import { EventEmitter } from 'events' ; import React , { useState , useEffect , useContext } from 'react' ; export interface Hwapan { width : number ; height : number ; layers : Layer [ ] ; } export interface Layer { name : string ; canvas : HTMLCanvasElement ; } export const emptyHwapan = { width : 0 , height : 0 , layers : [ ] , } ; interface HwapanContextValue { emitter : EventEmitter ; hwapan : Hwapan ; update : ( updateFn : UpdateFn ) => void ; } interface UpdateFn { ( hwapan ) : string | undefined ; } const hwapanContext = React . createContext < HwapanContextValue > ( null as any ) ; interface HwapanProviderProps { initialHwapan : Hwapan ; } export const HwapanProvider = ( { children } ) => { const [ hcv ] = useState ( ( ) => { const hcv = { emitter : new EventEmitter ( ) , hwapan : emptyHwapan , update : updateFn => { const event = updateFn ( hcv . hwapan ) ; hcv . emitter . emit ( event ?? 'update' ) ; } , } ; return hcv ; } ) ; return < hwapanContext . Provider value = { hcv } > { children } < /hwapanContext.Provider>; } ; export function useUpdateHwapan ( ) { return useContext ( hwapanContext ) . update ; } export function useHwapan < T > ( selector , event ? ) { const hcv = useContext ( hwapanContext ) ; const [ state , setState ] = useState ( selector ( hcv . hwapan ) ) ; useEffect ( ( ) => { const e = event ?? 'update' ; const handler = ( ) => { const newState = selector ( hcv . hwapan ) ; if ( state !== newState ) setState ( newState ) ; } ; hcv . emitter . addListener ( e , handler ) ; ( ) => hcv . emitter . removeListener ( e , handler ) ; } , [ hcv . emitter , state ] ) ; return state ; }