// sample-shapes.mts: an ES module written in TypeScript.
// Free sample from 99helpers.com/file-types/ts
// .mts means "always an ES module", like .mjs for JavaScript.
// sample-main.mts imports from this file: keep both in the same folder.

// Exported types: other files can use them, and they vanish from the
// JavaScript output.
export type Point = { x: number; y: number };

export type Shape =
  | { kind: "circle"; centre: Point; radius: number }
  | { kind: "rectangle"; corner: Point; width: number; height: number };

// Exported values: these exist when the code runs.
export const UNIT = "cm";

export function area(shape: Shape): number {
  // `kind` tells the shapes apart, so each case knows its own fields.
  switch (shape.kind) {
    case "circle":
      return Math.PI * shape.radius ** 2;
    case "rectangle":
      return shape.width * shape.height;
  }
}