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import { atom } from 'jotai'import type { Atom } from 'jotai'import { createMemoizeAtom } from './weakCache'
const memoizeAtom = createMemoizeAtom()
type Loadable<Value> =  | { state: 'loading' }  | { state: 'hasError'; error: unknown }  | { state: 'hasData'; data: Awaited<Value> }
const LOADING: Loadable<unknown> = { state: 'loading' }
export function loadable<Value>(anAtom: Atom<Value>): Atom<Loadable<Value>> {  return memoizeAtom(() => {    const loadableAtomCache = new WeakMap<      Promise<void>,      Atom<Loadable<Value>>    >()
    const catchAtom = atom((get) => {      let promise: Promise<void>      try {        const data = get(anAtom) as Awaited<Value>        const loadableAtom = atom({ state: 'hasData', data } as Loadable<Value>)        return loadableAtom      } catch (error) {        if (error instanceof Promise) {          promise = error        } else {          const loadableAtom = atom({            state: 'hasError',            error,          } as Loadable<Value>)          return loadableAtom        }      }      const cached = loadableAtomCache.get(promise)      if (cached) {        return cached      }      const loadableAtom = atom(        LOADING as Loadable<Value>,        async (get, set) => {          try {            const data: Value = await get(anAtom, { unstable_promise: true })            set(loadableAtom, { state: 'hasData', data })          } catch (error) {            set(loadableAtom, { state: 'hasError', error })          }        }      )      loadableAtom.onMount = (init) => {        init()      }      loadableAtomCache.set(promise, loadableAtom)      return loadableAtom    })
    const derivedAtom = atom((get) => {      const loadableAtom = get(catchAtom)      return get(loadableAtom)    })
    return derivedAtom  }, [anAtom])}