/**
 * Defines a type `T` that can also be `null`.
 * @category Utils — Options
 */
export type Nullable<T> = T | null;

/**
 * Defines a type `T` that can also be `null` or `undefined`.
 * @category Utils — Options
 */
export type Nullish<T> = T | null | undefined;

/**
 * An implementation of the Rust Option type in JavaScript.
 * It can be one of the following:
 * - <code>{@link Some}<T></code>: Meaning there is a value of type T.
 * - <code>{@link None}</code>: Meaning there is no value.
 *
 * @category Utils — Options
 */
export type Option<T> = Some<T> | None;

/**
 * Defines a looser type that can be used when serializing an {@link Option}.
 * This allows us to pass null or the Option value directly whilst still
 * supporting the Option type for use-cases that need more type safety.
 *
 * @category Utils — Options
 */
export type OptionOrNullable<T> = Option<T> | Nullable<T>;

/**
 * Represents an option of type `T` that has a value.
 *
 * @see {@link Option}
 * @category Utils — Options
 */
export type Some<T> = { __option: 'Some'; value: T };

/**
 * Represents an option of type `T` that has no value.
 *
 * @see {@link Option}
 * @category Utils — Options
 */
export type None = { __option: 'None' };

/**
 * Creates a new {@link Option} of type `T` that has a value.
 *
 * @see {@link Option}
 * @category Utils — Options
 */
export const some = <T>(value: T): Option<T> => ({ __option: 'Some', value });

/**
 * Creates a new {@link Option} of type `T` that has no value.
 *
 * @see {@link Option}
 * @category Utils — Options
 */
export const none = <T>(): Option<T> => ({ __option: 'None' });

/**
 * Whether the given data is an {@link Option}.
 * @category Utils — Options
 */
export const isOption = <T = unknown>(input: any): input is Option<T> =>
  input &&
  typeof input === 'object' &&
  '__option' in input &&
  ((input.__option === 'Some' && 'value' in input) ||
    input.__option === 'None');

/**
 * Whether the given {@link Option} is a {@link Some}.
 * @category Utils — Options
 */
export const isSome = <T>(option: Option<T>): option is Some<T> =>
  option.__option === 'Some';

/**
 * Whether the given {@link Option} is a {@link None}.
 * @category Utils — Options
 */
export const isNone = <T>(option: Option<T>): option is None =>
  option.__option === 'None';