Sync: Attachment Store APIs for accessing attachment metadata

Introduced two new API methods to AttachmentStoreBase:
- ReadMetadata
- ReadAllMetadata

Added unimplemented overrides for these two methods into 5 classes that
derive from AttachmentStoreBase. For now the only class that has a real
implementation and unit test coverage of the new methods
is AttachmentStoreHandle.
I'll provide implementation and test coverage for all other classes
in the next change.

BUG=435205

Review URL: https://codereview.chromium.org/736093003

Cr-Commit-Position: refs/heads/master@{#305168}

15 files changed, 214 insertions, 0 deletions

diff --git a/sync/BUILD.gn b/sync/BUILD.gn
index 237ffe6..67b12b3 100644
--- a/sync/BUILD.gn
+++ b/sync/BUILD.gn
@@ -18,6 +18,8 @@ source_set("sync_core") {
     "api/attachments/attachment.h",
     "api/attachments/attachment_id.cc",
     "api/attachments/attachment_id.h",
+    "api/attachments/attachment_metadata.cc",
+    "api/attachments/attachment_metadata.h",
     "api/attachments/attachment_store.cc",
     "api/attachments/attachment_store.h",
     "api/string_ordinal.h",
@@ -548,6 +550,7 @@ static_library("test_support_sync_api") {
 test("sync_unit_tests") {
   sources = [
     "api/attachments/attachment_id_unittest.cc",
+    "api/attachments/attachment_metadata_unittest.cc",
     "api/attachments/attachment_unittest.cc",
     "api/sync_change_unittest.cc",
     "api/sync_data_unittest.cc",
diff --git a/sync/api/attachments/attachment_metadata.cc b/sync/api/attachments/attachment_metadata.cc
new file mode 100644
index 0000000..202de23
--- /dev/null
+++ b/sync/api/attachments/attachment_metadata.cc
@@ -0,0 +1,24 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sync/api/attachments/attachment_metadata.h"
+
+namespace syncer {
+
+AttachmentMetadata::AttachmentMetadata(const AttachmentId& id, size_t size)
+    : id_(id), size_(size) {
+}
+
+AttachmentMetadata::~AttachmentMetadata() {
+}
+
+const AttachmentId& AttachmentMetadata::GetId() const {
+  return id_;
+}
+
+size_t AttachmentMetadata::GetSize() const {
+  return size_;
+}
+
+}  // namespace syncer
diff --git a/sync/api/attachments/attachment_metadata.h b/sync/api/attachments/attachment_metadata.h
new file mode 100644
index 0000000..10761f8
--- /dev/null
+++ b/sync/api/attachments/attachment_metadata.h
@@ -0,0 +1,41 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SYNC_API_ATTACHMENTS_ATTACHMENT_METADATA_H_
+#define SYNC_API_ATTACHMENTS_ATTACHMENT_METADATA_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "sync/api/attachments/attachment_id.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+// This class represents immutable Attachment metadata.
+//
+// It is OK to copy and return AttachmentMetadata by value.
+class SYNC_EXPORT AttachmentMetadata {
+ public:
+  AttachmentMetadata(const AttachmentId& id, size_t size);
+  ~AttachmentMetadata();
+
+  // Default copy and assignment are welcome.
+
+  // Returns this attachment's id.
+  const AttachmentId& GetId() const;
+
+  // Returns this attachment's size in bytes.
+  size_t GetSize() const;
+
+ private:
+  AttachmentId id_;
+  size_t size_;
+};
+
+typedef std::vector<syncer::AttachmentMetadata> AttachmentMetadataList;
+
+}  // namespace syncer
+
+#endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_METADATA_H_
diff --git a/sync/api/attachments/attachment_metadata_unittest.cc b/sync/api/attachments/attachment_metadata_unittest.cc
new file mode 100644
index 0000000..06477d0
--- /dev/null
+++ b/sync/api/attachments/attachment_metadata_unittest.cc
@@ -0,0 +1,21 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sync/api/attachments/attachment_metadata.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace syncer {
+
+class AttachmentMetadataTest : public testing::Test {};
+
+TEST_F(AttachmentMetadataTest, Create) {
+  AttachmentId id = AttachmentId::Create();
+  size_t size = 42;
+  AttachmentMetadata metadata(id, size);
+  EXPECT_EQ(metadata.GetId(), id);
+  EXPECT_EQ(metadata.GetSize(), size);
+}
+
+}  // namespace syncer
diff --git a/sync/api/attachments/attachment_store.h b/sync/api/attachments/attachment_store.h
index 3c41a27..6c7791a 100644
--- a/sync/api/attachments/attachment_store.h
+++ b/sync/api/attachments/attachment_store.h
@@ -10,6 +10,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "sync/api/attachments/attachment.h"
 #include "sync/api/attachments/attachment_id.h"
+#include "sync/api/attachments/attachment_metadata.h"
 #include "sync/base/sync_export.h"
 
