#!/usr/bin/env bash

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

Notifies via mail when a service has failed. You need to place the following in the service which should be checked:

[Unit]
Description=...
OnFailure=systemd_failure_notify@%n.service
...

You should place the <scriptname>'s service into systemd's user and systemd's system folder so it can be used by global and user services.

If no CONFIG_FILE is given, HOME/.systemd_failure_notify.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:
- SYSTEMD_FAILURE_NOTIFY_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;

SYSTEMD_FAILURE_NOTFY_SERVICE=$1
if [ -z "$SYSTEMD_FAILURE_NOTFY_SERVICE" ]; then
	echo "No service given";
	echo "";
	usage;
	exit 1;
fi

SYSTEMD_FAILURE_NOTFY_HOSTNAME=$(hostname)
SYSTEMD_FAILURE_NOTFY_USER=$(whoami)
SYSTEMD_FAILURE_NOTIFY_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 "$2" "$HOME/.systemd_failure_notify.conf"

SUBJECT="[systemd $SYSTEMD_FAILURE_NOTFY_HOSTNAME for $SYSTEMD_FAILURE_NOTFY_USER] $SYSTEMD_FAILURE_NOTFY_SERVICE RUN FAILED"
MESSAGE="$SYSTEMD_FAILURE_NOTFY_SERVICE run failed"
echo $MESSAGE|mailx -Ssendwait -s "$SUBJECT" $SYSTEMD_FAILURE_NOTIFY_MAIL_ADDRESS;