/**
 * @license
 * Copyright 2018 Google LLC
 *
 * 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 { OnlineState } from '../core/types';
import { AsyncQueue } from '../util/async_queue';
import { FirestoreError } from '../util/error';
/**
 * A component used by the RemoteStore to track the OnlineState (that is,
 * whether or not the client as a whole should be considered to be online or
 * offline), implementing the appropriate heuristics.
 *
 * In particular, when the client is trying to connect to the backend, we
 * allow up to MAX_WATCH_STREAM_FAILURES within ONLINE_STATE_TIMEOUT_MS for
 * a connection to succeed. If we have too many failures or the timeout elapses,
 * then we set the OnlineState to Offline, and the client will behave as if
 * it is offline (get()s will return cached data, etc.).
 */
export declare class OnlineStateTracker {
    private asyncQueue;
    private onlineStateHandler;
    /** The current OnlineState. */
    private state;
    /**
     * A count of consecutive failures to open the stream. If it reaches the
     * maximum defined by MAX_WATCH_STREAM_FAILURES, we'll set the OnlineState to
     * Offline.
     */
    private watchStreamFailures;
    /**
     * A timer that elapses after ONLINE_STATE_TIMEOUT_MS, at which point we
     * transition from OnlineState.Unknown to OnlineState.Offline without waiting
     * for the stream to actually fail (MAX_WATCH_STREAM_FAILURES times).
     */
    private onlineStateTimer;
    /**
     * Whether the client should log a warning message if it fails to connect to
     * the backend (initially true, cleared after a successful stream, or if we've
     * logged the message already).
     */
    private shouldWarnClientIsOffline;
    constructor(asyncQueue: AsyncQueue, onlineStateHandler: (onlineState: OnlineState) => void);
    /**
     * Called by RemoteStore when a watch stream is started (including on each
     * backoff attempt).
     *
     * If this is the first attempt, it sets the OnlineState to Unknown and starts
     * the onlineStateTimer.
     */
    handleWatchStreamStart(): void;
    /**
     * Updates our OnlineState as appropriate after the watch stream reports a
     * failure. The first failure moves us to the 'Unknown' state. We then may
     * allow multiple failures (based on MAX_WATCH_STREAM_FAILURES) before we
     * actually transition to the 'Offline' state.
     */
    handleWatchStreamFailure(error: FirestoreError): void;
    /**
     * Explicitly sets the OnlineState to the specified state.
     *
     * Note that this resets our timers / failure counters, etc. used by our
     * Offline heuristics, so must not be used in place of
     * handleWatchStreamStart() and handleWatchStreamFailure().
     */
    set(newState: OnlineState): void;
    private setAndBroadcast;
    private logClientOfflineWarningIfNecessary;
    private clearOnlineStateTimer;
}