/** 
 * @file lltimer.h
 * @brief Cross-platform objects for doing timing 
 *
 * $LicenseInfo:firstyear=2000&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_TIMER_H					
#define LL_TIMER_H

#if LL_LINUX || LL_DARWIN
#include <sys/time.h>
#endif
#include <limits>

#include "stdtypes.h"

#include <string>
#include <list>
// units conversions
#include "llunits.h"
#ifndef USEC_PER_SEC
    const U32	USEC_PER_SEC	= 1000000;
#endif
const U32	SEC_PER_MIN		= 60;
const U32	MIN_PER_HOUR	= 60;
const U32	USEC_PER_MIN	= USEC_PER_SEC * SEC_PER_MIN;
const U32	USEC_PER_HOUR	= USEC_PER_MIN * MIN_PER_HOUR;
const U32	SEC_PER_HOUR	= SEC_PER_MIN * MIN_PER_HOUR;
const F64 	SEC_PER_USEC 	= 1.0 / (F64) USEC_PER_SEC;

constexpr U64 MSEC_PER_SEC = 1e3;

class LL_COMMON_API LLTimer 
{
public:
	static LLTimer *sTimer;				// global timer
	
protected:	
	U64 mLastClockCount;
	U64 mExpirationTicks;
	bool mStarted;

public:
	LLTimer();
	~LLTimer() = default;

	static void initClass();
	static void cleanupClass();

	// Return a high precision number of seconds since the start of
	// this application instance.
	static F64SecondsImplicit getElapsedSeconds()
	{
		if (sTimer) 
	{
		return sTimer->getElapsedTimeF64();
	}
		else
		{
			return 0;
		}
	}

	// Return a high precision usec since epoch
	static U64MicrosecondsImplicit getTotalTime();

	// Return a high precision seconds since epoch
	static F64SecondsImplicit getTotalSeconds();


	// MANIPULATORS
	void start() { reset(); mStarted = TRUE; }
	void stop() { mStarted = FALSE; }
	void reset();								// Resets the timer
	void setLastClockCount(U64 current_count);		// Sets the timer so that the next elapsed call will be relative to this time
	void setTimerExpirySec(F32SecondsImplicit expiration);
	BOOL checkExpirationAndReset(F32 expiration);
	BOOL hasExpired() const;
	F32SecondsImplicit getElapsedTimeAndResetF32();	// Returns elapsed time in seconds with reset
	F64SecondsImplicit getElapsedTimeAndResetF64();

	F32SecondsImplicit getRemainingTimeF32() const;

	static BOOL knownBadTimer();

	// ACCESSORS
	F32SecondsImplicit getElapsedTimeF32() const;			// Returns elapsed time in seconds
	F64SecondsImplicit getElapsedTimeF64() const;			// Returns elapsed time in seconds

	bool getStarted() const { return mStarted; }


	static U64 getCurrentClockCount();		// Returns the raw clockticks
};

//
// Various functions for initializing/accessing clock and timing stuff.  Don't use these without REALLY knowing how they work.
//
struct TimerInfo
{
	TimerInfo();
	void update();

	F64HertzImplicit		mClockFrequency;
	F64SecondsImplicit		mClockFrequencyInv;
	F64MicrosecondsImplicit	mClocksToMicroseconds;
	U64						mTotalTimeClockCount;
	U64						mLastTotalTimeClockCount;
};

TimerInfo& get_timer_info();

LL_COMMON_API U64 get_clock_count();

// Sleep for milliseconds
LL_COMMON_API void ms_sleep(U32 ms);
LL_COMMON_API void micro_sleep(U64 us);

// Returns the correct UTC time in seconds, like time(NULL).
// Useful on the viewer, which may have its local clock set wrong.
LL_COMMON_API time_t time_corrected();

static inline time_t time_min()
{
	if (sizeof(time_t) == 4)
	{
		return (time_t) INT_MIN;
	} else {
#ifdef LLONG_MIN
		return (time_t) LLONG_MIN;
#else
		return (time_t) LONG_MIN;
#endif
	}
}

static inline time_t time_max()
{
	if (sizeof(time_t) == 4)
	{
		return (time_t) INT_MAX;
	} else {
#ifdef LLONG_MAX
		return (time_t) LLONG_MAX;
#else
		return (time_t) LONG_MAX;
#endif
	}
}

// Correction factor used by time_corrected() above.
extern LL_COMMON_API S32 gUTCOffset;

// Is the current computer (in its current time zone)
// observing daylight savings time?
LL_COMMON_API BOOL is_daylight_savings();

// Converts internal "struct tm" time buffer to Pacific Standard/Daylight Time
// Usage:
// S32 utc_time;
// utc_time = time_corrected();
// struct tm* internal_time = utc_to_pacific_time(utc_time, gDaylight);
LL_COMMON_API struct tm* utc_to_pacific_time(time_t utc_time, BOOL pacific_daylight_time);

LL_COMMON_API void microsecondsToTimecodeString(U64MicrosecondsImplicit current_time, std::string& tcstring);
LL_COMMON_API void secondsToTimecodeString(F32SecondsImplicit current_time, std::string& tcstring);

U64MicrosecondsImplicit LL_COMMON_API totalTime();					// Returns current system time in microseconds

#endif
