#!/bin/bash

# Warning : this script calls heavily on sudo for swapfile manipulation.
# This is not clean.
# But it is easier in my workflow.
# Please consider removing all "sudo" from this file,
# and calling it with administrative rights
# if you want to use it in a proper way.

usage="$0 -d DIR -n NAME -s SIZE -p PRIO add|remove
Add or remove swapfiles to micro-manage disk usage.
  -i      : Interactively prompt for parameters. 
            (other options are NOT ignored, but set as preselection)
  -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
  -f      : Do not edit fstab with the changes. Default: edit fstab
  -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
FSTAB=true
sep="\n\t#############\n"

while getopts ifhp:s:n:d: arg ; do
	case $arg in
		h) echo -e "$usage" ; exit 0 ;;
		i) INT=true ;;
		f) FSTAB=false ;;
		d) SWAP_FOLDER="$OPTARG" ;;
		n) SWAP_FILENAME="$OPTARG" ;;
		s) 
			if test "$OPTARG" -gt 0 2> /dev/null ; then
				SWAP_SIZE="$OPTARG"
			else
				echo -e "invalid argument: -s $OPTARG\t (size expected in MB without suffix)"
				exit 1
			fi
			;;
		p) SWAP_PRIO_MAX="$OPTARG" ;;
		*) echo -e "$usage" ; echo "Invalid option: $arg"; exit 1 ;;
	esac
done

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

if test "$1" = "add" ; then
	MODE="add"
elif test "$1" = "remove" ; then
	MODE="remove"
elif test "$INT" != true ; then
	echo -e "$usage"
	echo "You must provide either add or remove !"
	exit 1
fi

if test "$INT" = true ; then

	if test "$MODE" != "add" -a "$MODE" != "remove" ; then
		until test "$REPLY" = "add" -o "$REPLY" = "remove" -o "$REPLY" = "quit"
		do 
			read -p "Mode [add|remove|quit]:	" 
		done

		test "$REPLY" = "quit" && exit 0
		
		MODE=$REPLY
		unset REPLY
	fi 
	
	until test -d "$REPLY"
	do 
		read -e -i "$SWAP_FOLDER" -p "Directory :	" 
	done
	
	SWAP_FOLDER=$REPLY
	unset REPLY
	
	if test "$MODE" = "add" ; then
			
		read -e -i "$SWAP_FILENAME" -p "Filename :	" 
		
		SWAP_FILENAME=$REPLY
		unset REPLY
			
		until test "$REPLY" -gt 0 2> /dev/null ;
		do 
			read -e -i "$SWAP_SIZE" -p "Swapfile size (MiB) :	" 
		done
		
		SWAP_SIZE="$REPLY"
		unset REPLY
		
		until test "$REPLY" -gt 0 2> /dev/null ;
		do 
			read -e -i "$SWAP_PRIO_MAX" -p "Swap priority {0-1000} :	" 
		done

		SWAP_PRIO_MAX="$REPLY"
		unset REPLY
		
	fi
	
	until test "$REPLY" = "y" -o "$REPLY" = "n"
	do 
		read -e -i "$(test "$FSTAB" = true && echo y || echo n)" -p "Update fstab ? [y|n]:	" 
	done

	test "$REPLY" = "n" && FSTAB=false
	unset REPLY

	echo ; echo "    About to run the following command:"
	echo $0 -d "$SWAP_FOLDER" -n "$SWAP_FILENAME" -s "$SWAP_SIZE" -p "$SWAP_PRIO_MAX" -f "$MODE"
	
	until test "$REPLY" = "y" -o "$REPLY" = "n"
	do 
		read -p "Proceed ? [y|n]:	" 
	done

	test "$REPLY" != "y" && exit 1
fi


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


if test "$FSTAB" = true ; then
	
	echo -e "$sep Editing /etc/fstab accordingly$sep"
	tmpfile=/tmp/swapctl.fstab
	
	if test "$MODE" = "add" ; then
		cat /etc/fstab > $tmpfile
		echo -e "$swapfile\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 "[ \e[4ma\\e[0mccept changes | \e[4me\e[0mdit file | dis\e[4mc\e[0mard changes | show \e[4md\e[0miff ]"
		read -p "[ a | e | c | d ]:    " prompt
		
		case $prompt in
			a|accept)
				mv /etc/fstab.2 /etc/fstab.3
				mv /etc/fstab.1 /etc/fstab.2
				mv /etc/fstab /etc/fstab.1
				mv $tmpfile /etc/fstab
				echo -e "$sep Changes accepted. New contents of /etc/fstab :$sep"
				cat /etc/fstab | more
				break
			;;
			e|edit)
				${EDITOR:-nano} $tmpfile
			;;
			c|discard)
				echo -e "$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
fi