1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_DRIVE_EVENT_LOGGER_H_
6#define CHROME_BROWSER_DRIVE_EVENT_LOGGER_H_
7
8#include <deque>
9#include <string>
10#include <vector>
11
12#include "base/basictypes.h"
13#include "base/compiler_specific.h"
14#include "base/logging.h"
15#include "base/synchronization/lock.h"
16#include "base/time/time.h"
17
18namespace drive {
19
20// The default history size used by EventLogger.
21const int kDefaultHistorySize = 1000;
22
23// EventLogger is used to collect and expose text messages for diagnosing
24// behaviors of Google APIs stuff. For instance, the collected messages are
25// exposed to chrome:drive-internals.
26class EventLogger {
27 public:
28  // Represents a single event log.
29  struct Event {
30    Event(int id, logging::LogSeverity severity, const std::string& what);
31    int id;  // Monotonically increasing ID starting from 0.
32    logging::LogSeverity severity;  // Severity of the event.
33    base::Time when;  // When the event occurred.
34    std::string what;  // What happened.
35  };
36
37  // Creates an event logger that keeps the latest kDefaultHistorySize events.
38  EventLogger();
39  ~EventLogger();
40
41  // Logs a message and its severity.
42  // Can be called from any thread as long as the object is alive.
43  void Log(logging::LogSeverity severity, const std::string& what);
44
45  // Sets the history size. The existing history is cleared.
46  // Can be called from any thread as long as the object is alive.
47  void SetHistorySize(size_t history_size);
48
49  // Gets the list of latest events (the oldest event comes first).
50  // Can be called from any thread as long as the object is alive.
51  std::vector<Event> GetHistory();
52
53 private:
54  std::deque<Event> history_;  // guarded by lock_.
55  size_t history_size_;  // guarded by lock_.
56  int next_event_id_;  // guarded by lock_.
57  base::Lock lock_;
58
59  DISALLOW_COPY_AND_ASSIGN(EventLogger);
60};
61
62}  // namespace drive
63
64#endif  // CHROME_BROWSER_DRIVE_EVENT_LOGGER_H_
65