 namespace base {
@@ -42,6 +43,9 @@ class SYNC_EXPORT AttachmentStoreBase {
                               scoped_ptr<AttachmentIdList>)> ReadCallback;
   typedef base::Callback<void(const Result&)> WriteCallback;
   typedef base::Callback<void(const Result&)> DropCallback;
+  typedef base::Callback<void(const Result&,
+                              scoped_ptr<AttachmentMetadataList>)>
+      ReadMetadataCallback;
 
   AttachmentStoreBase();
   virtual ~AttachmentStoreBase();
@@ -84,6 +88,21 @@ class SYNC_EXPORT AttachmentStoreBase {
   // successfully.
   virtual void Drop(const AttachmentIdList& ids,
                     const DropCallback& callback) = 0;
+
+  // Asynchronously reads metadata for the attachments identified by |ids|.
+  //
+  // |callback| will be invoked when finished. AttachmentStore will attempt to
+  // read metadata for all attachments specified in ids. If any of the
+  // metadata entries do not exist or could not be read, |callback|'s Result
+  // will be UNSPECIFIED_ERROR.
+  virtual void ReadMetadata(const AttachmentIdList& ids,
+                            const ReadMetadataCallback& callback) = 0;
+
+  // Asynchronously reads metadata for all attachments in the store.
+  //
+  // |callback| will be invoked when finished. If any of the metadata entries
+  // could not be read, |callback|'s Result will be UNSPECIFIED_ERROR.
+  virtual void ReadAllMetadata(const ReadMetadataCallback& callback) = 0;
 };
 
 // AttachmentStore is an interface exposed to data type and AttachmentService
diff --git a/sync/internal_api/attachments/attachment_service_impl_unittest.cc b/sync/internal_api/attachments/attachment_service_impl_unittest.cc
index db0cff3..b83af16 100644
--- a/sync/internal_api/attachments/attachment_service_impl_unittest.cc
+++ b/sync/internal_api/attachments/attachment_service_impl_unittest.cc
@@ -41,6 +41,15 @@ class MockAttachmentStore : public AttachmentStore,
     NOTREACHED();
   }
 
+  void ReadMetadata(const AttachmentIdList& ids,
+                    const ReadMetadataCallback& callback) override {
+    NOTREACHED();
+  }
+
+  void ReadAllMetadata(const ReadMetadataCallback& callback) override {
+    NOTREACHED();
+  }
+
   // Respond to Read request. Attachments found in local_attachments should be
   // returned, everything else should be reported unavailable.
   void RespondToRead(const AttachmentIdSet& local_attachments) {
diff --git a/sync/internal_api/attachments/attachment_store_handle.cc b/sync/internal_api/attachments/attachment_store_handle.cc
index bfb637a..d770b6a 100644
--- a/sync/internal_api/attachments/attachment_store_handle.cc
+++ b/sync/internal_api/attachments/attachment_store_handle.cc
@@ -67,4 +67,20 @@ void AttachmentStoreHandle::Drop(const AttachmentIdList& ids,
                                             callback));
 }
 
