#!/bin/sh

prog=${0##*/}
version=3.18.1-r1
files_to_move="boot efi apks syslinux.cfg .alpine-release"
read_only_mounts=
umounts=
uninstalls=
destdir=

cleanup_tmpdata() {
	if [ -d "$destdir" -a -d "$destdir/.new" ]; then
		rm -rf "$destdir"/.new
	fi
}

cleanup_mounts() {
	local i=
	cd /
	sync
	sleep 1
	for i in $read_only_mounts; do
		mount -o remount,ro "$i" || echo "Warning: Failed to remount as read-only. Is modloop mounted?"
	done
	read_only_mounts=""
	if [ -n "$umounts" ]; then
		umount $umounts
		umounts=""
	fi
}

cleanup_installs() {
	if [ -n "$uninstalls" ]; then
		apk del --quiet $uninstalls
		uninstalls=""
	fi
}

cleanup() {
	cleanup_tmpdata
	cleanup_mounts
	cleanup_installs
}

trap cleanup EXIT
trap "exit 2" INT TERM QUIT

die() {
	echo "$@" >&2
	exit 1
}


# find device for mountpoint
find_dev() {
	local mnt="${1%/}" # strip trailing /
	awk "\$2 == \"$mnt\" {print \$1}" /proc/mounts
}

# check if given device is on usb bus
on_usb_bus() {
	local dev="$1"
	[ -e /sys/block/$dev ] || return 1
	local sysdev="$(readlink -f /sys/block/$dev/device)"
	test "${sysdev##*/usb[0-9]}" != "$sysdev"
}

vecho() {
	[ -z "$verbose" ] && return 0
	echo "$@"
}

# check if given dir is read-only
is_read_only() {
	local tmpfile="$(mktemp -p "$1" 2>/dev/null)"
	[ -z "$tmpfile" ] && return 0
	rm -f "$tmpfile"
	return 1
}

# find what disk this partition belongs to
find_disk_dev() {
	local i= sysfsname="${1#/dev/}"
	sysfsname=${sysfsname//\/!}	# cciss/c0d0 -> cciss!c0d0
	if [ -e /sys/block/$sysfsname ]; then
		echo "/dev/${sysfsname//!/'/'}"
		return 0
	fi
	for i in /sys/block/*/$sysfsname; do
		[ -e "$i" ] || continue
		echo "$i" | cut -d/ -f4 | sed -e 's:!:/:g' -e 's:^:/dev/:'
		return 0
	done
	return 1
}

find_syslinux_cfg() {
	# find where new syslinux.cfg is
	for i in boot/syslinux/syslinux.cfg syslinux.cfg; do
		if [ -e "$1"/$i ]; then
			syslinux_cfg=$i
			vecho "Found $syslinux_cfg"
			break
		fi
	done
}

fix_syslinux_kernel() {
	echo "Fixing $syslinux_cfg: kernel $1 -> $2"
		sed -i -e "/^\s*[Kk][Ee][Rr][Nn][Ee][Ll]\s/s|$1|$2|" \
 			"$destdir/$syslinux_cfg"
}

fix_syslinux_initrd() {
	echo "Fixing $syslinux_cfg: initrd $1 -> $2"
	sed -i -e "/^\s*[Ii][Nn][Ii][Tt][Rr][Dd]\s/s|$1|$2|" \
		-e "/^\s*[Aa][Pp][Pp][Ee][Nn][Dd]\s/s|initrd=$1|initrd=$2|" \
			"$destdir/$syslinux_cfg"
}

check_syslinux() {
	if [ -z "$syslinux_cfg" ]; then
		find_syslinux_cfg "$destdir"
	fi
	if [ -z "$syslinux_cfg" ]; then
		die "Could not find any syslinux.cfg. Aborting"
	fi

	# kernels
	for i in $(awk 'tolower($1) == "kernel" {print $2}' "$destdir"/$syslinux_cfg); do
		k="${destdir%/}/${i#/}"
		f=${k##*/}

		if [ -e "$k" ] && [ "${f#vmlinuz}" != "$f" ]; then
			continue
		fi

		if [ -e "${k%/*}"/vmlinuz-$f ] && [ -n "$fix_syslinux_cfg" ]; then
			fix_syslinux_kernel "$i" "${i%/*}"/vmlinuz-$f
		elif ! [ -e "$k" ]; then
			echo "Warning: $syslinux_cfg: kernel $k  was not found"
			echo "         Run $0 -f -c "$destdir" to fix"
		fi
	done

