/**
 * Copyright (c) 2025 Databricks Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import IClientContext from '../contracts/IClientContext';
import IAuthentication from '../connection/contracts/IAuthentication';
export interface FeatureFlagContext {
    telemetryEnabled?: boolean;
    lastFetched?: Date;
    refCount: number;
    cacheDuration: number;
}
/**
 * Per-host feature-flag cache used to gate telemetry emission. Responsibilities:
 *   - dedupe in-flight fetches (thundering-herd protection);
 *   - ref-count so context goes away when the last consumer closes;
 *   - clamp server-provided TTL into a safe band.
 *
 * Shares HTTP plumbing (agent, user agent) with DatabricksTelemetryExporter.
 * Consumer wiring lands in a later PR in this stack (see PR description).
 */
export default class FeatureFlagCache {
    private context;
    private authProvider?;
    private contexts;
    private fetchPromises;
    private readonly userAgent;
    private readonly CACHE_DURATION_MS;
    private readonly MIN_CACHE_DURATION_S;
    private readonly MAX_CACHE_DURATION_S;
    private readonly FEATURE_FLAG_NAME;
    constructor(context: IClientContext, authProvider?: IAuthentication | undefined);
    getOrCreateContext(host: string): FeatureFlagContext;
    releaseContext(host: string): void;
    isTelemetryEnabled(host: string): Promise<boolean>;
    /**
     * Strips the `-oss` suffix the feature-flag API does not accept. The server
     * keys off the SemVer triplet only, so anything appended would 404.
     */
    private getDriverVersion;
    private fetchFeatureFlag;
    /**
     * Retries transient network errors once before giving up. Without a retry
     * a single hiccup would leave telemetry disabled for the full cache TTL
     * (15 min). One retry gives an ephemeral DNS / connection-reset failure
     * a second chance without pushing sustained load at a broken endpoint.
     */
    private fetchWithRetry;
    private getAuthHeaders;
}