#!/bin/bash
# -*- mode: sh; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
# vim: et sts=4 sw=4

#  SPDX-License-Identifier: LGPL-2.1+
#
#  Copyright © 2020-2021 Collabora Ltd.
#  Copyright © 2020-2021 Valve Corporation.
#
#  This file is part of steamos-customizations.
#
#  steamos-customizations is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public License as
#  published by the Free Software Foundation; either version 2.1 of the License,
#  or (at your option) any later version.

set -euo pipefail

declare -r ROOTDEV=/dev/disk/by-partsets/self/rootfs

# default and future guess
fstype=btrfs

usage() {
    cat <<EOF
Usage: ${0##*/} enable|disable|status

Enable or disable read-only on the current running SteamOS.
EOF
}

# mark root partition writable
read_write_extfs() {
    tune2fs -O ^read-only "$ROOTDEV"
    mount -o remount,rw /
}
read_write_btrfs() {
    mount -o remount,rw /
    btrfs property set / ro false
}
read_write() {
    if ! status >/dev/null; then
        echo "Warning: The rootfs is already read-write!" >&2
        echo "         Nothing is performed." >&2
        return
    fi
    read_write_$fstype
}

#
# mark root partition read-only
read_only_btrfs() {
    btrfs property set / ro true
}
read_only_extfs() {
    mount -o remount,ro /
    tune2fs -O read-only "$ROOTDEV"
}
read_only() {
    if status >/dev/null; then
        echo "Warning: The rootfs is already read-only!" >&2
        echo "         Nothing is performed." >&2
        return
    fi
    sync /
    read_only_$fstype
}

status_extfs() {
    if tune2fs -l "$ROOTDEV" | grep -q '^Filesystem features: .*read-only.*$'
    then
        echo "enabled"
        return
    else
        echo "disabled"
        return 1
    fi
}
status_btrfs() {
    prop_val=$(btrfs property get / ro)
    if [[ $prop_val = "ro=true" ]]
    then
        echo "enabled"
    else
        echo "disabled"
        return 1
    fi
}
status() {
    status_$fstype
}


toggle() {
    if status >/dev/null
    then
        read_write
    else
        read_only
    fi
    status
}

# determine file system type and set the fstype variable used above
get_fstype() {
    declare -r FSTYPE=$(findmnt -fn --output FSTYPE /)
    case "$FSTYPE" in
    ext4)
        fstype=extfs
        ;;
    btrfs)
        fstype=btrfs
        ;;
    *)
        echo "Unrecognized root filesystem type $FSTYPE"
        exit 1
    esac
}

# Ideally status will be root-free, alas tune2fs (ext4 rootfs)
# does not like that.
if [[ "$(id -u)" -ne 0 ]]; then
    echo "$(basename $0) needs to be run as root"
    exit 1
fi

get_fstype

case "${1:-}" in
    disable)
        read_write
        ;;
    enable)
        read_only
        ;;
    toggle)
        toggle
        ;;
    status)
        status
        ;;
    *)
        usage
        exit 1
esac