Create a variations component, so that it can be re-used.

Moving this code out of chrome/ paves the way for server-controlled system
field trials on ChromeOS. This allows building a new ChromeOS daemon binary
that depends on the new variations target, without needing to depend on all of
chrome/.

This CL moves several files from chrome/common/metrics and
chrome/browser/metrics into a separate component/variations target and
updates all the include paths referencing these. It does not do additional
cleanup, such as changing namespaces - this is left for a follow-up cleanup
CL.

BUG=266007
TEST=Existing unit tests.
R=joi@chromium.org, jwd@chromium.org, sky@chromium.org

Review URL: https://codereview.chromium.org/23097007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@220339 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 236 insertions, 0 deletions

diff --git a/components/variations/variations_associated_data.cc b/components/variations/variations_associated_data.cc
new file mode 100644
index 0000000..64a6d6e
--- /dev/null
+++ b/components/variations/variations_associated_data.cc
@@ -0,0 +1,236 @@
+// 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.
+
+#include "components/variations/variations_associated_data.h"
+
+#include <map>
+#include <utility>
+#include <vector>
+
+#include "base/memory/singleton.h"
+#include "components/variations/metrics_util.h"
+
+namespace chrome_variations {
+
+namespace {
+
+// The internal singleton accessor for the map, used to keep it thread-safe.
+class GroupMapAccessor {
+ public:
+  typedef std::map<ActiveGroupId, VariationID, ActiveGroupIdCompare>
+      GroupToIDMap;
+
+  // Retrieve the singleton.
+  static GroupMapAccessor* GetInstance() {
+    return Singleton<GroupMapAccessor>::get();
+  }
+
+  // Note that this normally only sets the ID for a group the first time, unless
+  // |force| is set to true, in which case it will always override it.
+  void AssociateID(IDCollectionKey key,
+                   const ActiveGroupId& group_identifier,
+                   const VariationID id,
+                   const bool force) {
+#if !defined(NDEBUG)
+    // Validate that all collections with this |group_identifier| have the same
+    // associated ID.
+    DCHECK_EQ(2, ID_COLLECTION_COUNT);
+    IDCollectionKey other_key = GOOGLE_WEB_PROPERTIES;
+    if (key == GOOGLE_WEB_PROPERTIES)
+      other_key = GOOGLE_UPDATE_SERVICE;
+    VariationID other_id = GetID(other_key, group_identifier);
+    DCHECK(other_id == EMPTY_ID || other_id == id);
+#endif
+
+    base::AutoLock scoped_lock(lock_);
+
+    GroupToIDMap* group_to_id_map = GetGroupToIDMap(key);
+    if (force ||
+        group_to_id_map->find(group_identifier) == group_to_id_map->end())
+      (*group_to_id_map)[group_identifier] = id;
+  }
+
+  VariationID GetID(IDCollectionKey key,
+                    const ActiveGroupId& group_identifier) {
+    base::AutoLock scoped_lock(lock_);
+    GroupToIDMap* group_to_id_map = GetGroupToIDMap(key);
+    GroupToIDMap::const_iterator it = group_to_id_map->find(group_identifier);
+    if (it == group_to_id_map->end())
+      return EMPTY_ID;
+    return it->second;
+  }
+
+  void ClearAllMapsForTesting() {
+    base::AutoLock scoped_lock(lock_);
+
+    for (int i = 0; i < ID_COLLECTION_COUNT; ++i) {
+      GroupToIDMap* map = GetGroupToIDMap(static_cast<IDCollectionKey>(i));
+      DCHECK(map);
+      map->clear();
+    }
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<GroupMapAccessor>;
+
+  // Retrieves the GroupToIDMap for |key|.
+  GroupToIDMap* GetGroupToIDMap(IDCollectionKey key) {
+    return &group_to_id_maps_[key];
+  }
+
+  GroupMapAccessor() {
+    group_to_id_maps_.resize(ID_COLLECTION_COUNT);
+  }
+  ~GroupMapAccessor() {}
+
+  base::Lock lock_;
+  std::vector<GroupToIDMap> group_to_id_maps_;
+
+  DISALLOW_COPY_AND_ASSIGN(GroupMapAccessor);
+};
+
+// Singleton helper class that keeps track of the parameters of all variations
+// and ensures access to these is thread-safe.
+class VariationsParamAssociator {
+ public:
+  typedef std::pair<std::string, std::string> VariationKey;
+  typedef std::map<std::string, std::string> VariationParams;
+
+  // Retrieve the singleton.
+  static VariationsParamAssociator* GetInstance() {
+    return Singleton<VariationsParamAssociator>::get();
+  }
+
+  bool AssociateVariationParams(const std::string& trial_name,
