#!/hint/sh

# Set XDG_RUNTIME_DIR if we can
if [ -z "$XDG_RUNTIME_DIR" ] && shopt -q login_shell && type flock &>/dev/null; then
	_diy_xdg_runtime_login() {
		export XDG_RUNTIME_DIR="$XDG_CACHE_HOME/xdg-runtime-dir/$HOSTNAME"
		# There's a race condition here, between the `ln -s` and `flock`.
		# But it's not like I'll be hammering a box with logins.
		if [ ! -d "$XDG_RUNTIME_DIR" ]; then
			local tmp="$(mktemp -d --tmpdir -- "${USER}@${HOSTNAME}-runtime.XXXXXXXXXX")"
			mkdir -p -- "$XDG_CACHE_HOME/xdg-runtime-dir"
			ln -sfT -- "$tmp" "$XDG_RUNTIME_DIR"
		fi
		if ! [ /dev/fd/7 -ef "$XDG_CACHE_HOME/xdg-runtime-dir/.lock" ]; then
			exec 7>"$XDG_CACHE_HOME/xdg-runtime-dir/.lock"
			if flock -sn 7; then
				# Unfortunately this doesn't survive across exec(1).
				trap _diy_xdg_runtime_logout EXIT
			fi
		fi
	}
	_diy_xdg_runtime_logout() {
		if flock -xn 7; then
			rm -rf -- "$(readlink "$XDG_RUNTIME_DIR")"
		fi
	}
	_diy_xdg_runtime_login
fi