#!/bin/bash

if [ `id -u` -gt 0 ]; then
    exec sudo "$0" "$@"
fi

if [ -z "$1" ]; then
    ROOT="/overlay/lower"
else
    ROOT="$1"
fi

if [ ! -d "$ROOT" ]; then
    echo "$ROOT directory not found"
    exit 1
fi

is_mounted () {
    if [ -z "$1" ]; then
        echo "is_mounted <directory>"
        return 1
    fi
    if test -d "$1" && mountpoint -q "$1"; then
        return 0
    else
        return 1
    fi
}

not_mounted () {
    if [ -z "$1" ]; then
        echo "not_mounted <directory>"
        return 1
    fi
    if test -d "$1" && ! mountpoint -q "$1"; then
        return 0
    else
        return 1
    fi
}

test_mountpoints () {
    if [ -z "$1" -o -z "$2" ]; then
        echo "test_mountpoints <source_mountpoint> <destination_mountpoint>"
        return 1
    fi

    SOURCE=$1
    DESTINATION=$2

    if is_mounted "$SOURCE" && not_mounted "$DESTINATION"; then
        return 0
    else
        return 1
    fi
}

mount -o remount,rw "$ROOT" || { echo "error remounting $ROOT rw"; exit 1; }
if is_mounted /boot; then
    mount -o remount,rw /boot || { echo "error remounting /boot rw"; exit 1; }
fi

for DIR in boot run; do
    if test_mountpoints "/$DIR" "$ROOT/$DIR"; then
        mount --rbind "/$DIR" "$ROOT/$DIR"
    fi
done

if test_mountpoints /sys "$ROOT/sys"; then
    mount -t sysfs sysfs "$ROOT/sys"
fi
if test_mountpoints /proc "$ROOT/proc"; then
    mount -t proc proc "$ROOT/proc"
fi
if test_mountpoints /dev "$ROOT/dev"; then
    mount -t devtmpfs devtmpfs "$ROOT/dev"
fi

IMCHROOTED="$ROOT" chroot "$ROOT"

if is_mounted "$ROOT/sys"; then
    umount -f "$ROOT/sys"
fi
if is_mounted "$ROOT/proc"; then
    umount -f "$ROOT/proc"
fi
if is_mounted "$ROOT/dev"; then
    umount -f "$ROOT/dev"
fi

# with mount --rbind /run $ROOT/run, umounting $ROOT/run is problematic as it's busy and if you umount -lf it umounts directories in /run/.
# I think because / is an overlay of $ROOT. So we don't unmount $ROOT/run
for DIR in boot; do
    if is_mounted "$ROOT/$DIR"; then
        umount -lf "$ROOT/$DIR"
    fi
done

if is_mounted /boot; then
    mount -o remount,ro /boot
fi

mount -o remount,ro "$ROOT" || {
    echo "Failed to remount $ROOT read-only, possibly because of an open file."
    echo "The best thing to do would be to reboot now"
    exit $?
}

exit 0