sumtime

#!/bin/bash

unit=$1
case $unit in
	"-h" | "--help" )
		echo "Pipe in times, or type and ctrl-d when done
Define largest unit with m (minutes), h (hours), or d (days); defaults to hours"
	;;
	"" )
		unit="h"
	;;
esac

times=$(cat)

days=0
hours=0
minutes=0
seconds=0

for t in $times; do
	# adds zeros to smaller times
	case $unit in
		"m" | "min" )
			t="00:00:${t}"
		;;
		"h" | "hour")
			t="00:${t}"
		;;
		* ) ;;
	esac

	# breaks time into units
	IFS=':'
	read -ra parts <<< "$t"
	IFS=' '
	d=${parts[0]}
	h=${parts[1]}
	m=${parts[2]}
	s=${parts[3]}

	# changes empty units to 0 for math
	if [ "$h" = "" ]; then h=0; fi
	if [ "$m" = "" ]; then m=0; fi
	if [ "$s" = "" ]; then s=0; fi

	# sums all units (forcing decimal math, can get confused with leading 0's otherwise)
	days=$[10#$days+10#$d]
	hours=$[10#$hours+10#$h]
	minutes=$[10#$minutes+10#$m]
	seconds=$[10#$seconds+10#$s]
done

# "simple" round function. black magic.
round(){
	echo $(printf %.$2f $(echo "scale=$2;(((10^$2)*$1)+0.5)/(10^$2)" | bc))
};

# takes a time int and a break int, returns extra and new current
# example:
# spillup 100 60.0
# > 1 40
spillup(){
	extralarge=$(echo "${1} / ${2}" | bc -l)
	decsmall=$(echo "(${extralarge} % 1) * ${2}" | bc)
	# extra large units
	echo $(round $(echo "scale=0;${extralarge} - (${extralarge} % 1)" | bc) 0)
	# new small units
	echo $(round $decsmall 0);
}

# spills extra time up units for formatting
if (( seconds >= 60 )); then
	{
	  read -r extra
	  read -r new
	} <<< "$( spillup ${seconds} 60.0 )"
	minutes=$[$minutes+$extra]
	seconds=$new
fi
if (( minutes >= 60 )); then
	{
	  read -r extra
	  read -r new
	} <<< "$( spillup ${minutes} 60.0 )"
	hours=$[$hours+$extra]
	minutes=$new
fi
if (( hours >= 24 )); then
	{
	  read -r extra
	  read -r new
	} <<< "$( spillup ${hours} 24.0 )"
	days=$[$days+$extra]
	hours=$new
fi

echo "${days}:${hours}:${minutes}:${seconds}"