ts-attempt.ts

// Inspired from a package I think is called ts-attempt but can't find it anymore.

const failSymbol = Symbol('fail')

type Ok<T> = T
type Fail = { [failSymbol]: true; error: unknown }

type Result<T> = Ok<T> | Fail

export async function attempt<T>(fn: () => Promise<T>): Promise<Result<T>> {
  try {
    return await fn()
  } catch (error) {
    return { [failSymbol]: true, error }
  }
}

export function isFail<T>(result: Result<T>): result is Fail {
  return typeof result === 'object' && result !== null && failSymbol in result
}

export function isOk<T>(result: Result<T>): result is Ok<T> {
  return !isFail(result)
}

// ----------

// https://www.npmjs.com/package/tuple-it
// Pretty much copied from ☝️ with minor change and name changes

type TryCatchResult<T> = [TryCatchError] | [null, T]

export async function trycatch<T = unknown>(
  maybePromise: Promise<T> | PromiseLike<T> | T
): Promise<TryCatchResult<T>> {
  try {
    return [null, await maybePromise]
  } catch (error) {
    return [new TryCatchError(error)]
  }
}

export class TryCatchError<E = unknown> extends Error {
  error: E

  constructor(error: E) {
    const message =
      error instanceof Error
        ? error.message
        : 'Promise rejected with a non instance of Error'

    super(message)

    this.error = error
  }
}