#!/bin/bash

################################################################################
# CONFIGURATION
################################################################################

# check every TIMEOUT seconds (default 300 = 5 min)
TIMEOUT=300
# user credentials
USERNAME="ur goip username"
PASSWORD="ur goip password"
DOMAIN="urdomain.goip.it"
# Discord webhook
DISCORD_WEBHOOK_URL="" # leave empty to disable
DISCORD_WEBHOOK_MESSAGE_UPDATE="DNS entry for $DOMAIN has been updated successfully. ($(date))"
DISCORD_WEBHOOK_MESSAGE_FAIL="DNS entry update for $DOMAIN failed. ($(date))"

################################################################################
# END OF CONFIGURATION
################################################################################

function discord_update_message {
    if [ -n $DISCORD_WEBHOOK_URL ]; then
        local MESSAGE='{"username": "DNS Record Updater", "content": "'"$1"'"}'
        wget -qO - --post-data="$MESSAGE" --header='Content-Type:application/json' "$DISCORD_WEBHOOK_URL"
    fi
}

function get_ip {
    # get a string in format 'ip=x.x.x.x' by splitting out a json over multiple lines and removing characters
    local IP=$(wget -4qO - "https://api.myip.com" | sed 's/[\{\}]//g;s/,/\n/g' | sed -n 's/"//g;s/:/=/g;/ip/p')
    if [ -z $IP ]; then
        echo "Getting my own IP failed." >&2
        echo "ip=0.0.0.0"
    else
        echo $IP
    fi
}

function set_ip {
    wget -qO - "https://goip.it/setip?username=$USERNAME&password=$PASSWORD&subdomain=$DOMAIN&$1"
    local EXIT_CODE="$?"
    echo "" # add newline after wget output
    if [ $EXIT_CODE -ne 0 ]; then
        echo "Setting a new IP using wget failed with exit code $EXIT_CODE." >&2
        discord_update_message "$DISCORD_WEBHOOK_MESSAGE_FAIL"
    else
        discord_update_message "$DISCORD_WEBHOOK_MESSAGE_UPDATE"
    fi
}

IP="ip=0.0.0.0"
while true; do
    NEW_IP=$(get_ip)
    if [ $IP != $NEW_IP ]; then
        echo -e "IP has changed. New IP:\n$NEW_IP"
        IP="$NEW_IP"
        set_ip "$IP"
    fi
    sleep $TIMEOUT
done