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| import { useState, useEffect } from 'preact/hooks'; | |
| const cache = new Map<string, any>(); | |
| const inflight = new Map<string, Promise<any>>(); | |
| export interface SWRResponse<T> { | |
| data: T | undefined; | |
| error: Error | null; | |
| loading: boolean; | |
| } | |
| export function useSWR<T>(key: string | null, fetcher: (key: string) => Promise<T>): SWRResponse<T> { | |
| const [data, setData] = useState<T | undefined>(cache.get(key ?? '')); | |
| const [error, setError] = useState<Error | null>(null); | |
| const [loading, setLoading] = useState(!cache.has(key ?? '')); | |
| useEffect(() => { | |
| if (!key) return; | |
| (async () => { | |
| if (inflight.has(key)) { | |
| try { | |
| const result = await inflight.get(key); | |
| setData(result); | |
| setError(null); | |
| } catch (err) { | |
| setError(err as Error); | |
| } finally { | |
| setLoading(false); | |
| } | |
| return; | |
| } | |
| setLoading(true); | |
| const promise = fetcher(key); | |
| inflight.set(key, promise); | |
| try { | |
| const result = await promise; | |
| cache.set(key, result); | |
| setData(result); | |
| setError(null); | |
| } catch (err) { | |
| setError(err as Error); | |
| } finally { | |
| setLoading(false); | |
| inflight.delete(key); | |
| } | |
| })(); | |
| }, [key]); | |
| return { data, error, loading }; | |
| } |
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