/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#pragma once

#include <react/debug/flags.h>
#include <chrono>
#include <functional>

namespace facebook::react {

class HighResDuration;
class HighResTimeStamp;

/*
 * A class representing a duration of time with high precision.
 *
 * @see __docs__/README.md for more information.
 */
class HighResDuration {
  friend class HighResTimeStamp;
  friend constexpr HighResDuration operator-(const HighResTimeStamp &lhs, const HighResTimeStamp &rhs);
  friend constexpr HighResTimeStamp operator+(const HighResTimeStamp &lhs, const HighResDuration &rhs);
  friend constexpr HighResTimeStamp operator-(const HighResTimeStamp &lhs, const HighResDuration &rhs);

 public:
  constexpr HighResDuration() : chronoDuration_(std::chrono::steady_clock::duration()) {}

  static constexpr HighResDuration zero()
  {
    return HighResDuration(std::chrono::steady_clock::duration::zero());
  }

  static constexpr HighResDuration fromChrono(std::chrono::steady_clock::duration chronoDuration)
  {
    return HighResDuration(chronoDuration);
  }

  static constexpr HighResDuration fromNanoseconds(int64_t units)
  {
    return HighResDuration(std::chrono::nanoseconds(units));
  }

  static constexpr HighResDuration fromMilliseconds(int64_t units)
  {
    return HighResDuration(std::chrono::milliseconds(units));
  }

  constexpr int64_t toNanoseconds() const
  {
    return std::chrono::duration_cast<std::chrono::nanoseconds>(chronoDuration_).count();
  }

  // @see https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp
  static constexpr HighResDuration fromDOMHighResTimeStamp(double units)
  {
    auto nanoseconds = static_cast<int64_t>(units * 1e6);
    return fromNanoseconds(nanoseconds);
  }

  // @see https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp
  constexpr double toDOMHighResTimeStamp() const
  {
    return static_cast<std::chrono::duration<double, std::milli>>(chronoDuration_).count();
  }

  constexpr HighResDuration operator+(const HighResDuration &rhs) const
  {
    return HighResDuration(chronoDuration_ + rhs.chronoDuration_);
  }

  constexpr HighResDuration operator+(const std::chrono::steady_clock::duration &rhs) const
  {
    return HighResDuration(chronoDuration_ + rhs);
  }

  constexpr HighResDuration operator-(const HighResDuration &rhs) const
  {
    return HighResDuration(chronoDuration_ - rhs.chronoDuration_);
  }

  constexpr HighResDuration operator-(const std::chrono::steady_clock::duration &rhs) const
  {
    return HighResDuration(chronoDuration_ - rhs);
  }

  constexpr HighResDuration &operator+=(const HighResDuration &rhs)
  {
    chronoDuration_ += rhs.chronoDuration_;
    return *this;
  }

  constexpr HighResDuration &operator+=(const std::chrono::steady_clock::duration &rhs)
  {
    chronoDuration_ += rhs;
    return *this;
  }

  constexpr HighResDuration &operator-=(const HighResDuration &rhs)
  {
    chronoDuration_ -= rhs.chronoDuration_;
    return *this;
  }

  constexpr HighResDuration &operator-=(const std::chrono::steady_clock::duration &rhs)
  {
    chronoDuration_ -= rhs;
    return *this;
  }

  constexpr bool operator==(const HighResDuration &rhs) const
  {
    return chronoDuration_ == rhs.chronoDuration_;
  }

  constexpr bool operator==(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ == rhs;
  }

  constexpr bool operator!=(const HighResDuration &rhs) const
  {
    return chronoDuration_ != rhs.chronoDuration_;
  }

  constexpr bool operator!=(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ != rhs;
  }

  constexpr bool operator<(const HighResDuration &rhs) const
  {
    return chronoDuration_ < rhs.chronoDuration_;
  }

  constexpr bool operator<(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ < rhs;
  }

  constexpr bool operator<=(const HighResDuration &rhs) const
  {
    return chronoDuration_ <= rhs.chronoDuration_;
  }

  constexpr bool operator<=(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ <= rhs;
  }

  constexpr bool operator>(const HighResDuration &rhs) const
  {
    return chronoDuration_ > rhs.chronoDuration_;
  }

  constexpr bool operator>(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ > rhs;
  }

  constexpr bool operator>=(const HighResDuration &rhs) const
  {
    return chronoDuration_ >= rhs.chronoDuration_;
  }

  constexpr bool operator>=(const std::chrono::steady_clock::duration &rhs) const
  {
    return chronoDuration_ >= rhs;
  }

  constexpr operator std::chrono::steady_clock::duration() const
  {
    return chronoDuration_;
  }

 private:
  explicit constexpr HighResDuration(std::chrono::steady_clock::duration chronoDuration)
      : chronoDuration_(chronoDuration)
  {
  }

  std::chrono::steady_clock::duration chronoDuration_;
};

