class ThingParticleSystem {

  ArrayList particles;    // An arraylist for all the particles
  Vector3D ac = new Vector3D(0,0);
  Vector3D ve = new Vector3D(0,0);
  Vector3D lo = new Vector3D(0,0);
  float minMass = minMass_;
  int count =0;
  int mateCounter = 0;
  float mgX = width-width/6;
  float mgY = height/2;
  Vector3D mgV = new Vector3D(mgX, mgY); 

  //Constructor
  ThingParticleSystem() {
    particles = new ArrayList();              // Initialize the arraylist
    for (int i = 0; i < maxThings; i++) {
      lo = new Vector3D(random(width),random(height));
      DNA dna = new DNA();
      particles.add(new Thing(ac,ve,lo,random(8,13), dna));
    }
  }

  ArrayList getThings(){
    return particles;
  }

  void run() {

    noStroke();
    fill(random(230,255),random(10,200),random(10,50),random(5,15));
    ellipseMode(CENTER);
    ellipse(mgX,mgY,random(height/6-10,height/6+10),random(height/6-10,height/6+10));

    //Deal with death 
    for (int i = particles.size()-1; i >= 0; i--) {
      Thing t = (Thing) particles.get(i);
      if (t.getMass() < minMass){
        particles.remove(i);
      }

      //If just mated, add force to leave mating grond
      if (t.get_justMated()){
        //println("Just mated - adding force");
        if (t.getSex() == "male"){
          Vector3D dir = new Vector3D (random(-100000,0),random(100000));     // Calculate direction of force
          t.add_force(dir);
        }
        else{
          Vector3D dir = new Vector3D (random(-10000000,0),random(-10000000,0));     // Calculate direction of force
          dir.mult(10);
          t.add_force(dir);
        }
        if (mateCounter > 300){
          t.set_justMated(false);
          mateCounter = 0;
          //println("Just mated period over");
        }
        else{
          mateCounter++;
        }
        t.go();
      } 
      else{
        updateParticle(t);
      }
    }
  }

  void updateParticle(Thing t){
    String attractionType;

    //Look at other particles
    for (int j = 0; j < particles.size(); j++) {      
      Thing tj = (Thing) particles.get(j);

      // Make sure we are not calculating gravtional pull on oneself
      if (t.getX() != tj.getX() && t.getY() != tj.getY()) {    
        //If they are close enough, they will mate
        if (t.getSex() == "male" && tj.getSex() == "female"){
          attractionType = "straight";
        }
        else if (t.getSex() == "female" && tj.getSex() == "male"){
          attractionType = "straight";
        }
        else{
          attractionType = "gay";
        }

        if (attractionType == "straight"){
          if (abs(t.getX()-tj.getX()) < dMin && abs(t.getY() - tj.getY()) < dMin) {    
            t.set_mating(true);
            tj.set_mating(true);
          }
          else{
            t.set_mating(false);
            tj.set_mating(false);
          }
        }
        else{
          if (abs(t.getX()-tj.getX()) < dMin && abs(t.getY() - tj.getY()) < dMin) {    
            Vector3D f = t.calcRepForce(tj);          // Use the function we wrote above
            t.add_force(f);                            // Add the force to the object to affect its acceleration
          }
        }

        if (attractionType == "straight" && t.get_mating() == false && tj.get_mating() == false){
          Vector3D f = t.calcGravForce(tj,attractionType);          // Use the function we wrote above
          t.add_force(f);                            // Add the force to the object to affect its acceleration
        }
        //Add mating ground force
        else if (t.get_mating() && tj.get_mating()){
          //If within mating grounds, reproduce
          if (abs(t.getX()-mgV.x) < dMin && abs(t.getY() - mgV.y) < dMin) {    
          
            Thing child = reproduce(t,tj);
             particles.add(child);
             Vector3D dir = Vector3D.sub(t.getLoc(), mgV);     // Calculate direction of force
             float d = dir.magnitude(); 
             dir.normalize();
             dir.mult(d);                                  // Get force vector --> magnitude * direction
             t.add_force(dir);
             tj.add_force(dir);
          
