"""
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.

How many Sundays fell **on the first of the month** during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
"""

import time


def timer(func):
    def wrapper(*args, **kwargs):
        start_time = time.time()
        result = func(*args, **kwargs)
        end_time = time.time()
        print(f"Execution time: {end_time - start_time} seconds")
        return result

    return wrapper


def is_leap_year(year: int) -> bool:
    return (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)


def days_in_years(years: list[int]) -> int:
    leapyears = [year for year in years if is_leap_year(year)]
    return sum([366 if year in leapyears else 365 for year in years])


def count_sundays(start_year: int | str, end_year: int | str) -> int:
    start_year = int(start_year) if isinstance(start_year, str) else start_year
    end_year = int(end_year) if isinstance(end_year, str) else end_year
    if start_year < 1900 or start_year > end_year:
        raise ValueError(f"Invalid year range {start_year} to {end_year}")
    last_days = days_in_years(list(range(1900, start_year)))
    year_list = list(range(start_year, end_year + 1))
    days = days_in_years(year_list) + (last_days % 7)
    sundays = days // 7
    return sundays


def days_month(year: int, month: int) -> int:
    if month in [1, 3, 5, 7, 8, 10, 12]:
        return 31
    elif month in [4, 6, 9, 11]:
        return 30
    elif month == 2:
        return 29 if is_leap_year(year) else 28
    else:
        raise ValueError(f"Invalid month {month}")


def days_sunday_month(start_year: int, end_year: int) -> int:
    count = 0
    outday = days_in_years(list(range(1900, start_year))) % 7
    for year in range(start_year, end_year + 1):
        for month in range(1, 13):
            if outday == 6:
                count += 1
            outday = (outday + days_month(year, month)) % 7
    return count


@timer
def main() -> None:
    print(f"Number of Sundays between 1901 and 2000: {count_sundays(1901, 2000)}")


@timer
def main_first_day() -> None:
    print(
        f"Number of Sundays on the first of the month between 1901 and 2000: {days_sunday_month(1901, 2000)}"
    )


if __name__ == "__main__":
    main()
    main_first_day()