#include <GL/glut.h>

#include <experimental/filesystem>

#include <cstdlib>
#include <fstream>
#include <iostream>
#include <math.h> // fmod
#include <unistd.h>
#include <vector>

GLfloat light_diffuse[] = {1.0, 0.0, 0.0, 1.0};  /* Red diffuse light. */
GLfloat light_position[] = {1.0, 1.0, 1.0, 0.0};  /* Infinite light location. */

struct Point {
	float lat;
	float lon;
	float ele;
};

static std::vector<std::vector<Point> > tracks;

// TODO(dev):
//  As per https://www.opengl.org/resources/libraries/glut/spec3/node11.html
//  "Therefore, GLUT programs should not assume the window was created at the specified size or position.
//   A GLUT program should use the window's reshape callback to determine the true size of the window."

void draw(const std::vector<Point> &points)
{
	// glLineWidth(1.0f);

	// Draw bike path
	glBegin(GL_LINE_STRIP);
	for(auto p : points)
	{
		auto val = (50 + (p.ele * 10)) / 180.0;
		glColor3d(val, val, val);
		glVertex3f(p.lat, p.ele, p.lon);
	}
	glEnd();

	// usleep(100000);

	glutPostRedisplay();
}

void display()
{
	// RESET:
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	static double asdf = -10.0;
	asdf += 0.02;
	if(asdf > 15.0)
		asdf = -15.0;
	gluLookAt(-15, 12.0, -asdf,  /* eye is at */
	          0.0, 6.0, 0.0,  /* center is at */
	          0.0, 1.0, 0.0);    /* up is in positive Y direction */

	// DRAW TRACKS:
	for(auto track : tracks)
		draw(track);

	glutSwapBuffers();
}

void init()
{
	// dvereb:
	srand(time(NULL));

	glColor3d(1.0, 1.0, 1.0);

	/* Enable a single OpenGL light. */
	// glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
	// glLightfv(GL_LIGHT0, GL_POSITION, light_position);
	// glEnable(GL_LIGHT0);
	// glEnable(GL_LIGHTING);

	/* Use depth buffering for hidden surface elimination. */
	glEnable(GL_DEPTH_TEST);

	/* Setup the view of the cube. */
	glMatrixMode(GL_PROJECTION);
	gluPerspective( /* field of view in degree */ 70.0,
	                /* aspect ratio */ 1.0,
	                /* Z near */ 1.0, /* Z far */ 1000.0);
	glMatrixMode(GL_MODELVIEW);
	gluLookAt(-10.0, 25.0, -10.0,  /* eye is at */
	          0.0, 0.0, 0.0,  /* center is at */
	          0.0, 1.0, 0.0);    /* up is in positive Y direction */
}

int main(int argc, char *argv[])
{
	if(argc != 2)
	{
		std::cerr << "You pust pass the folder which contains gpx files." << std::endl;
		return -1;
	}

	std::vector<std::string> files;
	for(const auto& entry : std::experimental::filesystem::directory_iterator(argv[1]))
	{
		auto extension = entry.path().extension();
		if(extension == ".gpx")
			files.push_back(entry.path().filename());
	}

	float file_diff_lat = -8;
	float file_diff_lon = -8;
	for(auto file : files)
	{
		std::ifstream ifs(file);
		if(!ifs.is_open())
		{
			std::cerr << "Couldn't open " << file << "." << std::endl;
			return -2;
		}

		std::string line = "";
		bool first = true;
		float diff_lat, diff_lon, diff_ele;
		std::vector<Point> track;
		while(std::getline(ifs, line))
		{
			// get starting position of field NAME
			auto lat = line.find("lat=\"");
			if(lat == std::string::npos)
				continue;
			// get ending position of field DATA
			auto lat_to = line.find("\"", lat);
			if(lat_to == std::string::npos)
				continue;

			// get starting position of field NAME
			auto lon = line.find("lon=\"", lat_to);
			if(lon == std::string::npos)
				continue;
			// get ending position of field DATA
			auto lon_to = line.find("\"", lon);
			if(lon_to == std::string::npos)
				continue;

			auto ele = line.find("<ele>", lon_to);
			if(ele == std::string::npos)
				continue;
			auto ele_to = line.find("</ele>", ele);
			if(ele_to == std::string::npos)
				continue;

			Point p;
			try {
				p.lat = std::atof(line.substr(lat + 5, lat_to).c_str()) * 200;
				p.lon = std::atof(line.substr(lon + 5, lon_to).c_str()) * 200;
				p.ele = std::atof(line.substr(ele + 5, ele_to).c_str()) * 0.1;
			} catch (const std::exception &e) {
				std::cerr << "Error in file " << file << ", line \"" << line << "\"." << std::endl;
				continue;
			}

			if(first)
			{
				first = false;
				diff_lat = p.lat;
				diff_lon = p.lon;
				diff_ele = p.ele;
			}

			p.lat -= diff_lat + file_diff_lat;
			p.lon -= diff_lon + file_diff_lon;
			p.ele -= diff_ele;
			track.push_back(p);
		}
		tracks.push_back(track);
		file_diff_lat += 4;
		if(file_diff_lat > 5)
		{
			file_diff_lat = -8;
			file_diff_lon += 4;
		}

		ifs.close();
	}

	glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_ALPHA | GLUT_MULTISAMPLE);
	glutInit(&argc, argv);
	glutCreateWindow("test opengl program");
	glutDisplayFunc(display);

	// NOTE(dev): lmfao:
	// glutSetCursor(GLUT_CURSOR_SPRAY);
	glutSetCursor(GLUT_CURSOR_FULL_CROSSHAIR);

	init();
	glutMainLoop();

	return 0;
}