#include <stdio.h>

#ifdef _WIN32
#include <windows.h>
#endif

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

GLfloat angleInDegrees = 0.f;
GLfloat angleSpeed = 50.f;
int updatePeriodInMilliseconds = 10;

// Initialize OpenGL state
void init() {
	printf("Initializing\n");
	glClearColor(0.0, 0.0, 0.0, 1.0);
	
	// Also set up the projection matrix if you like. 
	// If you don't, x and y between -1 and 1 will be visible.
}

// This is called when the window needs to be drawn. 
// You can force a redraw with glutPostRedisplay() 
void renderScene() 
{
	printf("Window needs rendering\n");

	// Clear Color and Depth Buffers
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glPushMatrix();

	glLoadIdentity();
	glRotatef(angleInDegrees, 0.f, 0.f, 1.f);

	// Render your scene here, or call functions that render stuff
	glBegin(GL_TRIANGLES);
		glVertex3f(-0.5f, 0.f, 0.f);
		glVertex3f(0.5f, 0.f, 0.f);
		glVertex3f(0.f, 0.75f, 0.f);
	glEnd();

	glPopMatrix();

	glutSwapBuffers();
}

// This is called when the window size is changed
void changeSize(int w, int h) 
{
	printf("window size was changed\n");
}

// This is called around 100 times per second
void updateScene(int value) 
{
	angleInDegrees += angleSpeed * (updatePeriodInMilliseconds * .001);

	glutTimerFunc(updatePeriodInMilliseconds, updateScene, 0);
	glutPostRedisplay();
}

// This is called when a regular key is pressed
void processNormalKeys(unsigned char key, int x, int y) {
	printf("A normal key was pressed\n");

	switch(key) {
	case '1':
		printf("One was pressed\n");
		break;
	case 27:
		printf("Escape was pressed\n");
		exit(0);
		break;
	default:
		break;
	}
}

// This is called when a special key is pressed (arrows, f3, etc.)
void processSpecialKeys(int key, int x, int y) {
	printf("A special key was pressed\n");	
	switch(key) {
	case GLUT_KEY_DOWN:
		printf("Down was pressed\n");
		break;
	case GLUT_KEY_F1:
		printf("F1 was pressed\n");
		break;
	default:
		break;
	}
}

int main(int argc, char **argv) {
	// init GLUT and create window
	glutInit(&argc, argv); // don't remove this line
	glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
	glutInitWindowPosition(100, 100);
	glutInitWindowSize(400, 400);
	glutCreateWindow("GLUT Window");

	init(); // Initialize OpenGL state in this

	// register callbacks
	// you can remove the ones that you don't need and add other ones here 
	// you do these here once and forget about glut
	// glut will call them when they are needed
	glutDisplayFunc(renderScene);
	glutReshapeFunc(changeSize);
	glutTimerFunc(updatePeriodInMilliseconds, updateScene, 0);
	glutKeyboardFunc(processNormalKeys);
	glutSpecialFunc(processSpecialKeys);

	// enter GLUT event processing cycle. you no more have control. glut does.
	glutMainLoop();

	return 0;
}