/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2023, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include "obs-precomp.h"  // Precompiled headers
//
#include <mrpt/math/distributions.h>
#include <mrpt/obs/CObservation2DRangeScanWithUncertainty.h>

using namespace mrpt::obs;

CObservation2DRangeScanWithUncertainty::TEvalParams::TEvalParams()

	= default;

double CObservation2DRangeScanWithUncertainty::evaluateScanLikelihood(
	const CObservation2DRangeScan& otherScan, const TEvalParams& params) const
{
	ASSERT_EQUAL_(
		otherScan.getScanSize(), static_cast<size_t>(rangesMean.size()));
	ASSERT_EQUAL_(
		otherScan.getScanSize(), static_cast<size_t>(rangesCovar.rows()));
	ASSERT_EQUAL_(rangesCovar.rows(), rangesCovar.cols());
	ASSERT_(params.prob_outliers >= 0.0 && params.prob_outliers <= 1.0);
	ASSERT_(otherScan.maxRange > 0.0f);

	const double sensorRangeVar = mrpt::square(otherScan.stdError);
	const size_t N = rangesMean.size();

	const double max_var = mrpt::square(params.max_prediction_std_dev);
	double lik_sum = .0;
	size_t num_valid = 0;
	for (size_t i = 0; i < N; i++)
	{
		const double prediction_total_var = rangesCovar(i, i) + sensorRangeVar;

		if (prediction_total_var > max_var) { continue; }
		num_valid++;

		const double otherScanRange = otherScan.getScanRangeValidity(i)
			? otherScan.getScanRange(i)
			: otherScan.maxRange;

		const double likGauss = std::exp(
			-0.5 * mrpt::square(otherScanRange - rangesMean[i]) /
			prediction_total_var);
		double pi;
		if (otherScan.getScanRange(i) > rangesMean[i])
		{
			if (otherScan.getScanRangeValidity(i)) pi = likGauss;
			else
				pi = std::max(likGauss, params.prob_lost_ray);
		}
		else
			pi = std::max(likGauss, std::min(1.0, params.prob_outliers));

		double lpi = std::max(params.min_ray_log_lik, log(pi));
		lik_sum += lpi;
	}
	if (num_valid) lik_sum /= num_valid;
	lik_sum = exp(lik_sum);

	return lik_sum;
}
