countdown

#!/usr/bin/env python3
import os,re,sys,time

USAGE = """
USAGE: countdown TIME [REASON]
EXAMPLES: timer 5m30s pomodoro
          timer "1 minute"
          timer "5 hours 3 minute"

""".strip()

class ParseException(Exception): pass
def parse_time(arg): # minute only for now
    SPACE = r'[ ,]*'
    REGEX = re.compile(
        SPACE +
        r'(?:(?P<hours>\d+)(?:h|hour|hours))?' + SPACE +
        r'(?:(?P<minutes>\d+)(?:m|min|mins|minute|minutes))?' + SPACE +
        r'(?:(?P<seconds>\d+)(?:s|sec|secs|second|seconds))?' + SPACE
    )
    m = REGEX.fullmatch(arg)
    if not m: raise ParseException("Unrecognized time format")
    hours = int(m.group('hours') or 0)
    minutes = int(m.group('minutes') or 0)
    seconds = int(m.group('seconds') or 0)
    t = seconds + minutes * 60 + hours * 3600
    if t <= 0: raise ParseException("Unrecognized time format")
    return t
def astime(seconds):
    minutes, seconds = seconds // 60, seconds % 60
    hours, minutes = minutes // 60, minutes % 60
    if hours > 0:
        return "{}:{:02}:{:02}".format(hours,minutes,seconds)
    else:
        return "{:02}:{:02}".format(minutes,seconds)
def print_status(total, elapsed, reason=None):
    remaining = total - elapsed
    remaining, elapsed = round(remaining), round(elapsed)
    sys.stdout.write("\033[F\033[K") # Cursor up one line

    if reason:
        print("{} remaining, {} elapsed || {}".format(astime(remaining),astime(elapsed), reason))
    else:
        print("{} remaining, {} elapsed".format(astime(remaining),astime(elapsed)))
    return remaining <= 0

def wait(a, reason=None):
    try:
        seconds = parse_time(a)
    except ParseException:
        print(USAGE, file=sys.stderr)
        print("Unrecognized time format: {}".format(sys.argv[1]), file=sys.stderr)
        sys.exit(1)
    start_time = float(time.time())
    elapsed = float(time.time())-start_time
    done = print_status(seconds, elapsed, reason)
    try:
        while not done:
            time.sleep(1)
            elapsed = float(time.time())-start_time
            done = print_status(seconds, elapsed, reason)
    except KeyboardInterrupt:
        sys.exit(2)

if __name__ == '__main__':
    args = sys.argv[1:]
    if len(args) == 1:
        wait(args[0])
    elif len(args) == 2:
        wait(args[0], args[1])
    else:
        print(USAGE, file=sys.stderr)
        sys.exit(1)