/* Copyright (C) 2009 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * =========================================================================
 * File        : timer.cpp
 * Project     : 0 A.D.
 * Description : platform-independent high resolution timer
 * =========================================================================
 */

#include "precompiled.h"
#include "timer.h"

#include <numeric>
#include <math.h>
#include <float.h>
#include <stdarg.h>

#include "lib/posix/posix_time.h"
#if OS_WIN
#include "lib/sysdep/os/win/whrt/whrt.h"
#endif
#if OS_UNIX
# include <unistd.h>
#endif

#if OS_UNIX || OS_WIN
# define HAVE_GETTIMEOFDAY 1
#else
# define HAVE_GETTIMEOFDAY 0
#endif

#if (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0) || OS_WIN
# define HAVE_CLOCK_GETTIME 1
#else
# define HAVE_CLOCK_GETTIME 0
#endif

// rationale for wrapping gettimeofday and clock_gettime, instead of just
// emulating them where not available: allows returning higher-resolution
// timer values than their us / ns interface, via double [seconds].
// they're also not guaranteed to be monotonic.

#if HAVE_GETTIMEOFDAY
static struct timespec start;
#elif HAVE_CLOCK_GETTIME
static struct timeval start;
#endif


//-----------------------------------------------------------------------------
// timer API

void timer_LatchStartTime()
{
#if OS_WIN
	// whrt_Time starts at zero, nothing needs to be done.
#elif HAVE_CLOCK_GETTIME
	(void)clock_gettime(CLOCK_REALTIME, &start);
#elif HAVE_GETTIMEOFDAY
	gettimeofday(&start, 0);
#endif
}


double timer_Time()
{
	double t;

#if OS_WIN
	t = whrt_Time();
#elif HAVE_CLOCK_GETTIME
	struct timespec cur;
	(void)clock_gettime(CLOCK_REALTIME, &cur);
	t = (cur.tv_sec - start.tv_sec) + (cur.tv_nsec - start.tv_nsec)*1e-9;
#elif HAVE_GETTIMEOFDAY
	struct timeval cur;
	gettimeofday(&cur, 0);
	t = (cur.tv_sec - start.tv_sec) + (cur.tv_usec - start.tv_usec)*1e-6;
#else
# error "timer_Time: add timer implementation for this platform!"
#endif

	// make sure time is monotonic (never goes backwards)
	static double t_last = 0.0;
	if(t < t_last)
		t = t_last+DBL_EPSILON;
	t_last = t;

	return t;
}


double timer_Resolution()
{
	// may take a while to determine, so cache it
	static double cached_res = 0.0;
	if(cached_res != 0.0)
		return cached_res;

	double res = 0.0;

#if OS_WIN
	res = whrt_Resolution();
#elif HAVE_CLOCK_GETTIME
	struct timespec ts;
	if(clock_getres(CLOCK_REALTIME, &ts) == 0)
		res = ts.tv_nsec * 1e-9;
#else
	const double t0 = timer_Time();
	double t1, t2;
	do t1 = timer_Time(); while(t1 == t0);
	do t2 = timer_Time(); while(t2 == t1);
	res = t2-t1;
#endif

	cached_res = res;
	return res;
}


//-----------------------------------------------------------------------------
// client API

// intrusive linked-list of all clients. a fixed-size limit would be
// acceptable (since timers are added manually), but the list is easy
// to implement and only has the drawback of exposing TimerClient to users.
//
// do not use std::list et al. for this! we must be callable at any time,
// especially before NLSO ctors run or before heap init.
static size_t num_clients;
static TimerClient* clients;


TimerClient* timer_AddClient(TimerClient* tc, const char* description)
{
	tc->sum.SetToZero();

	tc->description = description;

	// insert at front of list
	tc->next = clients;
	clients = tc;
	num_clients++;

	return tc;
}


void timer_BillClient(TimerClient* tc, TimerUnit t0, TimerUnit t1)
{
	tc->sum.AddDifference(t0, t1);
	tc->num_calls++;
}


void timer_DisplayClientTotals()
{
	debug_printf("TIMER TOTALS (%d clients)\n", num_clients);
	debug_printf("-----------------------------------------------------\n");

	while(clients)
	{
		// (make sure list and count are consistent)
		debug_assert(num_clients != 0);
		TimerClient* tc = clients;
		clients = tc->next;
		num_clients--;

		const std::string duration = tc->sum.ToString();
		debug_printf("  %s: %s (%dx)\n", tc->description, duration.c_str(), tc->num_calls);
	}

	debug_printf("-----------------------------------------------------\n");
}