android_webview/browser/metrics/aw_metrics_service_client.h

// Copyright 2017 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 ANDROID_WEBVIEW_BROWSER_METRICS_AW_METRICS_SERVICE_CLIENT_H_
#define ANDROID_WEBVIEW_BROWSER_METRICS_AW_METRICS_SERVICE_CLIENT_H_

#include <memory>
#include <string>

#include "android_webview/browser/lifecycle/webview_app_state_observer.h"
#include "base/macros.h"
#include "base/metrics/field_trial.h"
#include "base/no_destructor.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "components/embedder_support/android/metrics/android_metrics_service_client.h"
#include "components/metrics/enabled_state_provider.h"
#include "components/metrics/metrics_log_uploader.h"
#include "components/metrics/metrics_service_client.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"

namespace android_webview {

// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
// TODO(https://crbug.com/1012025): remove this when the kInstallDate pref has
// been persisted for one or two milestones. Visible for testing.
enum class BackfillInstallDate {
  kValidInstallDatePref = 0,
  kCouldNotGetPackageManagerInstallDate = 1,
  kPersistedPackageManagerInstallDate = 2,
  kMaxValue = kPersistedPackageManagerInstallDate,
};

// AwMetricsServiceClient is a singleton which manages WebView metrics
// collection.
//
// Metrics should be enabled iff all these conditions are met:
//  - The user has not opted out (controlled by GMS).
//  - The app has not opted out (controlled by manifest tag).
//  - This client is in the 2% sample (controlled by client ID hash).
// The first two are recorded in |user_consent_| and |app_consent_|, which are
// set by SetHaveMetricsConsent(). The last is recorded in |is_in_sample_|.
//
// Metrics are pseudonymously identified by a randomly-generated "client ID".
// WebView stores this in prefs, written to the app's data directory. There's a
// different such directory for each user, for each app, on each device. So the
// ID should be unique per (device, app, user) tuple.
//
// To avoid the appearance that we're doing anything sneaky, the client ID
// should only be created and retained when neither the user nor the app have
// opted out. Otherwise, the presence of the ID could give the impression that
// metrics were being collected.
//
// WebView metrics set up happens like so:
//
//   startup
//      │
//      ├────────────┐
//      │            ▼
//      │         query GMS for consent
//      ▼            │
//   Initialize()    │
//      │            ▼
//      │         SetHaveMetricsConsent()
//      │            │
//      │ ┌──────────┘
//      ▼ ▼
//   MaybeStartMetrics()
//      │
//      ▼
//   MetricsService::Start()
//
// All the named functions in this diagram happen on the UI thread. Querying GMS
// happens in the background, and the result is posted back to the UI thread, to
// SetHaveMetricsConsent(). Querying GMS is slow, so SetHaveMetricsConsent()
// typically happens after Initialize(), but it may happen before.
//
// Each path sets a flag, |init_finished_| or |set_consent_finished_|, to show
// that path has finished, and then calls MaybeStartMetrics(). When
// MaybeStartMetrics() is called the first time, it sees only one flag is true,
// and does nothing. When MaybeStartMetrics() is called the second time, it
// decides whether to start metrics.
//
// If consent was granted, MaybeStartMetrics() determines sampling by hashing
// the client ID (generating a new ID if there was none). If this client is in
// the sample, it then calls MetricsService::Start(). If consent was not
// granted, MaybeStartMetrics() instead clears the client ID, if any.

class AwMetricsServiceClient : public ::metrics::AndroidMetricsServiceClient,
                               public WebViewAppStateObserver {
  friend class base::NoDestructor<AwMetricsServiceClient>;

 public:
  // This interface define the tasks that depend on the
  // android_webview/browser directory.
  class Delegate {
   public:
    Delegate();
    virtual ~Delegate();

    // Not copyable or movable
    Delegate(const Delegate&) = delete;
    Delegate& operator=(const Delegate&) = delete;
    Delegate(Delegate&&) = delete;
    Delegate& operator=(Delegate&&) = delete;

    virtual void RegisterAdditionalMetricsProviders(
        metrics::MetricsService* service) = 0;
    virtual void AddWebViewAppStateObserver(
        WebViewAppStateObserver* observer) = 0;
    virtual bool HasAwContentsEverCreated() const = 0;
  };

  static AwMetricsServiceClient* GetInstance();
  static void SetInstance(
      std::unique_ptr<AwMetricsServiceClient> aw_metrics_service_client);

  AwMetricsServiceClient(std::unique_ptr<Delegate> delegate);
  ~AwMetricsServiceClient() override;

  // metrics::MetricsServiceClient
  int32_t GetProduct() override;

  // WebViewAppStateObserver
  void OnAppStateChanged(WebViewAppStateObserver::State state) override;

  // metrics::AndroidMetricsServiceClient:
  void OnMetricsStart() override;
  int GetSampleRatePerMille() override;
  int GetPackageNameLimitRatePerMille() override;
  void RegisterAdditionalMetricsProviders(
      metrics::MetricsService* service) override;

 private:
  bool app_in_foreground_ = false;
  std::unique_ptr<Delegate> delegate_;

  DISALLOW_COPY_AND_ASSIGN(AwMetricsServiceClient);
};

}  // namespace android_webview

#endif  // ANDROID_WEBVIEW_BROWSER_METRICS_AW_METRICS_SERVICE_CLIENT_H_