year_month_weekday.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
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Copyright(c) 2025 John Wellbelove
 
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#ifndef ETL_IN_CHRONO_H
  #error DO NOT DIRECTLY INCLUDE THIS FILE. USE CHRONO.H
#endif
 
namespace etl
{
  namespace chrono
  {
    //*************************************************************************
    //*************************************************************************
    class year_month_weekday
    {
    public:
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR year_month_weekday()
        : y()
        , m()
        , wdi()
      {
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 year_month_weekday(const etl::chrono::year&    y_, 
                                         const etl::chrono::month&   m_, 
                                         const etl::chrono::weekday_indexed& wdi_) ETL_NOEXCEPT
        : y(y_)
        , m(m_)
        , wdi(wdi_)
      {
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 year_month_weekday(const etl::chrono::sys_days& sd) ETL_NOEXCEPT
      {
        // Extract year, month, and day
        year_month_day ymd = year_month_day{sd};
 
        etl::chrono::year  yr  = ymd.year();
        etl::chrono::month mth = ymd.month();
        etl::chrono::day   dy  = ymd.day();
 
        // Get the weekday from sys_days
        etl::chrono::weekday wd = etl::chrono::weekday{sd};
 
        // Count how many times this weekday has occurred in the month so far
        // We walk backward from the given day in steps of 7 days
        unsigned index = 1;
        
        for (int offset = static_cast<int>(dy) - 7; offset > 0; offset -= 7) 
        {
          ++index;
        }
 
        y = yr;
        m = mth;
        wdi = etl::chrono::weekday_indexed{ wd, index };
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 year_month_weekday(const etl::chrono::local_days& ld) ETL_NOEXCEPT
      {
        year_month_weekday ymwd(sys_days(ld.time_since_epoch()));
 
        y   = ymwd.year();
        m   = ymwd.month();
        wdi = ymwd.weekday_indexed();
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::year year() const ETL_NOEXCEPT
      {
        return y;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::month month() const ETL_NOEXCEPT
      {
        return m;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::weekday weekday() const ETL_NOEXCEPT
      {
        return wdi.weekday();
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 unsigned index() const ETL_NOEXCEPT
      {
        return wdi.index();
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::weekday_indexed weekday_indexed() const ETL_NOEXCEPT
      {
        return wdi;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 bool ok() const ETL_NOEXCEPT
      {       
        return y.ok() && m.ok() && wdi.ok();
      }
 
      //***********************************************************************
      //***********************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 operator etl::chrono::sys_days() const ETL_NOEXCEPT
      {
        if (ok())
        {
          etl::chrono::year_month_weekday ymwd(*this);
          etl::chrono::year_month_day ymd{ ymwd.year(), ymwd.month(), etl::chrono::day(1) };
 
          etl::chrono::sys_days sd = ymd;
 
          unsigned int target_wd = ymwd.weekday().c_encoding();
          unsigned int target_index = ymwd.index();
 
          etl::chrono::weekday first_weekday(static_cast<int>(sd.time_since_epoch().count()));
 
          int first_wd = first_weekday.c_encoding();
          int offset = (target_wd - first_wd + 7) % 7;
          int day_of_month = offset + static_cast<int>(target_index - 1) * 7;
 
          etl::chrono::year_month_day result(year(), month(), etl::chrono::day(day_of_month));
 
          return etl::chrono::sys_days(result);
        }
        else
        {
          return etl::chrono::sys_days();
        }
      }
 
