#!/bin/sh

set -e

_DEVICE="${1}"

# Exit if user has not specified a device to install
if [ -z "${_DEVICE}" ]
then
	echo "E: Usage: ${0} DEVICE"
	exit 1
else
	shift
fi

_DIRECTORY="/boot/extlinux"

# Exit if user is unprivileged
if [ "$(id -u)" -ne 0 ]
then
	echo "E: need root privileges"
	exit 1
fi

# Exit if user has specified a non-existing device
if [ ! -e "${_DEVICE}" ]
then
	echo "E: cannot access \"${_DEVICE}\": No such device"
	exit 1
fi

# Exit if user has specified an invalid device
if [ ! -b "${_DEVICE}" ]
then
	echo "E: cannot access \"${_DEVICE}\": No valid device"
	exit 1
fi

# Checking extlinux directory
echo -n "P: Checking for EXTLINUX directory..."

# Creating extlinux directory
if [ ! -e "${_DIRECTORY}" ]
then
	echo " not found."

	echo -n "P: Creating EXTLINUX directory..."
	mkdir -p "${_DIRECTORY}"
	echo " done: ${_DIRECTORY}"
else
	echo " found."
fi

# Searching syslinux MBR
if [ ! -e /usr/lib/extlinux/mbr.bin ]
then
	echo "E: /usr/lib/extlinux/mbr.bin: No such file"
	exit 1
fi

# Saving old MBR
echo -n "P: Saving old MBR..."
dd if="${_DEVICE}" of=/boot/mbr-$(basename "${_DEVICE}").old bs=440 count=1 2> /dev/null
echo " done: /boot/mbr-$(basename "${_DEVICE}").old"

# Writing syslinux MBR
echo -n "P: Writing new MBR..."
dd if=/usr/lib/extlinux/mbr.bin of="${_DEVICE}" bs=440 count=1 2> /dev/null
echo " done: ${_DEVICE}"

# Writing extlinux loader
echo "P: Installing EXTLINUX..."
extlinux --install "${_DIRECTORY}" ${@}