m in plan, 8 m tall, over the claim box
	constexpr double CellXY = 4.0, CellZ = 8.0;
	constexpr int32 MapNx = 473, MapNy = 365, MapNz = 220;
	/** Cell of a world point (metres); false outside the claim box. */
	THEDESCENT_API bool CellOf(const FVector& Pm, FIntVector& OutCell);
}

/** The survey map: what sonar has hit (3D) and where the player has been (2D). Fills the PDA map. */
UCLASS()
class THEDESCENT_API UDescentMapSubsystem : public UDescentWorldSubsystem
{
	GENERATED_BODY()

public:
	static UDescentMapSubsystem* Get(const UWorld* World);
	virtual void OnWorldBeginPlay(UWorld& InWorld) override;
	virtual void Deinitialize() override;

	void Mark(const FVector& Pm);
	void Visit(const FVector& Pm);
	bool IsKnown(const FVector& Pm) const;
	int32 KnownCells = 0, VisitedCells = 0;
	/** 0 AUTO (reference depth +- 60 m), 1 ALL, 2 fixed depth +- 40 m. */
	int32 SliceMode = 0;
	double SliceDepthM = 1800.0;
	void FillWindow();

private:
	void Step(double Dt);
	TBitArray<> Known, Visited;
	double WindowTimer = 0.0;
	FDescentHandle StepHandle;
};

/** Active sonar: pings march rays through the rock (420 per sim step); each hit is a point that appears as the ping front reaches it and lives 20 s. */
UCLASS()
class THEDESCENT_API UDescentSonarSubsystem : public UDescentWorldSubsystem
{
	GENERATED_BODY()

public:
	static UDescentSonarSubsystem* Get(const UWorld* World);
	virtual void OnWorldBeginPlay(UWorld& InWorld) override;
	virtual void Deinitialize() override;

	/** R: a ping from whatever the player controls (Tender, helm, or the handheld sonar while swimming). */
	bool PingFromPlayer(FString* OutWhyNot = nullptr);
	bool Ping(const FVector& OriginM, double RangeM, int32 Rays);
	/** Kind 2 unknown contact (red), 3 beacon (amber). */
	void AddContact(const FVector& Pm, double LifeSec, int32 Kind, const FString& Label);

	int32 PointsAlive() const;
	int32 NumContacts() const { return Contacts.Num(); }
	int32 RaysPending() const;
	int32 Pings = 0, Hits = 0;
	double CooldownLeft = 0.0, LastRangeM = 0.0;
	FVector LastOriginM = FVector::ZeroVector;

	struct FContact { FVector P = FVector::ZeroVector; double Born = 0.0, Life = 16.0; int32 Kind = 2; FString Label; };
	const TArray<FContact>& GetContacts() const { return Contacts; }

private:
	struct FPoint { FVector P = FVector::ZeroVector; double Born = 0.0; float Dist = 0.f; };
	struct FPing { FVector O = FVector::ZeroVector; double Range = 0.0, T0 = 0.0; int32 Next = 0, Rays = 0; FQuat Rot = FQuat::Identity; };
	void Step(double Dt);
	void WriteHud();
	TArray<FPoint> Points;
	int32 Head = 0;
	TArray<FPing> Active;
	TArray<FContact> Contacts;
	double Now = 0.0;
	FRandomStream Rng{ 1180 };
	FDescentHandle StepHandle, LateHandle;
};