src/lib/util/clock.h

// Copyright 2017 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.

#ifndef COBALT_SRC_LIB_UTIL_CLOCK_H_
#define COBALT_SRC_LIB_UTIL_CLOCK_H_

#include <chrono>
#include <memory>
#include <optional>
#include <string>

#include "src/public/lib/clock_interfaces.h"
#include "src/public/lib/compat/clock.h"
#include "src/public/lib/statusor/statusor.h"

namespace cobalt::util {

// A clock that returns the real system time.
class SystemClock : public SystemClockInterface {
 public:
  std::chrono::system_clock::time_point now() override { return std::chrono::system_clock::now(); }
};

// Allows us to mock out a clock for tests.
// A clock that returns the real system time.
class SteadyClock : public SteadyClockInterface {
 public:
  std::chrono::steady_clock::time_point now() override { return std::chrono::steady_clock::now(); }
};

// A clock that returns the boot time, i.e. the amount of time since the OS booted.
class BootClock : public BootClockInterface {
 public:
  compat::boot_clock::time_point now() override { return compat::boot_clock::now(); }
};

// A wrapper for a SystemClockInterface that is always accurate.
class AlwaysAccurateClock : public util::ValidatedClockInterface {
 public:
  explicit AlwaysAccurateClock(std::unique_ptr<SystemClockInterface> system_clock)
      : system_clock_(std::move(system_clock)) {}

  std::optional<std::chrono::system_clock::time_point> now() override {
    return system_clock_->now();
  }

 private:
  std::unique_ptr<SystemClockInterface> system_clock_;
};

// A CivilTimeConverterInterface that converts a time point to a time struct with respect to
// UTC, regardless of the time zone identifier that is passed to `civil_time()`.
//
// This is the fallback converter that is used to compute civil times for metrics with the
// OTHER_TIME_ZONE policy in the case where no CivilTimeConverterInterface was provided to the
// CobaltService.
class UtcTimeConverter : public util::CivilTimeConverterInterface {
 public:
  [[nodiscard]] lib::statusor::StatusOr<std::tm> civil_time(
      std::chrono::system_clock::time_point time, const std::string& /*time_zone*/) const override {
    std::time_t time_t = std::chrono::system_clock::to_time_t(time);
    std::tm time_struct;
    gmtime_r(&time_t, &time_struct);
    return time_struct;
  }
};

}  // namespace cobalt::util

#endif  // COBALT_SRC_LIB_UTIL_CLOCK_H_