#!/bin/bash
# if you need to add something to path:
#PATH=$PATH:/path/to/java:/path/to/signal-cli
# for some cases you should explicitly specify JAVA_HOME in
# order for signal-cli to work
#export JAVA_HOME=/var/packages/Java8/target/j2sdk-image/jre

# username of the sending entity (phone number in international format)
SIGNAL_USER="+1123123123123"

# phone number of the user that receives the notification
NOTIFY_NUMBER="+132132132132"

# now go to the bottom of the script and specify the checks

mkdir -p ~/.signal-monitoring && cd ~/.signal-monitoring

function log {
	echo "$1" >> ~/.signal-monitoring/log
}

# arguments: notify_text
function notify {
	echo $1 | signal-cli -u ${SIGNAL_USER} send $NOTIFY_NUMBER
	log "Sending notification ${1}"
}

# arguments: check_name description
function check_passed {
	check_name=$1
	description=$2
	check_filename="${check_name}-error"

	log "check_passed ${check_name} ${description}"

	if [ -f ${check_filename} ]
		then
			rm -f $check_filename
			notify "${description}"
		fi
}

# arguments: check_name description
function check_failed {
	check_name=$1
	description=$2
	check_filename="${check_name}-error"

	log "check_failed ${check_name} ${description}"

	FOUND=`find ~/.signal-monitoring -mmin -60 -name ${check_name}-error -not -empty -print`
	if [ -z "$FOUND" ]
	  then # we don't have recent notification (60 minutes)
		echo "${description}" > "${check_filename}"
		notify "${description}"
	  fi
}


# argument: hostname
function check_ping {
		server=$1
		if ping -c 5 -q $server > /dev/null 2>&1
			then
				check_passed ${server}-ping "${server} ping is up"
			else
				check_failed ${server}-ping "${server} ping is not responding"
			fi
}

# arguments: check_name url content_to_look_for
function check_url {
		check_name=$1
		url=$2
		content_to_look_for=$3
		if wget -q -O - "$url" | grep "$content_to_look_for" > /dev/null 2>&1
			then
				check_passed ${check_name}-url "${check_name} UP: ${url} now contains ${content_to_look_for}"
			else
				check_failed ${check_name}-url "${check_name} DOWN: ${url} does not contain ${content_to_look_for}"
			fi
}

# here are the checks

# check pings
check_ping my-first.server.com
check_ping my-second.server.com

check_url my-first.server.com "https://my-first.server.com/url/index.html" "Welcome to My First Server"
check_url my-third.server.com "https://my-third.server.com/index.html" "Welcome to My Third Server"

# Leave this if you don't use signal-cli outside of this script,
# otherwise comment out, see readme
signal-cli -u $SIGNAL_USER receive > /dev/null 2>&1