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+/* -*- Mode: c++ -*- */
+/***************************************************************************
+ *            sample_selection.h
+ *
+ *  Mon Mar  4 23:58:12 CET 2019
+ *  Copyright 2019 André Nusser
+ *  andre.nusser@googlemail.com
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo 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; either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  DrumGizmo 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 DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include "sample_selection.h"
+
+#include <hugin.hpp>
+
+#include "powerlist.h"
+#include "random.h"
+#include "settings.h"
+
+namespace
+{
+
+// Minimum sample set size.
+// Smaller means wider 'velocity groups'.
+// Limited by sample set size, ie. only kicks in if sample set size is smaller
+// than this number.
+std::size_t const MIN_SAMPLE_SET_SIZE = 26u;
+
+float pow2(float f)
+{
+	return f*f;
+}
+
+} // end anonymous namespace
+
+SampleSelection::SampleSelection(Settings& settings, Random& rand, const PowerList& powerlist)
+	: settings(settings), rand(rand), powerlist(powerlist)
+{
+}
+
+void SampleSelection::setSelectionAlg(SelectionAlg alg)
+{
+	this->alg = alg;
+}
+
+void SampleSelection::finalise()
+{
+	last.assign(powerlist.getPowerListItems().size(), 0);
+}
+
+const Sample* SampleSelection::get(level_t level, std::size_t pos)
+{
+	// TODO: switch objective to default at some point
+	switch (alg)
+	{
+		case SelectionAlg::Objective:
+			return getObjective(level, pos);
+			break;
+		case SelectionAlg::Old:
+		default:
+			return getOld(level, pos);
+	}
+}
+
+const Sample* SampleSelection::getOld(level_t level, std::size_t pos)
+{
+	auto velocity_stddev = settings.velocity_stddev.load();
+
+	const auto& samples = powerlist.getPowerListItems();
+	if(!samples.size())
+	{
+		return nullptr; // No samples to choose from.
+	}
+
+	int retry = settings.sample_selection_retry_count.load();
+
+	Sample* sample{nullptr};
+
+	auto power_max = powerlist.getMaxPower();
+	auto power_min = powerlist.getMinPower();
+	float power_span = power_max - power_min;
+
+	// Width is limited to at least 10. Fixes problem with instrument with a
+	//  sample set smaller than MIN_SAMPLE_SET_SIZE.
+	float width = std::max(samples.size(), MIN_SAMPLE_SET_SIZE);
+
+	// Spread out at most ~2 samples away from center if all samples have a
+	// uniform distribution over the power spectrum (which they probably don't).
+	float mean_stepwidth = power_span / width;
+
+	// Cut off mean value with stddev/2 in both ends in order to make room for
+	//  downwards expansion on velocity 0 and upwards expansion on velocity 1.
+	float mean = level * (power_span - mean_stepwidth) + (mean_stepwidth / 2.0);
+	float stddev = velocity_stddev * mean_stepwidth;
+
+	float power{0.f};
+
+	// note: loop is executed once + #retry
+	do
+	{
+		--retry;
+
+		// Select normal distributed value between
+		//  (stddev/2) and (power_span-stddev/2)
+		float lvl = rand.normalDistribution(mean, stddev);
+
+		// Adjust this value to be in range
+		//  (power_min+stddev/2) and (power_max-stddev/2)
+		lvl += power_min;
+
+		DEBUG(rand,
+			  "level: %f, lvl: %f (mean: %.2f, stddev: %.2f, mean_stepwidth: %f, power_min: %f, power_max: %f)\n",
+			  level, lvl, mean, stddev, mean_stepwidth, power_min, power_max);
+
+		for (auto& item: samples)
+		{
+			if (sample == nullptr || std::fabs(item.power - lvl) < std::fabs(power - lvl))
+			{
+				sample = item.sample;
+				power = item.power;
+			}
+		}
+	} while (lastsample == sample && retry >= 0);
+
+	DEBUG(rand, "Found sample with power %f\n", power);
+
+	lastsample = sample;
+
+	return sample;
+}
+
+const Sample* SampleSelection::getObjective(level_t level, std::size_t pos)
+{
+	auto velocity_stddev = settings.velocity_stddev.load();
+
+	const auto& samples = powerlist.getPowerListItems();
+	if(!samples.size())
+	{
+		return nullptr; // No samples to choose from.
+	}
+
+	auto power_max = powerlist.getMaxPower();
+	auto power_min = powerlist.getMinPower();
+	float power_span = power_max - power_min;
+
+	// Width is limited to at least 10. Fixes problem with instrument with a
+	// sample set smaller than MIN_SAMPLE_SET_SIZE.
+	float width = std::max(samples.size(), MIN_SAMPLE_SET_SIZE);
+
+	// Spread out at most ~2 samples away from center if all samples have a
+	// uniform distribution over the power spectrum (which they probably don't).
+	float mean_stepwidth = power_span / width;
+
+	// Cut off mean value with stddev/2 in both ends in order to make room for
+	// downwards expansion on velocity 0 and upwards expansion on velocity 1.
+	float mean = level * (power_span - mean_stepwidth) + (mean_stepwidth / 2.0);
+	float stddev = settings.enable_velocity_modifier.load() ? velocity_stddev * mean_stepwidth : 0.;
+
+	std::size_t index_opt = 0;
+	float power_opt{0.f};
+	float value_opt{std::numeric_limits<float>::max()};
+	// TODO: those are mostly for debugging at the moment
+	float random_opt = 0.;
+	float distance_opt = 0.;
+	float recent_opt = 0.;
+
+	// Select normal distributed value between
+	// (stddev/2) and (power_span-stddev/2)
+	float lvl = rand.normalDistribution(mean, stddev);
+
+	// Adjust this value to be in range
+	// (power_min+stddev/2) and (power_max-stddev/2)
+	lvl += power_min;
+
+	DEBUG(rand, "level: %f, lvl: %f (mean: %.2f, stddev: %.2f, mean_stepwidth: %f,"
+		"power_min: %f, power_max: %f)\n", level, lvl, mean, stddev, mean_stepwidth,
+		power_min, power_max);
+
+	// TODO: expose parameters to GUI
+	float alpha = 1.0;
+	float beta = 1.0;
+	float gamma = .5;
+
+	// TODO: start with most promising power value and then stop when reaching far values
+	// which cannot become opt anymore
+	for (std::size_t i = 0; i < samples.size(); ++i)
+	{
+		auto const& item = samples[i];
+
+		// compute objective function value
+		auto random = rand.floatInRange(0.,1.);
+		auto distance = item.power - lvl;
+		auto recent = (float)settings.samplerate/std::max<std::size_t>(pos - last[i], 1);
+		auto value = alpha*pow2(distance) + beta*pow2(recent) + gamma*random;
+
+		if (value < value_opt)
+		{
+			index_opt = i;
+			power_opt = item.power;
+			value_opt = value;
+			random_opt = random;
+			distance_opt = distance;
+			recent_opt = recent;
+		}
+	}
+
+	DEBUG(rand, "Chose sample with index: %d, value: %f, power %f, random: %f, distance: %f, recent: %f", (int)index_opt, value_opt, power_opt, random_opt, distance_opt, recent_opt);
+
+	last[index_opt] = pos;
+	return samples[index_opt].sample;
+}