Shapes Sum Type with Visitor Patten

ShapesVisit.java

import java.util.List;

// Visitor interface
interface ShapeVisitor<T> {
  T visit(Circle circle);
  T visit(Rectangle rectangle);
  T visit(Triangle triangle);
  T visit(Pentagon pentagon);
}

sealed interface Shape permits Circle, Rectangle, Triangle, Pentagon {
  <T> T accept(ShapeVisitor<T> visitor);
}

record Circle(double radius) implements Shape {
  @Override
  public <T> T accept(ShapeVisitor<T> visitor) {
    return visitor.visit(this);
  }
}

record Rectangle(double width, double height) implements Shape {
  @Override
  public <T> T accept(ShapeVisitor<T> visitor) {
    return visitor.visit(this);
  }
}

record Triangle(double side1, double side2, double side3) implements Shape {
  @Override
  public <T> T accept(ShapeVisitor<T> visitor) {
    return visitor.visit(this);
  }
}

record Pentagon(double side) implements Shape {
  @Override
  public <T> T accept(ShapeVisitor<T> visitor) {
    return visitor.visit(this);
  }
}

// Visitor for calculating area
class AreaCalculator implements ShapeVisitor<Double> {
  @Override
  public Double visit(Circle circle) {
    return Math.PI * circle.radius() * circle.radius();
  }

  @Override
  public Double visit(Rectangle rectangle) {
    return rectangle.width() * rectangle.height();
  }

  @Override
  public Double visit(Triangle triangle) {
    double s = (triangle.side1() + triangle.side2() + triangle.side3()) / 2;
    return Math.sqrt(s * (s - triangle.side1()) * (s - triangle.side2()) * (s - triangle.side3()));
  }

  @Override
  public Double visit(Pentagon pentagon) {
    return (0.25) * Math.sqrt(5 * (5 + 2 * Math.sqrt(5))) * pentagon.side() * pentagon.side();
  }
}

// Visitor for calculating perimeter
class PerimeterCalculator implements ShapeVisitor<Double> {
  @Override
  public Double visit(Circle circle) {
    return 2 * Math.PI * circle.radius();
  }

  @Override
  public Double visit(Rectangle rectangle) {
    return 2 * (rectangle.width() + rectangle.height());
  }

  @Override
  public Double visit(Triangle triangle) {
    return triangle.side1() + triangle.side2() + triangle.side3();
  }

  @Override
  public Double visit(Pentagon pentagon) {
    return 5 * pentagon.side();
  }
}

// Visitor for getting shape info
class InfoVisitor implements ShapeVisitor<String> {
  @Override
  public String visit(Circle circle) {
    return "Circle with radius: %.2f, area: %.2f, perimeter: %.2f".formatted(circle.radius(), new AreaCalculator().visit(circle), new PerimeterCalculator().visit(circle));
  }

  @Override
  public String visit(Rectangle rectangle) {
    return "Rectangle with width: %.2f , height: %.2f, area: %.2f, perimeter: %.2f".formatted(rectangle.width(), rectangle.height(), new AreaCalculator().visit(rectangle), new PerimeterCalculator().visit(rectangle));
  }

  @Override
  public String visit(Triangle triangle) {
    return "Triangle with sides: %.2f, %.2f, %.2f, area: %.2f, perimeter: %.2f".formatted(triangle.side1(), triangle.side2(), triangle.side3(), new AreaCalculator().visit(triangle), new PerimeterCalculator().visit(triangle));
  }

  @Override
  public String visit(Pentagon pentagon) {
    return "Pentagon with side: %.2f, area: %.2f, perimeter: %.2f".formatted(pentagon.side(), new AreaCalculator().visit(pentagon), new PerimeterCalculator().visit(pentagon));
  }
}

// Visitor for scaling shapes
class ScaleVisitor implements ShapeVisitor<Shape> {
  private final double scaleFactor;

  public ScaleVisitor(double scaleFactor) {
    this.scaleFactor = scaleFactor;
  }

  @Override
  public Shape visit(Circle circle) {
    return new Circle(circle.radius() * scaleFactor);
  }

  @Override
  public Shape visit(Rectangle rectangle) {
    return new Rectangle(rectangle.width() * scaleFactor, rectangle.height() * scaleFactor);
  }

  @Override
  public Shape visit(Triangle triangle) {
    return new Triangle(triangle.side1() * scaleFactor, triangle.side2() * scaleFactor, triangle.side3() * scaleFactor);
  }

  @Override
  public Shape visit(Pentagon pentagon) {
    return new Pentagon(pentagon.side() * scaleFactor);
  }
}

class Shapes {
  public static void main(String[] args) {
    List<Shape> shapes = List.of(new Circle(5), new Triangle(3, 3, 3), new Rectangle(3, 5), new Pentagon(5.6));

    InfoVisitor infoVisitor = new InfoVisitor();
    ScaleVisitor scaleVisitor = new ScaleVisitor(2);

    System.out.println("\nShapes:");
    shapes.stream().map(s -> s.accept(infoVisitor)).forEach(System.out::println);

    System.out.println("\nShapes scaled by 2:");
    shapes.stream().map(s -> s.accept(scaleVisitor)).map(s -> s.accept(infoVisitor)).forEach(System.out::println);
  }
}