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// 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.
#include <set>
#include <string>
#include <utility>
#include <vector>
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/metrics/field_trial.h"
#include "base/observer_list.h"
#include "base/synchronization/lock.h"
#include "components/variations/synthetic_trials.h"
#include "components/variations/variations_associated_data.h"
namespace base {
template <typename T>
struct DefaultSingletonTraits;
namespace variations {
// A helper class for maintaining client experiments and metrics state
// transmitted in custom HTTP request headers.
// This class is a thread-safe singleton.
class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
public SyntheticTrialObserver {
class Observer {
// Called when variation ids headers are updated.
virtual void VariationIdsHeaderUpdated(
const std::string& variation_ids_header,
const std::string& variation_ids_header_signed_in) {}
virtual ~Observer() {}
static VariationsHttpHeaderProvider* GetInstance();
// Returns the value of the client data header, computing and caching it if
// necessary. If |is_signed_in| is false, variation ids that should only be
// sent for signed in users (i.e. GOOGLE_WEB_PROPERTIES_SIGNED_IN entries)
// will not be included.
std::string GetClientDataHeader(bool is_signed_in);
// Returns a space-separated string containing the list of current active
// variations (as would be reported in the |variation_id| repeated field of
// the ClientVariations proto). Does not include variation ids that should be
// sent for signed-in users only. The returned string is guaranteed to have a
// a leading and trailing space, e.g. " 123 234 345 ".
std::string GetVariationsString();
// Result of ForceVariationIds() call.
enum class ForceIdsResult {
INVALID_VECTOR_ENTRY, // Invalid entry in |variation_ids|.
INVALID_SWITCH_ENTRY, // Invalid entry in |command_line_variation_ids|.
// Sets *additional* variation ids and trigger variation ids to be encoded in
// the X-Client-Data request header. This is intended for development use to
// force a server side experiment id. |variation_ids| should be a list of
// strings of numeric experiment ids. Ids explicitly passed in |variation_ids|
// and those in the comma-separated |command_line_variation_ids| are added.
ForceIdsResult ForceVariationIds(
const std::vector<std::string>& variation_ids,
const std::string& command_line_variation_ids);
// Methods to register or remove observers of variation ids header update.
void AddObserver(Observer* observer);
void RemoveObserver(Observer* observer);
// Resets any cached state for tests.
void ResetForTesting();
friend struct base::DefaultSingletonTraits<VariationsHttpHeaderProvider>;
typedef std::pair<VariationID, IDCollectionKey> VariationIDEntry;
~VariationsHttpHeaderProvider() override;
// base::FieldTrialList::Observer:
// This will add the variation ID associated with |trial_name| and
// |group_name| to the variation ID cache.
void OnFieldTrialGroupFinalized(const std::string& trial_name,
const std::string& group_name) override;
// metrics::SyntheticTrialObserver:
void OnSyntheticTrialsChanged(
const std::vector<SyntheticTrialGroup>& groups) override;
// Prepares the variation IDs cache with initial values if not already done.
// This method also registers the caller with the FieldTrialList to receive
// new variation IDs.
void InitVariationIDsCacheIfNeeded();
// Looks up the associated id for the given trial/group and adds an entry for
// it to |variation_ids_set_| if found.
void CacheVariationsId(const std::string& trial_name,
const std::string& group_name,
IDCollectionKey key);
// Takes whatever is currently in |variation_ids_set_| and recreates
// |variation_ids_header_| with it. Assumes the the |lock_| is currently
// held.
void UpdateVariationIDsHeaderValue();
// Generates a base64-encoded proto to be used as a header value for the given
// |is_signed_in| state.
std::string GenerateBase64EncodedProto(bool is_signed_in);
// Adds *additional* variation ids and trigger variation ids to be encoded in
// the X-Client-Data request header.
bool AddDefaultVariationIds(const std::vector<std::string>& variation_ids);
// Returns the currently active set of variation ids, which includes any
// default values, synthetic variations and actual field trial variations.
std::set<VariationIDEntry> GetAllVariationIds();
// Guards access to variables below.
base::Lock lock_;
// Whether or not we've initialized the caches.
bool variation_ids_cache_initialized_;
// Keep a cache of variation IDs that are transmitted in headers to Google.
// This consists of a list of valid IDs, and the actual transmitted header.
std::set<VariationIDEntry> variation_ids_set_;
// Provides the google experiment ids forced from command line.
std::set<VariationIDEntry> default_variation_ids_set_;
// Variations ids from synthetic field trials.
std::set<VariationIDEntry> synthetic_variation_ids_set_;
std::string cached_variation_ids_header_;
std::string cached_variation_ids_header_signed_in_;
// List of observers to notify on variation ids header update.
// Makes sure list is empty on destruction.
base::ObserverList<Observer, true>::Unchecked observer_list_;
} // namespace variations