//A very simple opengl/GLUT program
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <vector>

using namespace std;

//global variables - necessary evil when using GLUT
//global width and height
int GW;
int GH;
//current mouse position in pixel coordinate
int x;
int y;
//a structure to store 2D points  - this could also be a class
typedef struct vector2 {
  float x;
  float y;
  //constructor which takes input values
  vector2(float in_x, float in_y) : x(in_x), y(in_y) {}
  //default constructor
  vector2() : x(0), y(0) {}
} vector2;

//keep track of which drawing mode we are in points or square
//mode ==0 means draw square otherwise draw points
int mode;

//an stl vector to keep track off all the points clicked by the mouse
vector<vector2> all_points;

//helper drawing routines
void draw_square() {
  glBegin(GL_POLYGON);
    glColor3f(1.0, 0.0, 0.0);
		glVertex2f(-0.5,-0.5); 
    glColor3f(0.0, 1.0, 0.0); 
		glVertex2f(-0.5,0.5);
	  glColor3f(0.0, 0.0, 1.0);
		glVertex2f(0.5,0.5); 
		glColor3f(0.0, 0.0, 0.0);  
		glVertex2f(0.5,-0.5);
	glEnd();
}


void draw_all_pts() {
  glPointSize(2.0);
  glBegin(GL_POINTS);
    glColor3f(0.5, 0.2, 0.8);
    //iterate through all the points and draw them
    for (int i=0; i < all_points.size(); i++) {
      glVertex2f(all_points[i].x, all_points[i].y);
    }
  glEnd();
}

//the reshape callback
void reshape(int w, int h) {
  GW = w;
  GH = h;

  glViewport(0, 0, w, h);
  glLoadIdentity();
  gluOrtho2D( -(float)w/h, (float)w/h, -1, 1);
}

//the display call back - all drawing should be done in this function
void display() {
	glClear(GL_COLOR_BUFFER_BIT);

  if (mode == 0)
    draw_square();
  else
    draw_all_pts();

	glFlush();
}

//conversion from pixel to world - unsimplified
float p2w_x(int p_x) {
}

float p2w_y(int p_y) {
}

//the mouse button callback
void mouse(int button, int state, int x, int y) {
  if (button == GLUT_LEFT_BUTTON) {
    if (state == GLUT_DOWN) { /* if the left button is clicked */
      printf("mouse clicked at %d %d\n", x, y);
      all_points.push_back(vector2(p2w_x(x), p2w_y(GH-1-y)));
      glutPostRedisplay();
    }
  }
}

//the mouse move callback
void mouseMove(int x, int y) {
  printf("mouse moved at %d %d\n", x, y);
}

//the keyboard callback
void keyboard(unsigned char key, int x, int y ){
  switch( key ) {
    case 'm':
      mode = !mode;
      glutPostRedisplay();
      break;
    case 'q': case 'Q' :
      exit( EXIT_SUCCESS );
      break;
    case 'h' : case 'H' :
      printf("hello!\n");
      break;
  }
}

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

	glutInit( &argc, argv );

  //intializations
	glutInitWindowSize(200, 200);
	glutInitWindowPosition(100, 100);
	glutCreateWindow( "My Second Window" );
	glClearColor(1.0, 1.0, 1.0, 1.0);
  //global variable intialization
  GW = GH = 200;
  mode = 0;
  //register the callback functions
	glutDisplayFunc( display );
  glutMouseFunc( mouse );
  glutMotionFunc( mouseMove );
  glutKeyboardFunc( keyboard );
  glutReshapeFunc( reshape );

	glutMainLoop();
}