// Copyright (c) 2010 The Chromium OS 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 METRICS_LIBRARY_H_
#define METRICS_LIBRARY_H_

#include <sys/types.h>
#include <string>
#include <unistd.h>

#include <base/basictypes.h>
#include <base/compiler_specific.h>
#include <base/memory/scoped_ptr.h>
#include <gtest/gtest_prod.h>  // for FRIEND_TEST

#include "policy/libpolicy.h"

class MetricsLibraryInterface {
 public:
  virtual void Init() = 0;
  virtual bool SendToUMA(const std::string& name, int sample,
                         int min, int max, int nbuckets) = 0;
  virtual bool SendEnumToUMA(const std::string& name, int sample, int max) = 0;
  virtual bool SendSparseToUMA(const std::string& name, int sample) = 0;
  virtual bool SendUserActionToUMA(const std::string& action) = 0;
  virtual ~MetricsLibraryInterface() {}
};

// Library used to send metrics to both Autotest and Chrome/UMA.
class MetricsLibrary : public MetricsLibraryInterface {
 public:
  MetricsLibrary();
  virtual ~MetricsLibrary();

  // Initializes the library.
  virtual void Init() OVERRIDE;

  // Returns whether or not the machine is running in guest mode.
  bool IsGuestMode();

  // Returns whether or not metrics collection is enabled.
  bool AreMetricsEnabled();

  // Sends histogram data to Chrome for transport to UMA and returns
  // true on success. This method results in the equivalent of an
  // asynchronous non-blocking RPC to UMA_HISTOGRAM_CUSTOM_COUNTS
  // inside Chrome (see base/histogram.h).
  //
  // |sample| is the sample value to be recorded (|min| <= |sample| < |max|).
  // |min| is the minimum value of the histogram samples (|min| > 0).
  // |max| is the maximum value of the histogram samples.
  // |nbuckets| is the number of histogram buckets.
  // [0,min) is the implicit underflow bucket.
  // [|max|,infinity) is the implicit overflow bucket.
  //
  // Note that the memory allocated in Chrome for each histogram is
  // proportional to the number of buckets. Therefore, it is strongly
  // recommended to keep this number low (e.g., 50 is normal, while
  // 100 is high).
  bool SendToUMA(const std::string& name, int sample,
                 int min, int max, int nbuckets);

  // Sends linear histogram data to Chrome for transport to UMA and
  // returns true on success. This method results in the equivalent of
  // an asynchronous non-blocking RPC to UMA_HISTOGRAM_ENUMERATION
  // inside Chrome (see base/histogram.h).
  //
  // |sample| is the sample value to be recorded (1 <= |sample| < |max|).
  // |max| is the maximum value of the histogram samples.
  // 0 is the implicit underflow bucket.
  // [|max|,infinity) is the implicit overflow bucket.
  //
  // An enumeration histogram requires |max| + 1 number of
  // buckets. Note that the memory allocated in Chrome for each
  // histogram is proportional to the number of buckets. Therefore, it
  // is strongly recommended to keep this number low (e.g., 50 is
  // normal, while 100 is high).
  virtual bool SendEnumToUMA(const std::string& name,
                             int sample,
                             int max) OVERRIDE;

  // Sends sparse histogram sample to Chrome for transport to UMA.  Returns
  // true on success.
  //
  // |sample| is the 32-bit integer value to be recorded.
  virtual bool SendSparseToUMA(const std::string& name, int sample) OVERRIDE;

  // Sends a user action to Chrome for transport to UMA and returns true on
  // success. This method results in the equivalent of an asynchronous
  // non-blocking RPC to UserMetrics::RecordAction.  The new metric must be
  // added to chrome/tools/extract_actions.py in the Chromium repository, which
  // should then be run to generate a hash for the new action.
  //
  // Until http://crosbug.com/11125 is fixed, the metric must also be added to
  // chrome/browser/chromeos/external_metrics.cc.
  //
  // |action| is the user-generated event (e.g., "MuteKeyPressed").
  virtual bool SendUserActionToUMA(const std::string& action) OVERRIDE;

  // Sends a signal to UMA that a crash of the given |crash_kind|
  // has occurred.  Used by UMA to generate stability statistics.
  bool SendCrashToUMA(const char *crash_kind);

  // Sends a "generic Chrome OS event" to UMA.  This is an event name
  // that is translated into an enumerated histogram entry.  Event names
  // are added to metrics_library.cc.  Optionally, they can be added
  // to histograms.xml---but part of the reason for this is to simplify
  // the addition of events (at the cost of having to look them up by
  // number in the histograms dashboard).
  bool SendCrosEventToUMA(const std::string& event);

  // Sends to Autotest and returns true on success.
  static bool SendToAutotest(const std::string& name, int value);

 private:
  friend class CMetricsLibraryTest;
  friend class MetricsLibraryTest;
  FRIEND_TEST(MetricsLibraryTest, AreMetricsEnabled);
  FRIEND_TEST(MetricsLibraryTest, FormatChromeMessage);
  FRIEND_TEST(MetricsLibraryTest, FormatChromeMessageTooLong);
  FRIEND_TEST(MetricsLibraryTest, IsDeviceMounted);
  FRIEND_TEST(MetricsLibraryTest, SendMessageToChrome);
  FRIEND_TEST(MetricsLibraryTest, SendMessageToChromeUMAEventsBadFileLocation);

  // Sets |*result| to whether or not the |mounts_file| indicates that
  // the |device_name| is currently mounted.  Uses |buffer| of
  // |buffer_size| to read the file.  Returns false if any error.
  bool IsDeviceMounted(const char* device_name,
                       const char* mounts_file,
                       char* buffer, int buffer_size,
                       bool* result);

  // Sends message to Chrome for transport to UMA and returns true on success.
  bool SendMessageToChrome(const std::string& message);

  // Serializes a name/value pair into a message buffer.
  //
  // The serialized format is: | LENGTH | NAME | \0 | VALUE | \0 |
  //
  // where LENGTH is a 32-bit integer in native endianness, and NAME and VALUE
  // are null-terminated strings (the zero bytes are explicitly shown above).
  const std::string FormatChromeMessage(const std::string& name,
                                        const std::string& value);

  // This function is used by tests only to mock the device policies.
  void SetPolicyProvider(policy::PolicyProvider* provider);

  // Time at which we last checked if metrics were enabled.
  static time_t cached_enabled_time_;

  // Cached state of whether or not metrics were enabled.
  static bool cached_enabled_;

  std::string uma_events_file_;
  std::string consent_file_;

  scoped_ptr<policy::PolicyProvider> policy_provider_;

  DISALLOW_COPY_AND_ASSIGN(MetricsLibrary);
};

#endif  // METRICS_LIBRARY_H_