///|
/// Measures a handful of shapes and prints what it found.
///
/// Run it from the project root with `moon run cmd/main`, or from the
/// editor's MoonBit menu with **Run** and `cmd/main`.
fn main {
  let circles = [
    @shapes.Circle::{ radius: 1.0, },
    @shapes.Circle::{ radius: 2.5, },
    @shapes.Circle::{ radius: 0.5, },
  ]
  let rects = [
    @shapes.Rect::{ width: 3.0, height: 4.0, },
    @shapes.Rect::{ width: 1.5, height: 1.5, },
  ]
  report("circles", circles)
  report("rectangles", rects)
  report("nothing at all", ([] : Array[@shapes.Circle]))
}

///|
/// report prints the total and the largest of a list, and says so plainly when
/// the list is empty rather than letting the error escape.
fn[T : @shapes.Area + Show] report(what : String, shapes : Array[T]) -> Unit {
  println("── \{what} ──")
  try {
    let sum = @shapes.total(shapes)
    println("  total area: \{sum}")
  } catch {
    @shapes.NoShapes => println("  no shapes were given")
  }
  match @shapes.largest(shapes) {
    Some(shape) => println("  largest:    \{shape}")
    None => println("  largest:    none")
  }
  println("")
}