/*
    Copyright (C) 2014 Tim Mayberry

    This program 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.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifndef __libpbd_timing_h__
#define __libpbd_timing_h__

#include <glib.h>

#include <stdint.h>

#include <string>
#include <vector>

#include "pbd/libpbd_visibility.h"

namespace PBD {

LIBPBD_API bool get_min_max_avg_total (const std::vector<uint64_t>& values, uint64_t& min, uint64_t& max, uint64_t& avg, uint64_t& total);

LIBPBD_API std::string timing_summary (const std::vector<uint64_t>& values);

/**
 * This class allows collecting timing data using two different
 * techniques. The first is using start() and update() and then
 * calling elapsed() to get the elapsed time. This is useful when
 * you want to measure the elapsed time between two different
 * execution points. e.g
 *
 * timing.start();
 * do_stuff();
 * timing.update();
 * cerr << "do_stuff took: "
 *      << timing.elapsed()
 *      << "usecs" << endl;
 *
 * The other is timing intervals using start() and calling
 * get_interval() periodically to measure the time intervals
 * between the same execution point. The difference is necessary
 * to get the most accurate timing information when timing
 * intervals but I didn't feel it necessary to have two separate
 * classes.
 */
class LIBPBD_API Timing
{
public:

	Timing ()
		: m_start_val(0)
		, m_last_val(0)
	{ start ();}

	bool valid () const {
		return (m_start_val != 0 && m_last_val != 0);
	}

	void start () {
		m_start_val = g_get_monotonic_time ();
		m_last_val = 0;
	}

	void update () {
		m_last_val = g_get_monotonic_time ();
	}

	void reset () {
		m_start_val = m_last_val = 0;
	}

	uint64_t get_interval () {
		uint64_t elapsed = 0;
		update ();
		if (valid()) {
			elapsed = m_last_val - m_start_val;
			m_start_val = m_last_val;
			m_last_val = 0;
		}
		return elapsed;
	}

	/// @return Elapsed time in microseconds
	uint64_t elapsed () const {
		return m_last_val - m_start_val;
	}

	/// @return Elapsed time in milliseconds
	uint64_t elapsed_msecs () const {
		return elapsed () / 1000;
	}

private:

	uint64_t m_start_val;
	uint64_t m_last_val;

};

class LIBPBD_API TimingData
{
public:
	TimingData () : m_reserve_size(256)
	{ reset (); }

	void start_timing () {
		m_timing.start ();
	}

	void add_elapsed () {
		m_timing.update ();
		if (m_timing.valid()) {
			m_elapsed_values.push_back (m_timing.elapsed());
		}
	}

	void add_interval () {
		uint64_t interval = m_timing.get_interval ();
		m_elapsed_values.push_back (interval);
	}

	void reset () {
		m_elapsed_values.clear ();
		m_elapsed_values.reserve (m_reserve_size);
	}

	std::string summary () const
	{ return timing_summary (m_elapsed_values); }

	bool get_min_max_avg_total (uint64_t& min,
	                            uint64_t& max,
	                            uint64_t& avg,
	                            uint64_t& total) const
	{ return PBD::get_min_max_avg_total (m_elapsed_values, min, max, avg, total); }

	void reserve (uint32_t reserve_size)
	{ m_reserve_size = reserve_size; reset (); }

	uint32_t size () const
	{ return m_elapsed_values.size(); }

private:

	Timing m_timing;

	uint32_t m_reserve_size;

	std::vector<uint64_t> m_elapsed_values;
};

class LIBPBD_API Timed
{
public:
	Timed (TimingData& data)
		: m_data(data)
	{
		m_data.start_timing ();
	}

	~Timed ()
	{
		m_data.add_elapsed ();
	}

private:

	TimingData& m_data;

};

} // namespace PBD

#endif // __libpbd_timing_h__