// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <stdio.h>

#include <fbl/string.h>
#include <fbl/vector.h>

// This is a convenience library for outputting the raw data produced by a
// performance test in JSON format.  This allows reporting the time taken
// by each run of a test case, for example.
//
// This uses the JSON output format described in the Fuchsia Tracing
// Usage Guide:
// https://fuchsia.googlesource.com/fuchsia/+/HEAD/garnet/docs/tracing_usage_guide.md#benchmark-result-export
//
// Having a library for this should allow us to more easily change the JSON
// output format while ensuring that various performance tests are updated
// to produce the current version of the output format.

namespace perftest {

void WriteJSONString(FILE* out_file, const char* string);

struct SummaryStatistics {
  double min;
  double max;
  double mean;
  double std_dev;
  double median;
};

// This represents the results for a particular test case.  It contains a
// sequence of values, which are typically the times taken by each run of
// the test case, in order.
struct TestCaseResults {
  TestCaseResults(const fbl::String& test_suite, const fbl::String& label, const fbl::String& unit)
      : test_suite(test_suite), label(label), unit(unit) {}

  void AppendValue(double value) { values.push_back(value); }

  // A caller may check for errors using ferror().
  void WriteJSON(FILE* out_file) const;

  SummaryStatistics GetSummaryStatistics() const;

  fbl::String test_suite;
  fbl::String label;
  fbl::String unit;
  fbl::Vector<double> values;
  uint64_t bytes_processed_per_run = 0;
};

// This represents the results for a set of test cases.
//
// The test cases may be kept in the order in which they were run, in case
// ordering is significant.  (For example, it might turn out that one test
// case affects a later test case.)
class ResultsSet {
 public:
  fbl::Vector<TestCaseResults>* results() { return &results_; }

  TestCaseResults* AddTestCase(const fbl::String& test_suite, const fbl::String& label,
                               const fbl::String& unit);

  // A caller may check for errors using ferror().
  void WriteJSON(FILE* out_file) const;

  // Writes the data to a file, in JSON format.  Returns whether this was
  // successful; prints an error to stderr if this was not successful.
  bool WriteJSONFile(const char* output_filename) const;

  void PrintSummaryStatistics(FILE* out_file) const;

 private:
  fbl::Vector<TestCaseResults> results_;
};

}  // namespace perftest