sclass Base {
  S text;
}

sclass CirclesAndLines extends Base {
  new L<Circle> circles;
  new L<Line> lines;

  Circle addCircle(S imageID, double x, double y) {
    ret addCircle(imageID, x, y, "");
  }
  
  Circle addCircle(S imageID, double x, double y, S text) {
    ret addAndReturn(circles, nu(Circle, +x, +y, +text, img := loadImage2(imageID)));
  }
  
  Line addLine(Circle a, Circle b) {
    Line line = findWhere(Line, +a, +b);
    if (line == null)
      lines.add(line = nu(Line, +a, +b));
    ret line;
  }
  
  Line addArrow(Circle a, Circle b) {
    ret addArrow(a, b, "");
  }
  
  Line addArrow(Circle a, Circle b, S text) {
    Line line = findWhere(Line, +a, +b);
    if (line == null)
      ret addAndReturn(lines, nu(Arrow, +a, +b, +text));
    line.text += " / " + text;
    ret line;
  }
  
  BufferedImage makeImage(int w, int h) {
    BufferedImage bg = renderTiledBackground(#1007195, w, h);
    for (Line l : lines) {
      Pt a = l.a.pt(w, h), b = l.b.pt(w, h);
      if (l << Arrow)
        drawThoughtArrow(bg, l.a.img, a.x, a.y, l.b.img, b.x, b.y, l.color);
      else
        drawThoughtLine(bg, l.a.img, a.x, a.y, l.b.img, b.x, b.y, l.color);
      if (nempty(l.text))
        drawThoughtLineText(bg, l.a.img, a.x, a.y, l.b.img, b.x, b.y, l.text, l.color);
    }
    for (Circle c : circles) {
      Pt p = c.pt(w, h);
      drawThoughtCircle(bg, c.img, p.x, p.y);
      if (nempty(c.text))
        drawThoughtCircleText(bg, c.img, p, c.text);
    }
    ret bg;
  }
  
  Canvas showAsFrame() {
    fO makeImg = func(int w, int h) { makeImage(w, h) };
    final ImageSurface canvas = jcanvas(makeImg);
    disableImageSurfaceSelector(canvas);
    new CircleDragger(canvas, r { updateCanvas(canvas, makeImg) }, circles);
    showFrame(canvas);
    ret canvas;
  }
}

sclass Circle extends Base {
  BufferedImage img;
  double x, y;
  
  Pt pt(ImageSurface is) {
    ret pt(is.getWidth(), is.getHeight());
  }
  
  Pt pt(int w, int h) {
    ret new Pt(iround(x*w), iround(y*h));
  }
  
  bool contains(ImageSurface is, Pt p) {
    ret pointDistance(p, pt(is)) <= thoughtCircleSize(img)/2+1;
  }
}

sclass Line {
  Circle a, b;
  Color color = Color.white;
  
  Line setColor(Color color) {
    this.color = color;
    this;
  }
}

Line > Arrow {}

sclass CircleDragger extends MouseAdapter {
  ImageSurface is;
  L<Circle> circles;
  O update;
  int dx, dy;
  Circle circle;

  *(ImageSurface *is, O *update, L<Circle> *circles) {
    if (containsInstance(is.tools, CircleDragger)) ret;
    is.tools.add(this);
    is.addMouseListener(this);
    is.addMouseMotionListener(this);
  }

  public void mousePressed(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1) {
      Pt p = is.pointFromEvent(e);
      circle = findCircle(p);
      if (circle != null) {
        dx = p.x-iround(circle.x*is.getWidth());
        dy = p.y-iround(circle.y*is.getHeight());
      }
    }
  }

  public void mouseDragged(MouseEvent e) {
    if (circle != null) {
      Pt p = is.pointFromEvent(e);
      circle.x = (p.x-dx)/(double) is.getWidth();
      circle.y = (p.y-dy)/(double) is.getHeight();
      callF(update);
    }
  }

  public void mouseReleased(MouseEvent e) {
    mouseDragged(e);
    circle = null;
  }
  
  Circle findCircle(Pt p) {
    new Lowest<Circle> best;
    for (Circle c : circles)
      if (c.contains(is, p))
        best.put(c, pointDistance(p, c.pt(is)));
    ret best.get();
  }
  
  Circle findCircle(S text) {
    for (Circle c : circles)
      if (eqic(c.text, text))
        ret c;
    null;
  }
}