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/*
* Copyright 2018 Google
*
* 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 <Foundation/Foundation.h>
#import "Firestore/Source/Core/FSTTypes.h"
@class FSTDispatchQueue;
@protocol FSTOnlineStateDelegate;
NS_ASSUME_NONNULL_BEGIN
/**
* A component used by the FSTRemoteStore to track the FSTOnlineState (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
* kMaxWatchStreamFailures within kOnlineStateTimeout for a connection to succeed. If we have too
* many failures or the timeout elapses, then we set the FSTOnlineState to Offline, and
* the client will behave as if it is offline (getDocument() calls will return cached data, etc.).
*/
@interface FSTOnlineStateTracker : NSObject
- (instancetype)initWithWorkerDispatchQueue:(FSTDispatchQueue *)queue;
- (instancetype)init NS_UNAVAILABLE;
/** A delegate to be notified on FSTOnlineState changes. */
@property(nonatomic, weak) id<FSTOnlineStateDelegate> onlineStateDelegate;
/**
* Called by FSTRemoteStore when a watch stream is started (including on each backoff attempt).
*
* If this is the first attempt, it sets the FSTOnlineState to Unknown and starts the
* onlineStateTimer.
*/
- (void)handleWatchStreamStart;
/**
* Called by FSTRemoteStore when a watch stream fails.
*
* Updates our FSTOnlineState as appropriate. The first failure moves us to FSTOnlineStateUnknown.
* We then may allow multiple failures (based on kMaxWatchStreamFailures) before we actually
* transition to FSTOnlineStateOffline.
*/
- (void)handleWatchStreamFailure;
/**
* Explicitly sets the FSTOnlineState to the specified state.
*
* Note that this resets the timers / failure counters, etc. used by our Offline heuristics, so
* it must not be used in place of handleWatchStreamStart and handleWatchStreamFailure.
*/
- (void)updateState:(FSTOnlineState)newState;
@end
NS_ASSUME_NONNULL_END
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