Make local store final again, and take steps towards extracting logic about user state into a separate class.

Author: tom-andersen

firebase-firestore/src/main/java/com/google/firebase/firestore/local/IndexBackfiller.java

@@ -39,12 +39,12 @@ public class IndexBackfiller {
 
   private final Scheduler scheduler;
   private final Persistence persistence;
-  private final LocalStore localStore;
+  private final UserComponents components;
   private int maxDocumentsToProcess = MAX_DOCUMENTS_TO_PROCESS;
 
-  public IndexBackfiller(Persistence persistence, AsyncQueue asyncQueue, LocalStore localStore) {
+  public IndexBackfiller(Persistence persistence, AsyncQueue asyncQueue, UserComponents components) {
     this.persistence = persistence;
-    this.localStore = localStore;
+    this.components = components;
     this.scheduler = new Scheduler(asyncQueue);
   }
 
@@ -92,7 +92,7 @@ public int backfill() {
 
   /** Writes index entries until the cap is reached. Returns the number of documents processed. */
   private int writeIndexEntries() {
-    IndexManager indexManager = localStore.getIndexManager();
+    IndexManager indexManager = components.getIndexManager();
     Set<String> processedCollectionGroups = new HashSet<>();
     int documentsRemaining = maxDocumentsToProcess;
     while (documentsRemaining > 0) {
@@ -112,8 +112,8 @@ private int writeIndexEntries() {
    */
   private int writeEntriesForCollectionGroup(
       String collectionGroup, int documentsRemainingUnderCap) {
-    IndexManager indexManager = localStore.getIndexManager();
-    LocalDocumentsView localDocumentsView = localStore.getLocalDocuments();
+    IndexManager indexManager = components.getIndexManager();
+    LocalDocumentsView localDocumentsView = components.getLocalDocuments();
     // Use the earliest offset of all field indexes to query the local cache.
     IndexOffset existingOffset = indexManager.getMinOffset(collectionGroup);
 

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LocalStore.java

@@ -99,7 +99,7 @@
  * <p>The LocalStore must be able to efficiently execute queries against its local cache of the
  * documents, to provide the initial set of results before any remote changes have been received.
  */
-public class LocalStore implements BundleCallback {
+public final class LocalStore implements BundleCallback, UserComponents {
   /**
    * The maximum time to leave a resume token buffered without writing it out. This value is
    * arbitrary: it's long enough to avoid several writes (possibly indefinitely if updates come more
@@ -192,10 +192,12 @@ private void startMutationQueue() {
     persistence.runTransaction("Start MutationQueue", () -> mutationQueue.start());
   }
 
+  @Override
   public IndexManager getIndexManager() {
     return indexManager;
   }
 
+  @Override
   public LocalDocumentsView getLocalDocuments() {
     return localDocuments;
   }

firebase-firestore/src/main/java/com/google/firebase/firestore/local/UserComponents.java

@@ -0,0 +1,14 @@
+package com.google.firebase.firestore.local;
+
+/**
+ * Components that depends on user identity.
+ *
+ * To avoid holding a direct reference to instances, implementation will provide instances that
+ * are updated according to user changes. This will require instantiating new instances, so clients
+ * should never retain a copy, but instead always use get methods for the most up to date instance.
+ */
+public interface UserComponents {
+    IndexManager getIndexManager();
+
+    LocalDocumentsView getLocalDocuments();
+}

firebase-firestore/src/test/java/com/google/firebase/firestore/local/IndexBackfillerTest.java

@@ -85,10 +85,18 @@ public void setUp() {
             persistence.getMutationQueue(User.UNAUTHENTICATED, indexManager),
             documentOverlayCache,
             indexManager);
-    LocalStore localStore = mock(LocalStore.class);
-    when(localStore.getIndexManager()).thenReturn(indexManager);
-    when(localStore.getLocalDocuments()).thenReturn(localDocumentsView);
-    backfiller = new IndexBackfiller(persistence, new AsyncQueue(), localStore);
+    UserComponents components = new UserComponents() {
+      @Override
+      public IndexManager getIndexManager() {
+        return indexManager;
+      }
+
+      @Override
+      public LocalDocumentsView getLocalDocuments() {
+        return localDocumentsView;
+      }
+    };
+    backfiller = new IndexBackfiller(persistence, new AsyncQueue(), components);
   }
 
   @After