//
// This is example code from Chapter 9.8 "The Date class" of 
// "Programming -- Principles and Practice Using C++" by Bjarne Stroustrup
//

#include "Chrono.h"

namespace Chrono {

// member function definitions:

//------------------------------------------------------------------------------

   Date::Date(int yy, Month mm, int dd)
      : y(yy), m(mm), d(dd)
   {
      if (!is_date(yy,mm,dd)) throw Invalid();
   }

//------------------------------------------------------------------------------

   const Date& default_date()
   {
      static const Date dd(2001,Month::jan,1); // start of 21st century
      return dd;
   }

//------------------------------------------------------------------------------

   Date::Date()
      :y(default_date().year()),
       m(default_date().month()),
       d(default_date().day())
   {
   }

//------------------------------------------------------------------------------

   void Date:: add_day(int n)
   {
      // ...
   }

//------------------------------------------------------------------------------

   void Date::add_month(int n)
   {
      // ...
   }

//------------------------------------------------------------------------------

   void Date::add_year(int n)
   {
      if (m==Month::feb && d==29 && !leapyear(y+n)) { // beware of leap years!
         m = Month::mar;        // use March 1 instead of February 29
         d = 1;
      }
      y+=n;
   }

//------------------------------------------------------------------------------

// helper functions:

   bool is_date(int y, Month  m, int d)
   {
      // assume that y is valid

      if (d<=0) return false;            // d must be positive

      int days_in_month = 31;            // most months have 31 days

      switch (m) {
      case Month::feb:                        // the length of February varies
         days_in_month = (leapyear(y))?29:28;
         break;
      case Month::apr: case Month::jun: case Month::sep: case Month::nov:
         days_in_month = 30;                // the rest have 30 days
         break;
      }

      if (days_in_month<d) return false;

      return true;
   } 

//------------------------------------------------------------------------------

   bool leapyear(int y)
   {
      // See exercise ???
      return false;
   }

//------------------------------------------------------------------------------

   bool operator==(const Date& a, const Date& b)
   {
      return a.year()==b.year()
         && a.month()==b.month()
         && a.day()==b.day();
   }

//------------------------------------------------------------------------------

   bool operator!=(const Date& a, const Date& b)
   {
      return !(a==b);
   }

//------------------------------------------------------------------------------

   ostream& operator<<(ostream& os, const Date& d)
   {
      return os << '(' << d.year()
                << ',' << int(d.month())
                << ',' << d.day() 
                << ')';
   }

//------------------------------------------------------------------------------

   istream& operator>>(istream& is, Date& dd)
   {
      int y, m, d;
      char ch1, ch2, ch3, ch4;
      is >> ch1 >> y >> ch2 >> m >> ch3 >> d >> ch4;
      if (!is) return is;
      if (ch1!='(' || ch2!=',' || ch3!=',' || ch4!=')') { // oops: format error
         is.clear(ios_base::failbit);                    // set the fail bit
         return is;
      }
      dd = Date(y,Month(m),d);     // update dd
      return is;
   }

//------------------------------------------------------------------------------

   enum Day {
      sunday, monday, tuesday, wednesday, thursday, friday, saturday
   };

//------------------------------------------------------------------------------

   Day day_of_week(const Date& d)
   {
      // ...
      return sunday;
   }

//------------------------------------------------------------------------------

   Date next_Sunday(const Date& d)
   {
      // ...
      return d;
   }

//------------------------------------------------------------------------------

   Date next_weekday(const Date& d)
   {
      // ...
      return d;
   }

//------------------------------------------------------------------------------

} // Chrono

//------------------------------------------------------------------------------

int main()
   try
      {
         Chrono::Date holiday(1978, Chrono::Month::jul, 4); // initialization
         Chrono::Date d2 = Chrono::next_Sunday(holiday);
         Chrono::Day  d  = day_of_week(d2);
         cout << "holiday is " << holiday << " d2 is " << d2 << endl;
         return holiday != d2;
      }
   catch (Chrono::Date::Invalid&) {
      cerr << "error: Invalid date\n"; 
      return 1;
   }
   catch (...) {
      cerr << "Oops: unknown exception!\n"; 
      return 2;
   }

//------------------------------------------------------------------------------