#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "Core/DescentHandle.h"
#include "DescentEnvironment.generated.h"

class UDirectionalLightComponent;
class UDescentLightPool;
class UExponentialHeightFogComponent;
class UMaterialParameterCollection;
class UPostProcessComponent;

/** Where the camera is: in the sea (the water post-process applies) or inside dry air (the carrier's interior). */
UENUM()
enum class EDescentEnv : uint8
{
	Water,
	Dry,
};

/**
 * The look of the world (DESIGN_UE.md section 7): there is no sky, no sky light and no global illumination. A pixel is lit
 * by local lights with an art-directed falloff, the surface sun (only near the top of the Throat), a small ambient term in
 * the materials, emissive surfaces, and one post-process material (PP_Water) that turns distance into water. Exposure is
 * manual and fixed. This actor owns the pieces of that: volumetric-only height fog, one unbound post-process component
 * (manual exposure, the reworked bloom of U12, vignette, grain), the surface sun, the light pool, and it writes
 * MPC_Descent once per frame in the Environment late step (after the camera has moved).
 *
 * Dry interiors (U6): when the environment query says the camera is dry (a carrier registers its hull), the volumetric fog
 * fades out over 0.3 s and marine snow is hidden; PP_Water itself leaves every pixel with custom stencil 1 alone, so the
 * interior is never fogged whichever way the camera looks.
 *
 * It is the ONLY authority for exposure, fog and post-process: nothing else (the showcase rig, the scenarios) brings an environment.
 */
UCLASS()
class THEDESCENT_API ADescentEnvironment : public AActor
{
	GENERATED_BODY()

public:
	ADescentEnvironment();

	static ADescentEnvironment* Get(const UWorld* World);

	virtual void BeginPlay() override;
	virtual void EndPlay(const EEndPlayReason::Type Reason) override;

	EDescentEnv GetEnvState() const { return EnvState; }
	UDescentLightPool* GetLightPool() const { return LightPool; }

	/** Descent.Look.Set: Exposure, Bloom, WaterPP, Volumetric, Snow, Lamp. False and an error text for an unknown parameter. */
	bool SetLookParam(const FString& Name, double Value, FString& OutError);

	/** L(Z) of section 2.7. */
	static double SurfaceLightAt(double ZMetres);

	// ---- numbers for the `env` state section ----
	double SurfaceLight = 0.0;
	double FogDensityValue = 0.0;
	bool bVolumetricOn = true;
	bool bSunOn = false;
	double TemperatureC = 0.0;
	int32 SnowInstancesVisible = 0;
	bool bSnowSwitch = true;
	double WaterAmount = 1.0;
	bool bVolumetricSwitch = true;

private:
	void UpdateLook(double Dt);
	void CommitLights();

	UPROPERTY()
	TObjectPtr<UExponentialHeightFogComponent> Fog;
	UPROPERTY()
	TObjectPtr<UPostProcessComponent> PostProcess;
	UPROPERTY()
	TObjectPtr<UDirectionalLightComponent> Sun;
	UPROPERTY()
	TObjectPtr<UDescentLightPool> LightPool;
	UPROPERTY()
	TObjectPtr<UMaterialParameterCollection> Mpc;

	EDescentEnv EnvState = EDescentEnv::Water;
	double VolBlend = 1.0;          // 1 = volumetric fog fully on, 0 = off (dry)
	FDescentHandle EnvHandle;
	FDescentHandle PoolHandle;
	FVector LastCameraUU = FVector::ZeroVector;
	bool bBlendableAdded = false;
};