/*
 * A class representing a specific point in time with high precision.
 *
 * @see __docs__/README.md for more information.
 */
class HighResTimeStamp {
  friend constexpr HighResDuration operator-(const HighResTimeStamp &lhs, const HighResTimeStamp &rhs);
  friend constexpr HighResTimeStamp operator+(const HighResTimeStamp &lhs, const HighResDuration &rhs);
  friend constexpr HighResTimeStamp operator-(const HighResTimeStamp &lhs, const HighResDuration &rhs);

 public:
  HighResTimeStamp() noexcept : chronoTimePoint_(chronoNow()) {}

  static HighResTimeStamp now() noexcept
  {
    return HighResTimeStamp(chronoNow());
  }

  static HighResDuration unsafeOriginFromUnixTimeStamp() noexcept
  {
    static auto origin = computeUnsafeOriginFromUnixTimeStamp();
    return origin;
  }

  static constexpr HighResTimeStamp min() noexcept
  {
    return HighResTimeStamp(std::chrono::steady_clock::time_point::min());
  }

  static constexpr HighResTimeStamp max() noexcept
  {
    return HighResTimeStamp(std::chrono::steady_clock::time_point::max());
  }

  // @see https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp
  static constexpr HighResTimeStamp fromDOMHighResTimeStamp(double units)
  {
    auto nanoseconds = static_cast<int64_t>(units * 1e6);
    return HighResTimeStamp(std::chrono::steady_clock::time_point(std::chrono::nanoseconds(nanoseconds)));
  }

  // @see https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp
  constexpr double toDOMHighResTimeStamp() const
  {
    return HighResDuration(chronoTimePoint_.time_since_epoch()).toDOMHighResTimeStamp();
  }

  // This method is expected to be used only when converting time stamps from
  // external systems.
  static constexpr HighResTimeStamp fromChronoSteadyClockTimePoint(
      std::chrono::steady_clock::time_point chronoTimePoint)
  {
    return HighResTimeStamp(chronoTimePoint);
  }

#ifdef REACT_NATIVE_DEBUG
  static void setTimeStampProviderForTesting(std::function<std::chrono::steady_clock::time_point()> &&timeStampProvider)
  {
    getTimeStampProvider() = std::move(timeStampProvider);
  }
#endif

  // This method is provided for convenience, if you need to convert
  // HighResTimeStamp to some common epoch with time stamps from other sources.
  constexpr std::chrono::steady_clock::time_point toChronoSteadyClockTimePoint() const
  {
    return chronoTimePoint_;
  }

  constexpr bool operator==(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ == rhs.chronoTimePoint_;
  }

  constexpr bool operator!=(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ != rhs.chronoTimePoint_;
  }

  constexpr bool operator<(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ < rhs.chronoTimePoint_;
  }

  constexpr bool operator<=(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ <= rhs.chronoTimePoint_;
  }

  constexpr bool operator>(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ > rhs.chronoTimePoint_;
  }

  constexpr bool operator>=(const HighResTimeStamp &rhs) const
  {
    return chronoTimePoint_ >= rhs.chronoTimePoint_;
  }

  constexpr HighResTimeStamp &operator+=(const HighResDuration &rhs)
  {
    chronoTimePoint_ += rhs.chronoDuration_;
    return *this;
  }

  constexpr HighResTimeStamp &operator-=(const HighResDuration &rhs)
  {
    chronoTimePoint_ -= rhs.chronoDuration_;
    return *this;
  }

 private:
  explicit constexpr HighResTimeStamp(std::chrono::steady_clock::time_point chronoTimePoint)
      : chronoTimePoint_(chronoTimePoint)
  {
  }

  std::chrono::steady_clock::time_point chronoTimePoint_;

  static HighResDuration computeUnsafeOriginFromUnixTimeStamp() noexcept
  {
    auto systemNow = std::chrono::system_clock::now();
    auto steadyNow = std::chrono::steady_clock::now();
    return HighResDuration(systemNow.time_since_epoch() - steadyNow.time_since_epoch());
  }

#ifdef REACT_NATIVE_DEBUG
  static std::function<std::chrono::steady_clock::time_point()> &getTimeStampProvider()
  {
    static std::function<std::chrono::steady_clock::time_point()> timeStampProvider = nullptr;
    return timeStampProvider;
  }

  static std::chrono::steady_clock::time_point chronoNow()
  {
    auto &timeStampProvider = getTimeStampProvider();
    return timeStampProvider != nullptr ? timeStampProvider() : std::chrono::steady_clock::now();
  }
#else
  inline static std::chrono::steady_clock::time_point chronoNow()
  {
    return std::chrono::steady_clock::now();
  }
#endif
};

inline constexpr HighResDuration operator-(const HighResTimeStamp &lhs, const HighResTimeStamp &rhs)
{
  return HighResDuration(lhs.chronoTimePoint_ - rhs.chronoTimePoint_);
}

inline constexpr HighResTimeStamp operator+(const HighResTimeStamp &lhs, const HighResDuration &rhs)
{
  return HighResTimeStamp(lhs.chronoTimePoint_ + rhs.chronoDuration_);
}

inline constexpr HighResTimeStamp operator-(const HighResTimeStamp &lhs, const HighResDuration &rhs)
{
  return HighResTimeStamp(lhs.chronoTimePoint_ - rhs.chronoDuration_);
}

} // namespace facebook::react