#ifndef VAPGROUPER_H
#define VAPGROUPER_H

#include <vector>
#include <unordered_map>
#include <cmath>

#include "../../math/Median.h"

#include "WiFiMeasurements.h"

class VAPGrouper {

public:

	/** the mode denotes the algorithm that is used for grouping VAPs together */
	enum class Mode {

		/** do NOT group */
		DISABLED,

		/** group VAPs by setting the MAC's last digit to zero */
		LAST_MAC_DIGIT_TO_ZERO,

	};

	/** describes how to calculate the final signal-strengh of the VAP-grouped entry */
	enum class Aggregation {

		/** use the average signal-strength of all grouped APs */
		AVERAGE,

		/** use the median signal-strength of all grouped APs */
		MEDIAN,

		/** use the maximum signal-strength of all grouped APs */
		MAXIMUM,

	};

private:

	/** the mode to use for grouping VAPs */
	const Mode mode;

	/** the signal-strength aggregation algorithm to use */
	const Aggregation agg;

public:

	/** ctor */
	VAPGrouper(const Mode mode, const Aggregation agg) : mode(mode), agg(agg) {

	}


	/** get a vap-grouped version of the given input */
	WiFiMeasurements group(const WiFiMeasurements& original) const {

		// first, group all VAPs into a vector [one vector per VAP-group]
		std::unordered_map<MACAddress, std::vector<WiFiMeasurement>> grouped;

		for (const WiFiMeasurement& m : original.entries) {

			// the vap-base-mac this entry belongs to
			const MACAddress baseMAC = getBaseMAC(m.getAP().getMAC());
			grouped[baseMAC].push_back(m);

		}

		// output
		WiFiMeasurements result;

		// perform aggregation on each VAP-group
		for (auto it : grouped) {

			const MACAddress& base = it.first;
			const std::vector<WiFiMeasurement>& vaps = it.second;

			// group all VAPs into one measurement
			const WiFiMeasurement groupedMeasurement = groupVAPs(base, vaps);

			// add it to the result-vector
			result.entries.push_back(groupedMeasurement);

		}

		// done
		return result;

	}

	/** get the VAP-base-MAC-Address that is the same for all APs that belong to a VAP-Group */
	MACAddress getBaseMAC(const MACAddress& mac) const {

		switch(mode) {
		case Mode::DISABLED:					return mac;
		case Mode::LAST_MAC_DIGIT_TO_ZERO:		return lastMacDigitToZero(mac);
		default:								throw Exception("unsupported vap-grouping mode given");
		}

	}

private:

	/** combine all of the given VAPs into one entry using the configured aggregation method */
	WiFiMeasurement groupVAPs(const MACAddress& baseMAC, const std::vector<WiFiMeasurement>& vaps) const {

		// the resulting entry is an AP with the base-MAC all of the given VAPs have in common
		const AccessPoint baseAP(baseMAC);

		// the resultign timestamp
		const Timestamp baseTS = vaps.front().getTimestamp();

		// calculate the rssi using the configured aggregate function
		float rssi = NAN;
		switch(agg) {
			case Aggregation::AVERAGE:	rssi = getAVG(vaps); break;
			case Aggregation::MEDIAN:	rssi = getMedian(vaps); break;
			case Aggregation::MAXIMUM:	rssi = getMax(vaps); break;
			default:					throw Exception("unsupported vap-aggregation method");
		}

		// create the result measurement
		return WiFiMeasurement(baseAP, rssi, baseTS);

	}

private:

	/** get the average signal strength */
	inline float getAVG(const std::vector<WiFiMeasurement>& vaps) const {

		float rssi = 0;
		for (const WiFiMeasurement& vap : vaps) {
			rssi += vap.getRSSI();
		}
		return rssi / vaps.size();

	}

	/** get the median signal strength */
	inline float getMedian(const std::vector<WiFiMeasurement>& vaps) const {

		Median<float> median;
		for (const WiFiMeasurement& vap : vaps) {
			median.add(vap.getRSSI());
		}
		return median.get();

	}

	/** get the maximum signal strength */
	inline float getMax(const std::vector<WiFiMeasurement>& vaps) const {

		float max = -9999999;
		for (const WiFiMeasurement& vap : vaps) {
			if (vap.getRSSI() > max) {max = vap.getRSSI();}
		}
		return max;

	}

private:

	/** convert the MAC by setting the last (right-most) digit to zero (0) */
	static inline MACAddress lastMacDigitToZero(const MACAddress& mac) {
		std::string str = mac.asString();
		str.back() = '0';
		return MACAddress(str);
	}


};

#endif // VAPGROUPER_H