+                                const std::string& group_name,
+                                const VariationParams& params) {
+    base::AutoLock scoped_lock(lock_);
+
+    if (IsFieldTrialActive(trial_name))
+      return false;
+
+    const VariationKey key(trial_name, group_name);
+    if (ContainsKey(variation_params_, key))
+      return false;
+
+    variation_params_[key] = params;
+    return true;
+  }
+
+  bool GetVariationParams(const std::string& trial_name,
+                          VariationParams* params) {
+    base::AutoLock scoped_lock(lock_);
+
+    const std::string group_name =
+        base::FieldTrialList::FindFullName(trial_name);
+    const VariationKey key(trial_name, group_name);
+    if (!ContainsKey(variation_params_, key))
+      return false;
+
+    *params = variation_params_[key];
+    return true;
+  }
+
+  void ClearAllParamsForTesting() {
+    base::AutoLock scoped_lock(lock_);
+    variation_params_.clear();
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<VariationsParamAssociator>;
+
+  VariationsParamAssociator() {}
+  ~VariationsParamAssociator() {}
+
+  // Tests whether a field trial is active (i.e. group() has been called on it).
+  // TODO(asvitkine): Expose this as an API on base::FieldTrial.
+  bool IsFieldTrialActive(const std::string& trial_name) {
+    base::FieldTrial::ActiveGroups active_groups;
+    base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
+    for (size_t i = 0; i < active_groups.size(); ++i) {
+      if (active_groups[i].trial_name == trial_name)
+        return true;
+    }
+    return false;
+  }
+
+  base::Lock lock_;
+  std::map<VariationKey, VariationParams> variation_params_;
+
+  DISALLOW_COPY_AND_ASSIGN(VariationsParamAssociator);
+};
+
+}  // namespace
+
+ActiveGroupId MakeActiveGroupId(const std::string& trial_name,
+                                const std::string& group_name) {
+  ActiveGroupId id;
+  id.name = metrics::HashName(trial_name);
+  id.group = metrics::HashName(group_name);
+  return id;
+}
+
+void AssociateGoogleVariationID(IDCollectionKey key,
+                                const std::string& trial_name,
+                                const std::string& group_name,
+                                VariationID id) {
+  GroupMapAccessor::GetInstance()->AssociateID(
+      key, MakeActiveGroupId(trial_name, group_name), id, false);
+}
+
+void AssociateGoogleVariationIDForce(IDCollectionKey key,
+                                     const std::string& trial_name,
+                                     const std::string& group_name,
+                                     VariationID id) {
+  GroupMapAccessor::GetInstance()->AssociateID(
+      key, MakeActiveGroupId(trial_name, group_name), id, true);
+}
+
+VariationID GetGoogleVariationID(IDCollectionKey key,
+                                 const std::string& trial_name,
+                                 const std::string& group_name) {
+  return GroupMapAccessor::GetInstance()->GetID(
+      key, MakeActiveGroupId(trial_name, group_name));
+}
+
+bool AssociateVariationParams(
+    const std::string& trial_name,
+    const std::string& group_name,
+    const std::map<std::string, std::string>& params) {
+  return VariationsParamAssociator::GetInstance()->AssociateVariationParams(
+      trial_name, group_name, params);
+}
+
+bool GetVariationParams(const std::string& trial_name,
+                        std::map<std::string, std::string>* params) {
+  return VariationsParamAssociator::GetInstance()->GetVariationParams(
+      trial_name, params);
+}
+
+std::string GetVariationParamValue(const std::string& trial_name,
+                                   const std::string& param_name) {
+  std::map<std::string, std::string> params;
+  if (GetVariationParams(trial_name, &params)) {
+    std::map<std::string, std::string>::iterator it = params.find(param_name);
+    if (it != params.end())
+      return it->second;
+  }
+  return std::string();
+}
+
+// Functions below are exposed for testing explicitly behind this namespace.
+// They simply wrap existing functions in this file.
+namespace testing {
+
+void ClearAllVariationIDs() {
+  GroupMapAccessor::GetInstance()->ClearAllMapsForTesting();
+}
+
+void ClearAllVariationParams() {
+  VariationsParamAssociator::GetInstance()->ClearAllParamsForTesting();
+}
+
+}  // namespace testing
+
+}  // namespace chrome_variations