int posx[] = new int [50];
int posy[] = new int [50];
int sign[] = new int [50];
int counter = 0;
int moveit = 0;
float move[] = new float[2];

void setup(){
  size(500,500);
  textAlign(CENTER, CENTER);
  circle(width/2,height/2,20);
  move[0] = 250;
  move[1] = 250;
  stroke(0);

}

PVector crearVector(float x, float y){
  PVector v = new PVector(0,0);
  for(int i = 0; i < counter; i++){
    PVector ind = vectorCampo(i,x,y);
    v.add(ind);
  }
  return v;
}

PVector vectorCampo(int i,float x, float y){
  float multiplicador = int(sqrt(pow(posx[i]-x,2)+pow(posy[i]-y,2)));
  multiplicador = map(multiplicador,0,500,sqrt(50),0);
  multiplicador *= -multiplicador * sign[i];
  PVector campo = new PVector(posx[i]-x,posy[i]-y);
  campo.normalize();
  campo.mult(multiplicador);
  strokeWeight(1);
  stroke(255,0,0);
  if (sign[i] == -1) stroke (50,50,200);
  arrow(x,y,x+campo.x,y+campo.y);
  stroke(0);
  return campo;
}

void draw(){
  background(255);
  PVector v = crearVector(mouseX,mouseY);
  stroke(0);
  textSize(10);
  text("Controles:\nW para que se mueva la partícula central (positiva)\nS para que deje de moverse la partícula central\nD para que regrese al centro",width/2,40);
  textSize(20);
  strokeWeight(3);
  if(counter > 0) arrow(mouseX,mouseY,mouseX+v.x,mouseY+v.y);

    v = crearVector(move[0],move[1]);
    //v.normalize();
    float mult = map(v.mag(),0,1,0,0.001/counter);
    v.mult(mult);
    stroke(0);
    //arrow(move[0],move[1],move[0]+v.x,move[1]+v.y);
    //println(v.mag()+ " vx: " + v.x + " vy: " + v.y);
  if(moveit == 1){
    move[0] += v.x;
    move[1] += v.y;
  }
  circle(move[0],move[1],10);
  strokeWeight(1);
  for(int i = 0; i < counter; i++){
    fill(255);
    if(sign[i] == 1){
      fill(255,0,0);
      circle(posx[i],posy[i],20);
      fill(0);
      text("+",posx[i],posy[i]-3);
    }
    else{
      fill(50,50,200);
      circle(posx[i],posy[i],20);
      fill(0);
      text("-",posx[i],posy[i]-3);
    }
  }
}

void mousePressed(){
  posx[counter] = mouseX;
  posy[counter] = mouseY;
  if(mouseButton == LEFT){
    sign[counter] = 1;
  }
  else if(mouseButton == RIGHT){
    sign[counter] = -1;
  }
}

void mouseReleased(){
  counter++;
}

void arrow(float x1, float y1, float x2, float y2) {
  line(x1, y1, x2, y2);
  pushMatrix();
  translate(x2, y2);
  float a = atan2(x1-x2, y2-y1);
  rotate(a);
  line(0, 0, -3, -3);
  line(0, 0, 3, -3);
  popMatrix();
}

void keyPressed(){
  if(key == 'W' || key == 'w') moveit = 1;
  if(key == 'S' || key == 's') moveit = 0;
  if(key == 'D' || key == 'd'){
    move[0] = 250;
    move[1] = 250;
  }
}