	#initramfs
	initrds=$(awk 'tolower($1) == "initrd" {gsub(",", " "); for (i=2; i<=NF; i++) print $i}' \
			"$destdir"/$syslinux_cfg)
	for i in $(awk 'tolower($1) == "append" {print $0}' \
			"$destdir"/$syslinux_cfg); do
		case $i in
			initrd=*) initrds=${i#initrd=};;
		esac
	done

	for i in $initrds; do
		if [ -e "$destdir"/$i ]; then
			continue
		fi
		fname=${i##*/}
		flavor=${fname%.gz}

		new=${i%/*}/initramfs-$flavor
		if [ -e "$destdir"/$new ] && [ -n "$fix_syslinux_cfg" ]; then
			fix_syslinux_initrd "$i" "$new"
		else
			echo "Warning: initrd $i was not found. System will likely not boot"
			echo "         Run $0 -f -c "$destdir" to fix"
		fi
	done
}

version_check() {
	local new_dir="$1" old_dir="$2"
	# check if its same version
	local to_version="$(cat "$new_dir"/.alpine-release)"
	if [ -n "$upgrade" ] && [ -e "$old_dir"/.alpine-release ]; then
		local from_version="$(cat "$old_dir"/.alpine-release)"
		if [ -z "$force" ] && [ -n "$to_version" ] && [ "$from_version" = "$to_version" ]; then
			die "Source and target seems to have same version ($from_version). Aborting."
		fi
		echo "Upgrading $dest from $from_version to $to_version"
	else
		echo "Installing $dest to $to_version"
	fi
}

usage() {
	cat <<-__EOF__
		$prog $version
		usage: $prog [-fhUusv] SOURCE [DEST]
		       $prog -c DIR

		Copy the contents of SOURCE to DEST and make DEST bootable.

		SOURCE can be a directory or a ISO image. DEST can be a mounted directory
		or a device. If DEST is ommitted /media/usb will be used.

		Options:
		 -f  Force overwrite existing files. Will overwrite syslinux.cfg if upgrade.
		 -h  Show this help.
		 -k  fix kernel and initrd name in syslinux.cfg if needed.
		 -U  Replace current alpine_dev in syslinux.cfg with UUID if UUID found.
		 -u  Upgrade mode. Keep existing syslinux.cfg and don't run syslinux.
		 -s  Force run syslinux, even if upgrade mode.
		 -v  Verbose mode. Display whats going on.

		 -c  Check syslinux.cfg in destination DIR. Use with -f to fix.

	__EOF__
	exit 1
}

while getopts "c:fhkUusv" opt; do
	case "$opt" in
	c) check_syslinux="$OPTARG";;
	f) force=1; fix_syslinux_cfg=1;;
	h) usage;;
	k) fix_syslinux_cfg=1;;
	U) replace_alpine_dev=1;;
	u) upgrade=1;;
	s) syslinux=1;;
	v) verbose=1;;
	esac
done

shift $(($OPTIND - 1))

src=${1}
dest=${2:-/media/usb}

if [ -n "$check_syslinux" ]; then
	destdir="$check_syslinux"
	check_syslinux
	exit 0
fi

[ -z "$src" ] && usage

# find target device
if [ -d "$dest" ]; then
	dest=${dest%/} # strip trailing /
	if ! awk '{print $2}' /proc/mounts | grep -q "^$dest\$"; then
		mount "$dest" || die "Failed to mount $dest"
		umounts="$umounts $dest"
	elif [ -n "$syslinux" ]; then
		die "Cannot run syslinux on mounted device"
	else
		nosyslinux=1
	fi
	destdir="$dest"
	dest=$(find_dev "$destdir")
elif [ -b "$dest" ]; then
	destdir="/media/${dest##*/}"
	mkdir -p "$destdir"
	mount "$dest" "$destdir" || die "Failed to mount $dest on $destdir"
	umounts="$umounts $destdir"
fi

# remount as rw if needed
if is_read_only "$destdir"; then
	vecho "Remounting $destdir as read/write"
	mount -o remount,rw "$dest" || die "Failed to remount $destdir as rw"
	read_only_mounts="$read_only_mounts $destdir"
fi

# fish out label, uuid and type
eval $(blkid $dest | cut -d: -f2-)

vecho "Using $dest as target (mounted on $destdir)"

