#!/usr/bin/env bash

# This script reads user@host lines from ~/.server_hosts. Each host
# is a RHEL-like operating system where the dnf-utils and
# dnf-automatic packages are installed. dnf-automatic is configured
# to download and apply updates periodically. The 'needs-restarting'
# command provided by the dnf-utils packages is assumed to be
# available on each host. Each host is checked via SSH to see if it
# needs-restarting after core libraries and services have been
# updated since the last boot-up. If a restart has been initiated for
# a given host, notify-send will notify the user.

set -euo pipefail

HOST_FILE="${HOME}/.server_hosts"
host_array=()
RED='\033[1;31m'
YELLOW='\033[1;33m'
GREEN='\033[1;32m'
NC='\033[0m'

# Read hosts from ~/.server_hosts
while IFS= read -r line; do
    host=$(echo $line)
    host_array+=($host)
done < "${HOST_FILE}"

for host in "${host_array[@]}"; do
    hostname=$(echo $host | cut --delimiter="@" --fields=2)
    if ssh "$host" -- sudo needs-restarting -r >/dev/null; then
        echo -e "$hostname: ${GREEN}OK${NC}"
    else
        ssh "$host" -- sudo systemctl reboot >/dev/null
        echo -e "$hostname: ${RED}Restart initiated${NC}"
        notify-send "$hostname: Restart initiated"
    fi
done