Add 10 second timeout waiting for connection before client behaves as-if offline. (#872)

[Port of https://github.com/firebase/firebase-js-sdk/commit/0fa319e5e019dd0d40ab441d2ff9f8f6d4724e43]

* Refactored FSTOnlineState tracking out of FSTRemoteStore and into new
  FSTOnlineStateTracker component.
* Added a 10 second timeout to transition from OnlineState.Unknown to
  OnlineState.Offline rather than waiting indefinitely for the stream to
  succeed or fail.
* Removed hack to run SpecTests using an FSTDispatchQueue that wrapped
  dispatch_get_main_queue(). This was incompatible with [FSTDispatchQueue
  runDelayedCallbacksUntil:] since it queues work and blocks waiting for
  it to complete. Now spec tests create / use a proper FSTDispatchQueue.
* Added a SpecTest to verify OnlineState timeout behavior.
* Misc cleanup:
    * Renamed FSTOnlineState states: Failed => Offline, Healthy => Online
    * Renamed FSTTimerIds (ListenStreamConnection => ListenStreamConnectionBackoff)
    * Added ability to run timers from spec tests.

4 files changed, 21 insertions, 12 deletions

diff --git a/Firestore/Source/Core/FSTEventManager.mm b/Firestore/Source/Core/FSTEventManager.mm
index bc204a0..b02fc5f 100644
--- a/Firestore/Source/Core/FSTEventManager.mm
+++ b/Firestore/Source/Core/FSTEventManager.mm
@@ -169,9 +169,9 @@ NS_ASSUME_NONNULL_BEGIN
     return YES;
   }
 
-  // NOTE: We consider OnlineState.Unknown as online (it should become Failed
-  // or Online if we wait long enough).
-  BOOL maybeOnline = onlineState != FSTOnlineStateFailed;
+  // NOTE: We consider OnlineState.Unknown as online (it should become Offline or Online if we
+  // wait long enough).
+  BOOL maybeOnline = onlineState != FSTOnlineStateOffline;
   // Don't raise the event if we're online, aren't synced yet (checked
   // above) and are waiting for a sync.
   if (self.options.waitForSyncWhenOnline && maybeOnline) {
@@ -180,7 +180,7 @@ NS_ASSUME_NONNULL_BEGIN
   }
 
   // Raise data from cache if we have any documents or we are offline
-  return !snapshot.documents.isEmpty || onlineState == FSTOnlineStateFailed;
+  return !snapshot.documents.isEmpty || onlineState == FSTOnlineStateOffline;
 }
 
 - (BOOL)shouldRaiseEventForSnapshot:(FSTViewSnapshot *)snapshot {
diff --git a/Firestore/Source/Core/FSTFirestoreClient.mm b/Firestore/Source/Core/FSTFirestoreClient.mm
index fb86e0b..288cbe2 100644
--- a/Firestore/Source/Core/FSTFirestoreClient.mm
+++ b/Firestore/Source/Core/FSTFirestoreClient.mm
@@ -181,7 +181,9 @@ NS_ASSUME_NONNULL_BEGIN
                                             workerDispatchQueue:self.workerDispatchQueue
                                                     credentials:_credentialsProvider];
 
-  _remoteStore = [FSTRemoteStore remoteStoreWithLocalStore:_localStore datastore:datastore];
+  _remoteStore = [[FSTRemoteStore alloc] initWithLocalStore:_localStore
+                                                  datastore:datastore
+                                        workerDispatchQueue:self.workerDispatchQueue];
 
   _syncEngine = [[FSTSyncEngine alloc] initWithLocalStore:_localStore
                                               remoteStore:_remoteStore
diff --git a/Firestore/Source/Core/FSTTypes.h b/Firestore/Source/Core/FSTTypes.h
index 877ec94..688b2bf 100644
--- a/Firestore/Source/Core/FSTTypes.h
+++ b/Firestore/Source/Core/FSTTypes.h
@@ -65,12 +65,18 @@ typedef void (^FSTVoidMaybeDocumentArrayErrorBlock)(
 typedef void (^FSTTransactionBlock)(FSTTransaction *transaction,
                                     void (^completion)(id _Nullable, NSError *_Nullable));
 
-/** Describes the online state of the Firestore client */
+/**
+ * Describes the online state of the Firestore client. Note that this does not indicate whether
+ * or not the remote store is trying to connect or not. This is primarily used by the View /
+ * EventManager code to change their behavior while offline (e.g. get() calls shouldn't wait for
+ * data from the server and snapshot events should set metadata.isFromCache=true).
+ */
 typedef NS_ENUM(NSUInteger, FSTOnlineState) {
   /**
    * The Firestore client is in an unknown online state. This means the client is either not
    * actively trying to establish a connection or it is currently trying to establish a connection,
-   * but it has not succeeded or failed yet.
+   * but it has not succeeded or failed yet. Higher-level components should not operate in
+   * offline mode.
    */
   FSTOnlineStateUnknown,
 
@@ -79,13 +85,14 @@ typedef NS_ENUM(NSUInteger, FSTOnlineState) {
    * successful connection and there has been at least one successful message received from the
    * backends.
    */
-  FSTOnlineStateHealthy,
+  FSTOnlineStateOnline,
 
   /**
-   * The client considers itself offline. It is either trying to establish a connection but
-   * failing, or it has been explicitly marked offline via a call to `disableNetwork`.
+   * The client is either trying to establish a connection but failing, or it has been explicitly
+   * marked offline via a call to `disableNetwork`. Higher-level components should operate in
+   * offline mode.
    */
-  FSTOnlineStateFailed
+  FSTOnlineStateOffline
 };
 
 NS_ASSUME_NONNULL_END
diff --git a/Firestore/Source/Core/FSTView.mm b/Firestore/Source/Core/FSTView.mm
index d6b4558..b2a39cb 100644
--- a/Firestore/Source/Core/FSTView.mm
+++ b/Firestore/Source/Core/FSTView.mm
@@ -337,7 +337,7 @@ static NSComparisonResult FSTCompareDocumentViewChangeTypes(FSTDocumentViewChang
 }
 
 - (FSTViewChange *)applyChangedOnlineState:(FSTOnlineState)onlineState {
-  if (self.isCurrent && onlineState == FSTOnlineStateFailed) {
+  if (self.isCurrent && onlineState == FSTOnlineStateOffline) {
     // If we're offline, set `current` to NO and then call applyChanges to refresh our syncState
     // and generate an FSTViewChange as appropriate. We are guaranteed to get a new FSTTargetChange
     // that sets `current` back to YES once the client is back online.