// Copyright 2014 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_METRICS_EXTENSIONS_METRICS_PROVIDER_H_
#define CHROME_BROWSER_METRICS_EXTENSIONS_METRICS_PROVIDER_H_

#include <string>

#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "components/metrics/metrics_provider.h"

class Profile;

namespace extensions {
class ExtensionSet;
}

namespace metrics {
class MetricsStateManager;
class SystemProfileProto;
}

// ExtensionsMetricsProvider groups various constants and functions used for
// reporting extension IDs with UMA reports (after hashing the extension IDs
// for privacy).
class ExtensionsMetricsProvider : public metrics::MetricsProvider {
 public:
  // Holds on to |metrics_state_manager|, which must outlive this object, as a
  // weak pointer.
  explicit ExtensionsMetricsProvider(
      metrics::MetricsStateManager* metrics_state_manager);
  virtual ~ExtensionsMetricsProvider();

  // metrics::MetricsProvider:

  // Writes the hashed list of installed extensions into the specified
  // SystemProfileProto object.
  virtual void ProvideSystemProfileMetrics(
      metrics::SystemProfileProto* system_profile) OVERRIDE;

 protected:
  // Exposed for the sake of mocking in test code.

  // Retrieves the set of extensions installed in the current profile.
  // TODO(mvrable): If metrics are ever converted to being per-profile, then
  // this should be updated to return extensions installed in a specified
  // profile.
  virtual scoped_ptr<extensions::ExtensionSet> GetInstalledExtensions();

  // Retrieves the client ID.
  virtual uint64 GetClientID();

  // Hashes the extension extension ID using the provided client key (which
  // must be less than kExtensionListClientKeys) and to produce an output value
  // between 0 and kExtensionListBuckets-1.
  static int HashExtension(const std::string& extension_id, uint32 client_key);

 private:
  // Returns the profile for which extensions will be gathered.  Once a
  // suitable profile has been found, future calls will continue to return the
  // same value so that reported extensions are consistent.
  Profile* GetMetricsProfile();

  // The MetricsStateManager from which the client ID is obtained.
  metrics::MetricsStateManager* metrics_state_manager_;

  // The profile for which extensions are gathered.  Once a profile is found
  // its value is cached here so that GetMetricsProfile() can return a
  // consistent value.
  Profile* cached_profile_;

  DISALLOW_COPY_AND_ASSIGN(ExtensionsMetricsProvider);
};

#endif  // CHROME_BROWSER_METRICS_EXTENSIONS_METRICS_PROVIDER_H_