cal.py

#!/usr/bin/env python
#
# cal.py
# ------
# Copyright (c) 2017 Chandranath Gunjal. Available under the MIT License
#
#  A friendlier cal - converts month names.
#
#  o With no arguments, print calendar for current month & year
#  o With two arguments, assumes month & year are given
#  o With one argument
#    - the argument is assumed to be a month (if valid) for this year.
#    - a "month+/-" format uses the next/prev year.
#    - a lone "+/-" prints the next/prev month's calendar.
#    - a leading zero forces the argument to be a "year".
#
import calendar
import datetime
import getopt
import sys


def month2num(given: str) -> int:
    """Convert a given month name to numeric"""
    month_names = [
        "january",
        "february",
        "march",
        "april",
        "may",
        "june",
        "july",
        "august",
        "september",
        "october",
        "november",
        "december",
    ]

    given = given.lower()
    for i, month in enumerate(month_names, 1):
        if month.startswith(given):
            return i
    return 0


def determine_year_month(args: list) -> list[int]:
    """Determine the year/month. Returns [year] or [year, month]"""
    today = datetime.date.today()
    cur_month, cur_year = today.month, today.year

    # 0 args - calendar for current year & month
    if len(args) == 0:
        return [cur_year, cur_month]

    # 2 args - calendar for given year &  month
    if len(args) == 2:
        m = month2num(args[0])
        return [int(args[1]), int(args[0])] if (m == 0) else [int(args[1]), m]

    # 1 argument - multiple possibilities
    arg = args[0]

    # cal + ==> next month
    if arg == "+":
        return [cur_year + 1, 1] if (cur_month == 12) else [cur_year, cur_month + 1]

    # cal - ==> prev month
    if arg == "-":
        return [cur_year - 1, 12] if (cur_month == 1) else [cur_year, cur_month - 1]

    # cal jun+ or cal 12+ ==> given month for next year
    if arg.endswith("+"):
        m = month2num(arg[:-1])
        return [cur_year + 1, int(arg[:-1])] if (m == 0) else [cur_year + 1, m]

    # cal jun- or cal 12- ==> given month for prev year
    if arg.endswith("-"):
        m = month2num(arg[:-1])
        return [cur_year - 1, int(arg[:-1])] if (m == 0) else [cur_year - 1, m]

    # cal 0nn ==> assume as year
    if arg.startswith("0"):
        return [int(arg)]

    # cal numeric ==> assume as month if in 1..12
    if arg.isnumeric():
        m = int(arg)
        return [cur_year, m] if (1 <= m <= 12) else [m]

    # cal any ==> convert month if possible
    m = month2num(arg)
    return [int(arg)] if (m == 0) else [cur_year, m]


def print_calendar(ym: list[int]) -> None:
    """Print calendar for [year, month]."""
    tc = calendar.TextCalendar(firstweekday=6)
    tc.pryear(ym[0]) if len(ym) == 1 else tc.prmonth(ym[0], ym[1])
    return


# Main
# ====
if __name__ == "__main__":
    synopsis = """usage: cal.py -h [mth][+|-] | mth year | [0]year
    Month names (shortened or otherwise) can be used.
    """

    def usage():
        """Print usage and exit"""
        print(synopsis)
        sys.exit(2)

    def parse_args(argv):
        """Parse command line arguments"""
        try:
            opts, args = getopt.getopt(argv, "h", ["help"])
        except getopt.GetoptError:
            usage()

        for opt, arg in opts:
            if opt in ["-h", "--help"]:
                usage()

        if len(args) > 2:
            usage()
        return args

    # main
    cmd_args = parse_args(sys.argv[1:])
    try:
        ym = determine_year_month(cmd_args)
        print_calendar(ym)
    except Exception:
        usage()