import { type Logger } from "./logger.ts";
/**
 * How to fetch and cache a given value, as passed to {@link PollingCachedValue}.
 */
export interface PollingCachedValueOptions<ValueType> {
    /** The name of the cached value (for tracing/logs). */
    name: string;
    /** The logger to derive this value's child logger from. */
    logger: Logger;
    /** Fetches a fresh value. Rejections are retried according to the retry policy. */
    fetch: () => Promise<ValueType>;
    /**
     * The default time-to-live before the value gets refreshed, overridable per run
     * via {@link PollingCachedValue.start}.
     * If undefined the value never expires; use {@link PollingCachedValue.refresh} to clear the cache.
     */
    ttlMillis?: number;
    /** Called when a new value is cached. Use to emit changes if needed. */
    onValueCached?: (value: ValueType) => void;
    /**
     * Determines whether a non-transient error should be cached.
     * By default errors are not cached, i.e. the next attempt retries the fetch.
     */
    shouldCacheError?: (error: unknown) => boolean;
}
/**
 * Defines a generic mechanism to fetch and cache a value, refreshing it periodically.
 */
export declare class PollingCachedValue<ValueType> {
    private readonly opts;
    private cached?;
    private fetchPromise?;
    private ttlTimeoutHandle?;
    private isStopped;
    private ttlMillis?;
    private readonly logger;
    /**
     * Build a generic mechanism allowing to fetch and cache a given value.
     * @param opts - Describes what to fetch and how to cache it, see {@link PollingCachedValueOptions}.
     */
    constructor(opts: PollingCachedValueOptions<ValueType>);
    /**
     * Gets the cached value if any.
     */
    get(): ValueType | undefined;
    /**
     * Ensures that the value was fetched once before getting the actual cached value.
     */
    wait(): Promise<ValueType | undefined>;
    /**
     * Call this as early as possible and when the value can already be fetched.
     * @param ttlMillis - The time-to-live before the value gets refreshed, overriding the one
     *     given at construction. If omitted the configured default is kept.
     */
    start(ttlMillis?: number): void;
    /**
     * Call when the client is stopped, or when the cached value is no longer needed.
     */
    stop(): void;
    /**
     * Force to refresh.
     * @throws
     */
    refresh(): Promise<ValueType | undefined>;
    /**
     * Internal fetch method
     * @param force - if set to true will force a fetch of the value even if a fetch is already in progress.
     * @private
     */
    private doFetch;
    /**
     * Gracefully handle transient error retries, respect retry_after_millis for rate limits.
     * @private
     */
    private fetchWithRetryPolicy;
}
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