#!/bin/sh

usage() {
	cat <<EOF
Usage: $0 update|remove --spec <prio>:<path>:<alt-path>

EOF
	exit 1
}

errmsg() {
	echo "$0: $@" >&2
}

uci_() {
	$UCI ${UCI_CONFIG_DIR:+-c $UCI_CONFIG_DIR} "$@"
}

check_path() {
	local path="${IPKG_INSTROOT}$1"

	[ -L "$path" -o ! -e "$path" ] || {
		errmsg "$0: $path exists and is not an symbolic file"
		exit 1
	}
}

update_path() {
	local path="$1"
	local found_section found_altpath
	local found_prio=-1 found_prio_altpath
	local IFS cur altpath

	config_load opkg
	config_foreach find_path alternatives "$prio" "$path"
	if [ -n "$found_prio_altpath" ]; then
		IFS=:; set -- $found_prio_altpath; altpath=$2; IFS="$oIFS"
		cur="$(readlink -f "$path")"
		if [ "$cur" != "$altpath" ]; then
			errmsg "link $path -> $altpath"
			ln -sf "$altpath" "${IPKG_INSTROOT}$path"
		fi
	elif [ -n "$found_section" ]; then
		errmsg "remove empty alternatives section for $path"
		uci_ delete "opkg.$found_section"
		uci_ commit opkg
		rm -f "${IPKG_INSTROOT}$path"
	fi
}

find_altpath() {
	local cfgaltpath="$1"
	local cfg="$2"
	local prio="$3"
	local altpath="$4"
	local cfgprio cfgaltpath_
	local oIFS="$IFS"; IFS=:; set -- $cfgaltpath; cfgprio="$1"; cfgaltpath_="$2"; IFS="$oIFS"

	if [ "$cfgaltpath_" = "$altpath" ]; then
		found_altpath="$cfgaltpath"
	fi
	if [ "$cfgprio" -gt "$found_prio" ]; then
		found_prio="$cfgprio"
		found_prio_altpath="$cfgaltpath"
	fi
}

find_path() {
	local cfg="$1"
	local prio="$2"
	local path="$3"
	local altpath="$4"
	local cfgpath

	config_get cfgpath "$cfg" path
	[ "$cfgpath" = "$path" ] || return
	found_section="$cfg"
	config_list_foreach "$cfg" altpath find_altpath "$cfg" "$prio" "$altpath"
}

cmd_update() {
	local spec="$1"
	local prio path altpath
	local oIFS="$IFS"
	local found_section found_altpath
	local found_prio=-1 found_prio_altpath

	IFS=:; set -- $spec; IFS="$oIFS"
	prio="$1"
	path="$2"
	altpath="$3"
	check_path "$path"
	if [ ! -e "${IPKG_INSTROOT}$altpath" ]; then
		errmsg "$altpath does not exist"
		return 1
	fi

	config_load opkg
	config_foreach find_path alternatives "$prio" "$path" "$altpath"
	if [ -z "$found_section" ]; then
		found_section="$(uci_ add opkg alternatives)"
		uci_ set opkg.$found_section.path=$path
	fi
	if [ -n "$found_altpath" ]; then
		if [ "$found_altpath" != "$prio:$altpath" ]; then
			# update priority
			uci_ del_list opkg.$found_section.altpath=$found_altpath
			uci_ add_list opkg.$found_section.altpath=$prio:$altpath
		fi
	else
		uci_ add_list opkg.$found_section.altpath=$prio:$altpath
	fi
	uci_ commit opkg
	update_path "$path"
}

cmd_remove() {
	local spec="$1"
	local prio path altpath
	local oIFS="$IFS"
	local found_section found_altpath
	local found_prio=-1 found_prio_altpath

	IFS=:; set -- $spec; IFS="$oIFS"
	prio="$1"
	path="$2"
	altpath="$3"
	check_path "$path"

	config_load opkg
	config_foreach find_path alternatives "$prio" "$path" "$altpath"
	if [ -n "$found_section" -a -n "$found_altpath" ]; then
		uci_ del_list opkg.$found_section.altpath=$found_altpath
		uci_ commit opkg
		update_path "$path"
	else
		errmsg "spec $spec not found"
	fi
}

. ${IPKG_INSTROOT}/lib/functions.sh

UCI="${UCI:-/sbin/uci}"
UCI_STATE_DIR="${IPKG_INSTROOT}/var/state"
ARG_CMD=
ARG_SPEC=
while [ "$#" -gt 0 ]; do
	case "$1" in
		update|remove)
			ARG_CMD="$1"
			shift
			;;
		--spec)
			ARG_SPEC="$2";
			shift 2
			;;
		*) usage ;;
	esac
done

[ -n "$ARG_CMD" -a -n "$ARG_SPEC" ] || usage

cmd_$ARG_CMD "$ARG_SPEC"