#pragma once

#include "CoreMinimal.h"
#include "Core/DescentMath.h"
#include "World/DescentWorldTypes.h"

namespace Descent::World
{
	class FDescentWorldDef;

	/**
	 * The primitives that can affect one region, gathered from the world definition's bucket grid (port of v2
	 * `gatherLists`, same margins). Pointers into the definition's arrays, which never move after Build(), so a list
	 * is valid for the life of the process and may be used from any thread (each thread builds its own).
	 */
	struct FPrimList
	{
		TArray<const FSegment*, TInlineAllocator<48>> Segs;
		TArray<const FChamber*, TInlineAllocator<8>> Chambers;
		TArray<const FWell*, TInlineAllocator<4>> Wells;
		TArray<const FPore*, TInlineAllocator<32>> Pores;
		TArray<const FShelf*, TInlineAllocator<2>> Shelves;
		TArray<const FPinch*, TInlineAllocator<2>> Pinches;
		TArray<const FRing*, TInlineAllocator<2>> Rings;
		TArray<const FSpongeZone*, TInlineAllocator<1>> Sponges;
		bool bCanyon = false;
		bool bAbyss = false;

		void Reset()
		{
			Segs.Reset(); Chambers.Reset(); Wells.Reset(); Pores.Reset(); Shelves.Reset(); Pinches.Reset(); Rings.Reset(); Sponges.Reset();
			bCanyon = false; bAbyss = false;
		}
	};

	/**
	 * The density function of the world (DESIGN_UE.md section 2.2): signed, positive = rock, negative = water,
	 * approximately metres near surfaces. Immutable and thread-safe: it reads the definition and two noise tables.
	 */
	class THEDESCENT_API FDescentSDF
	{
	public:
		explicit FDescentSDF(const FDescentWorldDef& InDef);

		/** Unclamped density. */
		double GenRaw(const FVector& Pm, const FPrimList& L) const;
		/** Clamped to +-ClampD: what chunks store. */
		double Gen(const FVector& Pm, const FPrimList& L) const;
		/** Gathers the primitives for a sphere (Centre, Radius). */
		void Gather(const FVector& Centre, double Radius, FPrimList& Out) const;
		/** Density with a one-off gather: slow, for tests and build-time marches. */
		double GenRawSlow(const FVector& Pm) const;

		/** Gradient of GenRaw (points into rock), normalised; (0,0,1) if degenerate. */
		FVector GradientRaw(const FVector& Pm, const FPrimList& L, double H = 0.5) const;

		const Descent::FNoise3& Noise3() const { return NoiseA; }
		const Descent::FNoise3& NoiseB() const { return NoiseBObj; }

		// ---- the primitive distance functions (public so tests and the slice tool can use them) ----
		static double SegDistR(const FSegment& S, double X, double Y, double Z);
		static double SegDist3(const FVector& A, const FVector& B, double X, double Y, double Z);
		static double WellSDF(const FWell& W, double X, double Y, double Z);
		static double SlotSDF(const FShelf& S, double X, double Y);
		static double ShelfRock(const FShelf& S, double X, double Y, double Z, double Noise);
		static double PinchRock(const FPinch& P, double X, double Y, double Z);
		static double RingRock(const FRing& R, const FWell& W, double X, double Y, double Z);
		static double AbyssSDF(double X, double Y, double Z);
		static double BoxSDF(const FBox& B, double X, double Y, double Z);
		static double CanyonCentre(double X);   // Yc(X)
		static double CanyonFloor(double X);    // Zf(X)

		/** The sponge's own field (masked near carrier routes), exposed for the NoBypass test. */
		double SpongeSDF(const FSpongeZone& Z, double X, double Y, double Z2) const;

	private:
		const FDescentWorldDef& Def;
		Descent::FNoise3 NoiseA;
		Descent::FNoise3 NoiseBObj;
	};
}