          }
          else
          {
            Vector3D dir = Vector3D.sub(mgV, t.getLoc());     // Calculate direction of force
            float d = dir.magnitude(); 
            dir.normalize();
            dir.mult(d);                                  // Get force vector --> magnitude * direction
            t.add_force(dir);
            tj.add_force(dir);
          }
        }
        else{
          Vector3D f = t.calcRepForce(tj);          // Use the function we wrote above
          t.add_force(f);                            // Add the force to the object to affect its acceleration
          t.set_mating(false);
          tj.set_mating(false);
        }
      }

      //Add forces to contain objects within screen
      if (t.getY() < 0)
        t.add_force(new Vector3D(0,10));
      else if (t.getY() > height)
        t.add_force(new Vector3D(0,-10));
      if (t.getX() > width)
        t.add_force(new Vector3D(-10,0));
      else if (t.getX() < 0)
        t.add_force(new Vector3D(10,0));

      //Things follow mouse
      if (mousePressed) {
        Vector3D m = new Vector3D(mouseX,mouseY);
        Vector3D diff = Vector3D.sub(m,t.getLoc());
        diff.normalize();
        float factor = 1.0;  // Magnitude of Acceleration (not increasing it right now)
        diff.mult(factor);
        t.setAcc(diff);
      }
    }
    //EATING    
    for (int j = 0; j < fPs.total(); j++){
      Food fj = fPs.getParticle(j);
      float nx = fPs.getX(j);
      float ny = fPs.getY(j);

      Vector3D dir = Vector3D.sub(fj.getLoc(), t.getLoc());     // Calculate direction of force
      float d = dir.magnitude();                        // Distance between objects
      d = constrain(d,1,500);
      dir.normalize();
      float force = (t.getHunger() * fj.getMass()) / (d * d); 
      dir.mult(force);                      
      if (t.get_mating() == false){
        t.add_force(dir);  
        if(abs(nx - t.getX()) <= t.getMass()/2 && abs(ny - t.getY()) <= t.getMass()/2){
          t.addMass();
          fPs.remParticle(j);   
        }
      }
    }
    t.go();                                  // Implement the rest of the object's functionality
  }

  void addParticle() {
    DNA dna = new DNA();
    Vector3D location = new Vector3D(random(width),random(height));

    particles.add(new Thing(ac,ve,location,random(8,13),dna));
  }

  void remParticle(int i){
    if (particles.size() > 1){
      //particles.remove(i);
      Thing t = (Thing) particles.get(i);
      t.die();
    }
  }

  void delParticle(int i){
    if (particles.size() > 1){
      particles.remove(i);
    }
  }

  void delAllParticles(int i){
    particles.remove(i);
  }

  void addParticle(Thing t) {
    particles.add(t);
  }

  // A method to test if the particle system still has particles
  boolean dead() {
    if (particles.isEmpty()) {
      return true;
    } 
    else {
      return false;
    }
  }
  int total(){
    return particles.size();    
  }

  int numMales(){
    int num = 0;
    for (int i=0;i<particles.size();i++){
      Thing t = (Thing) particles.get(i);
      if (t.getSex() == "males"){
        num++;
      }
    }
    return num;
  }
  int numFemales(){
    int num = 0;
    for (int i=0;i<particles.size();i++){
      Thing t = (Thing) particles.get(i);
      if (t.getSex() == "females"){
        num++;
      }
    }
    return num;
  }

  Thing reproduce(Thing one, Thing two){
    DNA t1 = one.getDNA();
    DNA t2 = two.getDNA();
    DNA childDNA = t1.mate(t2);
    childDNA.mutate(mutationRate);

    Vector3D zero = new Vector3D(0,0); 
    Vector3D escape = new Vector3D(-1000,0);
    Thing child = new Thing(zero,escape,one.getLoc(),minMass*2,childDNA);

    one.set_mating(false);
    two.set_mating(false);
    one.set_justMated(true);
    two.set_justMated(true);
    child.set_justMated(true);

    //println("REPRODUCED");
    return child;
  }
}