/*
    Copyright (C) 2006 Paul Davis 
    
    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.
*/

#include <cstring>
#include <cmath>
#include <algorithm>
#include <ardour/amp.h>
#include <ardour/buffer_set.h>
#include <ardour/audio_buffer.h>

namespace ARDOUR {


/** Apply a declicked gain to the audio buffers of @a bufs */
void
Amp::run_in_place (BufferSet& bufs, nframes_t nframes, gain_t initial, gain_t target, bool invert_polarity)
{
	if (nframes == 0)
		return;

	if (bufs.count().n_audio() == 0)
		return;

	// assert(bufs.buffer_capacity(DataType::AUDIO) >= nframes);

	// if we don't need to declick, defer to apply_simple_gain
	if (initial == target) {
		if (target == 0.0) {
			for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
				memset (i->data(), 0, sizeof (Sample) * nframes);
			}
		} else if (target != 1.0) {
			for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
				apply_gain_to_buffer (i->data(), nframes, target);
			}
		}
		return;
	}

	const nframes_t declick = std::min ((nframes_t)128, nframes);
	gain_t         delta;
	double         fractional_shift = -1.0/declick;
	double         fractional_pos;
	gain_t         polscale = invert_polarity ? -1.0f : 1.0f;

	if (target < initial) {
		/* fade out: remove more and more of delta from initial */
		delta = -(initial - target);
	} else {
		/* fade in: add more and more of delta from initial */
		delta = target - initial;
	}

	for (BufferSet::audio_iterator i = bufs.audio_begin(); i != bufs.audio_end(); ++i) {
		Sample* const buffer = i->data();

		fractional_pos = 1.0;

		for (nframes_t nx = 0; nx < declick; ++nx) {
			buffer[nx] *= polscale * (initial + (delta * (0.5 + 0.5 * cos (M_PI * fractional_pos))));
			fractional_pos += fractional_shift;
		}
		
		/* now ensure the rest of the buffer has the target value applied, if necessary. */
		
		if (declick != nframes) {

			if (invert_polarity) {
				target = -target;
			}

			if (target == 0.0) {
				memset (&buffer[declick], 0, sizeof (Sample) * (nframes - declick));
			} else if (target != 1.0) {
				apply_gain_to_buffer (&buffer[declick], nframes - declick, target);
			}
		}
	}
}

void
Amp::apply_simple_gain (BufferSet& bufs, nframes_t nframes, gain_t target)
{
}


} // namespace ARDOUR