DndGamePlayer/app/renderer/shared/effects/useSceneMarkerState.ts

import { useEffect, useState } from 'react';

import { ipcChannels } from '../../../shared/ipc/contracts';
import type { SceneMarkerEvent, SceneMarkerState } from '../../../shared/types';
import { getDndApi } from '../dndApi';

export function useSceneMarkerState(): readonly [
  SceneMarkerState | null,
  { dispatch: (event: SceneMarkerEvent) => Promise<void> },
] {
  const api = getDndApi();
  const [state, setState] = useState<SceneMarkerState | null>(null);

  useEffect(() => {
    void api.invoke(ipcChannels.sceneMarker.getState, {}).then((r) => {
      setState((prev) => {
        if (prev && prev.revision > r.state.revision) return prev;
        return r.state;
      });
    });
    return api.on(ipcChannels.sceneMarker.stateChanged, ({ state: next }) => {
      setState((prev) => {
        if (prev && prev.revision > next.revision) return prev;
        return next;
      });
    });
  }, [api]);

  return [
    state,
    {
      dispatch: async (event) => {
        await api.invoke(ipcChannels.sceneMarker.dispatch, { event });
      },
    },
  ] as const;
}