#ifndef WIFIQUALITYANALYZER_H
#define WIFIQUALITYANALYZER_H

#include "WiFiMeasurements.h"
#include <unordered_set>

class WiFiQualityAnalyzer {

private:

	int historySize = 3;
	std::vector<WiFiMeasurements> history;
	float quality = 0;

public:

	/** attach the current measurement and infer the quality */
	void add(const WiFiMeasurements& mes) {

		// update the history
		history.push_back(mes);
		while(history.size() > historySize) {
			history.erase(history.begin());
		}

		// recalculate
		update();

	}

	/** get a quality score for the WiFi */
	float getQuality() const {
		return quality;
	}

private:

	/** re-calculate the current quality */
	void update() {

		const float qCnt = getQualityByCount();
		const float qAvgdB = getQualityByAvgDB();

		quality = qAvgdB;

	}

	/** score [0:1] based on the average sig-strength. the higher the better */
	float getQualityByAvgDB() const {

		// stats
		float sum = 0;
		float sum2 = 0;
		float cnt = 0;

		for (const WiFiMeasurements& mes : history) {
			for (const WiFiMeasurement& m : mes.entries) {
				const float rssi = m.getRSSI();
				sum += rssi;
				sum2 += rssi*rssi;
				++cnt;
			}
		}

		// average sig strength
		const float avg = sum/cnt;
		const float avg2 = sum2/cnt;
		const float stdDev = std::sqrt(avg2 - avg*avg);

		// avg rssi score
		const float minRSSI = -85;
		const float maxRSSI = -70;
		float score1 = (avg-minRSSI) / (maxRSSI-minRSSI);	// min = 0; max = 1
		if (score1 > 1) {score1 = 1;}
		if (score1 < 0) {score1 = 0;}
		//const float score1 = 1.0 - std::exp(-0.07 * (avg-minRSSI));

		// std dev score
		const float score2 = 1.0 - std::exp(-1.0 * stdDev);

		return score1 * score2;

	}

	/** quality score [0:1] according to the number of seen APs */
	float getQualityByCount() const {

		// distinct macs
		std::unordered_set<MACAddress> macs;
		for (const WiFiMeasurements& mes : history) {
			for (const WiFiMeasurement& m : mes.entries) {
				macs.insert(m.getAP().getMAC());
			}
		}

		// number of distinct macs
		const int cnt = macs.size();

		// see function plot. function between [0.0:1.0] has 0.5 around 7 seen APs
		return 1.0 - std::exp(-0.1 * cnt);

	}

};

#endif // WIFIQUALITYANALYZER_H