public class ParticleEngine {
  // alist to keep track of particles
  private ArrayList particles;
  private ArrayList springs;
  
  //the class constructor
  public ParticleEngine() {
    //create the list
    particles = new ArrayList();
    springs = new ArrayList();
  }
  
  public void addParticle(Particle particle) {
    //public function to add a particle
    particle.setEngine(this);
    particles.add(particle);
  }
  
  public void addSpring(Spring spring) {
    //public function to add a particle
    spring.setEngine(this);
    springs.add(spring);
  }
  
  //update function to update all springs and particles
  public void update() {
    //use a while loop to check all springs
    int i = 0;
    while (i<springs.size()) {
      //update it
      Spring s = (Spring) springs.get(i);
      s.update();
      if (!s.destroyed) {
        //if the particle is still alive, update it
        i++;
      } else {
        //if the particle is not remove it from the list
        springs.remove(i);
      }
    }
    
    i = 0;
    while (i<particles.size()) {
      //update it
      Particle p = (Particle) particles.get(i);
      p.update();
      if (!p.destroyed) {
        //if the particle is still alive, update it
        i++;
      } else {
        //if the particle is not remove it from the list
        particles.remove(i);
      }
    }    
  }
  
  //draw all particles
  public void draw() {
    for (int i=0; i<springs.size(); i++) {
      Spring s = (Spring) springs.get(i);
      s.draw();
    }
    for (int i=0; i<particles.size(); i++) {
      Particle p = (Particle) particles.get(i);
      p.draw();
    }
  }
  
  public Particle particleAt(float x, float y) {
    int i = particles.size();
    while(i>0) {
      i--;
      Particle p = (Particle) particles.get(i);
      float dx = p.x - x;
      float dy = p.y - y;
      if (dx * dx + dy * dy < p.size * p.size) {
        return p;
      }
    }
    return null;
  }
  
  public Particle findParticle(String label) {
    int i = particles.size();
    while(i>0) {
      i--;
      Particle p = (Particle) particles.get(i);
      if (p.label == label) {
        return p;
      }
    }
    return null;
  }
  
  public void connectParticles(String label1, String label2) {
    Particle particle1 = findParticle(label1);
    Particle particle2 = findParticle(label2);
    if (particle1 != null && particle2 != null) {
      addSpring(new Spring(particle1, particle2, 60, 0.02));
    }
  } 
  
  
}

public class Spring {
  // a reference to the engine
  private ParticleEngine engine;
  
  //the two particles the spring is connected too
  public Particle start;
  public Particle end;
  
  //spring length and constant
  public float springLength;
  public float springConstant;
   // flag to indicate whether or not the spring is destroyed
  public boolean destroyed;
  
  public Spring(Particle start, Particle end, float springLength, float springConstant) {
    this.start = start;
    this.end = end;
    this.springLength = springLength;
    this.springConstant = springConstant;
  }
  
  public void setEngine(ParticleEngine engine) {
    this.engine = engine;
  }
  
  public void update() {
    //use pythagoras to calculate distance between the particles
    float dx = end.x - start.x;
    float dy = end.y - start.y;
    float d = sqrt(dx * dx + dy * dy);
    //normalize the distance vector
    if (d>0){
      dx /= d;
      dy /= d;
    }
    //apply spring length and constant
    d -= springLength;
    d *= springConstant;
    
    //apply force on the particles
    start.velocityX += d*dx;
    start.velocityY += d*dy;
    end.velocityX -= d*dx;
    end.velocityY -= d*dy;
  }
  
  public void draw() {
    noFill();
    stroke(#029834);
    //strokeWeight(2);
    line(start.x, start.y, end.x, end.y);
  }
}

//variable to hold one object
ParticleEngine engine;
Particle lastParticle;
Particle dragging;


PFont font;
PImage mapImages2;

void setup() {
  size(700, 400);
  mapImages2 = loadImage("voetbalveld_480.gif");
  //create a particle engine
  engine = new ParticleEngine();
  smooth();
  font = createFont("SansSerif", 11);
  textFont(font);
  
  engine.addParticle(new Particle("Stekelenburg", random(0, 10), random(0, 10), 0, 0));
  engine.addParticle(new Particle("Van der Wiel", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Heitinga", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Mathijsen", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Van Bronckhorst", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Van Bommel", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("De Jong", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Sneijder", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Robben", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Elia", random(0, 400), random(0, 400), 0, 0));
  engine.addParticle(new Particle("Van Persie", random(0, 400), random(0, 400), 0, 0));
  
  
  
