sync: Per-type update application

sync/engine/sync_directory_update_handler.cc

Index: sync/engine/sync_directory_update_handler.cc
diff --git a/sync/engine/sync_directory_update_handler.cc b/sync/engine/sync_directory_update_handler.cc
index 0d7953bb483dd1f4907fe59780fe05cb4c0847fa..1a9bd1ec6de51c5317b816d9d716220e7cc86273 100644
--- a/sync/engine/sync_directory_update_handler.cc
+++ b/sync/engine/sync_directory_update_handler.cc
@@ -4,19 +4,25 @@
 
 #include "sync/engine/sync_directory_update_handler.h"
 
+#include "sync/engine/conflict_resolver.h"
 #include "sync/engine/process_updates_util.h"
+#include "sync/engine/update_applicator.h"
 #include "sync/sessions/status_controller.h"
 #include "sync/syncable/directory.h"
 #include "sync/syncable/syncable_model_neutral_write_transaction.h"
+#include "sync/syncable/syncable_write_transaction.h"
 
 namespace syncer {
 
 using syncable::SYNCER;
 
 SyncDirectoryUpdateHandler::SyncDirectoryUpdateHandler(
-    syncable::Directory* dir, ModelType type)
+    syncable::Directory* dir,
+    ModelType type,
+    scoped_refptr<ModelSafeWorker> worker)
   : dir_(dir),
-    type_(type) {}
+    type_(type),
+    worker_(worker) {}
 
 SyncDirectoryUpdateHandler::~SyncDirectoryUpdateHandler() {}
 
@@ -34,6 +40,91 @@ void SyncDirectoryUpdateHandler::ProcessGetUpdatesResponse(
   UpdateProgressMarker(progress_marker);
 }
 
+void SyncDirectoryUpdateHandler::ApplyUpdates(
+    sessions::StatusController* status) {
+  if (IsControlType(type_)) {
+    return;  // We don't process control types here.
+  }
+
+  if (!dir_->TypeHasUnappliedUpdates(type_)) {
+    return;  // No work to do.  Skip this type.
+  }
+
+  WorkCallback c = base::Bind(
+      &SyncDirectoryUpdateHandler::ApplyUpdatesImpl,
+      // We wait until the callback is executed.  We can safely use Unretained.
+      base::Unretained(this),
+      base::Unretained(status));
+  worker_->DoWorkAndWaitUntilDone(c);
+}
+
+SyncerError SyncDirectoryUpdateHandler::ApplyUpdatesImpl(
+    sessions::StatusController* status) {
+  syncable::WriteTransaction trans(FROM_HERE, syncable::SYNCER, dir_);
+
+  std::vector<int64> handles;
+  dir_->GetUnappliedUpdateMetaHandles(
+      &trans,
+      FullModelTypeSet(type_),
+      &handles);
+
+  // First set of update application passes.
+  UpdateApplicator applicator(dir_->GetCryptographer(&trans));
+  applicator.AttemptApplications(&trans, handles);
+  status->increment_num_updates_applied_by(applicator.updates_applied());
+  status->increment_num_hierarchy_conflicts_by(
+      applicator.hierarchy_conflicts());
+  status->increment_num_encryption_conflicts_by(
+      applicator.encryption_conflicts());
+
+  if (applicator.simple_conflict_ids().size() != 0) {
+    // Resolve the simple conflicts we just detected.
+    ConflictResolver resolver;
+    resolver.ResolveConflicts(&trans,
+                              dir_->GetCryptographer(&trans),
+                              applicator.simple_conflict_ids(),
+                              status);
+
+    // Conflict resolution sometimes results in more updates to apply.
+    handles.clear();
+    dir_->GetUnappliedUpdateMetaHandles(
+        &trans,
+        FullModelTypeSet(type_),
+        &handles);
+
+    UpdateApplicator conflict_applicator(dir_->GetCryptographer(&trans));
+    conflict_applicator.AttemptApplications(&trans, handles);
+
+    // We count the number of updates from both applicator passes.
+    status->increment_num_updates_applied_by(
+        conflict_applicator.updates_applied());
+
+    // Encryption conflicts should remain unchanged by the resolution of simple
+    // conflicts.  Those can only be solved by updating our nigori key bag.
+    DCHECK_EQ(conflict_applicator.encryption_conflicts(),
+              applicator.encryption_conflicts());
+
+    // Hierarchy conflicts should also remain unchanged, for reasons that are
+    // more subtle.  Hierarchy conflicts exist when the application of a pending
+    // update from the server would make the local folder hierarchy
+    // inconsistent.  The resolution of simple conflicts could never affect the
+    // hierarchy conflicting item directly, because hierarchy conflicts are not
+    // processed by the conflict resolver.  It could, in theory, modify the
+    // local hierarchy on which hierarchy conflict detection depends.  However,
+    // the conflict resolution algorithm currently in use does not allow this.
+    DCHECK_EQ(conflict_applicator.hierarchy_conflicts(),
+              applicator.hierarchy_conflicts());
+
+    // There should be no simple conflicts remaining.  We know this because the
+    // resolver should have resolved all the conflicts we detected last time
+    // and, by the two previous assertions, that no conflicts have been
+    // downgraded from encryption or hierarchy down to simple.
+    DCHECK(conflict_applicator.simple_conflict_ids().empty());
+  }
+
+  return SYNCER_OK;
+}
+
 void SyncDirectoryUpdateHandler::UpdateSyncEntities(
     syncable::ModelNeutralWriteTransaction* trans,
     const SyncEntityList& applicable_updates,