#include <GL/glut.h>
#include <iostream>
#include <math.h>
#include "geometry.h"


inline double deg2Rad(double x){return 3.14159 * x/360.0;}



using namespace std;


// function prototypes
void display(void);
void reshape(int width, int height);
void keyboard(unsigned char key, int x, int y);
void arrowKeys(int key, int x, int y);
void init(void);

// viewpoint
// Let v be the vector from center (of focus) to the eye.
// Let v' be the projection of v onto the x-z plane.
// Then theta is the angle in degrees v 
//		makes with the x-z plane
//  And phi is the angle in degrees  v'
//		makes with the z-axis
//  d = ||v||
//  The user controls the eye position by adjusting
//  theta, phi, d, and center.

double theta=0.5, phi=0, d=150;
Tuple center(0,0,0);

// window
int width = 400;
int height = 400;



int 
main(int argc, char **argv)
{

  // set up window
  glutInitWindowSize(400, 400);
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutCreateWindow("Camera Demo");

  // register callback functions
  glutDisplayFunc(display);
  glutReshapeFunc(reshape); 
  glutKeyboardFunc(keyboard);
  glutSpecialFunc(arrowKeys);

  // initalize opengl parameters
  init();

  // loop until something happens
  glutMainLoop();
  return 0;           
}

void init()
{

  // initialize viewing system
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, 1.0, 1.0, 1000.0);
  glMatrixMode(GL_MODELVIEW);

  // shading model
  glEnable(GL_SMOOTH);
 

  // initialize background color to black
  glClearColor(0.0,0.0,0.0,0.0);

  // enable depth buffering
  glEnable(GL_DEPTH_TEST);

}



void reshape(int newWidth, int newHeight)
{
	width = newWidth;
	height = newHeight;
	// preserve aspect ratio
	if (width < height)
		glViewport(0,0,width,width);
	else
		glViewport(0,0,height,height);
}

void display()
{
    // Redraw scene
	glLoadIdentity();


	// compute eye position
	Tuple eye(0,0,0);
	eye[0] = center[0] + (float) d * cos(deg2Rad(theta)) * sin(deg2Rad(phi));
	eye[1] = center[1] + (float) 2*d * sin(deg2Rad(theta));
	eye[2] = center[2] + (float) d * cos(deg2Rad(theta)) * cos(deg2Rad(phi));

	// compute up vector
	// we use (0,1,0) as the default up position
	// this doesn't work if the eye is on the y-axis
	// but we just won't let the user do that
	Tuple up(0,1,0);

	gluLookAt(eye[0],eye[1],eye[2], center[0],center[1],center[2],up[0], up[1], up[2]);



	// clear buffers
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

//  now draw axis in x,y,z directions from origin
	glColor3f(1.0f, 1.0f, 1.0f);
	glBegin(GL_LINES);
		glVertex3f(0,0,0);
		glVertex3f(100,0,0);		
	glEnd();
	glBegin(GL_LINES);
		glVertex3f(0,0,0);
		glVertex3f(0,100,0);		
	glEnd();
	glBegin(GL_LINES);
		glVertex3f(0,0,0);
		glVertex3f(0,0,100);		
	glEnd();

	//  now draw axis in x,y,z directions from center
	glColor3f(0.0f, 1.0f, 1.0f);
	glBegin(GL_LINES);
		glVertex3f(center[0],center[1],center[2]);
		glVertex3f(center[0]+100,center[1],center[2]);		
	glEnd();
	glBegin(GL_LINES);
		glVertex3f(center[0],center[1],center[2]);
		glVertex3f(center[0],center[1]+100,center[2]);		
	glEnd();
	glBegin(GL_LINES);
		glVertex3f(center[0],center[1],center[2]);
		glVertex3f(center[0],center[1],center[2]+100);		
	glEnd();
	
	// draw to screen
	glutSwapBuffers();
}

void keyboard(unsigned char key, int mouseX, int mouseY)
{

	switch (key) {

		case 'h':
			cout << "Use '-' and '+' to zoom in and out." << endl;
			cout << "Use 'c' to reset center.";
			break;

		case '-':
			if (d>1)
				d--;
			break;

		case '+':
			d++;
			break;

		case 'c':
		case 'C': {
			float x,y,z;
			cout << "Enter x,y,z position of center of focus." << endl;
			cin >> x >> y >> z;
			center[0]=x;
			center[1]=y;
			center[2]=z;
			break;
				  }


	}
	glutPostRedisplay();
}

/*
*	This routine reads arrow keys and adjusts
*	camera position/orientation.
*/

void arrowKeys(int key, int x, int y)
{
	switch (key) {
		case GLUT_KEY_LEFT:
			phi -=2;  // change 
			break;

		case GLUT_KEY_RIGHT:
			phi +=2;

			break;

		case GLUT_KEY_UP:
			if (theta < 85)
				theta +=2;
			break;

		case GLUT_KEY_DOWN:
			if (theta >-85)
				theta -=2;
			break;

		default:
			break;
	}
	glutPostRedisplay();
}