// demonstration of common memory leak

#include <iostream>
#include <fstream>
#include <math.h>
#include <memory>
#include <string>
#include <algorithm>

using namespace std;

const double conv = 45.0/atan(1.0);

class GPScoords {
public:
	virtual ~GPScoords() { }
	virtual void load(istream &is) { is >> lat >> lon; lat /= conv; lon /= conv; }
	virtual void save(ostream &os) const { os << lat*conv << ' ' << lon*conv; }
	double distance(const GPScoords &gps) const {
		return acos(sin(lat)*sin(gps.lat) + cos(lat)*cos(gps.lat)*cos(lon-gps.lon))*6371.0;
	}
private:
	double lat, lon;
};

class GPStag : public GPScoords {
public:
	virtual ~GPStag() { }
	virtual void load(istream &is) { GPScoords::load(is); is >> mytag;  }
	virtual void save(ostream &os) const {
		GPScoords::save(os);
		os << ' ' << mytag;
	}
	void settag(const string &s) { mytag = s; }
	string tag() const { return mytag; } // prefer this to returning
		// "const string &" as this return can bind to an rval ref
private:
	string mytag;
};

typedef unique_ptr<GPScoords> GPSptr;
	
GPSptr loadGPS(istream &is) {
	char c;
	is >> c;
	GPSptr ret;
	if (c=='T') ret = GPSptr(new GPStag());
	else {
		is.putback(c);
		ret = GPSptr(new GPScoords());
	}
	ret->load(is);
	return ret;
}

class distsort {
public:
	distsort(shared_ptr<GPScoords> &center) : c(center) { }
	bool operator()(const GPSptr &p1, const GPSptr &p2) {
		return c->distance(*p1) < c->distance(*p2);
	}
private:
	const shared_ptr<GPScoords> c;
};

int main(int argc, char **argv) {
	fstream file;
	file.exceptions(ifstream::eofbit);
	vector<GPSptr> locs;
	shared_ptr<GPScoords> center;
	try {
		file.open(argc>1 ? argv[1] : "testgps2.txt");
		int n;
		file >> n;
		if (n) center = loadGPS(file); // note initializing shared_ptr
						// from non-const rval unique_ptr -- okay!
		for(int i=1;i<n;i++)
			locs.push_back(loadGPS(file));
		file.close();
	} catch (std::exception e) {
		cout << "file not properly formatted" << endl;
		return -1;
	}
	if (!center) return 0; // if no values, leave

	sort(locs.begin(),locs.end(),distsort(center));

	cout << "list, sorted from distance to ";
	center->save(cout); cout << endl;
	for(auto &x : locs) { // need & here (otherwise, asking for copy of ptr)
		x->save(cout); cout << endl;
	}
}