maybe

maybe.ts

export class Maybe<Value> {
  constructor(private readonly value: Value | undefined | null) {}

  static of<T>(value: T): Maybe<T> {
    return new Maybe(value)
  }

  static empty<T>(): Maybe<T> {
    return new Maybe<T>(undefined)
  }

  map<Output>(transform: (value: Value) => Output): Maybe<Output> {
    return this.value == undefined
      ? Maybe.empty()
      : Maybe.of(transform(this.value))
  }

  tryMap<Output, ErrorValue>(
    transform: (value: Value) => Output,
    onError: (error: unknown) => ErrorValue,
  ): Maybe<Output | ErrorValue> {
    try {
      return this.map(transform)
    } catch (error) {
      return Maybe.of(onError(error))
    }
  }
}