+void AttachmentStoreHandle::ReadMetadata(const AttachmentIdList& ids,
+                                         const ReadMetadataCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBase::ReadMetadata,
+                            base::Unretained(backend_.get()), ids, callback));
+}
+
+void AttachmentStoreHandle::ReadAllMetadata(
+    const ReadMetadataCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  backend_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AttachmentStoreBase::ReadAllMetadata,
+                            base::Unretained(backend_.get()), callback));
+}
+
 }  // namespace syncer
diff --git a/sync/internal_api/attachments/attachment_store_handle_unittest.cc b/sync/internal_api/attachments/attachment_store_handle_unittest.cc
index 637e374..0764ee0 100644
--- a/sync/internal_api/attachments/attachment_store_handle_unittest.cc
+++ b/sync/internal_api/attachments/attachment_store_handle_unittest.cc
@@ -24,10 +24,14 @@ class MockAttachmentStore : public AttachmentStoreBase {
   MockAttachmentStore(const base::Closure& read_called,
                       const base::Closure& write_called,
                       const base::Closure& drop_called,
+                      const base::Closure& read_metadata_called,
+                      const base::Closure& read_all_metadata_called,
                       const base::Closure& dtor_called)
       : read_called_(read_called),
         write_called_(write_called),
         drop_called_(drop_called),
+        read_metadata_called_(read_metadata_called),
+        read_all_metadata_called_(read_all_metadata_called),
         dtor_called_(dtor_called) {}
 
   ~MockAttachmentStore() override { dtor_called_.Run(); }
@@ -47,9 +51,20 @@ class MockAttachmentStore : public AttachmentStoreBase {
     drop_called_.Run();
   }
 
+  void ReadMetadata(const AttachmentIdList& ids,
+                    const ReadMetadataCallback& callback) override {
+    read_metadata_called_.Run();
+  }
+
+  void ReadAllMetadata(const ReadMetadataCallback& callback) override {
+    read_all_metadata_called_.Run();
+  }
+
   base::Closure read_called_;
   base::Closure write_called_;
   base::Closure drop_called_;
+  base::Closure read_metadata_called_;
+  base::Closure read_all_metadata_called_;
   base::Closure dtor_called_;
 };
 
@@ -61,6 +76,8 @@ class AttachmentStoreHandleTest : public testing::Test {
       : read_call_count_(0),
         write_call_count_(0),
         drop_call_count_(0),
+        read_metadata_call_count_(0),
+        read_all_metadata_call_count_(0),
         dtor_call_count_(0) {}
 
   virtual void SetUp() {
@@ -71,6 +88,10 @@ class AttachmentStoreHandleTest : public testing::Test {
                    base::Unretained(this)),
         base::Bind(&AttachmentStoreHandleTest::DropCalled,
                    base::Unretained(this)),
+        base::Bind(&AttachmentStoreHandleTest::ReadMetadataCalled,
+                   base::Unretained(this)),
+        base::Bind(&AttachmentStoreHandleTest::ReadAllMetadataCalled,
+                   base::Unretained(this)),
         base::Bind(&AttachmentStoreHandleTest::DtorCalled,
                    base::Unretained(this))));
     attachment_store_handle_ = new AttachmentStoreHandle(
@@ -87,12 +108,21 @@ class AttachmentStoreHandleTest : public testing::Test {
     NOTREACHED();
   }
 
