countdown

#!/usr/bin/env python3

import argparse
import re
import subprocess
import sys

from datetime import datetime, time, timedelta
from time import sleep


def seconds_until(time_str):
    """
    Calculates the number of seconds remaining until the time specified by the
    given string is reached.

    Args:
        time_str: string representing the target time.

    Returns:
        The calculated number of seconds, or -1 in case of error.
    """
    try:
        target_time = time(*(map(int, time_str.split(':'))))
    except ValueError:
        return -1

    target_datetime = datetime.combine(datetime.today(), target_time)
    seconds_delta = int((target_datetime - datetime.now()).total_seconds())

    if seconds_delta < 0:
        # We're already past the target time today, so we'll countdown until
        # the given time the next day
        seconds_delta = 86400 + seconds_delta

    return seconds_delta


def seconds_in(time_str):
    """
    Calculates the number of seconds corresponding to the time duration
    specified by the given string.

    Args:
        time_str: string representing the time duration.

    Returns:
        The calculated number of seconds, or -1 in case of error.
    """
    regex = re.compile(
        r'((?P<hours>\d+?)h)?((?P<minutes>\d+?)m)?((?P<seconds>\d+?)s)?$')

    time_parts = regex.match(time_str)
    if not time_parts:
        return -1

    time_parts = time_parts.groupdict()

    # If time_str was initially `2h3m50s`, then time_parts will now be
    # `{'hours': '2', 'seconds': '50', 'minutes': '3'}`

    time_params = {}
    for (name, param) in time_parts.items():
        if param:
            time_params[name] = int(param)
    seconds = int(timedelta(**time_params).total_seconds())

    # An erroneous input results in seconds being zero here. This should
    # probably be caught earlier (i.e. when parsing the regular expression
    # itself). Doing so will also allow us to remove the `if time_str == '0s'`
    # check at the beginning of the function.
    if seconds == 0:
        return -1

    return seconds


def calculate_seconds(time_str):
    """
    Calculates the number of seconds corresponding to the given string. The
    given string can either be a target time (e.g. 20:30) or a string
    representing a time duration (e.g. 2h45m).

    Args:
        time_str: string representing the time or time duration.

    Returns:
        The calculated number of seconds.
    """
    # Plain integers are assumed to be seconds
    try:
        seconds = int(time_str)
        return seconds
    except ValueError:
        pass

    if time_str == '0s':
        return 0

    if ':' in time_str:
        return seconds_until(time_str)
    else:
        return seconds_in(time_str)


# Set up command line arguments
parser = argparse.ArgumentParser(
    usage='%(prog)s [ARGUMENTS]',
    description='Start a countdown for the given time duration'
)
parser.add_argument(
    'time',
    help='time until or time-duration for which the countdown should run'
)
parser.add_argument(
    'message',
    nargs='?',
    default='Countdown complete!',
    help='message to be displayed when the countdown completes'
)
args = parser.parse_args()

seconds = calculate_seconds(args.time)

if seconds > 0:
    finishing_time = (datetime.now()
                      + timedelta(seconds=seconds)).strftime('%Y-%m-%d %H:%M:%S')
    print("Counting down {} seconds until {}".format(seconds, finishing_time))
elif seconds < 0:
    print("Unable to parse time duration '{}'".format(args.time))
    sys.exit(1)

while 1:
    try:
        while seconds > 0:
            m, s = divmod(seconds, 60)
            h, m = divmod(m, 60)
            sys.stdout.write("%02d:%02d:%02d" % (h, m, s))
            sys.stdout.flush()
            sleep(1.0)
            sys.stdout.write("\r\033[K")
            seconds -= 1

        print("Countdown complete!")
        ret = subprocess.call(['xmessage', '-buttons', 'Okay:0,Snooze 10 minutes:1', args.message])
        if ret == 0:
            break

        print("Snoozing for 10 minutes...")
        seconds = 600
    except KeyboardInterrupt:
        sys.stdout.write("\r\033[K")
        sys.stdout.write("%02d:%02d:%02d" % (h, m, s))
        sys.stdout.flush()

        print("\nCountdown stopped manually")
        break