// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/webui/flags/flags_ui_metrics.h"

#include <set>
#include <string>

#include "base/logging.h"
#include "base/metrics/histogram_functions.h"
#include "base/metrics/metrics_hashes.h"
#include "base/notreached.h"
#include "base/strings/string_util.h"

namespace flags_ui {

namespace {

// Records a set of feature switches (prefixed with "--").
void ReportAboutFlagsHistogramSwitches(const std::string& uma_histogram_name,
                                       const std::set<std::string>& switches) {
  for (const std::string& flag : switches) {
    int uma_id = testing::kBadSwitchFormatHistogramId;
    if (base::StartsWith(flag, "--", base::CompareCase::SENSITIVE)) {
      // Skip '--' before switch name.
      std::string switch_name(flag.substr(2));

      // Kill value, if any.
      const size_t value_pos = switch_name.find('=');
      if (value_pos != std::string::npos) {
        switch_name.resize(value_pos);
      }

      uma_id = GetSwitchUMAId(switch_name);
    } else {
      NOTREACHED() << "ReportAboutFlagsHistogram(): flag '" << flag
                   << "' has incorrect format.";
    }
    DVLOG(1) << "ReportAboutFlagsHistogram(): histogram='" << uma_histogram_name
             << "' '" << flag << "', uma_id=" << uma_id;
    base::UmaHistogramSparse(uma_histogram_name, uma_id);
  }
}

// Records a set of FEATURE_VALUE_TYPE features (suffixed with ":enabled" or
// "disabled", depending on their state).
void ReportAboutFlagsHistogramFeatures(const std::string& uma_histogram_name,
                                       const std::set<std::string>& features) {
  for (const std::string& feature : features) {
    int uma_id = GetSwitchUMAId(feature);
    DVLOG(1) << "ReportAboutFlagsHistogram(): histogram='" << uma_histogram_name
             << "' '" << feature << "', uma_id=" << uma_id;
    base::UmaHistogramSparse(uma_histogram_name, uma_id);
  }
}

}  // namespace

base::HistogramBase::Sample32 GetSwitchUMAId(const std::string& switch_name) {
  return static_cast<base::HistogramBase::Sample32>(
      base::HashMetricName(switch_name));
}

void ReportAboutFlagsHistogram(const std::string& uma_histogram_name,
                               const std::set<std::string>& switches,
                               const std::set<std::string>& features) {
  ReportAboutFlagsHistogramSwitches(uma_histogram_name, switches);
  ReportAboutFlagsHistogramFeatures(uma_histogram_name, features);
}

namespace testing {

const base::HistogramBase::Sample32 kBadSwitchFormatHistogramId = 0;

}  // namespace testing

}  // namespace flags_ui