import javafx.application.Application;
import javafx.geometry.Point2D;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class Exercise28_22 extends Application {
  @Override // Override the start method in the Application class
  public void start(Stage primaryStage) {
    // Create a scene and place it in the stage
    Scene scene = new Scene(new CirclePane(), 450, 350);
    primaryStage.setTitle("Exercise28_22"); // Set the stage title
    primaryStage.setScene(scene); // Place the scene in the stage
    primaryStage.show(); // Display the stage
  }

  /** Pane for displaying circles */
  class CirclePane extends Pane {

    public CirclePane() {
      this.setOnMouseClicked(e -> {
        if (!isInsideACircle(new Point2D(e.getX(), e.getY()))) {
          // Add a new circle
          getChildren().add(new Circle(e.getX(), e.getY(), 20));
          colorIfConnected();
        }
      });

      this.setOnMouseDragged(e -> {
        for (Node circle : this.getChildren()) {
          if (circle.contains(new Point2D(e.getX(), e.getY()))) {
            ((Circle) circle).setCenterX(e.getX());
            ((Circle) circle).setCenterY(e.getY());
            break;
          }
        }

        colorIfConnected();
      });
    }

    /**
     * Returns true if the point is inside an existing circle
     */
    private boolean isInsideACircle(Point2D p) {
      for (Node circle : this.getChildren()) {
        if (circle.contains(p)) {
          return true;
        }
      }

      return false;
    }

    /**
     * Color all circles if they are connected
     */
    private void colorIfConnected() {
      if (getChildren().size() == 0) {
        return; // No circles in the pane
      }
      // Build the edges
      java.util.List<AbstractGraph.Edge> edges = new java.util.ArrayList<>();
      for (int i = 0; i < getChildren().size(); i++) {
        for (int j = i + 1; j < getChildren().size(); j++) {
          if (overlaps((Circle) (getChildren().get(i)),
                  (Circle) (getChildren().get(j)))) {
            edges.add(new AbstractGraph.Edge(i, j));
            edges.add(new AbstractGraph.Edge(j, i));
          }
        }
      }

      // Create a graph with circles as vertices
      Graph<Node> graph = new UnweightedGraph<>((java.util.List<Node>) getChildren(), edges);
      AbstractGraph<Node>.Tree tree = graph.dfs(0); // a DFS tree
      boolean isAllCirclesConnected = getChildren().size() == tree
              .getNumberOfVerticesFound();

      for (Node circle : getChildren()) {
        if (isAllCirclesConnected) { // All circles are connected
          ((Circle) circle).setFill(Color.RED);
        } else {
          ((Circle) circle).setStroke(Color.BLACK);
          ((Circle) circle).setFill(Color.WHITE);
        }
      }
    }
  }

  public static boolean overlaps(Circle circle1, Circle circle2) {
    return new Point2D(circle1.getCenterX(), circle1.getCenterY()).
            distance(circle2.getCenterX(), circle2.getCenterY())
            <= circle1.getRadius() + circle2.getRadius();
  }

  /**
   * The main method is only needed for the IDE with limited
   * JavaFX support. Not needed for running from the command line.
   */
  public static void main(String[] args) {
    launch(args);
  }
}