  //engine.addParticle(new Particle("Heitinga", random(0, 400), random(0, 400), 0, 0));
  

  
  engine.findParticle("Stekelenburg").pin(320, 30);
  engine.findParticle("Van der Wiel").pin(120, 100);
  engine.findParticle("Van Bronckhorst").pin(550, 100);
  
  engine.findParticle("Robben").pin(120, 320);
  engine.findParticle("Elia").pin(550, 320);

   engine.connectParticles("Stekelenburg", "Heitinga");
   engine.connectParticles("Stekelenburg", "Van der Wiel");
   engine.connectParticles("Stekelenburg", "Mathijsen");
   engine.connectParticles("Stekelenburg", "Van Bronckhorst");
   
   engine.connectParticles("Heitinga", "Van der Wiel");
   engine.connectParticles("Heitinga", "Mathijsen");
   engine.connectParticles("Van Bronckhorst", "Mathijsen");
   engine.connectParticles("Van Bronckhorst", "De Jong");
   engine.connectParticles("De Jong", "Mathijsen");
   
    engine.connectParticles("De Jong", "Van Bommel");
    engine.connectParticles("Van der Wiel", "Van Bommel");
    engine.connectParticles("Heitinga", "Van Bommel");
    
    engine.connectParticles("Van Bommel", "Sneijder");
    engine.connectParticles("De Jong", "Sneijder");

    engine.connectParticles("Robben", "Van Bommel");  
    engine.connectParticles("Robben", "Sneijder");
    engine.connectParticles("Elia", "Sneijder");
    engine.connectParticles("Elia", "De Jong");
    
    engine.connectParticles("Elia", "Van Persie");
    engine.connectParticles("Robben", "Van Persie");
    engine.connectParticles("Van Persie", "Sneijder");
    engine.connectParticles("Van Bronckhorst", "Elia");
    engine.connectParticles("Robben", "Van der Wiel");
}

void draw() {
  image(mapImages2, 0, 0, 700, 400);
  //update the particles
  engine.update();
  //clear the background
 
  //draw the particles
  engine.draw();
  fill(#000000);
  strokeWeight(2);
  
  fill(#FFFFFF);
  text("Opstelling voor vanavond :-) ", 10, 30);
  
}

void mousePressed() {
  dragging = engine.particleAt(mouseX, mouseY);
  if (dragging!=null) {
    dragging.dragged = true;
    lastParticle = dragging;
  }
}

void mouseReleased() {
  if (dragging!=null) {
    dragging.dragged=false;
    dragging = null;
  }
}
  

public class Particle {
  //a reference to the engine
  protected ParticleEngine engine;
  //a position
  public float x;
  public float y;
  // a velocity
  public float velocityX;
  public float velocityY;
  // a gravity
  protected float gravityX;
  protected float gravityY;
  // damping to simulate friction
  protected float damping;
  // color
  protected color col;
  //size
  protected float size;
  // variables to keep track of how long the particle is alive and how long it will live
  protected int life;
  protected int living;
  
  PImage mapImages;
  
  // flag to indicate whether or not the particle is destroyed
  public boolean destroyed;
  
  //flag to indicate the particle is being dragged
  public boolean dragged;

  public boolean pinned ;
  
  public String label; 
  
  
  
  //constructor, set initial variables
  public Particle(String label, float x, float y, float velocityX, float velocityY) {
    engine = null;
    this.label = label; 
    this.x = x;
    this.y = y;
    this.velocityX = velocityX;
    this.velocityY = velocityY;
    gravityX = random(-0.5,0.5);
    gravityY = random(-0.5,0.5);
    damping = 0.9;
    //randomize the color
    col = color(255, 255, 255);
    //randomize the size
    size = 30;
    //set life to -1 to live forever
    life = -1;
    living = 0;
    
    //set flags
    destroyed = false;
    dragged = false;
    pinned = false;
    mapImages = loadImage("shirt.png");
  }
  
  public void setEngine(ParticleEngine engine) {
    this.engine = engine;
  }
  
  //a method to set the particles position and velocity
  public void setPos(float x, float y, float velocityX, float velocityY) {
    this.x = x;
    this.y = y;
    this.velocityX = velocityX;
    this.velocityY = velocityY;
  }
  
  //a method to update the particle (should be called avery frame
  public void update() {
    if (dragged) {
      x = mouseX;
      y = mouseY;
      velocityX =0;
      velocityY =0;
      return;
    }
    if (pinned) {
      velocityX =0;
      velocityY =0;
      return;
    }
    
    //apply gravity
     velocityX += gravityX;
     velocityY += gravityY;
     //apply damping
     velocityX *= damping;
     velocityY *= damping;
     //apply speed
     x += velocityX;
     y += velocityY;
     if (life>0) {
       life--;
       if (life<=0) destroyed = true;
     }
  } 
  
  public void draw() {
   if (destroyed) return;
    //draw the particle
    //noStroke();
    // use alpha to fade away when life gets low
    fill(col);
    image(mapImages, x, y, size, size);
   
    fill(0);
    text(label, x-textWidth(label)*0.2, y+50);
  }
  
  public void pin(float x, float y) {
    this.x = x;
    this.y = y;
    pinned = true;
  }
}