#ifndef LOGDISTANCEMODEL_H
#define LOGDISTANCEMODEL_H

#include <cmath>

class LogDistanceModel {

public:

	/** convert from RSSI to a distance (in meter) */
	static float rssiToDistance(const float txPower, const float pathLoss, const float rssi) {
		return pow(10, (txPower - rssi) / (10 * pathLoss));
	}

	/** convert from a distance (in meter) to the expected RSSI */
	static float distanceToRssi(const float txPower, const float pathLoss, const float distance_m) {
		if (distance_m <= 1) {return txPower;}
		return (txPower - (10 * pathLoss * std::log10(distance_m)));
	}

//	static float distanceAndRssiToPathLoss(const float txPower, const float rssi, const float distance_m) {
//		const float delta = txPower - rssi;
//		const float log = std::log10(distance_m) * 10.0f;
//		const float res = delta/log;

//		// sanity check
//		const float err = std::abs(rssi - distanceToRssi(txPower, res, distance_m));
//		if (err > 0.01) {throw Exception("error too high!");}

//		return res;
//	}

};

#include <vector>

class LogDistFastModel {

private:

	std::vector<float> lut;

public:

	LogDistFastModel() {
		lut.resize(2000);
		for (int i = 0; i < 2000; ++i) {
			lut[i] = std::log10(i/10.0f);
		}
	}

	float distanceToRssi(const float txPower, const float pathLoss, const float distance) const {
		if (distance <= 1) {return txPower;}
		return (txPower - (10 * pathLoss * lut[ (int) (distance*10) ]));
	}

};

#endif // LOGDISTANCEMODEL_H