Add filtering logic for client-side variations.

chrome/browser/metrics/variations_service.cc

Index: chrome/browser/metrics/variations_service.cc
diff --git a/chrome/browser/metrics/variations_service.cc b/chrome/browser/metrics/variations_service.cc
index e033bf870c7937836ad028e898cf92667df5186f..64a5f003682da2d7dbbf187cbd3f9077300d037e 100644
--- a/chrome/browser/metrics/variations_service.cc
+++ b/chrome/browser/metrics/variations_service.cc
@@ -5,6 +5,8 @@
 #include "chrome/browser/metrics/variations_service.h"
 
 #include "base/base64.h"
+#include "base/build_time.h"
+#include "base/version.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/browser_process.h"
@@ -22,6 +24,25 @@ namespace {
 const char kDefaultVariationsServer[] =
     "https://clients4.google.com/chrome-variations/seed";
 
+// Maps chrome_variations::Study_Channel enum values to corresponding
+// chrome::VersionInfo::Channel enum values.
+chrome::VersionInfo::Channel ConvertStudyChannelToVersionChannel(
+    chrome_variations::Study_Channel study_channel) {
+  switch (study_channel) {
+    case chrome_variations::Study_Channel_CANARY:
+      return chrome::VersionInfo::CHANNEL_CANARY;
+    case chrome_variations::Study_Channel_DEV:
+      return chrome::VersionInfo::CHANNEL_DEV;
+    case chrome_variations::Study_Channel_BETA:
+      return chrome::VersionInfo::CHANNEL_BETA;
+    case chrome_variations::Study_Channel_STABLE:
+      return chrome::VersionInfo::CHANNEL_STABLE;
+  }
+  // All enum values of |study_channel| were handled above.
+  NOTREACHED();
+  return chrome::VersionInfo::CHANNEL_UNKNOWN;
+}
+
 }  // namespace
 
 // Static
@@ -94,3 +115,90 @@ void VariationsService::StoreSeedData(const std::string& seed_data,
 
 VariationsService::VariationsService() {}
 VariationsService::~VariationsService() {}
+
+// static
+bool VariationsService::ShouldAddStudy(const chrome_variations::Study& study) {
+  const chrome::VersionInfo current_version_info;
+  if (!current_version_info.is_valid())
+    return false;
+
+  if (!CheckStudyChannel(study, chrome::VersionInfo::GetChannel())) {
+    DVLOG(1) << "Filtered out study " << study.name() << " due to version.";
+    return false;
+  }
+
+  if (!CheckStudyVersion(study, current_version_info.Version())) {
+    DVLOG(1) << "Filtered out study " << study.name() << " due to version.";
+    return false;
+  }
+
+  // Use build time and not system time to match what is done in field_trial.cc.
+  if (!CheckStudyDate(study, base::GetBuildTime())) {

[Ilya Sherman, 2012/05/07 22:49:04]

Hmm, this seems redundant with the version check.  Am I missing something, or is
this intentionally meant to be a convenient way to filter based on future
versions according to their release date?

[Alexei Svitkine (slow), 2012/05/08 14:43:25]

I agree, it's a bit strange. I think originally, the intention was to be able to
limit the trial to e.g. a period of a specific week, for example.

But in the end, we decided to use build time (at least for this original CL), so
that it's consistent with the field trials code expiry param. I agree that this
makes the original intent dubious since it's based on build time and not system
time.

We could discuss it in our weekly.

[Ilya Sherman, 2012/05/08 22:36:31]

That sounds good.  I think it would also be helpful to document the current
decision in the corresponding protocol buffer comments, so that it's less likely
anyone adding a server-side configuration would be surprised by this...

+    DVLOG(1) << "Filtered out study " << study.name() << " due to date.";
+    return false;
+  }
+
+  DVLOG(1) << "Kept study " << study.name() << ".";
+  return true;
+}
+
+// static
+bool VariationsService::CheckStudyChannel(
+    const chrome_variations::Study& study,
+    chrome::VersionInfo::Channel channel) {
+  for (int i = 0; i < study.channel_size(); ++i) {
+    if (ConvertStudyChannelToVersionChannel(study.channel(i)) == channel)
+      return true;
+  }
+  return false;
+}
+
+// static
+bool VariationsService::CheckStudyVersion(const chrome_variations::Study& study,
+                                          const std::string& version_string) {
+  const Version current_version(version_string);
+  if (!current_version.IsValid()) {
+    DCHECK(false);

[Ilya Sherman, 2012/05/07 22:49:04]

nit: NOTREACHED()

+    return false;
+  }
+
+  if (study.has_min_version()) {
+    const Version min_version(study.min_version());
+    if (!min_version.IsValid())
+      return false;
+    if (current_version.CompareTo(min_version) < 0)
+      return false;
+  }
+
+  if (study.has_max_version()) {
+    const Version max_version(study.max_version());
+    if (!max_version.IsValid())
+      return false;
+    if (current_version.CompareTo(max_version) > 0)
+      return false;
+  }
+
+  return true;
+}
+
+// static
+bool VariationsService::CheckStudyDate(const chrome_variations::Study& study,
+                                       const base::Time& date_time) {
+  const base::Time epoch = base::Time::UnixEpoch();
+
+  if (study.has_start_date()) {
+    const base::Time start_date =
+        epoch + base::TimeDelta::FromMilliseconds(study.start_date());
+    if (date_time < start_date)
+      return false;
+  }
+
+  if (study.has_expiry_date()) {
+    const base::Time expiry_date =
+        epoch + base::TimeDelta::FromMilliseconds(study.expiry_date());
+    if (date_time >= expiry_date)
+      return false;
+  }
+
+  return true;
+}