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Co-authored-by: gatzjames <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,170 @@ | ||
| import { useCallback, useEffect, useState, useSyncExternalStore } from 'react'; | ||
|
|
||
| interface CacheEntry { | ||
| value: Promise<string> | string; | ||
| timestamp: number; | ||
| version?: string; | ||
| subscribers: (() => void)[]; | ||
| } | ||
|
|
||
| // Adopted from https://css-tricks.com/pre-caching-image-with-react-suspense/ | ||
| class ImageCache { | ||
| __cache: Record<string, CacheEntry> = {}; | ||
| ttl: number; | ||
|
|
||
| constructor({ ttl }: { ttl: number }) { | ||
| this.ttl = ttl; | ||
| } | ||
|
|
||
| read(base: string, version: string) { | ||
| const value = `${base}${version ? `?${version}` : ''}`; | ||
| const now = Date.now(); | ||
| if (this.__cache[base] && this.__cache[base].value instanceof Promise) { | ||
| // If the value is a Promise, throw it to indicate that the cache is still loading | ||
| throw this.__cache[base].value; | ||
| } else if ( | ||
| this.__cache[base] && | ||
| (this.__cache[base].version === version || | ||
| now - this.__cache[base].timestamp < this.ttl) | ||
| ) { | ||
| // If the value is an HTMLImageElement, the version matches, and hasn't expired, return it | ||
| return this.__cache[base].value; | ||
| } else { | ||
| // Otherwise, load the image and add it to the cache | ||
| const promise = new Promise<string>(resolve => { | ||
| const img = new Image(); | ||
| img.onload = () => { | ||
| if (!this.__cache[base]) { | ||
| this.__cache[base] = { | ||
| value, | ||
| timestamp: now, | ||
| version, | ||
| subscribers: [], | ||
| }; | ||
| } else { | ||
| this.__cache[base].value = value; | ||
| this.__cache[base].timestamp = now; | ||
| this.__cache[base].version = version; | ||
| } | ||
| resolve(value); | ||
| // Notify all subscribers | ||
| if (!this.__cache[base].subscribers) { | ||
| this.__cache[base].subscribers = []; | ||
| } | ||
| this.__cache[base].subscribers.forEach(callback => callback()); | ||
| }; | ||
| img.onerror = () => { | ||
| // infinitely suspended if the image fails to load | ||
| this.__cache[base].value = new Promise(() => {}); | ||
| throw this.__cache[base].value; | ||
| }; | ||
| img.src = value; | ||
| }); | ||
| this.__cache[base].value = promise; | ||
| this.__cache[base].timestamp = now; | ||
| this.__cache[base].version = version; | ||
| if (!this.__cache[base].subscribers) { | ||
| this.__cache[base].subscribers = []; | ||
| } | ||
| throw promise; | ||
| } | ||
| } | ||
|
|
||
| subscribe(base: string, callback: () => void) { | ||
| if (!this.__cache[base]) { | ||
| this.__cache[base] = { | ||
| value: new Promise(() => {}), | ||
| timestamp: 0, | ||
| subscribers: [], | ||
| }; | ||
| } | ||
| if (!this.__cache[base].subscribers) { | ||
| this.__cache[base].subscribers = []; | ||
| } | ||
| if (!this.__cache[base].subscribers.includes(callback)) { | ||
| this.__cache[base].subscribers.push(callback); | ||
| } | ||
| return () => { | ||
| if (this.__cache[base] && this.__cache[base].subscribers) { | ||
| this.__cache[base].subscribers = this.__cache[base].subscribers.filter( | ||
| cb => cb !== callback | ||
| ); | ||
| } | ||
| }; | ||
| } | ||
|
|
||
| invalidate(src: string) { | ||
| const [base, version] = src.split('?'); | ||
| if (this.__cache[base] && this.__cache[base].version !== version) { | ||
| this.__cache[base].timestamp = 0; | ||
| this.read(base, version); | ||
| } | ||
| } | ||
|
|
||
| invalidateAll() { | ||
| Object.keys(this.__cache).forEach(src => this.invalidate(src)); | ||
| } | ||
| } | ||
|
|
||
| export function useImageCache(src: string, cache: ImageCache): string { | ||
| const [base, version] = src.split('?'); | ||
| const [imageSrc, setImageSrc] = useState<string | null>(null); | ||
|
|
||
| const subscribe = useCallback( | ||
| (callback: () => void) => { | ||
| return cache.subscribe(base, callback); | ||
| }, | ||
| [base, cache] | ||
| ); | ||
|
|
||
| const getSnapshot = () => { | ||
| try { | ||
| return cache.read(base, version); | ||
| } catch (promise) { | ||
| if (promise instanceof Promise) { | ||
| throw promise; | ||
| } | ||
| return null; | ||
| } | ||
| }; | ||
|
|
||
| const getServerSnapshot = () => null; | ||
|
|
||
| useEffect(() => { | ||
| setImageSrc(() => { | ||
| try { | ||
| const result = cache.read(base, version); | ||
| if (result instanceof Promise) { | ||
| throw result; | ||
| } | ||
|
|
||
| return result; | ||
| } catch (maybeResultPromise) { | ||
| if (maybeResultPromise instanceof Promise) { | ||
| throw maybeResultPromise; | ||
| } | ||
| return null; | ||
| } | ||
| }); | ||
| }, [cache, base, version]); | ||
|
|
||
| const cacheSrc = useSyncExternalStore( | ||
| subscribe, | ||
| getSnapshot, | ||
| getServerSnapshot | ||
| ); | ||
|
|
||
| if (typeof cacheSrc === 'string') { | ||
| return cacheSrc; | ||
| } | ||
|
|
||
| return imageSrc!; | ||
| } | ||
|
|
||
| export const avatarImageCache = new ImageCache({ | ||
| ttl: 10 * 60 * 1000, // 10 minutes | ||
| }); | ||
|
|
||
| export function useAvatarImageCache(src: string) { | ||
| return useImageCache(src, avatarImageCache); | ||
| } |