#!/bin/bash

# Adds date to output for simple logging
log_date() {
    echo "$(date +%m/%d/%Y\ %H:%M:%S) $1"
}

help() {
    echo "yum-autoupdate is a cron job script to automatically update system packages on CWP servers.

The cron job that runs this script exists in /etc/cron.d/yum_autoupdate 

USAGE: yum-autoupdate [--disable|--enable]
    --disable          Touches /etc/disable-auto-updates file to stop script from running updates
    --enable           Remove /etc/disable-auto-updates file to resume automatic updates via cron
    -h --help          Show this message and exit
"
}

disable_update() {
    if ! [[ -f /etc/disable-auto-updates ]]; then
        touch /etc/disable-auto-updates && \
        echo "Disabled automatic yum updates"
    else
        echo "Automatic yum updates are already disabled"
    fi
}

enable_update() {
    if [[ -f /etc/disable-auto-updates ]]; then
        rm -f /etc/disable-auto-updates && \
        echo "Enabled automatic yum updates"
    else
        echo "Automatic yum updates are already enabled"
    fi
}

# Run yum updates and log results with time stamps
run_update () {
    log_date "Beginning automatic yum updates cron..."
    pid_file=yum_autoupdate.pid
    pid=$(grep -oP '\d+' $pid_file 2>/dev/null)
    pid=${pid:=-1}

    # Make sure this script isn't already running
    if grep -Eq 'yum-autoupdate' /proc/$pid/cmdline 2>/dev/null; then
    log_date "Existing $pid_file process found with PID $pid"
    exit 1
    fi
    echo $$ > $pid_file

    if ! yum clean expire-cache &>/dev/null; then
        log_date "Failed to 'yum clean expire-cache"
    fi
    log_date "Initiating package updates..."
    if ! yum -y update -d 1; then
        log_date "Routine yum updates failed"
    else
        log_date "Routine yum updates completed."
    fi
}

# Command line options
while [[ "${#}" -gt 0 ]]; do
    case "${1}" in
        -h|--help)
            help
            exit
            ;;

        --disable)
            disable_update
            exit
            ;;

        --enable)
            enable_update
            exit
            ;;

        *)
            echo -e "Invalid argument '${1}'\n"
            help
            exit
            ;;
    esac
done

# Run updates unless disabled
if ! [[ -f /etc/disable-auto-updates ]]; then
    run_update
else
    log_date "Automatic yum updates are currently disabled. Exiting."
fi