/* Libraries we use */
#include <SDL/SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <iostream>
using namespace std;

/* Some definitions */
#define WIDTH 800
#define HEIGHT 800
#define TITLE "Josh's Wavefront Object Viewer"

/* Some global variables */
float	rotationMatrix[16];
int	startx, starty;
bool dragging = false;
float dist = 5.0;

void initgl(void)
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glEnable(GL_DEPTH_TEST);
	glShadeModel(GL_SMOOTH);
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	float pos[] = {0.0, -1.0, 0.0, 0.0};
	glLightfv(GL_LIGHT0, GL_POSITION, pos);
	glEnable(GL_CULL_FACE);
	glViewport(0, 0, WIDTH, HEIGHT);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.0, (GLfloat)WIDTH/(GLfloat)WIDTH, 0.01, 10000.0);
	gluLookAt(0, -dist, 0, 0, 0, 0, 0, 0, 1);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glGetFloatv(GL_MODELVIEW_MATRIX, rotationMatrix);
}

void display(void)
{
	glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
	glLoadIdentity();
	glMultMatrixf(rotationMatrix);
	glBegin(GL_QUADS);
		glVertex3f(0.5, -0.5, 0.0);
		glVertex3f(0.5, 0.5, 0.0);
		glVertex3f(-0.5, 0.5, 0.0);
		glVertex3f(-0.5, -0.5, 0.0);
	glEnd();
	SDL_GL_SwapBuffers();
}

/* The program's main entry point */
int	main(int argc, char * argv[])
{
	if (SDL_Init(SDL_INIT_VIDEO))
	{
		printf("Failed to initialize SDL!\n");
		return 1;
	}

	atexit(SDL_Quit);

	SDL_Surface * screen;
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	if (!(screen = SDL_SetVideoMode(WIDTH, HEIGHT, 32, SDL_OPENGL)))
	{
		printf("Failed to set video mode!\n");
		SDL_Quit();
		return 2;
	}
	SDL_WM_SetCaption(TITLE, TITLE);

	initgl();
	display();
	SDL_Event event;
	while (SDL_WaitEvent(&event))
	{
		if (event.type == SDL_QUIT)
			break;
		else if (event.type == SDL_KEYDOWN)
		{
			if (event.key.keysym.sym == SDLK_ESCAPE)
				break;
		}
		else if (event.type == SDL_MOUSEBUTTONDOWN)
		{
			if (event.button.button == SDL_BUTTON_LEFT)
			{
				if (event.button.state == SDL_PRESSED)
				{
					dragging = true;
					startx = event.button.x;
					starty = event.button.y;
				}
			}
			else if (event.button.button == 4)
			{
				dist *= 0.85;
				if (dist < 1.0f)
					dist = 1.0f;
				glMatrixMode(GL_PROJECTION);
				glLoadIdentity();
				gluPerspective(60.0, (GLfloat)WIDTH/(GLfloat)WIDTH, 0.01, 10000.0);
				gluLookAt(0, -dist, 0, 0, 0, 0, 0, 0, 1);
				glMatrixMode(GL_MODELVIEW);
				display();
			}
			else if (event.button.button == 5)
			{
				dist *= 1.2;
				glMatrixMode(GL_PROJECTION);
				glLoadIdentity();
				gluPerspective(60.0, (GLfloat)WIDTH/(GLfloat)WIDTH, 0.01, 10000.0);
				gluLookAt(0, -dist, 0, 0, 0, 0, 0, 0, 1);
				glMatrixMode(GL_MODELVIEW);
				display();
			}
		}
		else if (event.type == SDL_MOUSEBUTTONUP)
		{
			if (event.button.button == SDL_BUTTON_LEFT)
			{
				dragging = false;
			}
		}
		else if (event.type == SDL_MOUSEMOTION)
		{
			if (dragging)
			{
				glLoadIdentity();
				glRotatef(event.motion.y - starty, 1, 0, 0);
				glRotatef(event.motion.x - startx, 0, 0, 1);
				glMultMatrixf(rotationMatrix);
				glGetFloatv(GL_MODELVIEW_MATRIX, rotationMatrix);
				startx = event.motion.x;
				starty = event.motion.y;
				display();
			}
		}
	}

	return 0;
}