Adding a previews IO-thread blacklist

components/previews/previews_black_list.h

+// 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_PREVIEWS_PREVIEWS_BLACK_LIST_H_
+#define COMPONENTS_PREVIEWS_PREVIEWS_BLACK_LIST_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <queue>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "components/previews/previews_opt_out_store.h"
+
+namespace base {
+class Time;
+}
+
+namespace previews {
+class PreviewsBlackListItem;
+
+// Manages the state of black listed domains for the previews experiment. Loads
+// the stored black list from |opt_out_store| and manages an in memory black
+// list on the IO thread. Updates to the black list are stored in memory and
+// pushed to the store. Asynchronous modifications are stored in a queue and
+// executed in order. Reading from the black list is always synchronous, and if
+// the black list is not currently loaded (e.g., at startup, after clearing
+// browsing history), domains are reported as black listed.
+class PreviewsBlackList {
+ public:
+  PreviewsBlackList(std::unique_ptr<PreviewsOptOutStore> opt_out_store);

[tbansal1, 2016/09/13 23:52:45]

explicit.

[RyanSturm, 2016/09/14 16:44:30]

Done.

+  ~PreviewsBlackList();
+
+  typedef base::Closure QueueClosure;
+  typedef base::Callback<void(bool)> BlackListedCallback;
+
+  // Asynchronously adds a new navigation to |black_list_item_map_| and
+  // |opt_out_store_|. |opt_out| is whether the uesr opted out of the preview or
+  // navigated away from the page by another way.
+  void AddPreviewNavigation(const std::string& host_name,
+                            bool opt_out,
+                            PreviewsType type);
+
+  // Synchronously determines if |host_name| should be allowed to show previews.
+  // If LoadBlackListDone has not been called yet, this will always return

[tbansal1, 2016/09/13 23:52:45]

what is LoadBlackListDone?

[RyanSturm, 2016/09/14 16:44:30]

Done.

+  // false.
+  bool IsLoadedAndAllowed(const std::string& host_name);
+
+  // Asynchronously deletes all entries in |black_list_item_map_|. Informs
+  // |opt_out_store_| to delete entries between |begin_time| and |end_time|.

[tbansal1, 2016/09/13 23:52:45]

Generally, documentation of public functions should not refer to private
variables.

[RyanSturm, 2016/09/14 16:44:30]

Done.

+  // Reloads entries into memory from |opt_out_store_|. If |opt_out_store_| is
+  // null, resets all history in |black_list_item_map_|.
+  void ClearBlackList(const base::Time& begin_time, const base::Time& end_time);
+
+ private:
+  // Synchronously adds a new navigation to |black_list_item_map_|. Adds a new
+  // navigation to |opt_out_store_|. |opt_out| is whether the uesr opted out of
+  // the preview or navigated away from the page by another way.
+  void AddPreviewNavigationSync(const std::string& host_name,
+                                bool opt_out,
+                                PreviewsType type);
+
+  // Returns the PreviewsBlackListItem representing |host_name|. If there is no
+  // item for |host_name|, one will be created iff |create_if_needed| is true.
+  PreviewsBlackListItem* GetBlackListItem(std::string host_name,

[tbansal1, 2016/09/13 23:52:45]

pass std::string as const ref?

[RyanSturm, 2016/09/14 16:44:30]

Done.

+                                          bool create_if_needed);
+
+  // Synchronously deletes all entries in |black_list_item_map_|. Informs
+  // |opt_out_store_| to delete entries between |begin_time| and |end_time|.
+  // Reloads entries into memory from |opt_out_store_|. If |opt_out_store_| is
+  // null, resets all history in |black_list_item_map_|.
+  void ClearBlackListSync(const base::Time& begin_time,
+                          const base::Time& end_time);
+
+  // Callback passed to PreviewsOptOutStore::LoadBlackList. Moves the returned
+  // map into |black_list_item_map_| and runs any outstanding
+  // |pending_callbacks_|.
+  void LoadBlackListDone(std::unique_ptr<BlackListItemMap> black_list_item_map);
+
+  // Called while waiting for the black list to be loaded from |opt_out_store_|.
+  // Enqueues a task to run when PreviewsOptOutStore::LoadBlackList has
+  // completed. Maintains the order that tasks were called in.
+  void QueuePendingTask(QueueClosure callback);
+
+  // Map maintaining the black list in memory.
+  std::unique_ptr<BlackListItemMap> black_list_item_map_;
+
+  // Whether the black list is done being loaded from |opt_out_store_|.
+  bool loaded_;
+
+  // Backing store representation of the black list.
+  std::unique_ptr<PreviewsOptOutStore> opt_out_store_;
+
+  // Callbacks to be run after PreviewsOptOutStore::LoadBlackList has completed.
+  std::queue<QueueClosure> pending_callbacks_;
+
+  base::ThreadChecker thread_checker_;
+
+  base::WeakPtrFactory<PreviewsBlackList> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreviewsBlackList);
+};
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_PREVIEWS_BLACK_LIST_ITEM_H_