comment + remove action from outstanding get

Author: jmwski

firebase-database/src/main/java/com/google/firebase/database/connection/PersistentConnectionImpl.java

@@ -115,21 +115,15 @@ public String toString() {
   private static class OutstandingGet {
     private final Map<String, Object> request;
     private final ConnectionRequestCallback onComplete;
-    private final String action;
     private boolean sent;
 
     private OutstandingGet(
         String action, Map<String, Object> request, ConnectionRequestCallback onComplete) {
-      this.action = action;
       this.request = request;
       this.onComplete = onComplete;
       this.sent = false;
     }
 
-    private String getAction() {
-      return action;
-    }
-
     private ConnectionRequestCallback getOnComplete() {
       return onComplete;
     }
@@ -1172,7 +1166,7 @@ private void sendGet(final Long readId) {
       }
     }
     sendAction(
-        get.getAction(),
+        REQUEST_ACTION_GET,
         get.getRequest(),
         new ConnectionRequestCallback() {
           @Override

firebase-database/src/main/java/com/google/firebase/database/core/Repo.java

@@ -467,6 +467,29 @@ public void onRequestResult(String optErrorCode, String optErrorMessage) {
     this.rerunTransactions(affectedPath);
   }
 
+  /**
+   * The purpose of `getValue` is to return the latest known value satisfying `query`.
+   *
+   * <p>If the client is connected, this method will send a request to the server. If the client is
+   * not connected, then either:
+   *
+   * <p>1. The client was once connected, but not anymore. 2. The client has never connected, this
+   * is the first operation this repo is handling.
+   *
+   * <p>In case (1), it's possible that the client still has an active listener, with cached data.
+   * Since this is the latest known value satisfying the query, that's what getValue will return. If
+   * there is no cached data, `getValue` surfaces an "offline" error.
+   *
+   * <p>In case (2), `getValue` will trigger a time-limited connection attempt. If the client is
+   * unable to connect to the server, the will surface an "offline" error because there cannot be
+   * any cached data. On the other hand, if the client is able to connect, `getValue` will return
+   * the server's value for the query, if one exists.
+   *
+   * <p>`getValue` updates the client's persistence cache whenever it's able to retrieve a new
+   * server value. It does this by installing a short-lived tracked query.
+   *
+   * @param query - The query to surface a value for.
+   */
   public Task<DataSnapshot> getValue(Query query) {
     TaskCompletionSource<DataSnapshot> source = new TaskCompletionSource<>();
     this.scheduleNow(