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import { Subscribable } from './subscribable'
import { isServer } from './utils'
type Listener = (focused: boolean) => void
type SetupFn = (
setFocused: (focused?: boolean) => void,
) => (() => void) | undefined
export class FocusManager extends Subscribable<Listener> {
#focused?: boolean
#cleanup?: () => void
#setup: SetupFn
constructor() {
super()
this.#setup = (onFocus) => {
// addEventListener does not exist in React Native, but window does
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
if (!isServer && window.addEventListener) {
const listener = () => onFocus()
// Listen to visibilitychange
window.addEventListener('visibilitychange', listener, false)
return () => {
// Be sure to unsubscribe if a new handler is set
window.removeEventListener('visibilitychange', listener)
}
}
return
}
}
protected onSubscribe(): void {
if (!this.#cleanup) {
this.setEventListener(this.#setup)
}
}
protected onUnsubscribe() {
if (!this.hasListeners()) {
this.#cleanup?.()
this.#cleanup = undefined
}
}
setEventListener(setup: SetupFn): void {
this.#setup = setup
this.#cleanup?.()
this.#cleanup = setup((focused) => {
if (typeof focused === 'boolean') {
this.setFocused(focused)
} else {
this.onFocus()
}
})
}
setFocused(focused?: boolean): void {
const changed = this.#focused !== focused
if (changed) {
this.#focused = focused
this.onFocus()
}
}
onFocus(): void {
const isFocused = this.isFocused()
this.listeners.forEach((listener) => {
listener(isFocused)
})
}
isFocused(): boolean {
if (typeof this.#focused === 'boolean') {
return this.#focused
}
// document global can be unavailable in react native
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
return globalThis.document?.visibilityState !== 'hidden'
}
}
export const focusManager = new FocusManager()
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