#!/bin/sh

STOW_DIR=/etc/portage/stow
TARGET=/etc/portage

stowcmd="stow -d "$STOW_DIR" -t "$TARGET""

need_root() {
	if test $(id -u) -ne 0; then
		printf 'This action requires superuser access.\n'
		exit 1
	fi
}

add() {
	need_root
	$stowcmd -S "$@"
}

remove() {
	need_root
	$stowcmd -D "$@"
}

flush() {
	need_root
	list | xargs -- $stowcmd -D
}

rebuild() {
	need_root
	list | xargs -- $stowcmd -R
}

list() {
	subcmd="$1"
	shift
	case $subcmd in
		active) list_active;;
		all) list_all;;
		available) list_available;;
		*) list_active;;
	esac
}

list_active() {
	# XXX: -r for xargs is a GNU extension
	find /etc/portage/ -lname "*stow/*" -print0 2>/dev/null \
		| xargs -r0 readlink \
		| sed 's:.*stow/\([^/]\+\)/.*:\1:' \
		| sort -u
}

list_all() {
	ls -1 "$STOW_DIR"
}

list_available() {
	tmp="$(mktemp)" || exit 1
	list_active > "$tmp"
	list_all | comm -13 "$tmp" - 
	rm -f "$tmp"
}

cmd="$1"
shift
case $cmd in
	add) add "$@";;
	flush) flush;;
	list) list "$@";;
	rebuild) rebuild;;
	remove) remove "$@";;
	*) list_active;;
esac