/**
 * A value native can store directly inside an object.
 *
 * A `Set<string>` or `Set<number>` (of finite numbers) is converted to an array; an empty or
 * mixed-type `Set`, like an empty array, is dropped. Readonly collections are accepted because the
 * serializer only reads them.
 */
export type InsiderObjectLeaf =
  | string
  | number
  | boolean
  | Date
  | readonly string[]
  | readonly number[]
  | ReadonlySet<string>
  | ReadonlySet<number>;

/**
 * The one nesting level native stores: a nested value may hold leaves but not another object.
 * Named and exported so a nested object can be held in a variable and passed in, not only written
 * inline - `InsiderObject` itself is wider and does not fit here.
 */
export type InsiderNestedObject = { readonly [key: string]: InsiderObjectLeaf | undefined };

/**
 * One nesting level only: native stores an object inside an object, and drops anything deeper.
 * `undefined` is accepted so an optional property can be passed straight through; it is skipped at
 * runtime.
 */
export type InsiderObjectValue = InsiderObjectLeaf | InsiderNestedObject | undefined;

/**
 * Keys must match `^[a-z][0-9a-z_]*$` — lowercase, starting with a letter, `_` as the only
 * separator. A camelCase key is dropped by native at every nesting level, and a string value over
 * 500 characters is dropped with the key that carries it.
 */
export type InsiderObject = { readonly [key: string]: InsiderObjectValue };