#!/bin/bash
# This should be readable by /bin/sh, but I'm going to assume bash.

# Sets up XDG environmental variables, so programs using them don't have to
# worry about checking if they are set.
# http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

[[ -n $XDG_DATA_HOME ]] || export XDG_DATA_HOME="$HOME/.local/share"
[[ -n $XDG_CONFIG_HOME ]] || export XDG_CONFIG_HOME="$HOME/.config"
[[ -n $XDG_DATA_DIRS ]] || export XDG_DATA_DIRS="/usr/local/share/:/usr/share/"
[[ -n $XDG_CONFIG_DIRS ]] || export XDG_CONFIG_DIRS="/etc/xdg"
[[ -n $XDG_CACHE_HOME ]] || export XDG_CACHE_HOME="$HOME/.cache"

# Check if XDG_RUNTIME_DIR is set, but has a bogus setting
if [[ -n $XDG_RUNTIME_DIR ]] && [[ ! -d $XDG_RUNTIME_DIR ]]; then
	unset XDG_RUNTIME_DIR
fi

# Set XDG_RUNTIME_DIR if we can
if [[ -z $XDG_RUNTIME_DIR ]] && type flock &>/dev/null; then
	_diy_xdg_runtime_login() {
		export XDG_RUNTIME_DIR="$XDG_CACHE_HOME/xdg-runtime-dir/$HOSTNAME"
		readonly XDG_RUNTIME_DIR
		# There's a race condition here, between the `ln -s` and `flock`.
		# But it's not like I'll be hammering a box with logins.
		if [[ ! -d "$XDG_CACHE_HOME" ]]; then
			local tmp="$(mktemp --tmpdir -- "${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"
		fi
		if flock -sn 7; then
			trap _diy_xdg_runtime_logout EXIT
		fi
	}
	_diy_xdg_runtime_logout() {
		if flock -xn 7; then
			rm -rf -- "$(readlink "$XDG_RUNTIME_DIR")"
		fi
	}
	_diy_xdg_runtime_login
fi