# find parent device (i.e sda)
dev="$dest"
while [ -L "$dev" ]; do
	dev=$(readlink -f $dev)
done
parent_dev=$(find_disk_dev $dev)

# check if this files exist and not in upgrade mode
if [ -z "$upgrade" ] && [ -z "$force" ]; then
	for i in $files_to_move; do
		[ -e "$destdir"/$i ] && die "$destdir/$i already exists. Use -u to upgrade."
	done
fi

# remove partial upgrades if any
rm -rf "$destdir"/.new "$destdir"/.old
mkdir -p "$destdir"/.new || die "Failed to create $destdir/.new"

# copy data from source to .new
if [ -f "$src"/.alpine-release ]; then
	srcdir="$(echo $src | sed -r 's,/$,,')"
	version_check "$srcdir" "$destdir"
	for i in $files_to_move; do
		if [ -e "$srcdir"/$i ]; then
			vecho "Copying $srcdir/$i to $destdir/.new/"
			cp -dR "$srcdir"/$i "$destdir"/.new/
		fi
	done
else
	vecho "Extracting $src to $destdir/.new/"
	case "$src" in
	https://*|http://*|ftp://*)
		${WGET:-wget} -O - "$src" | (cd "$destdir"/.new; exec ${UNISO:-uniso}) \
			|| die "Failed to download or extract $src"
		echo ""
		;;
	*)
		(cd "$destdir"/.new; exec ${UNISO:-uniso}) < "$src" \
			|| die "Failed to download or extract $src"
		;;
	esac
	version_check "$destdir/.new" "$destdir"
fi

# find where new syslinux.cfg is
find_syslinux_cfg "$destdir"/.new

# abort early in case unexpected trouble
if [ -z "$syslinux_cfg" ]; then
	die "Could not find any syslinux.cfg on new iso?"
fi

# make sure files are really there before we replace existing
vecho "Flushing cache..."
sync

vecho "Replacing existing files..."
mkdir -p "$destdir"/.old || die "Failed to create $destdir/.old"

# move current files to .old
for i in $files_to_move; do
	if [ -e "$destdir"/$i ]; then
		mv "$destdir"/$i "$destdir"/.old/ || die "Failed to move $destdir/$i to $destdir/.old/"
	fi
done

# keep any existing syslinux.cfg
if [ -e "$destdir"/.old/$syslinux_cfg ]; then
	mv "$destdir"/.old/$syslinux_cfg "$destdir"/.new/$syslinux_cfg
elif [ -e "$destdir"/.old/syslinux.cfg ] \
		&& [ -e "$destdir"/.new/boot/syslinux/syslinux.cfg ]; then
	echo "Warning: moving syslinux.cfg to boot/syslinux/syslinux.cfg" >&2
	mv "$destdir"/.old/syslinux.cfg "$destdir"/.new/boot/syslinux
	if [ -z "$syslinux" ]; then
		echo "         You might need run: syslinux $dest" >&2
	fi
fi

# move .new to current
for i in $files_to_move; do
	if [ -e "$destdir"/.new/$i ]; then
		mv "$destdir"/.new/$i "$destdir"/ \
			|| die "Failed to move $destdir/.new/ to $destdir"
	fi
done

if [ -n "$replace_alpine_dev" -o -z "$upgrade" ] && [ -n "$UUID" ]; then
	sed -E -i -e "s/alpine_dev=[^ \t:]+/alpine_dev=UUID=$UUID/" \
		"$destdir"/$syslinux_cfg
fi

# verify syslinux.cfg
check_syslinux

# cleanup
[ -z "$keep_old" ] && rm -rf "$destdir"/.old "$destdir"/.new

# If we only copy then we are done.
if [ -n "$upgrade" ] && [ -z "$syslinux" ]; then
	exit 0
fi

# prevent running syslinux on mounted device
if [ -n "$nosyslinux" ]; then
	echo "Warning: Can not run syslinux on a mounted device"
	echo "         You might need run syslinux manually and install MBR manually"
	exit 0
fi

echo "Making $dest bootable..."

if ! [ -x "$(which syslinux)" ]; then
	apk add --quiet syslinux || die "Failed to install syslinux"
	uninstalls="syslinux"
fi

# we need to unmount the device before we can run syslinux
cleanup_mounts
fsync $dest
syslinux $dest

if [ -b $parent_dev ]; then
	dd if=/usr/share/syslinux/mbr.bin of=$parent_dev status=none
else
	echo "Warning: Could not find the parent device for $dest"
fi