# ShowSimpleDate.py

""" Module contains a script that illustrates
the use of the class SimpleDate."""

def isLeapYear(y):
    """ Returns True if y is a leap year. False otherwise
    
    PreC: y is a positive integer
    """
    return ((y%100>0) and y%4==0) or ((y%100==0) and (y%400==0))

class SimpleDate:
    """
    Represents a date.
    
    Attributes
       m : int, index of month
       d : int, day
       y : int, year
       s : str, date string
    """
    # Class variables...
    TheMonths =['','January','February','March','April','May','June',
                'July','August','September','October','November','December']
    nDays =[0,31,28,31,30,31,30,31,31,30,31,30,31]
    
    def __init__(self,s):
        """ Returns a SimpleDate representation of the date encoded in s.
        
        Pre: s is a date string of the form 'm/d/y' where m is a string that encodes the month
        index, d is a string that encodes the day, and y is a string that encodes the year.
        """
        v = s.split('/')
        self.m = int(v[0])
        self.d = int(v[1])
        self.y = int(v[2])
        self.s = s
    
    def __str__(self):
        """ Pretty prints the date encoded in self
        """
        return self.TheMonths[self.m]+' '+str(self.d)+', '+str(self.y)
    
    def Tomorrow(self):
        """ Returns a SimpleDate that encodes the date of the day after
        the date encoded by self."""
        m = self.m
        d = self.d
        y = self.y
        Last = self.nDays[m]
        if isLeapYear(y) and m==2:
            Last+=1
        if d<Last:
            d+=1
        else:
            d=1
            if m<12:
                m+=1
            else:
                m=1
                y+=1
        return SimpleDate(str(m)+'/'+str(d)+'/'+str(y))
    
    def isequal(self,other):
        """ Returns True if the date encoded in self is the same as
        the date encoded in other.
        
        PreC: other is a SimpleDate
        """
        
        return self.m==other.m and self.d==other.d and self.y==other.y
    
    def dateIndex(self):
        """ Returns an int that is the index  of the date encoded in self.
        Jan 1, 1600 has index 1 and increments daily.
        """
        idx = 1
        Day = SimpleDate('1/1/1600')
        while not Day.isequal(self):
            idx+=1
            Day = Day.Tomorrow()
        return idx
    
    def FutureDate(self,n):
        """Returns a SimpleDate that corresponds to n days after
        the date encoded ib self.
        
        PreC: n is a positive int
        """
        Day = self
        for k in range(n):
            Day = Day.Tomorrow()
        return Day
    
if __name__ == '__main__':
    # An initial date
    s1 = SimpleDate('7/4/1776')
    # Because of the __str__ method we can pretty print the SimpleDate object
    # referenced by s1:
    print '\n',s1
    # Create a SimpleDate that encodes the next day
    TheNextDay = s1.Tomorrow()
    print '\nThe Day after ',s1,' is',TheNextDay
    # Create another date and ascertain how many days have
    # passed since the initial date.
    s2 = SimpleDate('1/1/2015')
    DaysElapsed = s2.dateIndex() - s1.dateIndex()
    print '\n%s is %1d days after %s.'% (s2,DaysElapsed,s1)

   D = SimpleDate('4/10/2015')
   print '\n',D
   n = 12
   E = D.FutureDate(n)
   print '%1d days after rhis is' % n
   print E