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// Copyright 2016 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.
#include <string>
#include "base/macros.h"
class PrefRegistrySimple;
class PrefService;
namespace base {
class HistogramBase;
} // namespace base
namespace ntp_snippets {
// Counts requests to external services, compares them to a daily quota, reports
// them to UMA. In the application code, create one local instance for each type
// of requests, identified by the RequestType. The request counter is based on:
// - daily quota from a variation param "quota_|type|" in the NTPSnippets trial
// - pref "ntp.request_throttler.|type|.count" to store the current counter,
// - pref "ntp.request_throttler.|type|.day" to store current day to which the
// current counter value applies.
// Furthermore the counter reports to histograms:
// - "NewTabPage.RequestThrottler.RequestStatus_|type|" - status of each
// request;
// - "NewTabPage.RequestThrottler.PerDay_|type|" - the daily count of requests.
// Implementation notes: When extending this class for a new RequestType, please
// 1) define in in kRequestTypeInfo
// a) the string value for your |type| and
// b) constants for day/count prefs;
// 2) define a new RequestThrottlerTypes histogram suffix in histogram.xml
// (with the same string value as in 1a)).
class RequestThrottler {
// Enumeration listing all current applications of the request counter.
enum class RequestType {
RequestThrottler(PrefService* pref_service, RequestType type);
// Registers profile prefs for all RequestTypes. Called from
static void RegisterProfilePrefs(PrefRegistrySimple* registry);
// Returns whether quota is available for another request and reports this
// information to UMA. Interactive requests should be always granted (upon
// standard conditions) and should be only used for requests initiated by the
// user (if it is safe to assume that all users cannot generate an amount of
// requests we cannot handle).
bool DemandQuotaForRequest(bool interactive_request);
friend class RequestThrottlerTest;
// Used internally for working with a RequestType.
struct RequestTypeInfo;
// The array of info entries - one per each RequestType.
static const RequestTypeInfo kRequestTypeInfo[];
// Also emits the PerDay histogram if the day changed.
void ResetCounterIfDayChanged();
const char* GetRequestTypeName() const;
int GetQuota(bool interactive_request) const;
int GetCount(bool interactive_request) const;
void SetCount(bool interactive_request, int count);
int GetDay() const;
void SetDay(int day);
bool HasDay() const;
PrefService* pref_service_;
const RequestTypeInfo& type_info_;
// The quotas are hardcoded, but can be overridden by variation params.
int quota_;
int interactive_quota_;
// The histograms for reporting the requests of the given |type_|.
base::HistogramBase* histogram_request_status_;
base::HistogramBase* histogram_per_day_background_;
base::HistogramBase* histogram_per_day_interactive_;
} // namespace ntp_snippets