@actyx/sdk/src/util/typescript.ts

Actyx SDK

/*
 * Actyx SDK: Functions for writing distributed apps
 * deployed on peer-to-peer networks, without any servers.
 *
 * Copyright (C) 2021 Actyx AG
 */
/* eslint-disable @typescript-eslint/no-explicit-any */

/**
 * Base type for a tagged union with type as the tag field
 */

export type Tagged = { readonly type: string }
/**
 * Extract a case from a tagged union based on the (singleton) type of the tag
 */
export type SelectTag<T, Tag> = T extends { type: Tag } ? T : never
/**
 * Type transform that makes a nested type partial, while
 * leaving alone arrays, readonly arrays, functions and scalars
 */
/* eslint-disable @typescript-eslint/ban-types */
export type DeepPartial<T> = T extends ReadonlyArray<any>
  ? T
  : T extends Function
  ? T
  : T extends object
  ? { [K in keyof T]?: DeepPartial<T[K]> }
  : T
/* eslint-enable @typescript-eslint/ban-types */

export const todo: (...args: any[]) => never = () => {
  throw new Error('not implemented yet')
}

export const none: () => never = () => {
  throw new Error('there should have been something')
}

/**
 * Assert that from the type information, a piece of code can never be reached.
 * If it’s still reached at runtime, this throws an Error.
 * @public
 */
export const unreachable: (x?: never) => never = () => {
  throw new Error('Unreachable code!')
}

/**
 * Assert that from the type information, a certain statement can never be reached,
 * while installing a default value to return in case the type information was wrong
 * and the statement was in fact reached.
 * @public
 */
export function unreachableOrElse<T>(_: never, t: T): T {
  return t
}

/**
 * Avoids lint false positives like "Expression is always false. (strict-type-predicates)"
 */
export const lookup = <V>(m: { [k: string]: V }, k: string): V | undefined => m[k]

/**
 * Helpers for dealing with "type X = { [ key: K]: Y | undefined }
 */

type RecordKey = string | number | symbol
export type RWPartialRecord<K extends RecordKey, V> = { [P in K]?: V }
export type PartialRecord<K extends RecordKey, V> = Readonly<RWPartialRecord<K, V>>
export type PartialRecord2<K1 extends RecordKey, K2 extends RecordKey, V> = {
  readonly [P in K1]?: { readonly [T in K2]?: V }
}
export type RWKeyValueMap<T> = RWPartialRecord<string, T>
export type KeyValueMap<T> = PartialRecord<string, T>

export const isDefined = <T>(v: T): v is Exclude<T, undefined> => v !== undefined
export const valuesOf = <V>(m: PartialRecord<any, V>): Exclude<V, undefined>[] =>
  Object.values(m).filter(isDefined)

export const keysOf = <K extends RecordKey, V>(m: PartialRecord<K, V>): Extract<K, string>[] =>
  Object.keys(m) as any as Extract<K, string>[]

export const entriesOf = <K extends RecordKey, V>(
  obj: PartialRecord<K, V>,
): [Extract<K, string>, V][] =>
  Object.entries(obj).filter(([, x]) => isDefined(x)) as any as [Extract<K, string>, V][]

export const entriesOf2 = <K1 extends RecordKey, K2 extends RecordKey, V>(
  m1: PartialRecord2<K1, K2, V>,
): ReadonlyArray<[Extract<K1, string>, Extract<K2, string>, V]> =>
  entriesOf(m1).reduce<ReadonlyArray<[Extract<K1, string>, Extract<K2, string>, V]>>(
    (acc, [k1, m2]) =>
      acc.concat(
        entriesOf<K2, V>(m2).map(([k2, v]): [Extract<K1, string>, Extract<K2, string>, V] => [
          k1,
          k2,
          v,
        ]),
      ),
    [],
  )

export const toKeyValueMapF = <T, U>(
  getKey: (v: T) => string,
  map: (v: T) => U,
  xs: ReadonlyArray<T>,
): KeyValueMap<U> =>
  xs.reduce<RWKeyValueMap<U>>((acc, v) => {
    acc[getKey(v)] = map(v)
    return acc
  }, {})

export const toKeyValueMap = <T, K extends keyof T>(key: K, xs: ReadonlyArray<T>): KeyValueMap<T> =>
  xs.reduce((acc: any, v) => {
    acc[v[key]] = v
    return acc
  }, {})

export const tuple = <T extends any[]>(...data: T) => data

export const PartialRecord = {
  get<K extends RecordKey, V>(m: PartialRecord<K, V>, key: K): PartialRecord<K, V>[K] {
    return m[key]
  },
}

export const noop = () => undefined