import type { Lazy } from "../../util/lazy";
export type FetchState<T> = {
    isLoading: true;
    error?: undefined;
    data?: undefined;
} | {
    isLoading: false;
    error: Error;
    data?: undefined;
} | {
    isLoading: false;
    error?: undefined;
    data: T;
};
export type UseFetchCache<T> = {
    set: (key: string, value: T) => void;
    get: (key: string) => T | undefined;
    delete: (key: string) => void;
};
export type CacheValue<T> = {
    data: T;
    error: undefined;
} | {
    data: undefined;
    error: Error;
};
export type UseFetchResult<TData> = FetchState<TData> & {
    mutate: () => void;
};
export declare const useFetchExternalCache: <TKey, TData>(key: Lazy<TKey | null | undefined>, fetcher: (args: TKey) => Promise<TData>, cache: UseFetchCache<CacheValue<TData>>) => UseFetchResult<TData>;
/**
 * キーに対応するデータを非同期に取得するためのhook
 * 同じキーに対応するデータはキャッシュされる
 * useFetchを使う限り、キャッシュはhook呼び出し単位で保持される
 * useFetchExternalCacheを使うと、キャッシュを外部で管理できる
 * @param key
 * @param fetcher
 */
export declare const useFetch: <TKey, TData>(key: Lazy<TKey | null | undefined>, fetcher: (args: TKey) => Promise<TData>) => UseFetchResult<TData>;
export declare const keyToCacheKey: (key: unknown) => string;
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