import { useEffect , useState } from 'react' ; export function useSubscription < _value > ( { _getCurrentValue , _subscribe , } ) { const [ state , setState ] = useState ( ( ) => ( { _getCurrentValue , _subscribe , _value : _getCurrentValue ( ) , } ) ) ; let valueToReturn = state . _value ; if ( state . _getCurrentValue !== _getCurrentValue || state . _subscribe !== _subscribe ) { valueToReturn = _getCurrentValue ( ) ; setState ( { _getCurrentValue , _subscribe , _value : valueToReturn , } ) ; } useEffect ( ( ) => { let didUnsubscribe = false ; const checkForUpdates = ( ) => { if ( didUnsubscribe ) { return ; } const _value = _getCurrentValue ( ) ; setState ( ( prevState ) => { if ( prevState . _getCurrentValue !== _getCurrentValue || prevState . _subscribe !== _subscribe ) { return prevState ; } if ( prevState . _value === _value ) { return prevState ; } return { _getCurrentValue : prevState . _getCurrentValue , _subscribe : prevState . _subscribe , _value , } ; } ) ; } ; const unsubscribe = _subscribe ( checkForUpdates ) ; checkForUpdates ( ) ; return ( ) => { didUnsubscribe = true ; unsubscribe ( ) ; } ; } , [ _getCurrentValue , _subscribe ] ) ; return valueToReturn ; }