#pragma once

#include "CoreMinimal.h"
#include "Core/DescentHandle.h"
#include "Core/DescentWorldSubsystem.h"
#include "DescentFauna.generated.h"

class ADescentCarrier;
class UInstancedStaticMeshComponent;

/** Fauna (M8, requirements U3, U6; DESIGN_UE.md section 6.9): the school homes and the hull exclusion as plain data and pure functions. */
namespace Descent::Fauna
{
	struct FHomeDef
	{
		FVector PosM = FVector::ZeroVector;
		uint8 Species = 0;   // 0 silverfin (0.10 FU), 1 lanternfish (0.15 FU, glowing)
	};
	THEDESCENT_API const TArray<FHomeDef>& Homes();
	constexpr int32 SchoolSize = 26;
	constexpr double ActiveRangeM = 220.0, LeashM = 45.0;
	constexpr int32 MaxActiveHomes = 6;
	constexpr double HullSpawnMarginM = 6.0, HullSteerMarginM = 3.0, HullHardMarginM = 0.5;
	constexpr double CaptureM = 1.6, HandReachM = 2.6;
	/** U6: a fish at this carrier-local point with this distance to the hull (moon-pool shaft counted as hull). Moves it out when it is closer than the
	 *  hard margin and returns the outward acceleration to apply when it is inside the steer margin. */
	THEDESCENT_API FVector HullExclusion(FVector& InOutLocalM, bool* bOutWasInside = nullptr);
	THEDESCENT_API FName SpeciesName(uint8 Species);
}

/** Schools of fish and the lantern polyps. Only the six nearest homes within 220 m of the player are simulated and drawn. */
UCLASS()
class THEDESCENT_API UDescentFaunaSubsystem : public UDescentWorldSubsystem
{
	GENERATED_BODY()

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

	/** Tender suction: fish in the cone are pulled in and captured within 1.6 m of the nozzle. Returns the FU captured (never more than RoomFU). */
	double Suck(const FVector& NozzleM, const FVector& Dir, double RangeM, double Pull, double Dt, double RoomFU, bool& bOutTankFull);
	/** A swimmer's E: the nearest polyp within 2.6 m is taken. Returns "polyp" or NAME_None. */
	FName TakeByHand(const FVector& PosM);
	bool NearestPolyp(const FVector& PosM, double MaxM, FVector& OutM) const;
	/** Debug: puts a polyp cluster at a point (scenarios). */
	void AddPolypCluster(const FVector& PosM, const FVector& Normal);

	int32 ActiveHomes() const;
	int32 FishAlive() const;
	int32 NumPolyps() const;
	int32 InsideHull = 0, InsideHullEver = 0, Captured = 0, TakenByHand = 0, ProjectedOut = 0;
	double MinHullDistM = 1e9, NearestFishM = 1e9;
	/** The fish nearest to a world point (metres); false if none is simulated. */
	bool NearestFish(const FVector& PosM, FVector& OutM) const;

private:
	struct FFish { FVector P = FVector::ZeroVector, V = FVector::ZeroVector; double Sucked = 0.0; };
	struct FHome
	{
		Descent::Fauna::FHomeDef Def;
		int32 Alive = Descent::Fauna::SchoolSize;
		bool bActive = false, bPolypsMade = false;
		TArray<FFish> Fish;
		FVector Target = FVector::ZeroVector;
		double TargetTimer = 0.0, Regrow = 0.0;
	};
	struct FPolyp { FVector P = FVector::ZeroVector; bool bAlive = true; double Regrow = 0.0; };

	void Step(double Dt);
	void Activate(FHome& H);
	bool FreeWater(const FVector& PosM, double HullMargin) const;
	void UpdateVisuals();

	TArray<FHome> HomeStates;
	TArray<FPolyp> Polyps;
	FRandomStream Rng{ 20261006 };
	FDescentHandle StepHandle;
	UPROPERTY(Transient) TObjectPtr<AActor> Visual;
	UPROPERTY(Transient) TArray<TObjectPtr<UInstancedStaticMeshComponent>> Meshes;   // silverfin, lanternfish, polyps
};