// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/metrics/histogram_delta_serialization.h"

#include <vector>

#include "base/functional/callback_helpers.h"
#include "base/metrics/histogram.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/statistics_recorder.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

TEST(HistogramDeltaSerializationTest, DeserializeHistogramAndAddSamples) {
  std::unique_ptr<StatisticsRecorder> statistic_recorder(
      StatisticsRecorder::CreateTemporaryForTesting());
  HistogramDeltaSerialization serializer;
  std::vector<std::string> deltas;
  // Nothing was changed yet.
  serializer.PrepareAndSerializeDeltas(&deltas, true);
  EXPECT_TRUE(deltas.empty());

  HistogramBase* histogram = Histogram::FactoryGet(
      "TestHistogram", 1, 1000, 10, HistogramBase::kIPCSerializationSourceFlag);
  histogram->Add(1);
  histogram->Add(10);
  histogram->Add(100);
  histogram->Add(1000);

  serializer.PrepareAndSerializeDeltas(&deltas, true);
  EXPECT_FALSE(deltas.empty());

  HistogramDeltaSerialization::DeserializeAndAddSamples(deltas,
                                                        base::NullCallback());

  // The histogram has kIPCSerializationSourceFlag. So samples will be ignored.
  std::unique_ptr<HistogramSamples> snapshot(histogram->SnapshotSamples());
  EXPECT_EQ(1, snapshot->GetCount(1));
  EXPECT_EQ(1, snapshot->GetCount(10));
  EXPECT_EQ(1, snapshot->GetCount(100));
  EXPECT_EQ(1, snapshot->GetCount(1000));

  // Clear kIPCSerializationSourceFlag to emulate multi-process usage.
  histogram->ClearFlags(HistogramBase::kIPCSerializationSourceFlag);
  HistogramDeltaSerialization::DeserializeAndAddSamples(deltas,
                                                        base::NullCallback());

  std::unique_ptr<HistogramSamples> snapshot2(histogram->SnapshotSamples());
  EXPECT_EQ(2, snapshot2->GetCount(1));
  EXPECT_EQ(2, snapshot2->GetCount(10));
  EXPECT_EQ(2, snapshot2->GetCount(100));
  EXPECT_EQ(2, snapshot2->GetCount(1000));
}

// Tests that the MapperCallback can be used to conditionally rename or drop
// metrics as they are deserialized. This validates the pipeline's ability to
// intercept child process IPC metrics (like Webium) and fork them into separate
// histogram names without needing to hardcode the separation into the sender.
TEST(HistogramDeltaSerializationTest, DeserializeWithMapper) {
  std::unique_ptr<StatisticsRecorder> statistic_recorder(
      StatisticsRecorder::CreateTemporaryForTesting());
  HistogramDeltaSerialization serializer;
  std::vector<std::string> deltas;

  HistogramBase* histogram1 =
      Histogram::FactoryGet("TestHistogram1", 1, 1000, 10,
                            HistogramBase::kIPCSerializationSourceFlag);
  histogram1->Add(1);

  HistogramBase* histogram2 =
      Histogram::FactoryGet("TestHistogram2", 1, 1000, 10,
                            HistogramBase::kIPCSerializationSourceFlag);
  histogram2->Add(2);

  serializer.PrepareAndSerializeDeltas(&deltas, true);
  EXPECT_FALSE(deltas.empty());

  histogram1->ClearFlags(HistogramBase::kIPCSerializationSourceFlag);
  histogram2->ClearFlags(HistogramBase::kIPCSerializationSourceFlag);

  auto mapper =
      base::BindRepeating([](std::string_view name) -> std::string_view {
        if (name == "TestHistogram1") {
          return "";
        }
        if (name == "TestHistogram2") {
          return "RenamedHistogram2";
        }
        return name;
      });

  HistogramDeltaSerialization::DeserializeAndAddSamples(deltas, mapper);

  EXPECT_EQ(1, histogram1->SnapshotSamples()->GetCount(1));
  EXPECT_EQ(1, histogram2->SnapshotSamples()->GetCount(2));

  HistogramBase* renamed =
      StatisticsRecorder::FindHistogram("RenamedHistogram2");
  ASSERT_TRUE(renamed);
  EXPECT_EQ(1, renamed->SnapshotSamples()->GetCount(2));
}

}  // namespace base