from datetime import timedelta
import re

def parse_timedelta(s: str) -> timedelta:
	"""
	Parses a timespan. Format examples:
	"30m"
	"10s"
	"90d"
	"1h30m"
	"73d18h22m52s"
	"""
	p = re.compile('^(?:[0-9]+[dhms])+$')
	if p.match(s) is None:
		raise ValueError("Illegal timespan value '{s}'.")
	p = re.compile('([0-9]+)([dhms])')
	days = 0
	hours = 0
	minutes = 0
	seconds = 0
	for m in p.finditer(s):
		scalar = int(m.group(1))
		unit = m.group(2)
		if unit == 'd':
			days = scalar
		elif unit == 'h':
			hours = scalar
		elif unit == 'm':
			minutes = scalar
		elif unit == 's':
			seconds = scalar
	return timedelta(days=days, hours=hours, minutes=minutes, seconds=seconds)

def describe_timedelta(td: timedelta, max_components: int = 2) -> str:
	values = [
		td.days,
		td.seconds // 3600,
		(td.seconds // 60) % 60,
		td.seconds % 60,
	]
	units = [
		'day' if values[0] == 1 else 'days',
		'hour' if values[1] == 1 else 'hours',
		'minute' if values[2] == 1 else 'minutes',
		'second' if values[3] == 1 else 'seconds',
	]
	while len(values) > 1 and values[0] == 0:
		values.pop(0)
		units.pop(0)
	if len(values) > max_components:
		values = values[0:max_components]
		units = units[0:max_components]
	while len(values) > 1 and values[-1] == 0:
		values.pop(-1)
		units.pop(-1)
	tokens = []
	for i in range(len(values)):
		tokens.append(f'{values[i]} {units[i]}')
	return ' '.join(tokens)