WorkSpanCalculator.py

from datetime import datetime
import sys

START_DAY = datetime(2021, 7, 3)
WORK_SPAN_LENGTH = 4
DAYS_OFF_PER_SPAN = 1

def main() -> None:
    if helpMessageIsRequested():
        displayHelpMessage()
        return

    startDate, span, rest = readSysArgs()
    result, remainder = isBreakDay(datetime.now(), startDate, span, rest)
    printResults(result, remainder)


def helpMessageIsRequested() -> bool:
    if (len(sys.argv) > 1) and (sys.argv[1] == "-h"):
        return True
    return False


def displayHelpMessage() -> None:
    print("===Work Span Calculator===\n"+\
        "Determines whether a given day is a work or rest day for a given work rhythm.\n"+\
        "Default values: 4 day cycles with 1 rest day per cycle, starting on 2021-10-30.\n"+\
        "Rest days are consecutive at the start of each cycle.\n\nSYNTAX:\n"+\
        "python WorkSpanCalculator.py [cycle length] [rest days] [start date]")


def readSysArgs() -> (datetime, int, int):
    startDate = START_DAY
    span = WORK_SPAN_LENGTH
    rest = DAYS_OFF_PER_SPAN

    if len(sys.argv) > 1:
        span = int(sys.argv[1])
        if len(sys.argv) > 2:
            rest = int(sys.argv[2])
            if len(sys.argv) > 3:
                startDate = datetime.strptime(sys.argv[3], "%Y-%m-%d")
    return (startDate, span, rest)


def printResults(result: bool, remainder: int) -> None:
    if result:
        print("Today is a break day.")
    else:
        print("Today is a work day. The next rest day is in " + str(remainder) + " day(s).")


def getDaysSinceStart(targetDate: datetime, startDate: datetime = START_DAY) -> int:
    return (targetDate.date() - startDate.date()).days


def isBreakDay(targetDate: datetime, startDate: datetime = START_DAY, spanLength: int = WORK_SPAN_LENGTH, restDayCount: int = DAYS_OFF_PER_SPAN) -> (bool, int):
    cycleProgress = getDaysSinceStart(targetDate, startDate) % spanLength
    isRestDay = cycleProgress < restDayCount
    return (isRestDay, spanLength - cycleProgress)


if __name__ == "__main__":
    main()