#ifndef DaTe_H
#define DaTe_H

// Oldham, Jeffrey D.
// 2000Apr28
// CS3352

// Store a Year and Month

// To the user, months are numbered 1 = Jan, ..., 12 = Dec.
// Only years after January 0 are represented.  (Of course, year 0 did
// not exist.)
// To the implementer, months are numbered 0 = Jan, ..., 11 = Dec.

class Date {
public:
  Date(void) : mon(0) {}
  Date(const unsigned long y, const unsigned long m) : mon(m-1 + y * 12) {}

  unsigned long year(void) const { return mon / 12; }
  unsigned long month(void) const { return 1 + (mon % 12); }

  // Addition
  friend
  Date operator+(const Date & d, const unsigned long mos) {
    return Date(d.mon + mos);
  }

  friend
  Date operator+(const unsigned long mos, const Date & d1) {
    return d1 + mos;
  }

  // Subtraction
  friend
  Date operator-(const Date & d, const unsigned long mos) {
    return Date(d.mon - mos);
  }

  // Increment and Decrement Operators
  Date& operator++(void) { // prefix
    ++mon;
    return *this;
  }

  Date operator++(int) { // postfix
    Date answer = *this;
    ++mon;
    return answer;
  }

  Date& operator--(void) { // prefix
    if (mon != 0) --mon;
    return *this;
  }

  Date operator--(int) { // postfix
    Date answer = *this;
    if (mon != 0) --mon;
    return answer;
  }

  // Comparison Operators
  friend
  bool operator<(const Date & d1, const Date & d2) {
    return d1.mon < d2.mon;
  }

  friend
  bool operator>(const Date & d1, const Date & d2) {
    return d2 < d1;
  }

  friend
  bool operator==(const Date & d1, const Date & d2) {
    return !(d1 < d2) && !(d2 < d1);
  }

  friend
  bool operator!=(const Date & d1, const Date & d2) {
    return !(d1 == d2);
  }

  friend
  bool operator<=(const Date & d1, const Date & d2) {
    return !(d1 > d2);
  }

  friend
  bool operator>=(const Date & d1, const Date & d2) {
    return !(d1 < d2);
  }

#ifdef DEBUG
  friend
  ostream& operator<<(ostream& out, const Date & d) {
    return out << d.mon/12 << ' ' << 1+(d.mon%12);
  }
#endif // DEBUG

private:
  typedef unsigned long ul;
  ul mon;			// store year and month as number of
				// months since January, year 0 (which did not
				// exist :( )
  
  Date(const unsigned long m) : mon(m) {}
};

#endif // DaTe_H