+  static void ReadMetadataDone(const AttachmentStore::Result& result,
+                               scoped_ptr<AttachmentMetadataList> metadata) {
+    NOTREACHED();
+  }
+
   void ReadCalled() { ++read_call_count_; }
 
   void WriteCalled() { ++write_call_count_; }
 
   void DropCalled() { ++drop_call_count_; }
 
+  void ReadMetadataCalled() { ++read_metadata_call_count_; }
+
+  void ReadAllMetadataCalled() { ++read_all_metadata_call_count_; }
+
   void DtorCalled() { ++dtor_call_count_; }
 
   void RunMessageLoop() {
@@ -105,6 +135,8 @@ class AttachmentStoreHandleTest : public testing::Test {
   int read_call_count_;
   int write_call_count_;
   int drop_call_count_;
+  int read_metadata_call_count_;
+  int read_all_metadata_call_count_;
   int dtor_call_count_;
 };
 
@@ -131,6 +163,18 @@ TEST_F(AttachmentStoreHandleTest, MethodsCalled) {
   RunMessageLoop();
   EXPECT_EQ(drop_call_count_, 1);
 
+  attachment_store_handle_->ReadMetadata(
+      ids, base::Bind(&AttachmentStoreHandleTest::ReadMetadataDone));
+  EXPECT_EQ(read_metadata_call_count_, 0);
+  RunMessageLoop();
+  EXPECT_EQ(read_metadata_call_count_, 1);
+
+  attachment_store_handle_->ReadAllMetadata(
+      base::Bind(&AttachmentStoreHandleTest::ReadMetadataDone));
+  EXPECT_EQ(read_all_metadata_call_count_, 0);
+  RunMessageLoop();
+  EXPECT_EQ(read_all_metadata_call_count_, 1);
+
   // Releasing referehce to AttachmentStoreHandle should result in
   // MockAttachmentStore being deleted on backend loop.
   attachment_store_handle_ = NULL;
diff --git a/sync/internal_api/attachments/in_memory_attachment_store.cc b/sync/internal_api/attachments/in_memory_attachment_store.cc
index c1e366d..6dbc4fa 100644
--- a/sync/internal_api/attachments/in_memory_attachment_store.cc
+++ b/sync/internal_api/attachments/in_memory_attachment_store.cc
@@ -77,4 +77,17 @@ void InMemoryAttachmentStore::Drop(const AttachmentIdList& ids,
   callback_task_runner_->PostTask(FROM_HERE, base::Bind(callback, result));
 }
 
+void InMemoryAttachmentStore::ReadMetadata(
+    const AttachmentIdList& ids,
+    const ReadMetadataCallback& callback) {
+  // TODO(stanisc): implement this.
+  NOTIMPLEMENTED();
+}
+
+void InMemoryAttachmentStore::ReadAllMetadata(
+    const ReadMetadataCallback& callback) {
+  // TODO(stanisc): implement this.
+  NOTIMPLEMENTED();
+}
+
 }  // namespace syncer
diff --git a/sync/internal_api/attachments/on_disk_attachment_store.cc b/sync/internal_api/attachments/on_disk_attachment_store.cc
index 9af3104..76f96bc 100644
--- a/sync/internal_api/attachments/on_disk_attachment_store.cc
+++ b/sync/internal_api/attachments/on_disk_attachment_store.cc
@@ -157,6 +157,18 @@ void OnDiskAttachmentStore::Drop(const AttachmentIdList& ids,
   callback_task_runner_->PostTask(FROM_HERE, base::Bind(callback, result_code));
 }
 
