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// Copyright 2013 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 COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
#define COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
#include <map>
#include <string>
#include "base/metrics/field_trial.h"
#include "components/variations/active_field_trials.h"
// This file provides various helpers that extend the functionality around
// base::FieldTrial.
//
// This includes several simple APIs to handle getting and setting additional
// data related to Chrome variations, such as parameters and Google variation
// IDs. These APIs are meant to extend the base::FieldTrial APIs to offer extra
// functionality that is not offered by the simpler base::FieldTrial APIs.
//
// The AssociateGoogleVariationID and AssociateVariationParams functions are
// generally meant to be called by the VariationsService based on server-side
// variation configs, but may also be used for client-only field trials by
// invoking them directly after appending all the groups to a FieldTrial.
//
// Experiment code can then use the getter APIs to retrieve variation parameters
// or IDs:
//
// std::map<std::string, std::string> params;
// if (GetVariationParams("trial", ¶ms)) {
// // use |params|
// }
//
// std::string value = GetVariationParamValue("trial", "param_x");
// // use |value|, which will be "" if it does not exist
//
// VariationID id = GetGoogleVariationID(GOOGLE_WEB_PROPERTIES, "trial",
// "group1");
// if (id != variations::kEmptyID) {
// // use |id|
// }
namespace variations {
typedef int VariationID;
const VariationID EMPTY_ID = 0;
// A key into the Associate/Get methods for VariationIDs. This is used to create
// separate ID associations for separate parties interested in VariationIDs.
enum IDCollectionKey {
// This collection is used by Google web properties, transmitted through the
// X-Client-Data header.
GOOGLE_WEB_PROPERTIES,
// This collection is used by Google web properties for IDs that trigger
// server side experimental behavior, transmitted through the
// X-Client-Data header.
GOOGLE_WEB_PROPERTIES_TRIGGER,
// This collection is used by Google update services, transmitted through the
// Google Update experiment labels.
GOOGLE_UPDATE_SERVICE,
// The total count of collections.
ID_COLLECTION_COUNT,
};
// Associate a variations::VariationID value with a FieldTrial group for
// collection |key|. If an id was previously set for |trial_name| and
// |group_name|, this does nothing. The group is denoted by |trial_name| and
// |group_name|. This must be called whenever a FieldTrial is prepared (create
// the trial and append groups) and needs to have a variations::VariationID
// associated with it so Google servers can recognize the FieldTrial.
// Thread safe.
void AssociateGoogleVariationID(IDCollectionKey key,
const std::string& trial_name,
const std::string& group_name,
VariationID id);
// As above, but overwrites any previously set id. Thread safe.
void AssociateGoogleVariationIDForce(IDCollectionKey key,
const std::string& trial_name,
const std::string& group_name,
VariationID id);
// As above, but takes an ActiveGroupId hash pair, rather than the string names.
void AssociateGoogleVariationIDForceHashes(IDCollectionKey key,
const ActiveGroupId& active_group,
VariationID id);
// Retrieve the variations::VariationID associated with a FieldTrial group for
// collection |key|. The group is denoted by |trial_name| and |group_name|.
// This will return variations::kEmptyID if there is currently no associated ID
// for the named group. This API can be nicely combined with
// FieldTrial::GetActiveFieldTrialGroups() to enumerate the variation IDs for
// all active FieldTrial groups. Thread safe.
VariationID GetGoogleVariationID(IDCollectionKey key,
const std::string& trial_name,
const std::string& group_name);
// Same as GetGoogleVariationID(), but takes in a hashed |active_group| rather
// than the string trial and group name.
VariationID GetGoogleVariationIDFromHashes(IDCollectionKey key,
const ActiveGroupId& active_group);
// Associates the specified set of key-value |params| with the variation
// specified by |trial_name| and |group_name|. Fails and returns false if the
// specified variation already has params associated with it or the field trial
// is already active (group() has been called on it). Thread safe.
bool AssociateVariationParams(const std::string& trial_name,
const std::string& group_name,
const std::map<std::string, std::string>& params);
// Retrieves the set of key-value |params| for the variation associated with
// the specified field trial, based on its selected group. If the field trial
// does not exist or its selected group does not have any parameters associated
// with it, returns false and does not modify |params|. Calling this function
// will result in the field trial being marked as active if found (i.e. group()
// will be called on it), if it wasn't already. Currently, this information is
// only available from the browser process. Thread safe.
bool GetVariationParams(const std::string& trial_name,
std::map<std::string, std::string>* params);
// Retrieves a specific parameter value corresponding to |param_name| for the
// variation associated with the specified field trial, based on its selected
// group. If the field trial does not exist or the specified parameter does not
// exist, returns an empty string. Calling this function will result in the
// field trial being marked as active if found (i.e. group() will be called on
// it), if it wasn't already. Currently, this information is only available from
// the browser process. Thread safe.
std::string GetVariationParamValue(const std::string& trial_name,
const std::string& param_name);
// Expose some functions for testing.
namespace testing {
// Clears all of the mapped associations.
void ClearAllVariationIDs();
// Clears all of the associated params.
void ClearAllVariationParams();
} // namespace testing
} // namespace variations
#endif // COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
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