#!/usr/bin/env bash

# usage
usage() {
USAGE=$(cat <<EOF
Usage: check_updates [CONFIG_FILE (absolute path)]

If no CONFIG_FILE is given, HOME/.check_updates.conf is used. This fallback option
has to exist or the script will exit.

Configuration can be done in any file and any pre-defined variable can be overwritten.

The following are at least required for the script to work:
- CHECK_UPDATES_MAIL_ADDRESS="" // mail.rc has to be configured

You can copy this script to '/usr/local/bin' and use create a custom CONFIG_FILE as user. Examples can be found in '/usr/share/doc/<scriptname>'.
EOF
)
	echo "$USAGE";
}

set -e;

HOSTNAME=$(hostname)
UPDATES=$(checkupdates)
UPDATES_AMOUNT=$(checkupdates|wc -l)
CHECK_UPDATES_MAIL_ADDRESS="";

# check for config file
source_config() {
	local config=$1;
	local configFallback=$2;

	if [[ ! -f "$config" ]]; then
		if [[ ! -f "$configFallback" ]]; then
			echo "No config file specified and could not find default in '$configFallback'!";
			echo "";
			usage;
			exit 1;
		else
			config=$configFallback;
		fi
	fi

	set -a;
	source "$config";
	set +a;
}
source_config "$1" "$HOME/.check_updates.conf"

if [ "$UPDATES_AMOUNT" -gt "0" ]; then
	mailx -s "[updates $HOSTNAME]" $CHECK_UPDATES_MAIL_ADDRESS << EOF
There are $UPDATES_AMOUNT updates available on $HOSTNAME.

$UPDATES
EOF
fi