#!/bin/bash

usage="$0 -d DIR -n NAME -s SIZE -p PRIO add|remove
Add or remove swapfiles to micro-manage disk usage.
  -d DIR  : set DIRectory to place swapfile in. Default: /mnt
  -n NAME : set filename for the swapfile. Default: swapfileN
  -s SIZE : SIZE in MB (only when creating a swapfile). Default: 1024
  -p PRIO : Priority to use with swapon. Range from 0 to 1000. Default: 500
  -h      : Display this help and exit."

test $# -eq 0 && ( echo -e "$usage" ; echo "You must provide either 'add' or 'remove' !" ; exit 1 )

SWAP_FOLDER="/mnt"
SWAP_FILENAME="swapfile"
SWAP_SIZE="12"	#in MB
SWAP_PRIO_MAX=500	#range 0..1000
SWAP_PRIO_INC=10

while getopts hp:s:n:d: arg ; do
	case $arg in
		h) echo -e "$usage" ; exit 0 ;;
		d) SWAP_FOLDER="$OPTARG" ;;
		n) SWAP_FILENAME="$OPTARG" ;;
		s) SWAP_SIZE="$OPTARG" ;;
		p) SWAP_PRIO_MAX="$OPTARG" ;;
		*) echo -e "$usage" ; echo "Invalid option: $arg"; exit 1 ;;
	esac
done

shift $((( $OPTIND - 1 )))

if test "$1" = "add" ; then
	
	N=$(ls $SWAP_FOLDER/$SWAP_FILENAME* | wc -l)
	swapfile=$SWAP_FOLDER/$SWAP_FILENAME$N
	
	echo "Creating swapfile: $swapfile"
	
	sudo dd if=/dev/urandom of=$swapfile bs=1M count=$SWAP_SIZE status=progress
	sudo chmod 0600 $swapfile
	sudo mkswap $swapfile
	sudo swapon -p $((($SWAP_PRIO_MAX - $N * $SWAP_PRIO_INC))) $swapfile
	
	echo -e "\n\n\n\n"
	sudo swapon
	
elif test "$1" = "remove" ; then
	
	N=$(ls $SWAP_FOLDER/$SWAP_FILENAME* | wc -l)
	swapfile=$SWAP_FOLDER/$SWAP_FILENAME$((($N - 1)))
	
	echo "Removing swapfile: $swapfile"
	
	sudo swapoff $swapfile && sudo rm $swapfile
	
	echo -e "\n\n\n\n"
	sudo swapon
	
fi