      //***********************************************************************
      //***********************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 operator etl::chrono::local_days() const ETL_NOEXCEPT
      {
        return local_days(sys_days(*this).time_since_epoch());
      }
 
    private:
 
      etl::chrono::year    y;
      etl::chrono::month   m;
      etl::chrono::weekday_indexed wdi;
    };
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator +(const etl::chrono::year_month_weekday& ymwd,
                                                                      const etl::chrono::years& dy) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator +(const etl::chrono::years& dy,
                                                                      const etl::chrono::year_month_weekday& ymwd) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator +(const etl::chrono::year_month_weekday& ymwd,
                                                                      const etl::chrono::months& dm) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year(), ymwd.month() + dm, ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator +(const etl::chrono::months& dm,
                                                                      const etl::chrono::year_month_weekday& ymwd) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year(), ymwd.month() + dm, ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator -(const etl::chrono::year_month_weekday& ymwd,
                                                                      const etl::chrono::years& dy) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year() - dy, ymwd.month(), ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday operator -(const etl::chrono::year_month_weekday& ymwd,
                                                                      const etl::chrono::months& dm) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday(ymwd.year(), ymwd.month() - dm, ymwd.weekday_indexed());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 bool operator ==(const etl::chrono::year_month_weekday& lhs, 
                                            const etl::chrono::year_month_weekday& rhs) ETL_NOEXCEPT
    {
      return (lhs.year() == rhs.year())   && 
             (lhs.month() == rhs.month()) && 
             (lhs.weekday() == rhs.weekday());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 bool operator !=(const etl::chrono::year_month_weekday& lhs, 
                                            const etl::chrono::year_month_weekday& rhs) ETL_NOEXCEPT
    {
      return !(lhs == rhs);
    }
 
    //*************************************************************************
    //*************************************************************************
    class year_month_weekday_last
    {
    public:
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 year_month_weekday_last(const etl::chrono::year&         y_, 
                                              const etl::chrono::month&        m_, 
                                              const etl::chrono::weekday_last& wdl_) ETL_NOEXCEPT
        : y(y_)
        , m(m_)
        , wdl(wdl_)
      {
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::year year() const ETL_NOEXCEPT
      {
        return y;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::month month() const ETL_NOEXCEPT
      {
        return m;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::weekday weekday() const ETL_NOEXCEPT
      {
        return wdl.weekday();
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 etl::chrono::weekday_last weekday_last() const ETL_NOEXCEPT
      {
        return wdl;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last& operator +=(const etl::chrono::years& dy) ETL_NOEXCEPT
      {
        y += dy;
 
        return *this;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last& operator +=(const etl::chrono::months& dm) ETL_NOEXCEPT
      {
        m += dm;
 
        return *this;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last& operator -=(const etl::chrono::years& dy) ETL_NOEXCEPT
      {
        y -= dy;
 
        return *this;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last& operator -=(const etl::chrono::months& dm) ETL_NOEXCEPT
      {
        m -= dm;
 
        return *this;
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 operator etl::chrono::sys_days() const ETL_NOEXCEPT
      {
        // Get the last day of the month
        etl::chrono::year_month_day_last ymdl(year(), etl::chrono::month_day_last(month()));
        etl::chrono::day last_day = ymdl.day();
 
        // Walk backward from the last day to find the last occurrence of the target weekday
        unsigned d = static_cast<unsigned>(last_day);
        
        for (; d >= 1; --d)
        {
          etl::chrono::year_month_day ymd(year(), month(), etl::chrono::day(d));
          etl::chrono::sys_days ymd_sys_days = static_cast<etl::chrono::sys_days>(ymd);
          etl::chrono::weekday wd(static_cast<int>(ymd_sys_days.time_since_epoch().count()));
          
          if (wd == weekday())
          {
            return ymd_sys_days;
          }
        }
 
        // If not found (should not happen for valid input), return epoch
        return etl::chrono::sys_days();
      }
 
