Indoor/sensors/radio/WiFiGridNode.h

#ifndef WIFIGRIDNODE_H
#define WIFIGRIDNODE_H

#include <cstdint>
#include "AccessPoint.h"
#include "../../misc/Debug.h"

/**
 * rssi model-estimation for one AP, denoted by its index [among all APs present within the map]
 * the signal strength is stored as uint8_t and allows a granularity of 0.25 dB between -40 and -103 dB
 */
struct WiFiGridNodeAP {

private:

	static const uint8_t UNUSED_IDX = 255;

private:

	/** access-point index -> max 255 APs/Map */
	uint8_t idx;

	/** access-point rssi */
	uint8_t rssi;

public:

	/** empty ctor */
	WiFiGridNodeAP() : idx(UNUSED_IDX), rssi(0) {
		int i = 0; (void) i;
	}

	/** ctor */
	WiFiGridNodeAP(const int idx, const float rssi) : idx(idx), rssi(stretch(rssi)) {
		int i = 0; (void) i;
	}


	/** is this entry valid/used? */
	bool isValid() const {return idx != UNUSED_IDX;}

	/** set AP and its signal strength */
	void set(const int apIdx, const float rssi) {
		this->idx = apIdx;
		this->rssi = stretch(rssi);
	}

	/** get the predicted signal-strength */
	float getRSSI() const {return unstretch(rssi);}

	/** get the access-point's index */
	int getAPIdx() const {return idx;}

private:

	/** [-40:-103] -> [0:252] => this allows 0.25 steps */
	static inline int8_t stretch(float rssi) {
		if (rssi > -40) {rssi = -40;}
		if (rssi < -103) {rssi = -103;}
		return std::round((-rssi - 40) * 4);
	}

	/** [0:252] -> [-40:-103] */
	static inline float unstretch(const float rssi) {
		return -(rssi / 4.0f + 40.0f);
	}

};// __attribute__((packed));


/**
 * base-class for grid-nodes that contain wifi signal-strength estimations.
 * such estimations are calculated offline and added to each node.
 * this also allows for using very complex signal-strength estimation models
 */
template <int maxAccessPoints> struct WiFiGridNode {

	/** contains the 10 strongest APs measureable at this position */
	WiFiGridNodeAP strongestAPs[maxAccessPoints];


	/** ctor */
	explicit WiFiGridNode() : strongestAPs() {
		;
	}


	/** get the maximum number of APs each node is able to store */
	int getMaxAPs() const {return maxAccessPoints;}

	/**
	 * get the RSSI for the given AP
	 * returns 0 if unknown
	 */
	float getRSSI(const std::string& mac) const {
		return getRSSI(MACAddress(mac));
	}

	/**
	 * get the RSSI for the given AP
	 * returns 0 if unknown
	 */
	float getRSSI(const MACAddress mac) const {
		for (const WiFiGridNodeAP& ap : strongestAPs) {
			//std::cout << getMapAPs()[ap.getAPIdx()].getMAC().asString() << std::endl;
			//std::cout << mac.asString() << std::endl;
			if (!ap.isValid()) {break;}												// reached the end of all APs visible on this node
			if (getMapAPs()[ap.getAPIdx()].getMAC() == mac) {return ap.getRSSI();}	// does this APs MAC match with the requested MAC? -> found!
		}
		return 0;
	}

	/** get the number of access-points visible at this node */
	int getNumVisibleAPs() const {
		for (int i = 0; i < getMaxAPs(); ++i) {
			if (!strongestAPs[i].isValid()) {return i;}
		}
		return getMaxAPs();
	}

	/** shared vector of all accesspoints the are present within the map. the IDX referes to this vector */
	static std::vector<AccessPoint>& getMapAPs() {
		static std::vector<AccessPoint> list;
		return list;
	}


protected:

	static constexpr const char* name = "WiFiGridNode";

	/** serialize static members */
	static void staticSerialize(std::ostream& out) {

		// number of APs within map
		const int numAPs = getMapAPs().size();

		// serialize number and APs within map
		out.write((const char*) &numAPs, sizeof(numAPs));
		out.write((const char*) getMapAPs().data(), sizeof(getMapAPs()[0])*numAPs);

		Log::add(name, "serialized " + std::to_string(numAPs) + " APs");

	}

	/** deserialize static members */
	static void staticDeserialize(std::istream& inp) {

		// get number of APs within map
		int numAPs;
		inp.read((char*) &numAPs, sizeof(numAPs));

		// allocate
		getMapAPs().resize(numAPs);

		// deserialize APs within map
		inp.read((char*) getMapAPs().data(), sizeof(getMapAPs()[0])*numAPs);

		Log::add(name, "de-serialized " + std::to_string(numAPs) + " APs");
		std::string aps; for (const AccessPoint& ap : getMapAPs()) {aps += ap.getMAC().asString() + " ";}
		Log::add(name, aps);

	}




};// __attribute__((packed));

#endif // WIFIGRIDNODE_H