/*
    Copyright (C) 2013-2021 Carl Hetherington <cth@carlh.net>

    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.

*/


/** @file  src/audio_merger.cc
 *  @brief AudioMerger class.
 */


#include "audio_merger.h"
#include "dcpomatic_time.h"
#include <iostream>


using std::cout;
using std::list;
using std::make_pair;
using std::make_shared;
using std::max;
using std::min;
using std::pair;
using std::shared_ptr;
using boost::optional;
using namespace dcpomatic;


AudioMerger::AudioMerger (int frame_rate)
	: _frame_rate (frame_rate)
{

}


Frame
AudioMerger::frames (DCPTime t) const
{
	return t.frames_floor (_frame_rate);
}


/** Pull audio up to a given time; after this call, no more data can be pushed
 *  before the specified time.
 *  @param time Time to pull up to.
 *  @return Blocks of merged audio up to `time'.
 */
list<pair<shared_ptr<AudioBuffers>, DCPTime>>
AudioMerger::pull (DCPTime time)
{
	list<pair<shared_ptr<AudioBuffers>, DCPTime>> out;

	list<Buffer> new_buffers;

	_buffers.sort ([](Buffer const& a, Buffer const& b) {
		return a.time < b.time;
	});

	for (auto i: _buffers) {
		if (i.period().to <= time) {
			/* Completely within the pull period */
			DCPOMATIC_ASSERT (i.audio->frames() > 0);
			out.push_back (make_pair (i.audio, i.time));
		} else if (i.time < time) {
			/* Overlaps the end of the pull period */
			int32_t const overlap = frames(DCPTime(time - i.time));
			/* Though time > i.time, overlap could be 0 if the difference in time is less than one frame */
			if (overlap > 0) {
				auto audio = make_shared<AudioBuffers>(i.audio, overlap, 0);
				out.push_back (make_pair(audio, i.time));
				i.audio->trim_start (overlap);
				i.time += DCPTime::from_frames(overlap, _frame_rate);
				DCPOMATIC_ASSERT (i.audio->frames() > 0);
				new_buffers.push_back (i);
			}
		} else {
			/* Not involved */
			DCPOMATIC_ASSERT (i.audio->frames() > 0);
			new_buffers.push_back (i);
		}
	}

	_buffers = new_buffers;

	for (auto const& i: out) {
		DCPOMATIC_ASSERT (i.first->frames() > 0);
	}

	return out;
}


/** Push some data into the merger at a given time */
void
AudioMerger::push (std::shared_ptr<const AudioBuffers> audio, DCPTime time)
{
	DCPOMATIC_ASSERT (audio->frames() > 0);

	DCPTimePeriod period (time, time + DCPTime::from_frames (audio->frames(), _frame_rate));

	/* Mix any overlapping parts of this new block with existing ones */
	for (auto i: _buffers) {
		auto overlap = i.period().overlap(period);
		if (overlap) {
			int32_t const offset = frames(DCPTime(overlap->from - i.time));
			int32_t const frames_to_mix = frames(overlap->duration());
			if (i.time < time) {
				i.audio->accumulate_frames(audio.get(), frames_to_mix, 0, offset);
			} else {
				i.audio->accumulate_frames(audio.get(), frames_to_mix, offset, 0);
			}
		}
	}

	list<DCPTimePeriod> periods;
	for (auto i: _buffers) {
		periods.push_back (i.period());
	}

	/* Add the non-overlapping parts */
	for (auto i: subtract(period, periods)) {
		auto before = _buffers.end();
		auto after = _buffers.end();
		for (auto j = _buffers.begin(); j != _buffers.end(); ++j) {
			if (j->period().to == i.from) {
				before = j;
			}
			if (j->period().from == i.to) {
				after = j;
			}
		}

		/* Get the part of audio that we want to use */
		auto part = make_shared<AudioBuffers>(audio, frames(i.to) - frames(i.from), frames(DCPTime(i.from - time)));

		if (before == _buffers.end() && after == _buffers.end()) {
			if (part->frames() > 0) {
				/* New buffer */
				_buffers.push_back (Buffer (part, time, _frame_rate));
			}
		} else if (before != _buffers.end() && after == _buffers.end()) {
			/* We have an existing buffer before this one; append new data to it */
			before->audio->append (part);
		} else if (before ==_buffers.end() && after != _buffers.end()) {
			/* We have an existing buffer after this one; append it to the new data and replace */
			part->append (after->audio);
			after->audio = part;
			after->time = time;
		} else {
			/* We have existing buffers both before and after; coalesce them all */
			before->audio->append (part);
			before->audio->append (after->audio);
			_buffers.erase (after);
		}
	}
}


void
AudioMerger::clear ()
{
	_buffers.clear ();
}