#!/bin/sh

# File: live-swapfile - create and use a swap file
# Copyright: (C) 2009 Daniel Baumann <mail@daniel-baumann.ch>
# License: GPL-3+

set -e

# Options
_SWAP_DIRECTORY="${_SWAP_DIRECTORY:-/live/swap}"
_SWAP_FILE="${_SWAP_FILE:-swapfile.img}"

_SWAP_SIZE="${_SWAP_SIZE:-auto}"
_SWAP_FACTOR="${_SWAP_FACTOR:-2}"

_SWAP_PURGE="${_SWAP_PURGE:-true}"
_FORCE="${_FORCE:-true}"

case "${1}" in
	add)
		# Reading size of physical memory
		_MEM_TOTAL_KB="$(awk '/^MemTotal: / { print $2 }' /proc/meminfo)"
		_MEM_TOTAL_MB="$(expr ${_MEM_TOTAL_KB} / 1024)"

		echo "Found ${_MEM_TOTAL_MB} MB physical memory."

		# Setting size of new swapfile
		if [ -z "${_SWAP_SIZE}" ] || [ "${_SWAP_SIZE}" = "auto" ]
		then
			_SWAP_SIZE_KB="$(expr ${_MEM_TOTAL_KB} '*' ${_SWAP_FACTOR})"
			_SWAP_SIZE_MB="$(expr ${_SWAP_SIZE_KB} / 1024)"
		else
			_SWAP_SIZE_MB="${_SWAP_SIZE}"
		fi

		echo "Requesting ${_SWAP_SIZE_MB} MB swapfile."

		# Reading size of old swapfile
		if [ -e "${_SWAP_DIRECTORY}/${_SWAP_FILE}" ]
		then
			_SWAP_FILESIZE="$(ls -hl ${_SWAP_DIRECTORY}/${_SWAP_FILE} | awk '{ print $5 }')"

			echo "Found ${_SWAP_FILESIZE} MB swapfile."
		fi

		# Creating new swap file
		if [ "${_SWAP_FILESIZE}" != "${_SWAP_SIZE_MB}M" ]
		then
			if [ "${_FORCE}" = "true" ]
			then
				# Removing old swapfile
				rm -f "${_SWAP_DIRECTORY}/${_SWAP_FILE}"

				echo "Creating ${_SWAP_SIZE_MB} MB swapfile."

				mkdir -p "${_SWAP_DIRECTORY}"

				# Unfortunately, swapon does not support files
				# with holes, therefore we cannot preallocate.
				dd if=/dev/zero of="${_SWAP_DIRECTORY}/${_SWAP_FILE}"  bs=1024k count="${_SWAP_SIZE_MB}"
			else
				echo "Exit."
				return 1
			fi
		fi

		echo "Enabling ${_SWAP_DIRECTORY}/${_SWAP_FILE}."

		mkswap "${_SWAP_DIRECTORY}/${_SWAP_FILE}"
		swapon "${_SWAP_DIRECTORY}/${_SWAP_FILE}"
		;;

	rm|remove)
		if grep -qs "${_SWAP_DIRECTORY}/${_SWAP_FILE}" /proc/swaps
		then
			echo "Disabling ${_SWAP_DIRECTORY}/${_SWAP_FILE}."

			swapoff "${_SWAP_DIRECTORY}/${_SWAP_FILE}"
		fi

		if [ "${_SWAP_PURGE}" = "true" ]
		then
			echo "Removing ${_SWAP_DIRECTORY}/${_SWAP_FILE}."

			rm -f "${_SWAP_DIRECTORY}/${_SWAP_FILE}"

			__DIRECTORY="${_SWAP_DIRECTORY}"
			while [ "${__DIRECTORY}" != "/" ]
			do
				rmdir --ignore-fail-on-non-empty "${__DIRECTORY}"
				__DIRECTORY="$(dirname ${__DIRECTORY})"
			done
		fi
		;;

	*)
		echo "Usage: ${0} {add|remove}"
		exit 1
		;;
esac