// implementation of boids class...handles flocking
// Date: 23 Oct 2008
// Author: Don Allison

#include "boids.h"
#include <cstdlib>
#define _USE_MATH_DEFINES
#include <cmath>
#include "glut.h"
#include <ctime>

// default constructor...sets critter at random position between (-1.0, -1.0) and (1.0, 1.0)
boids::boids()
{
	x = newx = 2.0*rand()/RAND_MAX - 1.0;
	y = newy = 2.0*rand()/RAND_MAX - 1.0;
	vx = vy = 0.05;
	time = ntime = (double)clock()/CLOCKS_PER_SEC;

	return;
}



// destructor
boids::~boids()
{

	return;
}



// sets current x value of critter in world coordinates
void boids::setx(double u)
{
	x = u;
	return;
}



// sets current y value of critter in world coordinates
void boids::sety(double v)
{
	y = v;
	return;
}



// gets current x value of critter in world coordinates
double boids::getnextx(void)
{
	return newx;
}



// gets current y value of critter in world coordinates
double boids::getnexty(void)
{
	return newy;
}


// draws single flocking critter at current origin location
void boids::draw(void)
{
	double theta;

// handle orientation
	theta = atan2(vx, vy);
	if (vx*vy < 0)
		theta += M_PI;
	glRotatef(theta*180.0/M_PI, 0.0, 0.0, 1.0);
// set body color
	glColor3f(0.7, 0.0, 0.0);
// draw body
	glBegin(GL_POLYGON);
		glVertex2d(-0.03, 0.03);
		glVertex2d(-0.03, -0.03);
		glVertex2d(0.05, 0.0);
	glEnd();
// set eye color
	glColor3f(0.0, 0.0, 0.0);
// draw eye
	glTranslated(0.02, 0.0, 0.0);
	glutSolidSphere(0.01, 50, 50);

	return;
}



void boids::nextPosition()
{
	double t;

	time = ntime;
	ntime = (double)clock() / CLOCKS_PER_SEC;
	t = ntime - time;
	newx = x + vx*t;
	newy = y + vy*t;

	if (newx > 1.0)
	{
		newx = 1.0;
		vx = -vx;
	}
	else if (newx < -1.0)
	{
		newx = -1.0;
		vx = -vx;
	}

	if (newy > 1.0)
	{
		newy = 1.0;
		vy = -vy;
	}
	else if (y < -1.0)
	{
		newy = -1.0;
		vy = -vy;
	}
	return;
}