atomWithActorLogic.ts - derived atom example to integrate jotai and xstate

atomWithActorLogic.ts

import { type Getter, atom, useAtom } from "jotai";
import { useCallback } from "react";
import { useSyncExternalStoreWithSelector } from "use-sync-external-store/shim/with-selector";
import type {
  Actor,
  ActorOptions,
  ActorRefFromLogic,
  AnyActorLogic,
  AnyActorRef,
} from "xstate";
import { createActor } from "xstate";
// This import was inlined at the bottom of this file to work around dependency issues
// import { useSelector as useSelectorOriginal } from "@xstate/react";

export function atomWithActorLogic<TLogic extends AnyActorLogic>(
  logic: TLogic | ((get: Getter) => TLogic),
  options?: ActorOptions<TLogic>,
) {
  let actorRef: Actor<TLogic> | undefined = undefined;
  const actorAtom = atom((get) => {
    if (!actorRef) {
      actorRef = createActor(
        isGetter(logic) ? logic(get) : logic,
        isGetter(options) ? options(get) : options,
      );
      actorRef.start();
    }
    return actorRef;
  });
  // TODO use actorAtom.onMount() to offer something similar to useSelector?
  return actorAtom;
}

export function useSnapshot<TLogic extends AnyActorLogic>(
  actorAtom: ReturnType<typeof atomWithActorLogic<TLogic>>,
) {
  return useSelector(actorAtom, (x) => x);
}

type SyncExternalStoreSubscribe = Parameters<
  typeof useSyncExternalStoreWithSelector
>[0];

function defaultCompare<T>(a: T, b: T) {
  return a === b;
}

export function useSelector<TLogic extends AnyActorLogic, T>(
  actorAtom: ReturnType<typeof atomWithActorLogic<TLogic>>,
  selector: Parameters<
    typeof useSelectorOriginal<ActorRefFromLogic<TLogic>, T>
  >[1],
  compare?: Parameters<
    typeof useSelectorOriginal<ActorRefFromLogic<TLogic>, T>
  >[2],
) {
  const [actor] = useAtom(actorAtom);
  return useSelectorOriginal(actor, selector, compare);
}

const isGetter = <T>(v: T | ((get: Getter) => T)): v is (get: Getter) => T =>
  typeof v === "function";

// This was copied from @xstate/react. Adding here
// to use React 19 compatible dependencies.
function useSelectorOriginal<
  TActor extends Pick<AnyActorRef, "subscribe" | "getSnapshot"> | undefined,
  T,
>(
  actor: TActor,
  selector: (
    snapshot: TActor extends { getSnapshot(): infer TSnapshot }
      ? TSnapshot
      : undefined,
  ) => T,
  compare: (a: T, b: T) => boolean = defaultCompare,
): T {
  const subscribe: SyncExternalStoreSubscribe = useCallback(
    (handleStoreChange: () => void) => {
      if (!actor) {
        return () => {};
      }
      const { unsubscribe } = actor.subscribe(handleStoreChange);
      return unsubscribe;
    },
    [actor],
  );

  const boundGetSnapshot = useCallback(() => actor?.getSnapshot(), [actor]);

  const selectedSnapshot = useSyncExternalStoreWithSelector(
    subscribe,
    boundGetSnapshot,
    boundGetSnapshot,
    selector,
    compare,
  );

  return selectedSnapshot;
}

~LICENSE

MIT License

xstate: Copyright (c) 2015 David Khourshid
https://github.com/statelyai/xstate/blob/main/LICENSE

jotai-xstate: Copyright (c) 2020-2022 Poimandres
https://github.com/jotaijs/jotai-xstate/blob/main/LICENSE

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.