#!/bin/bash
set -e

# runs copyparty (or any other program really) in a chroot
#
# assumption: these directories, and everything within, are owned by root
sysdirs=( /bin /lib /lib32 /lib64 /sbin /usr )


# error-handler
help() { cat <<'EOF'

usage:
  ./prisonparty.sh <ROOTDIR> <UID> <GID> [VOLDIR [VOLDIR...]] -- copyparty-sfx.py [...]"

example:
  ./prisonparty.sh /var/lib/copyparty-jail 1000 1000 /mnt/nas/music -- copyparty-sfx.py -v /mnt/nas/music::rwmd"

EOF
exit 1
}


# read arguments
trap help EXIT
jail="$(realpath "$1")"; shift
uid="$1"; shift
gid="$1"; shift

vols=()
while true; do
	v="$1"; shift
	[ "$v" = -- ] && break  # end of volumes
	[ "$#" -eq 0 ] && break  # invalid usage
	vols+=( "$(realpath "$v")" )
done
pybin="$1"; shift
pybin="$(realpath "$pybin")"
cpp="$1"; shift
cpp="$(realpath "$cpp")"
cppdir="$(dirname "$cpp")"
trap - EXIT


# debug/vis
echo
echo "chroot-dir = $jail"
echo "user:group = $uid:$gid"
echo " copyparty = $cpp"
echo
printf '\033[33m%s\033[0m\n' "copyparty can access these folders and all their subdirectories:"
for v in "${vols[@]}"; do
	printf '\033[36m ├─\033[0m %s \033[36m ── added by (You)\033[0m\n' "$v"
done
printf '\033[36m ├─\033[0m %s \033[36m ── where the copyparty binary is\033[0m\n' "$cppdir"
printf '\033[36m ╰─\033[0m %s \033[36m ── the folder you are currently in\033[0m\n' "$PWD"
vols+=("$cppdir" "$PWD")
echo


# remove any trailing slashes
jail="${jail%/}"
cppdir="${cppdir%/}"


# bind-mount system directories and volumes
printf '%s\n' "${sysdirs[@]}" "${vols[@]}" | LC_ALL=C sort |
while IFS= read -r v; do
	[ -e "$v" ] || {
		# printf '\033[1;31mfolder does not exist:\033[0m %s\n' "/$v"
		continue
	}
	i1=$(stat -c%D.%i "$v"      2>/dev/null || echo a)
	i2=$(stat -c%D.%i "$jail$v" 2>/dev/null || echo b)
	[ $i1 = $i2 ] && continue
	
	mkdir -p "$jail$v"
	mount --bind "$v" "$jail$v"
done


# create a tmp
mkdir -p "$jail/tmp"
chmod 777 "$jail/tmp"


# run copyparty
/sbin/chroot --userspec=$uid:$gid "$jail" "$pybin" "$cpp" "$@" && rv=0 || rv=$?


# cleanup if not in use
lsof "$jail" | grep -qF "$jail" &&
	echo "chroot is in use, will not cleanup" ||
{
	mount | grep -qF " on $jail" |
	awk '{sub(/ type .*/,"");sub(/.* on /,"");print}' |
	LC_ALL=C sort -r  | tee /dev/stderr | tr '\n' '\0' | xargs -r0 umount
}
exit $rv