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import {  useCallback,  useContext,  useDebugValue,  useEffect,  useReducer,} from 'react'import type { Reducer } from 'react'import type { Atom, Scope } from './atom'import { getScopeContext } from './contexts'import { COMMIT_ATOM, READ_ATOM, SUBSCRIBE_ATOM } from './store'import type { VersionObject } from './store'
type Awaited<T> = T extends Promise<infer V> ? Awaited<V> : T
export function useAtomValue<Value>(  atom: Atom<Value>,  scope?: Scope): Awaited<Value> {  const ScopeContext = getScopeContext(scope)  const { s: store } = useContext(ScopeContext)
  const getAtomValue = useCallback(    (version?: VersionObject) => {      // This call to READ_ATOM is the place where derived atoms will actually be      // recomputed if needed.      const atomState = store[READ_ATOM](atom, version)      if ('e' in atomState) {        throw atomState.e // read error      }      if ('p' in atomState) {        throw atomState.p // read promise      }      if ('v' in atomState) {        return atomState.v as Awaited<Value>      }      throw new Error('no atom value')    },    [store, atom]  )
  // Pull the atoms's state from the store into React state.  const [[version, value, atomFromUseReducer], rerenderIfChanged] = useReducer<    Reducer<      readonly [VersionObject | undefined, Awaited<Value>, Atom<Value>],      VersionObject | undefined    >,    undefined  >(    useCallback(      (prev, nextVersion) => {        const nextValue = getAtomValue(nextVersion)        if (Object.is(prev[1], nextValue) && prev[2] === atom) {          return prev // bail out        }        return [nextVersion, nextValue, atom]      },      [getAtomValue, atom]    ),    undefined,    () => {      // NOTE should/could branch on mount?      const initialVersion = undefined      const initialValue = getAtomValue(initialVersion)      return [initialVersion, initialValue, atom]    }  )
  if (atomFromUseReducer !== atom) {    rerenderIfChanged(undefined)  }
  useEffect(() => {    // Call `rerenderIfChanged` whenever this atom is invalidated. Note    // that derived atoms may not be recomputed yet.    const unsubscribe = store[SUBSCRIBE_ATOM](atom, rerenderIfChanged)    rerenderIfChanged(undefined)    return unsubscribe  }, [store, atom])
  useEffect(() => {    store[COMMIT_ATOM](atom, version)  })
  useDebugValue(value)  return value}