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/**
 * @file range_finder_consistency_check.cpp
 */

#include "range_finder_consistency_check.hpp"

void RangeFinderConsistencyCheck::update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, uint64_t time_us)
{
	const float dt = static_cast<float>(time_us - _time_last_update_us) * 1e-6f;

	if ((_time_last_update_us == 0)
	    || (dt < 0.001f) || (dt > 0.5f)) {
		_time_last_update_us = time_us;
		_dist_bottom_prev = dist_bottom;
		return;
	}

	const float vel_bottom = (dist_bottom - _dist_bottom_prev) / dt;
	_innov = -vel_bottom - vz; // vel_bottom is +up while vz is +down

	const float var = 2.f * dist_bottom_var / (dt * dt); // Variance of the time derivative of a random variable: var(dz/dt) = 2*var(z) / dt^2
	_innov_var = var + vz_var;

	const float normalized_innov_sq = (_innov * _innov) / _innov_var;
	_test_ratio = normalized_innov_sq / (_gate * _gate);
	_signed_test_ratio_lpf.setParameters(dt, _signed_test_ratio_tau);
	const float signed_test_ratio = matrix::sign(_innov) * _test_ratio;
	_signed_test_ratio_lpf.update(signed_test_ratio);

	updateConsistency(vz, time_us);

	_time_last_update_us = time_us;
	_dist_bottom_prev = dist_bottom;
}

void RangeFinderConsistencyCheck::updateConsistency(float vz, uint64_t time_us)
{
	if (fabsf(_signed_test_ratio_lpf.getState()) >= 1.f) {
		_is_kinematically_consistent = false;
		_time_last_inconsistent_us = time_us;

	} else {
		if (fabsf(vz) > _min_vz_for_valid_consistency && _test_ratio < 1.f && ((time_us - _time_last_inconsistent_us) > _consistency_hyst_time_us)) {
			_is_kinematically_consistent = true;
		}
	}
}