      //*************************************************************************
      //*************************************************************************
      ETL_NODISCARD
      ETL_CONSTEXPR14 explicit operator etl::chrono::local_days() const ETL_NOEXCEPT
      {
        return local_days(sys_days(*this).time_since_epoch());
      }
 
    private:
 
      etl::chrono::year  y;
      etl::chrono::month m;
      etl::chrono::weekday_last wdl;
    };
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator +(const etl::chrono::year_month_weekday_last& ymwdl,
                                                                           const etl::chrono::years& dy) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year() + dy, ymwdl.month(), ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator +(const etl::chrono::years& dy,
                                                                           const etl::chrono::year_month_weekday_last& ymwdl) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year() + dy, ymwdl.month(), ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator +(const etl::chrono::year_month_weekday_last& ymwdl,
                                                                           const etl::chrono::months& dm) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year(), ymwdl.month() + dm, ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator +(const etl::chrono::months& dm,
                                                                           const etl::chrono::year_month_weekday_last& ymwdl) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year(), ymwdl.month() + dm, ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator -(const etl::chrono::year_month_weekday_last& ymwdl,
                                                                           const etl::chrono::years& dy) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year() - dy, ymwdl.month(), ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 etl::chrono::year_month_weekday_last operator -(const etl::chrono::year_month_weekday_last& ymwdl,
                                                                           const etl::chrono::months& dm) ETL_NOEXCEPT
    {
      return etl::chrono::year_month_weekday_last(ymwdl.year(), ymwdl.month() - dm, ymwdl.weekday_last());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 bool operator ==(const etl::chrono::year_month_weekday_last& lhs, 
                                            const etl::chrono::year_month_weekday_last& rhs) ETL_NOEXCEPT
    {
      return (lhs.year() == rhs.year())   &&
             (lhs.month() == rhs.month()) &&
             (lhs.weekday() == rhs.weekday());
    }
 
    //*************************************************************************
    //*************************************************************************
    inline ETL_CONSTEXPR14 bool operator !=(const etl::chrono::year_month_weekday_last& lhs, 
                                            const etl::chrono::year_month_weekday_last& rhs) ETL_NOEXCEPT
    {
      return !(lhs == rhs);
    }
  }
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_8BIT_TYPES
  template <>
  struct hash<etl::chrono::year_month_weekday>
  {
    size_t operator()(const etl::chrono::year_month_weekday& ymwd) const
    {
      etl::chrono::year::rep  y = static_cast<etl::chrono::year::rep>(static_cast<unsigned>(ymwd.year()));
      etl::chrono::month::rep m = static_cast<etl::chrono::month::rep>(static_cast<unsigned>(ymwd.month()));
      unsigned int  wd = ymwd.weekday().c_encoding();
 
      uint8_t buffer[sizeof(y) + sizeof(m) + sizeof(wd)];
 
      memcpy(buffer,                         &y, sizeof(y));
      memcpy(buffer + sizeof(y),             &m, sizeof(m));
      memcpy(buffer + sizeof(y) + sizeof(m), &wd, sizeof(wd));
 
      return etl::private_hash::generic_hash<size_t>(buffer, buffer + sizeof(y) + sizeof(m) + sizeof(wd));
    }
  };
#endif
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_8BIT_TYPES
  template <>
  struct hash<etl::chrono::year_month_weekday_last>
  {
    size_t operator()(const etl::chrono::year_month_weekday_last& ymwdl) const
    {
      etl::chrono::year::rep  y = static_cast<etl::chrono::year::rep>(static_cast<unsigned>(ymwdl.year()));
      etl::chrono::month::rep m = static_cast<etl::chrono::month::rep>(static_cast<unsigned>(ymwdl.month()));
      unsigned int  wd = ymwdl.weekday().c_encoding();
 
      uint8_t buffer[sizeof(y) + sizeof(m) + sizeof(wd)];
 
      memcpy(buffer,                         &y, sizeof(y));
      memcpy(buffer + sizeof(y),             &m, sizeof(m));
      memcpy(buffer + sizeof(y) + sizeof(m), &wd, sizeof(wd));
 
      return etl::private_hash::generic_hash<size_t>(buffer, buffer + sizeof(y) + sizeof(m) + sizeof(wd));
    }
  };
#endif
}