public class MyBoid {
  public int index;
  public Position position;
  public Speed speed;
  
  MyBoid(int idx) {
    this.index = idx;
    this.position = new Position(0, 0);
    this.speed = new Speed(0, 0);
  }
  
  public void move() {
    this.position.x += this.speed.x;
    this.position.y += this.speed.y;
  }
}

public class Position {
  public float x;
  public float y;
  
  Position(float ax, float ay) {
    this.x = ax;
    this.y = ay;
  }
}

public class Speed {
  public float x;
  public float y;
  
  Speed(float sx, float sy) {
    this.x = sx;
    this.y = sy;
  }
}

int i;
int j;
int nj;
float d;
float abs_speed;
float f_corr1;
float f_corr2;
float f_corr3;

int n = 30;

MyBoid[] bv = new MyBoid[n];
Position center = new Position(0, 0);
Speed avgspd = new Speed(0, 0);

MyBoid predator = new MyBoid(n + 1);
float distToPred = 0;

void setup() {
  size(480, 600);
  frameRate(60);
  noStroke();
  smooth();
  for(i=0; i<n; i++) {
    bv[i] = new MyBoid(i);
    bv[i].position.x = random(0, width);
    bv[i].position.y = random(0, height);
    bv[i].speed.x = random(0, 2);
    bv[i].speed.y = random(0, 2);
    predator.position.x = random(0, width);
    predator.position.y = random(0, height);
  }
}

void draw() {
  background(255,255,255);
  //fill(255,255,255,180);
  //rect(-10,-10,width+10,height+10);
  
  for(i=0; i<n; i++) {
    center.x = 0.0;
    center.y = 0.0;
    avgspd.x = 0.0;
    avgspd.y = 0.0;
    nj = 0;
    for(j=0; j<n; j++) {
      if(j != i) {
        d = dist(bv[i].position.x, bv[i].position.y, bv[j].position.x, bv[j].position.y);
        if(d < 50) {
          center.x += bv[j].position.x;
          center.y += bv[j].position.y;
          avgspd.x += bv[j].speed.x;
          avgspd.y += bv[j].speed.y;
          if(d < 20) {
            bv[i].speed.x -= ruleTwo(bv[i].position.x, bv[j].position.x, d);
            bv[i].speed.y -= ruleTwo(bv[i].position.y, bv[j].position.y, d);
          }
          nj += 1;
        }
      }
    }
    if(nj > 0) {
      bv[i].speed.x += ruleOne(bv[i].position.x, center.x/nj);
      bv[i].speed.y += ruleOne(bv[i].position.y, center.y/nj);
      bv[i].speed.x += ruleThree(bv[i].speed.x, avgspd.x/nj);
      bv[i].speed.y += ruleThree(bv[i].speed.y, avgspd.y/nj);
    }
    bv[i].speed.x -= 0.005*bv[i].speed.x;
    bv[i].speed.y -= 0.005*bv[i].speed.y;
    distToPred = dist(bv[i].position.x, bv[i].position.y, predator.position.x, predator.position.y);
    bv[i].speed.x -= ruleFour(bv[i].position.x, predator.position.x, distToPred);
    bv[i].speed.y -= ruleFour(bv[i].position.y, predator.position.y, distToPred);
    bv[i].move();
    
    if(bv[i].position.x > width) {
      bv[i].speed.x -= 0.1*(bv[i].position.x - width);
    }
    if (bv[i].position.x < 0) {
      bv[i].speed.x += -0.1*(bv[i].position.x);
    }
    if(bv[i].position.y > height) {
      bv[i].speed.y -= 0.1*(bv[i].position.y - height);
    }
    if (bv[i].position.y < 0) {
      bv[i].speed.y += -0.1*(bv[i].position.y);
    }
    fill(255,0,0);
    
    abs_speed = sqrt(bv[i].speed.x*bv[i].speed.x + bv[i].speed.y*bv[i].speed.y);
    if(abs_speed != 0) {
      f_corr1 = 10/abs_speed;
      f_corr2 = bv[i].speed.x/abs_speed;
      f_corr3 = -bv[i].speed.y/abs_speed;
      
