////////////////////////////////////////////////////////////////////////
//
// Support code for assignment 4 (cs411 f07)  
//
////////////////////////////////////////////////////////////////////////
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>


#define ABS(x) ((x)<0 ? -(x) : (x))


typedef struct{
  float x,y;
} Point;


int   vxMax,vyMax;             // current viewport
float wxMin,wxMax,wyMin,wyMax; // current window

Point pt[100];  // global point array
int ptNum = 0;  // current number of points
bool visible=true;
int activePt = -1;


int findMatchingPointIndex(float x, float y)
{
  // 
  // Find a point in the list
  //
  int i;

  for(i=0;i<ptNum;i++) 
    if((ABS(pt[i].x - x) < 1) && (ABS(pt[i].y - y) < 1)) break;

  if (i<ptNum) return i;
  else return -1;
}


void transformGlSelection(int x, int y, float *xv, float *yv)
{
  //
  // perform the inverse of the window-to-viewport transform
  //
  *xv=((float)(x-0)    /vxMax)*(wxMax-wxMin)+wxMin; 
  *yv=((float)(vyMax-y)/vyMax)*(wyMax-wyMin)+wyMin; 
}


void init(void) 
{
  glClearColor (0.0, 0.0, 0.0, 0.0);
  glEnable (GL_POINT_SMOOTH);
  glPointSize(8.0);
  glLineWidth(2.0);
}


void reshape (int w, int h)
{
  //
  // Map [-50..50][-50..50] to the entire viewport (aspect ratio may change)
  //
  glViewport(0, 0, vxMax = (GLsizei) w, vyMax = (GLsizei) h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(wxMin = -50.0, wxMax = 50.0, wyMin = -50.0, wyMax = 50.0, -1.0, 1.0);
  glMatrixMode(GL_MODELVIEW);
}


void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
     case 27:
       exit(0);
   }
}

void mouse(int button, int state, int x, int y) 
{
  float xv,yv;
  int i;

   switch (button) {
      case GLUT_LEFT_BUTTON:
        if (state == GLUT_DOWN){
          transformGlSelection(x,y,&xv,&yv);
          i=findMatchingPointIndex(xv, yv);
          if(i < 0){
            pt[ptNum].x=xv;
            pt[ptNum].y=yv;
            activePt = ptNum;
            ptNum++;
          }
          else activePt = i;
		}
		else if (state == GLUT_UP){
          activePt = -1;
		}
        break;
	  case GLUT_RIGHT_BUTTON:
		  if(state == GLUT_DOWN){
			  if(visible)
			  {
				  visible = false;
			  }
			  else
			  {
				 visible = true;
			  }
		  }
		  break;

      default:
         break;
   }
   glutPostRedisplay();
}


void motion(int x, int y) 
{
  float xv,yv;

  if(activePt < 0) return;
  transformGlSelection(x,y,&xv,&yv);
  pt[activePt].x=xv;
  pt[activePt].y=yv;

  glutPostRedisplay();
}

float B0(float u)
{
	float B0;
	if(u>=0 && u<1)
		B0=0.5*u*u;
	else if(u>=1 && u<2)
		B0=0.5*u*(2-u)+0.5*(u-1)*(3-u);
	else if(u>=2 && u<3)
		B0=0.5*(3-u)*(3-u);
	else
		B0=0;

	return B0;
}

float B1(float u)
{
	float B1;
	if(u>=1 && u<2)
		B1=0.5*(u-1)*(u-1);
	else if(u>=2 && u<3)
		B1=0.5*(u-1)*(3-u)+0.5*(u-2)*(4-u);
	else if(u>=3 && u<4)
		B1=0.5*(4-u)*(4-u);
	else 
		B1=0;

	return B1;

}

float B2(float u)
{
	float B2;
	if(u>=2 && u<3)
		B2=0.5*(u-2)*(u-2);
	else if(u>=3 && u<4)
		B2=0.5*(u-2)*(4-u)+0.5*(u-3)*(5-u);
	else if(u>=4 && u<5)
		B2=0.5*(5-u)*(5-u);
	else 
		B2=0;

	return B2;

}

float B3(float u)
{
	float B3;
	if(u>=3 && u<4)
		B3=0.5*(u-3)*(u-3);
	else if(u>=4 && u<5)
		B3=0.5*(u-3)*(5-u)+0.5*(u-4)*(6-u);
	else if(u>=5 && u<6)
		B3=0.5*(6-u)*(6-u);
	else 
		B3=0;

	return B3;

}



void display(void)
{
  int i,j;
  float u;

  glClear (GL_COLOR_BUFFER_BIT);
  glColor3f (1.0, 1.0, 1.0);

  glBegin(GL_POINTS);
  for(i=0;i<ptNum;i++) glVertex2f(pt[i].x,pt[i].y);
  if(activePt>=0){
    glColor3f(1.0,0.0,0.0);
    glVertex2f(pt[activePt].x,pt[activePt].y);
    glColor3f(1.0,1.0,1.0);
  }
  glEnd();



  //
  // YOUR CODE FOR GENERATING THE CURVE HERE
  //
  if(visible)
  {
  glBegin(GL_POINTS);
  Point curPt;
  for(j=0;j+3<ptNum;j++){
	  for(u=2;u<=4;){
	  curPt.x = pt[j].x*B0(u)+pt[j+1].x*B1(u)+pt[j+2].x*B2(u)+pt[j+3].x*B3(u);
  	  curPt.y = pt[j].y*B0(u)+pt[j+1].y*B1(u)+pt[j+2].y*B2(u)+pt[j+3].y*B3(u);
	  glColor3f(0.0,0.0,1.0);
	  glVertex2f(curPt.x,curPt.y);
	  glColor3f(1.0,1.0,1.0);
	  u+=0.005;
	  
	  }
  }
  glEnd();
  }


  // THIS IS AN EXAMPLE OF HOW TO ACCESS THE POINTS
  //
  for(i=0;i<ptNum;i++) printf("(%4.1f,%4.1f) ",pt[i].x,pt[i].y);
  printf("\n-----------------------------\n");


  glFlush ();
}



int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (500, 500); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);

   init ();
   glutDisplayFunc(display); 
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutMouseFunc(mouse);
   glutMotionFunc(motion);

   glutMainLoop();
   return 0;
}


////////////////////////////////////////////////////////////////////////
// EOF
////////////////////////////////////////////////////////////////////////