#ProjectEuler/Python/Problem19.py
#Matthew Ellison
# Created: 03-13-19
#Modified: 03-28-19
#How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
"""
You are given the following information, but you may prefer to do some research for yourself.
1 Jan 1900 was a Monday.
Thirty days has September,
April, June and November.
All the rest have thirty-one,
Saving February alone,
Which has twenty-eight, rain or shine.
And on leap years, twenty-nine.
A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
"""
#Unless otherwise listed, all of my non-standard imports can be gotten from my pyClasses repository at https://bitbucket.org/Mattrixwv/pyClasses
"""
	Copyright (C) 2019  Matthew Ellison

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
"""


from Stopwatch import Stopwatch


class DAYS:
	SUNDAY = 0
	MONDAY = 1
	TUESDAY = 2
	WEDNESDAY = 3
	THURSDAY = 4
	FRIDAY = 5
	SATURDAY = 6
	NUMBER_OF_DAYS = 7
	ERROR = 8
START_YEAR = 1901	#The year we start counting sundays
END_YEAR = 2000	#The year we stop counting sundays

#Return the day of the week that the date you pass into it is on
def getDay(month: int, day: int, year: int) -> DAYS:
	#Make sure the numebrs are within propper bounds
	if((month < 1) or (month > 12) or (day < 1) or (day > 31) or (year < 1)):
		return DAYS.ERROR

	numDays = 0	#The number of days between 01-01-0001 and the date given
	currentYear = 1
	currentMonth = 1
	currentDay = DAYS.SATURDAY
	day -= 1

	#Add the correct number of days for every year
	while(currentYear < year):
		if(isLeapYear(currentYear)):
			numDays += 366
		else:
			numDays += 365
		currentYear += 1
	#Add the correct number of days for eveyr month
	while(currentMonth < month):
		#February
		if(currentMonth == 2):
			if(isLeapYear(currentYear)):
				numDays += 29
			else:
				numDays += 28
		elif((currentMonth == 1) or (currentMonth == 3) or (currentMonth == 5) or (currentMonth == 7) or (currentMonth == 8) or (currentMonth == 10) or (currentMonth == 12)):
			numDays += 31
		#For 30 day months
		else:
			numDays += 30
		currentMonth += 1
	#Account for the weird year of 1752
	if(year > 1752):
		numDays -= 11
	elif(year == 1752):
		if(month > 9):
			numDays -= 11
		elif(month == 9):
			if(day >= 14):
				numDays -= 11
			#Days 3-13 were skipped that year
			elif((day > 2) and (day < 14)):
				return DAYS.ERROR
	#Add the correct number of days for every day
	numDays += day

	currentDay += numDays
	currentDay = currentDay % DAYS.NUMBER_OF_DAYS
	if(currentDay == DAYS.SUNDAY):
		return DAYS.SUNDAY
	elif(currentDay == DAYS.MONDAY):
		return DAYS.MONDAY
	elif(currentDay == DAYS.TUESDAY):
		return DAYS.TUESDAY
	elif(currentDay == DAYS.WEDNESDAY):
		return DAYS.WEDNESDAY
	elif(currentDay == DAYS.THURSDAY):
		return DAYS.THURSDAY
	elif(currentDay == DAYS.FRIDAY):
		return DAYS.FRIDAY
	elif(currentDay == DAYS.SATURDAY):
		return DAYS.SATURDAY
	else:
		return DAYS.ERROR

#Returns true if the year passed to it is a leap year
def isLeapYear(year: int) -> bool:
	if(year < 1):
		return False
	elif((year % 100) == 0):
		#This rule only applies at and after 1800
		if(year <= 1700):
			return True
		elif((year % 400) == 0):
			return True
	elif((year % 4) == 0):
		return True
	return False

def Problem19():
	totalSundays = 0	#Keep track of the number of sundays

	#Run for all years from start to end
	for year in range(START_YEAR, END_YEAR + 1):
		#Run for all months in the year
		for month in range(1, 13):
			day = getDay(month, 1, year)
			if(day == DAYS.ERROR):
				print("There was an error with the day")
				return
			elif(day == DAYS.SUNDAY):
				totalSundays += 1

	#Print the results
	print("There are " + str(totalSundays) + " Sundays that landed on the first of the month from " + str(START_YEAR) + " to " + str(END_YEAR))


#Run automatically if the script was called stand alone
if __name__ == "__main__":
	timer = Stopwatch()
	timer.start()
	Problem19()
	timer.stop()
	print("It took " + timer.getString() + " to run this algorithm")

""" Results:
There are 171 Sundays that landed on the first of the month from 1901 to 2000
It took 724.930 milliseconds to run this algorithm
"""