1 files changed, 110 insertions, 0 deletions
diff --git a/mobile/android/services/src/main/java/org/mozilla/gecko/sync/stage/SafeConstrainedServer11Repository.java b/mobile/android/services/src/main/java/org/mozilla/gecko/sync/stage/SafeConstrainedServer11Repository.java
new file mode 100644
index 000000000..733c887f0
--- /dev/null
+++ b/mobile/android/services/src/main/java/org/mozilla/gecko/sync/stage/SafeConstrainedServer11Repository.java
@@ -0,0 +1,110 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.sync.stage;
+
+import java.net.URISyntaxException;
+
+import org.mozilla.gecko.background.common.log.Logger;
+import org.mozilla.gecko.sync.InfoCollections;
+import org.mozilla.gecko.sync.InfoConfiguration;
+import org.mozilla.gecko.sync.InfoCounts;
+import org.mozilla.gecko.sync.JSONRecordFetcher;
+import org.mozilla.gecko.sync.net.AuthHeaderProvider;
+import org.mozilla.gecko.sync.repositories.ConstrainedServer11Repository;
+import org.mozilla.gecko.sync.repositories.Repository;
+import org.mozilla.gecko.sync.repositories.Server11RepositorySession;
+import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionCreationDelegate;
+
+import android.content.Context;
+
+/**
+ * This is a constrained repository -- one which fetches a limited number
+ * of records -- that additionally refuses to sync if the limit will
+ * be exceeded on a first sync by the number of records on the server.
+ *
+ * You must pass an {@link InfoCounts} instance, which will be interrogated
+ * in the event of a first sync.
+ *
+ * "First sync" means that our sync timestamp is not greater than zero.
+ */
+public class SafeConstrainedServer11Repository extends ConstrainedServer11Repository {
+
+  // This can be lazily evaluated if we need it.
+  private final JSONRecordFetcher countFetcher;
+
+  public SafeConstrainedServer11Repository(String collection,
+                                           String storageURL,
+                                           AuthHeaderProvider authHeaderProvider,
+                                           InfoCollections infoCollections,
+                                           InfoConfiguration infoConfiguration,
+                                           long batchLimit,
+                                           long totalLimit,
+                                           String sort,
+                                           JSONRecordFetcher countFetcher)
+    throws URISyntaxException {
+    super(collection, storageURL, authHeaderProvider, infoCollections, infoConfiguration,
+            batchLimit, totalLimit, sort);
+    if (countFetcher == null) {
+      throw new IllegalArgumentException("countFetcher must not be null");
+    }
+    this.countFetcher = countFetcher;
+  }
+
+  @Override
+  public void createSession(RepositorySessionCreationDelegate delegate,
+                            Context context) {
+    delegate.onSessionCreated(new CountCheckingServer11RepositorySession(this, this.getDefaultBatchLimit()));
+  }
+
+  public class CountCheckingServer11RepositorySession extends Server11RepositorySession {
+    private static final String LOG_TAG = "CountCheckingServer11RepositorySession";
+
+    /**
+     * The session will report no data available if this is a first sync
+     * and the server has more data available than this limit.
+     */
+    private final long fetchLimit;
+
+    public CountCheckingServer11RepositorySession(Repository repository, long fetchLimit) {
+      super(repository);
+      this.fetchLimit = fetchLimit;
+    }
+
+    @Override
+    public boolean shouldSkip() {
+      // If this is a first sync, verify that we aren't going to blow through our limit.
+      final long lastSyncTimestamp = getLastSyncTimestamp();
+      if (lastSyncTimestamp > 0) {
+        Logger.info(LOG_TAG, "Collection " + collection + " has already had a first sync: " +
+            "timestamp is " + lastSyncTimestamp  + "; " +
+            "ignoring any updated counts and syncing as usual.");
+      } else {
+        Logger.info(LOG_TAG, "Collection " + collection + " is starting a first sync; checking counts.");
+
+        final InfoCounts counts;
+        try {
+          // This'll probably be the same object, but best to obey the API.
+          counts = new InfoCounts(countFetcher.fetchBlocking());
+        } catch (Exception e) {
+          Logger.warn(LOG_TAG, "Skipping " + collection + " until we can fetch counts.", e);
+          return true;
+        }
+
+        Integer c = counts.getCount(collection);
+        if (c == null) {
+          Logger.info(LOG_TAG, "Fetched counts does not include collection " + collection + "; syncing as usual.");
+          return false;
+        }
+
+        Logger.info(LOG_TAG, "First sync for " + collection + ": " + c + " items.");
+        if (c > fetchLimit) {
+          Logger.warn(LOG_TAG, "Too many items to sync safely. Skipping.");
+          return true;
+        }
+      }
+      return super.shouldSkip();
+    }
+  }
+}