#include <iostream>
#include <stdexcept>
#include <chrono>
#include <thread>

#include <GL/glew.h>
#include <GL/freeglut.h>

#include "App.h"
#include "globals.h"


App* app_ptr = 0;
unsigned int const frames_per_second = 60.0;


typedef std::chrono::high_resolution_clock clock_type;

size_t frame_count = 0;
clock_type::time_point begin_time;

void begin() {
	app_ptr = new App(kWindowWidth, kWindowHeight);
	begin_time = clock_type::now();
}

void end() {
	auto end = clock_type::now();
	auto difference = end-begin_time;
	auto time_elapsed = difference.count()*clock_type::duration::period::num/(double)clock_type::duration::period::den;
	std::cout << "Did " << frame_count << " frames in " << time_elapsed << " seconds." << std::endl;
	std::cout << "That's " << frame_count/time_elapsed << " frames per second." << std::endl;
	delete app_ptr;
}


int main(int argc, char** argv) {
	// let glut create a window
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_ALPHA);
	glutInitWindowSize(kWindowWidth, kWindowHeight);
	glutCreateWindow("OpenGL");

	// we need glew for shaders
	auto err = glewInit();
	if(err != GLEW_OK) {
		throw std::runtime_error("A glew error");
	}

	// all callbacks (c++0x lambdas woei)
	glutDisplayFunc([] {
		auto const time_step = std::chrono::milliseconds(1000/frames_per_second);

		static auto previous_timepoint = clock_type::now();
		auto const current_timepoint = clock_type::now();
		auto const difference = current_timepoint - previous_timepoint;

		if(difference > time_step) {
			app_ptr->update();
			app_ptr->draw();
			glutSwapBuffers();
			//glFlush();

			++frame_count;
			if(frame_count == 7400) exit(0);

			previous_timepoint = current_timepoint-(difference%time_step);
		} else {
			usleep((time_step-difference).count()*1000000*clock_type::duration::period::num/(double)clock_type::duration::period::den/2);
			//std::sleep_for((time_step-difference)/2);
		}

		glutPostRedisplay();
	});
	glutReshapeFunc([](int w, int h) {app_ptr->resize(w, h);});
	glutCloseFunc(end);			// freeglut extension

	// my app-object
	begin();

	// GO!
	glutMainLoop();

	return 0;
}