// The particle class controls all movements & transformation

class Particle {

  float x, y, dx, dy, tx, ty, px, py, speed, tangle;
  float angle = random(-0.3, 0.3);
  float terrRadius = random(20, 80);        // territory radius, used for backOff()
  float initSize, typeSize, tSize;          // tSize = target size
  float maxSize, charSpace;                 // sets spacing for displayed text
  float maxSizeScalar = 4.0;               // sets the maximum size
  float resizeSpd = 0.05;
  boolean inString = false;                 // set if the character is used to display text

  Particle(float xpos, float ypos, float spd, float s) {
    x = xpos;
    y = ypos;
    tx = xpos;
    ty = ypos;
    px = xpos;
    py = ypos;
    speed = spd;
    initSize = s;
    tSize = initSize; 
    maxSize  = initSize*maxSizeScalar;
    charSpace = initSize;

  }

  void update() {    
    dx = mouseX - x;
    dy = mouseY - y;

    float d = dist(x, y, mouseX, mouseY);
    // back off when mouse comes too close
    if (d < terrRadius) {
      backOff();
    } 
    else {
      // idle movement: move sideways to cursor, random vertical movement
      idleMovement();
    }

    // attack
    if (mousePressed) {
      attack();
    }

    // update size
    if (abs(typeSize-tSize)>0.1) {
      typeSize += (tSize - typeSize)*resizeSpd;
    }

    // store previous position
    px = x;
    py = y;
  }

  void reset(float x, float y, int fs, float as){
    float angle = random(-TWO_PI, TWO_PI);
    float rx = random(fs/2);
    float ry = random(fs/3);
    speed =  random(as)+1.0;
    tx = x+rx*cos(angle);
    ty = y+ry*sin(angle);
    inString = false;
    decSize();
  }

  void backOff(){
    angle = (atan2(dy, dx)+PI);
    x += cos(angle) * speed * random(1, 2);
    y += sin(angle) * speed * random(1, 2);
  }

  void idleMovement(){
    // slow movement towards mouseX
    if (!inString) {
      tx += (mouseX - tx)*0.001+random(-3, 3);
      ty += (mouseY - ty)*0.001+random(-3, 3);
      // random movement
      tx += random(-1, 1)*0.5;
      ty += random(-1, 1)*0.2;
    } 
    else {
      // random movement
      tx += random(-1, 1);
      ty += random(-1, 1);
    }
    x += (tx - x)*speed*0.01;
    y += (ty - y)*speed*0.01;
  }

  void attack(){
    tangle = atan2(dy, dx);
    angle += (tangle-angle)*0.8;
    x += cos(angle) * speed * random(1, 6);
    y += sin(angle) * speed * random(1, 6);
    tSize = initSize;
  }

  void setTargetPos(int c, int s) {
    int charNum = c;
    int stringLength = s;
    tx = width/2 - stringLength*charSpace/2 + charSpace*c;
    ty = height/2 - tSize*2;
  }

  void incSize() {
    if (tSize < maxSize) {
      tSize += maxSize-initSize;
      charSpace = tSize/1.5;
    }
  }

  void decSize() {
    if (typeSize > initSize) {
      tSize = initSize;
      charSpace = initSize;
    }
  }

  void setInString() {
    inString = true;
  }
}