#!/bin/bash

sep="\n\t#############\n"
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."

if test $# -eq 0 ; then
	echo -e "$usage"
	echo "You must provide either 'add' or 'remove' !"
	exit 1
fi

SWAP_FOLDER="/mnt"
SWAP_FILENAME="swapfile"
SWAP_SIZE="1024"	#in MB
SWAP_PRIO_MAX=750	#range 0..1000
SWAP_PRIO_INC=50

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$N
	prio=$((($SWAP_PRIO_MAX - $N * $SWAP_PRIO_INC)))
	
	echo -e "$sep Creating swapfile: $swapfile$sep"
	
	sudo dd if=/dev/urandom of=$swapfile bs=1M count=$SWAP_SIZE status=progress
	sudo chmod 0600 $swapfile
	sudo mkswap $swapfile
	sudo swapon -p $prio $swapfile
	
	echo -e "\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 -e "$sep Removing swapfile: $swapfile$sep"
	
	sudo swapoff $swapfile && sudo rm $swapfile
	
	echo -e "\n\n"
	sudo swapon
	
fi

echo -e "$sep Editing /etc/fstab accordingly$sep"

tmpfile=/tmp/swapctl.fstab

if test $1 = "add" ; then
	cat /etc/fstab > $tmpfile
	echo -e "$swapfile\t\t\t\t\t\t\t\t\tnone\t\t\tswap\tsw,pri=$prio\t\t\t0\t\t0" >> $tmpfile
else
	cat /etc/fstab | grep -v $swapfile > $tmpfile
	
fi

echo -e  "# The lines below this one will be the new fstab file : \n\n $(cat $tmpfile)" | more

while true ; do
	
	echo -e "$sep What to do with this fstab ?"
	echo -e "[ \t\e[4ma\\e[0mccept changes | \e[4me\e[0mdit file | dis\e[4mc\e[0mard changes | show \e[4md\e[0miff ]"
	read prompt
	
	case $prompt in
		a|accept)
			sudo mv /etc/fstab.2 /etc/fstab.3
			sudo mv /etc/fstab.1 /etc/fstab.2
			sudo mv /etc/fstab /etc/fstab.1
			sudo mv $tmpfile /etc/fstab
			echo -e "$sep Changes accepted. New contents of /etc/fstab :$sep"
			cat /etc/fstab | more
			break
		;;
		e|edit)
			${EDITOR:-nano} $tmpfile
		;;
		c|discard)
			echo "$sep Changes discarded. /etc/fstab remains unchanged.$sep"
			break
		;;
		d|diff)
			echo -e "\n\n\tdiff\t\t/etc/fstab\t\t\t\t\t\t/tmp/swapctl.fstab\n"
			diff --tabsize=4 -E -Z -b -t -y /etc/fstab /tmp/swapctl.fstab | more
		;;
	esac
done