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

#pragma once

#include "HAL/PlatformTime.h"

/** Timer helper class. **/
class FRenderTimer
{
public:
	FRenderTimer()
		: CurrentDeltaTime(0.0f)
		, CurrentTime(0.0f)
	{
	}

	/**
	 *	Returns the current time, in seconds.
	 *	@return Current time, in seconds
	 */
	float GetCurrentTime() const
	{
		return CurrentTime;
	}

	/**
	 *	Returns the current delta time.
	 *	@return Current delta time (number of seconds that passed between the last two tick)
	 */
	float GetCurrentDeltaTime() const
	{
		return CurrentDeltaTime;
	}

	/**
	 *	Updates the timer.
	 *	@param DeltaTime	Number of seconds that have passed since the last tick
	 **/
	void Tick(float DeltaTime)
	{
		CurrentDeltaTime = DeltaTime;
		CurrentTime += DeltaTime;
	}

protected:
	/** Current delta time (number of seconds that passed between the last two tick). */
	float CurrentDeltaTime;
	/** Current time, in seconds. */
	float CurrentTime;
};

/** Whether to pause the global realtime clock for the rendering thread (read and write only on main thread). */
extern RENDERCORE_API bool GPauseRenderingRealtimeClock;

/** Global realtime clock for the rendering thread. */
extern RENDERCORE_API FRenderTimer GRenderingRealtimeClock;

/**
 * Encapsulates a latency timer that measures the time from when mouse input
 * is read on the gamethread until that frame is fully displayed by the GPU.
 */
struct FInputLatencyTimer
{
	/**
	 * Constructor
	 * @param InUpdateFrequency	How often the timer should be updated (in seconds).
	 */
	FInputLatencyTimer(float InUpdateFrequency)
		: UpdateFrequency(InUpdateFrequency)
	{
	}

	/** Potentially starts the timer on the gamethread, based on the UpdateFrequency. */
	RENDERCORE_API void GameThreadTick();

	/** @return The number of seconds of input latency. */
	inline float GetDeltaSeconds() const
	{
		return FPlatformTime::ToSeconds(DeltaTime);
	}

	/** Whether GInputLatencyTimer is initialized or not. */
	bool	bInitialized = false;

	/** Whether a measurement has been triggered on the gamethread. */
	bool	GameThreadTrigger = false;

	/** Whether a measurement has been triggered on the renderthread. */
	bool	RenderThreadTrigger = false;

	/** Start time (in FPlatformTime::Cycles). */
	uint32	StartTime = 0;

	/** Last delta time that was measured (in FPlatformTime::Cycles). */
	uint32	DeltaTime = 0;

	/** Last time we did a measurement (in seconds). */
	double	LastCaptureTime = 0.0f;

	/** How often we should do a measurement (in seconds). */
	float	UpdateFrequency;
};

/** Global input latency timer. Defined in UnrealClient.cpp */
extern RENDERCORE_API FInputLatencyTimer GInputLatencyTimer;

/** How many cycles the renderthread used (excluding idle time). It's set once per frame in FViewport::Draw. */
extern RENDERCORE_API uint32 GRenderThreadTime;

/** How many cycles the renderthread was waiting. It's set once per frame in FViewport::Draw. */
extern RENDERCORE_API uint32 GRenderThreadWaitTime;

/** How many cycles the rhithread used (excluding idle time). */
extern RENDERCORE_API uint32 GRHIThreadTime;

/** How many cycles the gamethread used (excluding idle time). It's set once per frame in FViewport::Draw. */
extern RENDERCORE_API uint32 GGameThreadTime;

/** How much idle time in the game thread. It's set once per frame in FViewport::Draw. */
extern RENDERCORE_API uint32 GGameThreadWaitTime;

/** How many cycles it took to swap buffers to present the frame. */
extern RENDERCORE_API uint32 GSwapBufferTime;

/** How many cycles the gamethread used, including dependent wait time. */
extern RENDERCORE_API uint32 GGameThreadTimeCriticalPath;

/** How many cycles the renderthread used, including dependent wait time. */
extern RENDERCORE_API uint32 GRenderThreadTimeCriticalPath;