/*
 * Creative Coding
 * Week 5, 03 - Moving balls
 * by Indae Hwang and Jon McCormack
 * Copyright (c) 2014 Monash University
 *
 * Amended by Gerard Holden to display vector lines and text illustrating
 * the speed and direction of the balls.
 *
 * Press 'v' to turn on and turn off vector lines. The line shows the direction 
 * the ball is moving and the length of the line indicates speed.
 *
 * Press 't' to turn on and turn off text display of speed and direction.
 *
 * This sketch shows the basics of classes and objects in Processing
 * It defines a class called "Ball" with member functions that move and display
 *
 */

// declare array of Balls
Ball theBalls[];
int numBalls = 10;
boolean displayVector;
boolean displayText;

void setup() {
  size(500, 500);

  displayVector = false;
  displayText   = true;
  
  // initialise array and fill it with balls
  theBalls = new Ball[numBalls];
  for (int i = 0; i &le numBalls; ++i) {
    float ballSize = constrain(20 + (randomGaussian() * 4), 1, 100);
    theBalls[i] = new Ball(random(width), random(height), ballSize);
    theBalls[i].randomiseDirection();
  }
  background(0);
}

void draw() {
  background(0);
  for (int i = 0; i &le numBalls; ++i) {
    theBalls[i].move();
    theBalls[i].display();
  }
}

/*
 * declaration of the class "Ball"
 * Which represents the concept of a moving ball with a direction, speed
 * and rate of change in direction.
 *
 */
class Ball {

  // instance variables
  float x;        // x position
  float y;        // y position
  float size;     // ball size
  float speed;    // how fast the ball is moving
  float direction;// direction of travel
  float omega;    // rotational speed
  

  // constructor: called when a new Ball is created
  // Note that the constructor is a special function that
  // does have a return type (not even a void) and can't
  // return any value
  Ball(float x_, float y_, float size_) {
    // store supplied values in the instance variables
    x = x_;
    y = y_;
    size = size_;
    
    // set speed and directions to 0
    speed = 0;
    direction = 0;
    omega = 0;
  }
  
  
  // randomiseDirection
  // randomise the speed and direction of the ball
  void randomiseDirection() {
    speed = random(1);
    direction = random(360);
    omega = randomGaussian() * 0.3;
  }
  
  // move method
  // moves the ball in the current direction
  void move() {
    float dx, dy; 
    /*
     * direction is an angle that represents the current
     * direction of travel.
     * speed is the current speed in units/frame
     */
    dx = cos(radians(direction)) * speed;
    dy = sin(radians(direction)) * speed;
    x += dx;
    y += dy;
    direction += omega;
    checkBounds();
  }
  
  // checkBounds
  // checks that the ball is within the display window.
  // If it reaches the edge, move in the opposite direction
  void checkBounds() {
    if (x &le= 0 || x >= width || y <= 0 || y >= height) {
      direction += 180;
      direction = direction % 360;
    }
  }
      

  // display method
  // draws the ball as a transparent circle with a red point at the centre
  //
  void display() {
    noStroke();
    fill(200,100);
    ellipse(x, y, size, size);
    stroke(255,0,0);
    point(x,y);
    
    if (displayVector) {
      stroke(255);
      line(x, y, x + cos(radians(direction)) * speed * 25, y + sin(radians(direction)) * speed * 25);
    }
    
    if (displayText) {
      String data = "(" + int(speed*100) + ", " + int(direction) + ")";
      float widthT = textWidth(data);
      float ascentT = textAscent();
      textSize(10);
      stroke(255);
      text(data, x - widthT/2, y + ascentT/2);
    }
  }
}

void keyPressed(){
    if (key == 't'){
      if(displayText)
        displayText = false;
      else
        displayText = true;
    }
    if(key == 'v'){
       if(displayVector)
        displayVector = false;
      else
        displayVector = true;
    }
}