result.js.flow

/* @flow */

type InspectOpts = {
  showHidden: boolean;
  depth: number;
  colors: boolean;
  customInspect: boolean;
  showProxy: boolean;
  maxArrayLength: number;
  breakLength: number;
}

type MatchBlock<T, F> = {
  Ok(value: T): void;
  Fail(failure: F): void;
}

export type Result<T, F> = {
  ok(errorMessage?: string): T;
  fail(errorMessage?: string): F;
  isOk(): boolean;
  isFail(): boolean;
  map(f: (value: T) => T): Result<T, F>;
  mapFail(f: (failure: F) => F): Result<T, F>;
  and<A>(rhsResult: A): Result<T, F> | A;
  or<A>(rhsResult: A): Result<T, F> | A;
  andThen<A>(f: (value: T) => A): Result<T, F> | A;
  orElse<A>(f: (failure: F) => A): Result<T, F> | A;
  toArray(): [T];
  unwrapOr<A>(defaultValue: A): T | A;
  unwrapOrElse<A>(defaultFn: (failure: F) => A): T | A;
  match(block: MatchBlock<T, F>): void;
  inspect(depth: number, opts?: InspectOpts): string;
  debug(logfn: (string: string) => void, opts?: InspectOpts): void;
  debugOk(logfn: (string: string) => void, opts?: InspectOpts): void;
  debugFail(logfn: (string: string) => void, opts?: InspectOpts): void;
}

declare export function ok<T, F>(result: Result<T, F>, errorMessage?: string): T;
declare export function fail<T, F>(result: Result<T, F>, errorMessage?: string): F;
declare export function isOk<T, F>(result: Result<T, F>): boolean;
declare export function isFail<T, F>(result: Result<T, F>): boolean;
declare export function map<T, F>(result: Result<T, F>, f: (value: T) => T): Result<T, F>;
declare export function mapFail<T, F>(result: Result<T, F>, f: (failure: F) => F): Result<T, F>;
declare export function and<A, T, F>(result: Result<T, F>, rhsResult: A): Result<T, F> | A;
declare export function or<A, T, F>(result: Result<T, F>, rhsResult: A): Result<T, F> | A;
declare export function andThen<A, T, F>(result: Result<T, F>, f: (value: T) => A): Result<T, F> | A;
declare export function orElse<A, T, F>(result: Result<T, F>, f: (failure: F) => A): Result<T, F> | A;
declare export function toArray<T, F>(result: Result<T, F>): [T];
declare export function unwrapOr<A, T, F>(result: Result<T, F>, defaultValue: A): T | A;
declare export function unwrapOrElse<A, T, F>(result: Result<T, F>, defaultFn: (failure: F) => A): T | A;
declare export function match<T, F>(result: Result<T, F>, block: MatchBlock<T, F>): void;
declare export function inspect<T, F>(result: Result<T, F>, depth: number, opts?: InspectOpts): string;
declare export function debug<T, F>(result: Result<T, F>, logfn: (string: string) => void, opts: ?InspectOpts): void;
declare export function debugOk<T, F>(result: Result<T, F>, logfn: (string: string) => void, opts: ?InspectOpts): void;
declare export function debugFail<T, F>(result: Result<T, F>, logfn: (string: string) => void, opts: ?InspectOpts): void;

declare export function Ok<T, F>(t: T): Result<T, F>
declare export function Fail<T, F>(f: F): Result<T, F>