Bug and style report from Shreq on Reddit

[linden2015]

Feedback at:
https://www.reddit.com/r/commandline/comments/fqrxg7/clockout_a_bash_script_to_calculate_totals_of_a/flsgqqt/

awk refactor at:
https://termbin.com/vjki
(copied because termbin expires)

#!/usr/bin/awk -f

function error(text)
{
	printf "%s: Error: %s\n", ARGV[0], text >"/dev/stderr"
	has_error=1
	exit(1)
}

function to_mins(time,    arr, hours, minutes)
{
	split(time, arr, ":")
	hours=arr[1]; minutes=arr[2]

	return hours * 60 + minutes
}

function time_diff(a, b,    diff)
{
	diff=to_mins(b) - to_mins(a)

	if (diff < 0)
		diff+=1440

	return diff
}

function pluralize(num, str)
{
	return (num " " str) (num != 1 ? "s" : "")
}

function pretty_time(mins,    hours, minutes, str)
{
	if ((hours=int(mins / 60)) > 0)
		str=" " pluralize(hours, "hr")
	if ((minutes=int(mins % 60)) > 0)
		str=str " " pluralize(minutes, "min")

	return str
}

function valid_time(time)
{
	return (time ~ /^([01]?[0-9]|2[0-4]):[0-5][0-9]$/)
}

{
	if (NF != 3 || !valid_time($2) || !valid_time($3))
		error("input file has incorrect format on line: " NR)

	categories[$1]=categories[$1] " " $2 "-" $3
}

END {
	if (has_error)
		exit(1)

	for (category in categories) {
		category_total=0

		split(categories[category], times)
		for (time in times) {
			split(times[time], arr, "-")
			from=arr[1]; to=arr[2]
			duration=time_diff(from, to)
			category_total+=duration

			printf "%-50s%5s\t%5s\t%d\n", \
				category, from, to, duration
		}
		total+=category_total
		if (category_total > duration)
			printf "└ Total: %d\n", category_total

		print ""
	}
	printf "Total:%s\n", pretty_time(total)
}