//%TITLE Days and Date Date Implementation
//                         See IDIDATE.HPP for documentation

#include "global.hpp"
#include "Date.hpp"
#include <string.h>

//  Days implementation
//  -------------------

  char*   Days::unit  = "day";

 ostream& Days::put(ostream& ls) const
 {ls << value << ' ' << Days::unit;
  if (abs(value) != 1) ls << 's';    //  Append English plural
  return ls;
 }

 istream& Days::get(istream& ls) 
 {ls >> value; return ls; }          //  (mainly for debugging)

//%SPACE 5

//  Date implementation
//  -------------------

//  Constant initialization
//  -----------------------

 LONG Date::BIAS                          // Internal representation
      = - CalendarInfo::DAYS_PER_400_YEARS * 5 // Origin date is December 30,
        + CalendarInfo::DAYS_PER_100_YEARS     //   1899, for compatibility
        + CalendarInfo::DAYS_PER_YEAR + 2;     //      with Lotus 1-2-3
//%SPACE 2
 SHORT Date::BIAS_WEEKDAY = 6;            // Origin date is a Saturday
//%SPACE 2
 short Date::century_break = 20;           // 2-digit year is 20yy if yy less
                                           //                 19yy otherwise
                                           // (user may override this one)


Date::Date (LONG yyyy, UINT ddd)           //  Year and day number
              : value(BIAS)                //  (no error check on ddd)
 {LONG years = yyyy - 1;                   //  Number of elapsed years
   value += years                          //  Convert years
              * CalendarInfo::DAYS_PER_YEAR//    to days
          + years / 4                      //  Apply
	  - years / 100                    //    leap-year
	  + years / 400                    //      adjustment
          + ddd;                           //  Add day number within year
  }



Date::Date (LONG yyyy, SHORT mm, SHORT dd)    //  Year-month-day
      : value(0)                        //  (with full error checking)
  {bool leap_year = CalendarInfo::isLeapYear(yyyy);
   if   (mm < 1 ||  mm > 12
                || dd < 1 || (dd > CalendarInfo::DAYS_IN_MONTH [mm]
		           && !(dd == 29 && mm == 2 && leap_year)))
      {clog << endl << "DATE01 -- Illegal value ("
	      << yyyy << '-' << mm << '-' << dd << "). ";}
      {int ddd = CalendarInfo::DAYS_BEFORE_MONTH [mm] + dd;
             ddd += (leap_year && (mm > 2)); //  First convert mm-dd to ddd
         value = Date(yyyy,ddd).value;}     //  Now use previous constructor
  }


Date::Date (CHAR yymmdd[6])                  //  ANSI 6-character string
  {if (strlen(yymmdd) != 6) return;          //  (check only on length)
   char charVal[6];
   for (int i = 0; i < 6; i++)               //  Convert characters
     charVal[i] = yymmdd[i] - '0';           //    to their values

   int   yy = charVal[0] * 10 + charVal[1];  //  Extract year
   short mm = charVal[2] * 10 + charVal[3];  //  Extract month
   short dd = charVal[4] * 10 + charVal[5];  //  Extract day

   yy += (yy < century_break) ? 2000 : 1900; //  Choose 20th or 21st century

   value = Date(yy,mm,dd).value;            //  Now use previous constructor
  }
//%SPACE 2
 ostream& Date::put(ostream& rs) const
 {return rs << year() << '-' << month()
                      << '-' << day();}

 istream& Date::get(istream& rs)
 {int y, m, d;
  rs >> y >> m >> d;
  value = Date(y,m,d).value;
  return rs;
 }
//%EJECT
 long        Date::yyyy = 0;              // Meaningless
 short       Date::mm   = 0;              //   initializations
 short       Date::dd   = 0;              //     required by the
 short       Date::ddd  = 0;              //       linking loader
 long        Date::cur_value = 0;


 void Date::set_ymd() const         //  Extract date subfields
 {if  (value == cur_value) return;  //  To avoid redundant calculation we
  cur_value  =  value;              //     save the results, but this won't
                                    //     won't work with multi-tasking.
  long ndays = value - BIAS;        //  Strip off origin date
  
  int           ngrps;
 
  ngrps      =  ndays / CalendarInfo::DAYS_PER_400_YEARS;
  yyyy       =  ngrps * 400;
  ndays     -=  ngrps * CalendarInfo::DAYS_PER_400_YEARS;
 
  ngrps      =  ndays / CalendarInfo::DAYS_PER_100_YEARS;
  yyyy      +=  ngrps * 100;
  ndays     -=  ngrps * CalendarInfo::DAYS_PER_100_YEARS;
 
  ngrps      =  ndays / CalendarInfo::DAYS_PER_4_YEARS;
  yyyy      +=  ngrps * 4;
  ndays     -=  ngrps * CalendarInfo::DAYS_PER_4_YEARS;
 
  if (ndays == 0)                           
        ndays = ddd = CalendarInfo::isLeapYear? 366 : 365;                
  else {ndays  += CalendarInfo::DAYS_PER_YEAR - 1;
        yyyy   += ndays / CalendarInfo::DAYS_PER_YEAR;
        ndays  %=  CalendarInfo::DAYS_PER_YEAR; ++ddd; 
       }
 
//  At this point, ndays is the day number within yyyy
  
  ddd = ndays;  
  if (CalendarInfo::isLeapYear(yyyy))
      if (ndays > 60) --ddd;
      else if (ndays=60) {mm = 2; dd = 29; return;}
  mm = (ddd + 28) / 29;
  if (dd < CalendarInfo::DAYS_BEFORE_MONTH[mm]) --mm;

  dd = dd - CalendarInfo::DAYS_BEFORE_MONTH[mm];
  if (mm==13) {mm=1; ++yyyy;}        
   
  return;}