[NTP Snippets] Persist snippets in a LevelDB instead of prefs

components/ntp_snippets/ntp_snippets_database.h

Index: components/ntp_snippets/ntp_snippets_database.h
diff --git a/components/ntp_snippets/ntp_snippets_database.h b/components/ntp_snippets/ntp_snippets_database.h
new file mode 100644
index 0000000000000000000000000000000000000000..122e0956d7da88fc39a449f393a6a71eb30e32a3
--- /dev/null
+++ b/components/ntp_snippets/ntp_snippets_database.h
@@ -0,0 +1,81 @@
+// Copyright 2016 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 COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_DATABASE_H_
+#define COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_DATABASE_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
+#include "components/leveldb_proto/proto_database.h"
+#include "components/ntp_snippets/ntp_snippet.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace ntp_snippets {
+
+class SnippetProto;
+
+class NTPSnippetsDatabase {
+ public:
+  using SnippetsLoadedCallback = base::Callback<void(NTPSnippet::PtrVector)>;
+
+  NTPSnippetsDatabase(
+      const base::FilePath& database_dir,
+      scoped_refptr<base::SequencedTaskRunner> file_task_runner);
+  ~NTPSnippetsDatabase();
+
+  // Loads all snippets from storage and passes them to |callback|. Only one
+  // concurrent fetch is supported; if there was already a fetch ongoing, the
+  // previous callback will be replaced.
+  void Load(const SnippetsLoadedCallback& callback);
+
+  // Adds or updates the given snippet.
+  void Save(const NTPSnippet& snippet);
+  // Adds or updates all the given snippets.
+  void Save(const NTPSnippet::PtrVector& snippets);
+
+  // Deletes the snippet with the given ID.
+  void Delete(const std::string& snippet_id);
+  // Deletes all the given snippets (identified by their IDs).
+  void Delete(const NTPSnippet::PtrVector& snippets);
+
+ private:
+  friend class NTPSnippetsDatabaseTest;
+
+  using KeyEntryVector =
+      leveldb_proto::ProtoDatabase<SnippetProto>::KeyEntryVector;

[Bernhard Bauer, 2016/05/25 15:01:15]

Out of curiosity: could we just use `using
leveldb_proto::ProtoDatabase<SnippetProto>::KeyEntryVector`?

[Marc Treib, 2016/05/27 14:03:12]

No - apparently that only works if leveldb_proto::ProtoDatabase<SnippetProto> is
a base class.

+
+  // Callbacks for ProtoDatabase operations.
+  void OnDatabaseInited(bool success);
+  void OnDatabaseLoaded(bool success,
+                        std::unique_ptr<std::vector<SnippetProto>> entries);
+  void OnDatabaseSaved(bool success);
+
+  void LoadImpl();
+
+  void SaveImpl(std::unique_ptr<KeyEntryVector> entries_to_save);
+
+  void DeleteImpl(std::unique_ptr<std::vector<std::string>> keys_to_remove);
+
+  std::unique_ptr<leveldb_proto::ProtoDatabase<SnippetProto>> database_;
+  bool database_inited_;

[Bernhard Bauer, 2016/05/25 15:01:15]

Nit: Can we use "initialized"?

[Marc Treib, 2016/05/27 14:03:12]

Done.

+
+  SnippetsLoadedCallback callback_;
+
+  base::WeakPtrFactory<NTPSnippetsDatabase> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(NTPSnippetsDatabase);
+};
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_DATABASE_H_