+void OnDiskAttachmentStore::ReadMetadata(const AttachmentIdList& ids,
+                                         const ReadMetadataCallback& callback) {
+  // TODO(stanisc): implement this.
+  NOTIMPLEMENTED();
+}
+
+void OnDiskAttachmentStore::ReadAllMetadata(
+    const ReadMetadataCallback& callback) {
+  // TODO(stanisc): implement this.
+  NOTIMPLEMENTED();
+}
+
 AttachmentStore::Result OnDiskAttachmentStore::OpenOrCreate(
     const base::FilePath& path) {
   DCHECK(CalledOnValidThread());
diff --git a/sync/internal_api/public/attachments/attachment_store_handle.h b/sync/internal_api/public/attachments/attachment_store_handle.h
index 012a603..d30e047 100644
--- a/sync/internal_api/public/attachments/attachment_store_handle.h
+++ b/sync/internal_api/public/attachments/attachment_store_handle.h
@@ -45,6 +45,9 @@ class SYNC_EXPORT AttachmentStoreHandle : public AttachmentStore,
   void Write(const AttachmentList& attachments,
              const WriteCallback& callback) override;
   void Drop(const AttachmentIdList& id, const DropCallback& callback) override;
+  void ReadMetadata(const AttachmentIdList& ids,
+                    const ReadMetadataCallback& callback) override;
+  void ReadAllMetadata(const ReadMetadataCallback& callback) override;
 
  private:
   ~AttachmentStoreHandle() override;
diff --git a/sync/internal_api/public/attachments/in_memory_attachment_store.h b/sync/internal_api/public/attachments/in_memory_attachment_store.h
index c586ef0..d0b8dda 100644
--- a/sync/internal_api/public/attachments/in_memory_attachment_store.h
+++ b/sync/internal_api/public/attachments/in_memory_attachment_store.h
@@ -30,6 +30,9 @@ class SYNC_EXPORT InMemoryAttachmentStore : public AttachmentStoreBase,
   void Write(const AttachmentList& attachments,
              const WriteCallback& callback) override;
   void Drop(const AttachmentIdList& ids, const DropCallback& callback) override;
+  void ReadMetadata(const AttachmentIdList& ids,
+                    const ReadMetadataCallback& callback) override;
+  void ReadAllMetadata(const ReadMetadataCallback& callback) override;
 
  private:
   scoped_refptr<base::SingleThreadTaskRunner> callback_task_runner_;
diff --git a/sync/internal_api/public/attachments/on_disk_attachment_store.h b/sync/internal_api/public/attachments/on_disk_attachment_store.h
index e8d6096..4d7c0fd 100644
--- a/sync/internal_api/public/attachments/on_disk_attachment_store.h
+++ b/sync/internal_api/public/attachments/on_disk_attachment_store.h
@@ -41,6 +41,9 @@ class SYNC_EXPORT OnDiskAttachmentStore : public AttachmentStoreBase,
   void Write(const AttachmentList& attachments,
              const WriteCallback& callback) override;
   void Drop(const AttachmentIdList& ids, const DropCallback& callback) override;
+  void ReadMetadata(const AttachmentIdList& ids,
+                    const ReadMetadataCallback& callback) override;
+  void ReadAllMetadata(const ReadMetadataCallback& callback) override;
 
   // Opens leveldb database at |path|. It will create directory and database if
   // it doesn't exist.
diff --git a/sync/sync.gyp b/sync/sync.gyp
index f49c8f8..7544fbf 100644
--- a/sync/sync.gyp
+++ b/sync/sync.gyp
@@ -63,6 +63,8 @@
         'api/attachments/attachment.h',
         'api/attachments/attachment_id.cc',
         'api/attachments/attachment_id.h',
+        'api/attachments/attachment_metadata.cc',
+        'api/attachments/attachment_metadata.h',
         'api/attachments/attachment_store.cc',
         'api/attachments/attachment_store.h',
         'api/string_ordinal.h',
diff --git a/sync/sync_tests.gypi b/sync/sync_tests.gypi
index 3eda426..b1ef9cf 100644
--- a/sync/sync_tests.gypi
+++ b/sync/sync_tests.gypi
@@ -260,6 +260,7 @@
       ],
       'sources': [
         'api/attachments/attachment_id_unittest.cc',
+        'api/attachments/attachment_metadata_unittest.cc',
         'api/attachments/attachment_unittest.cc',
         'api/sync_change_unittest.cc',
         'api/sync_data_unittest.cc',