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


// array of control points, first four are initialized

GLfloat ctrlpoints[100][3] = {
	{-100.0,-100.0, -20.0},{-50.0,50.0, -20.0},{50.0,-50.0,-20.0},{100.0,100.0,-20.0}};

int width=500,height=500;


void init();
void display();
void reshape(int w, int h);
void mouse(int button, int state, int x, int y);
void keyboard(unsigned char key, int x, int y);
int round(float x);

int currpoint=3;
int numctrlpoints=4;

enum {pointentry, notpointentry};
int currstate=notpointentry;
int newpoints=0;


main(int argc, char* argv[])
{
	
	/*  set up window */
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE );
	glutInitWindowSize(width,height);
	glutInitWindowPosition(100,100);
	glutCreateWindow("Bezier Curves");

	/* initialize state */
	init();
	cerr << "Right click to select control point.\nLeft click to place control point.\n";

	/* register call back functions */
	glutDisplayFunc(display);
	glutReshapeFunc(reshape);
	glutMouseFunc(mouse);
	glutKeyboardFunc(keyboard);

	/* wait until something happens */
	glutMainLoop();


	return 1;
}

void init()
{
	/*  clear color is black  */
	glClearColor(0.0,0.0,0.0,0.0);

	/*  define the viewing system */ 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-250.0, 250.0, -250.0, 250.0, 10.0, 50.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glShadeModel(GL_FLAT);
	
	glEnable(GL_MAP1_VERTEX_3);
	
}

void display()
{
	int i,j;

	glClear(GL_COLOR_BUFFER_BIT);

	// draw the polyline approximating the bezier curve
	glColor3f(1.0,1.0,1.0);
	for(j= 0; j<numctrlpoints-1; j+=3) {
		glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 4, &ctrlpoints[j][0]);
		glBegin(GL_LINE_STRIP);
			for (i=0;i<=30;i++)
				glEvalCoord1f((GLfloat) i/30.0);
		glEnd();
	}

	// draw the control points
	glPointSize(5.);
	glColor3f(1.0,1.0,0.0);
	glBegin(GL_POINTS);
	for(i=0;i<numctrlpoints+newpoints;i++) {
		if (i!=currpoint)
			glVertex3fv(&ctrlpoints[i][0]);
	}
	if (currpoint!=-1) {
		glColor3f(1.0,0.0,0.0);
		glVertex3fv(&ctrlpoints[currpoint][0]);
	}
	glEnd();


	glutSwapBuffers();

}

void reshape(int w, int h)
{
	/* width and height store current window dimensions */
	width = w;
	height = h;
	
	/*  map the projection plane to the entire window */
	glViewport(0,0,w,h);


}

void keyboard(unsigned char key, int x, int y)
{
	switch(key) {

	// add new points
	case 'a':
	case 'A':
		if (currstate=notpointentry) {
			currstate=pointentry;
			currpoint=numctrlpoints-1;
			newpoints=0;
			glutSetWindowTitle("Bezier Curves:  Add Points");
			glutPostRedisplay();
		}
		break;

	// delete points
	case 'd':
	case 'D':
		if (currstate==notpointentry) {
			if (numctrlpoints >4)
				numctrlpoints -= 3;
			else
				cerr << "Can't eliminate first set of control points.\n";
		}
		else {
			if (newpoints >0)
				newpoints --;
			else {
				glutSetWindowTitle("BezierCurves");
				currstate=notpointentry;
			}
		}
		glutPostRedisplay();
		break;
	default:
		break;
	}

	return;
}


void mouse(int button, int state, int x, int y)
{
	int i;
	float fx, fy;
	double pow(double x, double y),d,distance,dx,dy;

	fx=(float)(x*500.0)/(float) width  -250.0;
	fy=(float) (height-y)*500.0/(float) height -250.0;

	//  entering new points
	if (currstate == pointentry && state == GLUT_DOWN) {
		ctrlpoints[numctrlpoints+newpoints][0]=fx;
		ctrlpoints[numctrlpoints+newpoints][1]=fy;
		ctrlpoints[numctrlpoints+newpoints][2]=-20.0;
		newpoints++;
		if (newpoints == 3) {
			numctrlpoints+=3;
			currpoint=numctrlpoints-1;
			newpoints=0;
			currstate=notpointentry;
			glutSetWindowTitle("Bezier Curves");

		}
		glutPostRedisplay();
		cerr << "Adding Point (" << round(fx) <<"," << round(fy) << ").\n";
		return;
	}



	//  choosing new current point
	if (button==GLUT_RIGHT_BUTTON && state==GLUT_DOWN) {
		// find control point to move		
		d=(double) 2*(width+height);
		currpoint=-1;
		for (i=0;i <numctrlpoints;i++) {
			dx=(double) (fx-ctrlpoints[i][0]);
			dy=(double) (fy-ctrlpoints[i][1]);
			distance=pow(dx*dx + dy*dy, (double) 0.5);
			if (d > distance)  {
				d=distance;
				currpoint=i;
			}
		}
		glutPostRedisplay();
	}

	// moving current point 
	if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
		if (currpoint == -1)
			cerr << "You must choose point to move.\n";
		else {
			ctrlpoints[currpoint][0]= fx;
			ctrlpoints[currpoint][1]= fy;
			glutPostRedisplay();
		}

	}

	return;
}

int round(float x)
{
	if (x>=0.0)
		return (int) (x+0.5);
	return (int) (x-0.5);
}