# isOkDate-7.12.py
# Determine whether a calendar date in the form mm/dd/yyyy is OK
# Neal Nelson  2007.11.07

# This program illustrates the import of a user module
# This program can also be used as an module import

# The program is uninformative about why a date is not OK.

import string
from isLeapYear import isLeapYear

# Because these tables are constant we can define them globally 
daysInMonth = [31,28,31,30,31,30,31,30,31,31,30,31]
daysInLeapMonth = [31,29,31,30,31,30,31,30,31,31,30,31]

# Short circuit evaluation of "and" operation (p256 Zelle) insures
# that month, day, and year are correct before calling isOkDay.
# Zelle calls this the "operational" definition of the boolean operators.
def isOkDate(m,d,y):
  return isOkYear(y) and isOkMonth(m) and isOkDay(m,d,y)

def isOkYear(y):
  return y > 0

def isOkMonth(m):
  return m >= 1 and m <= 12

# month, day, year must already be OK.
def isOkDay(m,d,y):
  if isLeapYear(y):
    return d >= 1 and d <= daysInLeapMonth[m-1]
  else:
    return d >= 1 and d <= daysInMonth[m-1]

def main():
  print "This program determines whether a date in form mm/dd/yyyy is OK"

  try:
    dateStr = raw_input("Enter date (mm/dd/yyyy): ")
    dayStr, monthStr, yearStr = string.split(dateStr, '/')

    if isOkDate(int(dayStr), int(monthStr), int(yearStr)):
      print "Yes, %s is a well formed date" % dateStr
    else:
      print "No, %s is not a well formed date" % dateStr

  except:
    print "An input date must be in form mm/dd/yyyy, all with integers"

# Execute main only if this file is invoked directly from Python
if __name__ == "__main__":
  main()