#ifndef OPENVPN_TIME_TIME_H
#define OPENVPN_TIME_TIME_H

#include <limits>

#include <openvpn/common/platform.hpp>
#include <openvpn/common/exception.hpp>

#ifdef OPENVPN_PLATFORM_WIN
#include <time.h>     // for ::time() on Windows
#include <windows.h>  // for GetTickCount
#else
#include <sys/time.h> // for ::time() and ::gettimeofday()
#endif

namespace openvpn {
  OPENVPN_SIMPLE_EXCEPTION(get_time_error);

  template <typename T>
  class TimeType
  {
  public:
    enum { prec=1024 };
    typedef ::time_t base_type;
    typedef T type;

    class Duration
    {
      friend class TimeType;

    public:
      static Duration seconds(const T v) { return Duration(v * prec); }
      static Duration binary_ms(const T v) { return Duration(v); }
      static Duration infinite() { return Duration(std::numeric_limits<T>::max()); }

      Duration() : duration_(T(0)) {}

      bool defined() const { return duration_ != T(0); }
      bool operator!() const { return duration_ == T(0); }
      bool is_infinite() const { return duration_ == std::numeric_limits<T>::max(); }
      void set_infinite() { duration_ = std::numeric_limits<T>::max(); }
      void set_zero() { duration_ = T(0); }

      Duration operator+(const Duration& d) const
      {
	if (is_infinite() || d.is_infinite())
	  return infinite();
	else
	  return Duration(duration_ + d.duration_);
      }

      Duration& operator+=(const Duration& d)
      {
	if (is_infinite() || d.is_infinite())
	  set_infinite();
	else
	  duration_ += d.duration_;
	return *this;
      }

      void min(const Duration& d)
      {
	if (d.duration_ < duration_)
	  duration_ = d.duration_;
      }

      void max(const Duration& d)
      {
	if (d.duration_ > duration_)
	  duration_ = d.duration_;
      }

      Duration operator-(const Duration& d) const
      {
	if (d.duration_ >= duration_)
	  return Duration(0);
	else if (is_infinite())
	  return Duration::infinite();
	else
	  return Duration(duration_ - d.duration_);
      }

      Duration& operator-=(const Duration& d)
      {
	if (d.duration_ >= duration_)
	  set_zero();
	else if (!is_infinite())
	  duration_ -= d.duration_;
	return *this;
      }

      T to_seconds() const { return duration_ / prec; }
      T to_binary_ms() const { return duration_; }

      T to_milliseconds() const
      {
	return duration_ - (duration_ * T(3) / T(128)); // NOTE: assumes that prec == 1024
      }

      T raw() const { return duration_; }

#     define OPENVPN_DURATION_REL(OP) bool operator OP(const Duration& d) const { return duration_ OP d.duration_; }
      OPENVPN_DURATION_REL(==)
      OPENVPN_DURATION_REL(!=)
      OPENVPN_DURATION_REL(>)
      OPENVPN_DURATION_REL(<)
      OPENVPN_DURATION_REL(>=)
      OPENVPN_DURATION_REL(<=)
#     undef OPENVPN_DURATION_REL

    private:
      explicit Duration(const T duration) : duration_(duration) {}

      T duration_;
    };

    TimeType() : time_(T(0)) {}

    static TimeType zero() { return TimeType(T(0)); }
    static TimeType infinite() { return TimeType(std::numeric_limits<T>::max()); }

    bool is_infinite() const { return time_ == std::numeric_limits<T>::max(); }

    void reset() { time_ = 0; }
    void set_infinite() { time_ = std::numeric_limits<T>::max(); }

    bool defined() const { return time_ != 0; }
    bool operator!() const { return time_ == 0; }

    base_type seconds_since_epoch() const { return base_ + time_ / prec; }
    T fractional_binary_ms() const { return time_ % prec; }

    static TimeType now() { return TimeType(now_()); }

    void update() { time_ = now_(); }

    TimeType operator+(const Duration& d) const
    {
      if (is_infinite() || d.is_infinite())
	return infinite();
      else
	return TimeType(time_ + d.duration_);
    }

    TimeType& operator+=(const Duration& d)
    {
      if (is_infinite() || d.is_infinite())
	set_infinite();
      else
	time_ += d.duration_;
      return *this;
    }

    Duration operator-(const TimeType& t) const
    {
      if (t.time_ >= time_)
	return Duration(0);
      else if (is_infinite())
	return Duration::infinite();
      else
	return Duration(time_ - t.time_);
    }

    void min(const TimeType& t)
    {
      if (t.time_ < time_)
	time_ = t.time_;
    }

    void max(const TimeType& t)
    {
      if (t.time_ > time_)
	time_ = t.time_;
    }

#   define OPENVPN_TIME_REL(OP) bool operator OP(const TimeType& t) const { return time_ OP t.time_; }
    OPENVPN_TIME_REL(==)
    OPENVPN_TIME_REL(!=)
    OPENVPN_TIME_REL(>)
    OPENVPN_TIME_REL(<)
    OPENVPN_TIME_REL(>=)
    OPENVPN_TIME_REL(<=)
#   undef OPENVPN_TIME_REL

    T raw() const { return time_; }

    static void reset_base()
    {
      base_ = ::time(0);
#     ifdef OPENVPN_PLATFORM_WIN
        win_recalibrate(::GetTickCount());
#     endif
    }

  private:
    explicit TimeType(const T time) : time_(time) {}

#ifdef OPENVPN_PLATFORM_WIN

    static void win_recalibrate(const DWORD gtc)
    {
      gtc_last = gtc;
      gtc_base = ::time(0) - gtc_last/1000;
    }

    static T now_()
    {
      const DWORD gtc = ::GetTickCount();
      if (gtc < gtc_last)
	win_recalibrate(gtc);
      const time_t sec = gtc_base + gtc / 1000;
      const unsigned int msec = gtc % 1000;
      return T((sec - base_) * prec + msec * prec / 1000);
    }

    static DWORD gtc_last;
    static time_t gtc_base;

#else

    static T now_()
    {
      ::timeval tv;
      if (::gettimeofday(&tv, NULL) != 0)
	throw get_time_error();
      return T((tv.tv_sec - base_) * prec + tv.tv_usec * prec / 1000000);
    }

#endif

    static base_type base_;
    T time_;
  };

#ifdef OPENVPN_PLATFORM_WIN
  template <typename T> DWORD TimeType<T>::gtc_last;
  template <typename T> time_t TimeType<T>::gtc_base;
#endif

  template <typename T> typename TimeType<T>::base_type TimeType<T>::base_;

  typedef TimeType<unsigned long> Time;

  typedef Time* TimePtr;

} // namespace openvpn

#endif // OPENVPN_TIME_TIME_H