app_list: Search result launch history and boost.

chrome/browser/ui/app_list/search/history_data.h

+// Copyright 2013 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 CHROME_BROWSER_UI_APP_LIST_SEARCH_HISTORY_DATA_H_
+#define CHROME_BROWSER_UI_APP_LIST_SEARCH_HISTORY_DATA_H_
+
+#include <deque>
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/time.h"
+#include "chrome/browser/ui/app_list/search/history_types.h"
+
+namespace app_list {
+
+class HistoryDataObserver;
+class HistoryDataStore;
+
+// HistoryData stores the associations of the user typed queries and launched
+// search result id. There are two types of association: primary and secondary.
+// Primary is a 1-to-1 mapping between the query and result id. Secondary
+// is a 1-to-many mapping and only kept the last 5 to limit the data size.
+// If an association is added for the first time, it is added as a primary
+// association. Further associations added to the same query are added as
+// secondary. However, if a secondary association is added twice in a row, it
+// is promoted to primary and the current primary mapping is demoted into
+// secondary.
+class HistoryData : public base::SupportsWeakPtr<HistoryData> {
+ public:
+  typedef std::deque<std::string> SecondaryDeque;
+  // Defines data to be associated with a query.

[James Cook, 2013/05/23 21:51:08]

nit: extra line above might be more readable

[xiyuan, 2013/05/23 22:38:13]

Done.

+  struct Data {
+    Data();
+    ~Data();
+
+    // Primary result associated with the query.
+    std::string primary;
+
+    // Secondary results associated with the query from oldest to latest.
+    SecondaryDeque secondary;
+
+    // Last update time.
+    base::Time update_time;
+  };
+  typedef std::map<std::string, Data> Associations;
+
+  // Constructor of HistoryData. |store| is the storage to persist the data.
+  // |max_entry| is the maximum number of most recent query entries to keep.
+  // |max_secondary| is the maximum number of secondary associations to keep.
+  HistoryData(HistoryDataStore* store, size_t max_entry, size_t max_secondary);

[James Cook, 2013/05/23 21:51:08]

Maybe comment that max_entry is total entries, including secondary entries?  I
found it hard to understand the limits here.  Or call |max_entry| as
|max_primary|?

[xiyuan, 2013/05/23 22:38:13]

Renamed max_entry to max_primary.

+  ~HistoryData();
+
+  // Adds an association.
+  void Add(const std::string& query, const std::string& result_id);
+
+  // Gets all known search results that were launched using the given |query|
+  // or the queries that |query| is a prefix of.
+  scoped_ptr<KnownResults> GetKnownResults(const std::string& query) const;
+
+  void AddObserver(HistoryDataObserver* observer);
+  void RemoveObserver(HistoryDataObserver* observer);
+
+  const Associations& associations() const { return associations_; }
+
+ private:
+  // Invoked from |store| with loaded data.
+  void OnStoreLoaded(scoped_ptr<Associations> loaded_data);
+
+  // Trims the data to keep the most recent |max_entry_| queries.
+  void TrimEntries();
+
+  HistoryDataStore* store_;  // Not owned.
+  const size_t max_entry_;
+  const size_t max_secondary_;
+  ObserverList<HistoryDataObserver, true> observers_;
+
+  Associations associations_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistoryData);
+};
+
+}  // namespace app_list
+
+#endif  // CHROME_BROWSER_UI_APP_LIST_SEARCH_HISTORY_DATA_H_