      noFill();
      strokeWeight(1.2);
      stroke(200,0,34);

      pushMatrix();
        float myRot = atan2(-2*f_corr3,2*f_corr2);
        translate(bv[i].position.x+2*f_corr3,bv[i].position.y+2*f_corr2);
        rotate(myRot);
        pushMatrix();
        translate(4,0);
          line(0, 0, 10, 0);
          line(5, 5, 5, -5);
        popMatrix();
      popMatrix();
      
      fill(255,255,255);
      ellipse(bv[i].position.x+2*f_corr3,bv[i].position.y+2*f_corr2,10,10);
            
    }
    else triangle(bv[i].position.x, bv[i].position.y+10, bv[i].position.x-2, bv[i].position.y, bv[i].position.x+2, bv[i].position.y);
  }
  
  // predator movements
  nj = 0;
  center.x = 0;
  center.y = 0;
  for(j=0; j<n; j++) {
    d = dist(predator.position.x, predator.position.y, bv[j].position.x, bv[j].position.y);
    if(d < 100) {
      center.x += bv[j].position.x;
      center.y += bv[j].position.y;
      nj += 1;
    }
  }
  if(nj > 0) {
    predator.speed.x += 1.5*ruleOne(predator.position.x, center.x/nj);
    predator.speed.y += 1.5*ruleOne(predator.position.y, center.y/nj);
  }
  predator.speed.x -= 0.01*predator.speed.x;
  predator.speed.y -= 0.01*predator.speed.y;
  if(predator.position.x > width) {
      predator.speed.x -= 0.1*(predator.position.x - width);
    }
    if (predator.position.x < 0) {
      predator.speed.x += -0.1*(predator.position.x);
    }
    if(predator.position.y > height) {
      predator.speed.y -= 0.1*(predator.position.y - height);
    }
    if (predator.position.y < 0) {
      predator.speed.y += -0.1*(predator.position.y);
    }
  predator.move();
  //fill(158,0,34);
  abs_speed = sqrt(predator.speed.x*predator.speed.x + predator.speed.y*predator.speed.y);
  if(abs_speed != 0) {
    f_corr1 = 15/abs_speed;
    f_corr2 = predator.speed.x/abs_speed;
    f_corr3 = -predator.speed.y/abs_speed;
    
    noFill();
    //strokeWeight(1.2);
    stroke(50,70,135);

    float myPosX = predator.position.x;
    float myPosY = predator.position.y;
    
    float myVecX = 3*f_corr3;
    float myVecY = 3*f_corr2;
    
    float myTopX    = predator.position.x+ predator.speed.x*f_corr1;
    float myTopY    = predator.position.y+ predator.speed.y*f_corr1;
    
    //移動の更新
    myPosX = myPosX +myVecX;
    myPosY = myPosY +myVecY;
    
    float a = 5.0*2.2;
    float b = 3.48*2.2 *0.8;
    float c = 1.5*2 *2;  //矢印の角度

    pushMatrix();
      float myRot = atan2(-myVecX,myVecY);
      translate(myPosX,myPosY);
      rotate(myRot);
      pushMatrix();
      translate(4,0);
        line(0, 0, a,  0);
        line(a, 0, b, -c);
        line(a, 0, b,  c);
      popMatrix();
    popMatrix();
    
    fill(255,255,255);
    ellipse(myPosX,myPosY,10,10);
    stroke(0,0,0);
  }
  //}else{
    //triangle(predator.position.x, predator.position.y+15, predator.position.x-3, predator.position.y, predator.position.x+3, predator.position.y);
  //}
}



float ruleOne(float p, float c) {
  return (c - p)/1000;
}
float ruleTwo(float p, float p2, float d) {
  return ((20/(d+1)-1)*((p2 - p)/d));
}
float ruleThree(float s, float avgs) {
  return (avgs - s)/15;
}
float ruleFour(float p, float p_pred, float d) {
  if (d < 40)
    return ((40/(d+1)-1)*((p_pred - p)/d));
  else
    return 0.0;
}