#! /bin/bash

#set -x

FILE_IN="${1}"

left_list=()
right_list=()

while read -r l; do
  echo "reading new line [$l]"
  IFS=" "
  read -ra line_split <<< "${l}"
  unset IFS
  echo "first number [${line_split[0]}]"
  echo "second number [${line_split[1]}]"
  left_list+=("${line_split[0]}")
  right_list+=("${line_split[1]}")
done <"$FILE_IN"

echo "${left_list[@]}"
echo "${right_list[@]}"

if [[ ${#left_list[@]} -ne ${#right_list[@]} ]]; then
  echo "arrays dont match, wtf?"
  exit 1
else
  echo "length of lists ${#left_list[@]}"
fi

echo "sorting time"

IFS=$'\n'
mapfile sorted_left_list <<<"$(sort <<<"${left_list[*]}")"
mapfile sorted_right_list <<<"$(sort <<<"${right_list[*]}")"
unset IFS

echo "${sorted_left_list[@]}"
echo "${sorted_right_list[@]}"

sorted_list_diff=()

echo "adding time"

for i in "${!sorted_left_list[@]}"; do
  echo "left index: ${i} value: ${sorted_left_list[$i]}"
  echo "right index: ${i} value: ${sorted_right_list[$i]}"

  i_diff=$((${sorted_left_list[$i]}-${sorted_right_list[$i]}))

  echo "diff ${i_diff}"

  sorted_list_diff+=("${i_diff#-}")
done

echo "${sorted_list_diff[@]}"

final_out=0

for v in "${sorted_list_diff[@]}"; do
  final_out=$((final_out + v))
done

echo "final output: ${final_out}"