#include <iostream>
#include <cstring>
#include <string>
#include <stdio.h>
#include <cmath>


#ifdef __APPLE__
#include <GLUT/glut.h>  //apple include line
#else
#include <GL/glut.h> //linux and windows include line
#endif

using namespace std;


struct MainGraphics {
  int winheight, winwidth;
  float xs,ys, xe,ye; // for a line perhaps
  float theta;        // rotations or angles perhaps
  bool lineStart; // do I have the first point xs,ys yet or not?
};

MainGraphics graph;

void mydisplay();
void init();
void keyboard(unsigned char key, int x, int y);
void mouse(int button, int state, int x, int y);
void reshape(int,int);
void idle();



int main(int argc, char *argv[]) {
  glutInit(&argc, argv);
  init();
  glutMainLoop();
}



//the initialization function
void init() {
  graph.lineStart = false;
  //  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
  graph.winwidth = graph.winheight = 500;
  glutInitWindowSize(graph.winwidth, graph.winheight);
  glutInitWindowPosition(0,0);
  glutCreateWindow("Ramsey");
  glutDisplayFunc(mydisplay);
  glutKeyboardFunc(keyboard);
  glutMouseFunc(mouse);
  glutIdleFunc(idle);
  glutReshapeFunc(reshape);

  //clear to black and fill to "greenish"
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glColor3f(0.1, 1.0, 0.1);


  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  //to setup standard orthogonal view with clipping box as cube of side 2
  //with center at the origin. This is the default view  (uncomment below)
  //  gluOrtho2D(-2.0,2.0,-2.0,2.0);

  //the following sets up the screen as winwidth x winheight pixels

  gluOrtho2D(0, graph.winwidth, 0, graph.winheight);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();

}




void reshape(int w, int h)
{
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  //  if(w <= h)
  //    gluOrtho2D(-2.0,2.0,-2.0*h/w, 2.0f* h/w);
  //  else
  //    gluOrtho2D(-2.0 * w / h, 2.0 * w / h, -2.0, 2.0);
  gluOrtho2D(0,w,0,h);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glViewport(0,0,w,h);
  graph.winheight = h;
  graph.winwidth = w;
}

//text?

void text(string s, float x, float y) {
  glRasterPos2d(x,y);
  unsigned int i = 0;
  for (;i < s.length(); i++)     {      
      glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24,s[i]);
      
    }
}



//this function will draw our line using the dda algorithm
void DDADrawLine() {
  float dx = graph.xe - graph.xs;
  float dy = graph.ye - graph.ys;
  if ( fabs(dx) >= fabs(dy) ) { /// slope between -1 and 1

    if(graph.xe < graph.xs) {
      swap(graph.xe, graph.xs);
      swap(graph.ye, graph.ys);
    }
    //at this point, xs < xe and |dx| >= |dy|
    float m = dy / dx;
    float xCurrent = graph.xs, yCurrent = graph.ys;
    glBegin(GL_POINTS);
    while(xCurrent < graph.xe) {
      glVertex2d( (int) xCurrent, (int)(yCurrent+0.5) );
      xCurrent++;
      yCurrent += m;
    }
    glEnd();

  }

}


void DrawLine() {
       glBegin(GL_LINES);
       glVertex2f(graph.xs, graph.ys);
       glVertex2f(graph.xe, graph.ye);
       glEnd();
}

//the display function
//whatever is in here is what will be displayed
#define NUM_PTS 50.0
void mydisplay() {

  glClear(GL_COLOR_BUFFER_BIT);


  if(! graph.lineStart) {
    /* --draw the open gl line in orange
       glColor3f(1.0f, 0.5f, 0.2f);
       DrawLine();
    */
    glColor3f(0.6f, 0.0f, 0.6f); //some kind of purple/pink - blah meh grr
    DDADrawLine();
  }
  else { //draw a rubber band line
    glColor3f(0.6f, 0.6f, 1.0f); //light blue?
    DrawLine();
  }


  glutSwapBuffers();//double buffer only
}


//the keyboard function
void keyboard(unsigned char key, int x, int y) {
  y = graph.winheight - y;
  if(key == 'q' || key == 'Q' || key == 3) //q or escape
    exit(0);
  if(key =='p')
    printf("(%d,%d)\n", x, y);
}


//the mouse does stuff
void mouse(int button, int state, int x, int y) {
  y = graph.winheight - y;
  if(state==GLUT_DOWN  && button == GLUT_RIGHT_BUTTON) {
    exit(0); //close the program
  }
  else if(state == GLUT_UP && button == GLUT_LEFT_BUTTON) {
    graph.xs = graph.xe = x;
    graph.ys = graph.ye = y;      
    graph.lineStart = true; //end a line
  }
  else if(state==GLUT_DOWN && button == GLUT_LEFT_BUTTON)     {
    graph.xe = x;
    graph.ye = y;
    graph.lineStart = false;
  }


  //if the mouse is clicked - redraw
  glutPostRedisplay();
  
}




//idle is what to do when you're not rendering
//display only happens once until glutpostredisplay is called
//between redisplays - idle happens
void idle()  { 
}