#!/usr/bin/env bash

# Refactored by: Patrick Huber (22phuber@gmail.com)
# Description: Digs the current external Ipv4 and compares it to a Ipv4 locally stored in a file.
#              If the ips differ, aws cli is used to update a route 53 dns record with the new Ipv4. 
#              This script only supports Ipv4.
# Original script source:
#   - https://willwarren.com/2014/07/03/roll-dynamic-dns-service-using-amazon-route53/
# Dependencies:
#  - awscli # install AWS cli: https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-install.html
#  - dig
#  - mktemp
#  - grep
#
set -e
set -o pipefail

# INITIALIZE
{
    echo "[$(date)] Starting \"${BASH_SOURCE[0]}\"" \
    && trap finish EXIT \
    && trap 'Error in line: ${LINENO}' ERR \
    && cd "$(dirname "${BASH_SOURCE[0]}")";
} || exit 1

# VARIABLES
# AWS profile
aws_profile='default'
# AWS cli path
aws_binary_path='/usr/local/bin'
# set new PATH for AWS binary
if [[ ! ${PATH} == *"${aws_binary_path}"* ]]; then
    PATH=${PATH}:${aws_binary_path}
fi

# ipfile (caches last runs ip)
declare -r IPFILE="update-route53.ip"

# Hosted Zone ID e.g. BJBK35SKMM9OE
declare -r ZONEID="<your zone id>"
# The recordset you want to update e.g. example.com or www.example.com
declare -r RECORDSET="<you recordset>"
# The Time-To-Live of this recordset
declare -r TTL=300
# Use type A when using IPv4 address
declare -r TYPE="A"

# Change this if you want
COMMENT="Auto updating @ $(date)"

# FUNCTIONS

# desc: prints the date and "script finished" text
# usage: checkAwsCli
function finish () {
    echo -e "[$(date)] Script finished\n"
}

# desc: check if aws cli is present
# usage: checkAwsCli
# returns:
#   0 => if aws cli exists
#   1 => if aws cli could not be found
function checkAwsCli () {
    if [[ -x "$(command -v aws)" ]]; then # True if file exists and is executable.
        return 0
    else
        echo "Function [${FUNCNAME[0]}]: AWS cli is missing."
        return 1
    fi
}

# desc: simple validation for a given ipv4 address
#      checks:
#        - correct ip parts
#        - part values between 0 and 255 (inclusive)
# usage: validate_ipv4 "<ipv4>"
# returns:
#   0 => if validation was successful
#   1 => if validation has failed
function validate_ipv4() {
    if [[ $# -lt 1 ]] ; then
        echo "Function [${FUNCNAME[0]}]: Wrong argument count. Nothing validated"
        return 1
    fi
    local __ip="${1}"
    declare -a __ip_arr=${__ip//./ }

    if [[ ${__ip} =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        for ip_part in ${__ip_arr[@]}; do
            if [[ ! ${ip_part} -le 255 ]]; then return 1; fi
        done
        return 0
    fi
    return 1
}

# desc: chcek if given string is present in the given file
# usage: find_string_in_file "<string>" file
# returns:
#   0 => if string has been found
#   1 => if string has NOT been found
function find_string_in_file() {
    if [[ $# -lt 2 ]] ; then
        echo "Function [${FUNCNAME[0]}]: Wrong argument count. Nothing done"
        return 1
    fi
    local __string_to_find="${1}"
    shift 1
    local __file="${1}"

    grep -Fxq "${__string_to_find}" "${__file}" && return 0
    return 1
}

# desc: caches given ipv4 in given file
# usage: cache_ipv4 "<ipv4>" file
#   0 => if caching was successful
#   1 => if caching failed
function cache_ipv4 () {
    if [[ $# -lt 2 ]] ; then
        echo "Function [${FUNCNAME[0]}]: Wrong argument count. Nothing cached"
        return 1
    fi
    local __ip="${1}"
    shift 1
    local __file="${1}"

    validate_ipv4 "${__ip}" \
    && echo "${__ip}" > "${__file}" \
    && find_string_in_file "${__ip}" "${__file}" \
    && return 0
    return 1
}

# desc: update route 53 record
# usage: update_route53_record "<zoneid>" "<ipv4>" "<recordset>" "<type>" "<ttl>" "<comment>" "<aws-profile>"
#   0 => if route 53 record update was successful
#   1 => if route 53 record update failed
function update_route53_record () {
    if [[ $# -lt 7 ]] ; then
        echo "Function [${FUNCNAME[0]}]: Wrong argument count. Nothing updated"
        return 1
    fi
    local __zoneid="${1}"; shift
    local __ip="${1}"; shift
    local __recordset="${1}"; shift
    local __type="${1}"; shift
    local __ttl="${1}"; shift
    local __comment="${1}"; shift
    local __aws_profile="${1}";

    local __tmpFile;
    __tmpFile=$(mktemp /var/tmp/aws_route53_change-resource-record-set.json.XXXXXXXX)
    # trap temp file deletion on RETURN signal
    trap 'rm -rf "${__tmpFile}"' RETURN
    # heredoc section
cat << EOF > "${__tmpFile}"
{
  "Comment":"${__comment}",
  "Changes":[
    {
      "Action":"UPSERT",
      "ResourceRecordSet":{
        "ResourceRecords":[
          {
            "Value":"${__ip}"
          }
        ],
        "Name":"${__recordset}",
        "Type":"${__type}",
        "TTL":${__ttl}
      }
    }
  ]
}
EOF

    # Update the route 53 record
    aws --profile "${__aws_profile}" route53 change-resource-record-sets \
    --hosted-zone-id "${__zoneid}" \
    --change-batch "file://${__tmpFile}" \
    && return 0

    return 1
}


# MAIN
checkAwsCli || exit 1

# Get the external IP address
# https://unix.stackexchange.com/questions/22615/how-can-i-get-my-external-ip-address-in-a-shell-script
# example1: dig @resolver1.opendns.com A myip.opendns.com +short -4
# example2: dig @ns1-1.akamaitech.net ANY whoami.akamai.net +short -4
# example3: dig @ns1.google.com TXT o-o.myaddr.l.google.com +short -4 | sed -e 's#"##g'
IPv4=$(dig @resolver1.opendns.com A myip.opendns.com +short -4)

{
    # validate ipv4
    validate_ipv4 "${IPv4}" \
    && touch "${IPFILE}"; # touching ipfile (creates it, if it does not exist)
} || exit 1

# Check current ip with previously save ip from the ipfile
if (find_string_in_file "${IPv4}" "${IPFILE}" ); then
    echo "External IPv4 is still the same."
    exit 0
else
    echo "External Ipv4 has changed to ${IPv4}"
    # Update the record when the ip has changed
    if (update_route53_record "${ZONEID}" "${IPv4}" "${RECORDSET}" "${TYPE}" "${TTL}" "${COMMENT}" "${aws_profile}" ); then
        echo "AWS Route 53 record \"${RECORDSET}\" with type \"${TYPE}\" has been updated with value \"${IPv4}\" in zone ${ZONEID}"
        cache_ipv4 "${IPv4}" "${IPFILE}"
        exit 0
    else
        echo "Failed to update AWS Route 53 record: ${RECORDSET}"
        exit 1
    fi
fi

exit 0