#!/bin/sh
#
# plug - wrapper for udisksctl for LUKS-encrypted devices
#
# SPDX-FileCopyrightText: 2023 Daniel Kalak
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This program depends on udisks2, grep, and the GNU coreutils.
#
# The program assumes that there is a file $DISKSTXT. Empty lines and
# lines starting with "#" are ignored. All other lines represent one
# LUKS-encrypted device each. The lines are assumed to have 3
# whitespace-separated fields: the mount directory (usually
# /run/media/USER/FSLABEL; do not choose it on your own, but state the
# one udisksctl tells you during your first manual mount), the device
# file name of the LUKS-encrypted partition ("locked"), and the device
# file name of the decrypted/mapped partition containing the file system
# ("unlocked"). It is recommended to use device file names of the form
# /dev/disk/by-uuid/UUID; you can look up a UUID with lsblk -f.
#
# With the command "in", the program unlocks and mounts all available
# disks in $DISKSTXT using udisksctl. With "out", the program unmounts,
# locks, and powers off all available disks in $DISKSTXT using
# udisksctl.
#
# The program returns 0 on successful, 1 on bad, and 2 on idle usage.

usage_quit() {
	printf 'Usage: %s in|out\n'           "$(basename "$0")" >&2
	printf 'Environment variable DISKSTXT needs to be set\n' >&2
	exit 1
}

[ "$DISKSTXT" ] || usage_quit
[ "$#" = 1    ] || usage_quit

case "$1" in
'in'|'out') direction="$1" ;;
         *) usage_quit     ;;
esac

grep -v -e '^#' -e '^$' "$DISKSTXT" |
{
	while read -r mountdir locked unlocked
	do
		# Skip if the device isn't even plugged in.
		[ -b "$locked" ] || continue

		case "$direction" in
		'in')
			# Skip if it's already mounted.
			[ -d "$mountdir" ] && continue
			printf 'Plugging in %s...\n' "$mountdir"
			[ -b "$unlocked" ] || udisksctl unlock -b "$locked"
			udisksctl mount -b "$unlocked"
			did_something=yes
			;;
		'out')
			printf 'Unplugging %s...\n' "$mountdir"
			[ -d "$mountdir" ] && udisksctl unmount -b "$unlocked"
			[ -b "$unlocked" ] && udisksctl lock -b "$locked"
			udisksctl power-off -b "$locked"
			did_something=yes
			;;
		esac
	done

	if ! [ "$did_something" ]
	then
		printf 'Nothing to do\n' >&2
		exit 2
	fi
}

# The return value of the block above is passed on by default. We can
# make this explicit with "exit $?".