// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "OverridePassSequence.h"

struct FPaniniProjectionConfig
{
	static const FPaniniProjectionConfig Default;

	FPaniniProjectionConfig() = default;
	FPaniniProjectionConfig(const FViewInfo& View);

	bool IsEnabled() const
	{
		return D > 0.01f;
	}

	void Sanitize()
	{
		D = FMath::Max(D, 0.0f);
		ScreenFit = FMath::Max(ScreenFit, 0.0f);
	}

	// 0=none..1=full, must be >= 0.
	float D = 0.0f;

	// Panini hard vertical compression lerp (0=no vertical compression, 1=hard compression).
	float S = 0.0f;

	// Panini screen fit factor (lerp between vertical and horizontal).
	float ScreenFit = 1.0f;
};

enum class EUpscaleMethod : uint8
{
	Nearest,
	Bilinear,
	Directional,
	CatmullRom,
	Lanczos,
	Gaussian,
	SmoothStep,
	MAX
};

EUpscaleMethod GetUpscaleMethod();

enum class EUpscaleStage
{
	// Upscaling from the primary to the secondary view rect. The override output cannot be valid when using this stage.
	PrimaryToSecondary,

	// Upscaling in one pass to the final target size.
	PrimaryToOutput,

	// Upscaling from the secondary view rect to the final view size.
	SecondaryToOutput,

	MAX
};

/** Interface for custom spatial upscaling algorithm meant to be set on the FSceneViewFamily by ISceneViewExtension::BeginRenderViewFamily(). */
class RENDERER_API ISpatialUpscaler : public ISceneViewFamilyExtention
{
public:
	struct FInputs
	{
		// [Optional] Render to the specified output. If invalid, a new texture is created and returned.
		FScreenPassRenderTarget OverrideOutput;

		// [Required] The input scene color and view rect.
		FScreenPassTexture SceneColor;

		// Whether this is a secondary upscale to the final view family target.
		EUpscaleStage Stage = EUpscaleStage::MAX;
	};

	virtual const TCHAR* GetDebugName() const = 0;

	/** Create a new ISpatialUpscaler interface for a new view family. */
	virtual ISpatialUpscaler* Fork_GameThread(const class FSceneViewFamily& ViewFamily) const = 0;

	virtual FScreenPassTexture AddPasses(
		FRDGBuilder& GraphBuilder,
		const FViewInfo& View,
		const FInputs& PassInputs) const = 0;

	static FScreenPassTexture AddDefaultUpscalePass(
		FRDGBuilder& GraphBuilder,
		const FViewInfo& View,
		const FInputs& PassInputs,
		EUpscaleMethod Method,
		FPaniniProjectionConfig PaniniConfig);
};