#!/bin/sh
###########################################################################
##  Copyright (C) Wizardry and Steamworks 2015 - License: GNU GPLv3      ##
##  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  ##
##  rights of fair usage, the disclaimer and warranty conditions.        ##
###########################################################################

# This script sets a zone's A record on CloudFlare to point to an Airport 
# basestation's external IP address and is meant to be run regularly. 
#
# Requires a complete installation of SNMP along with relevant MIBs.
# On Debian, the packages: snmp, snmp-mibs-downloader must be installed.
# Airport MIB file must be downloaded from Apple and installed accordingly.

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

# Airport IP or hostname
AIRPORT_LOCAL_ADDRESS='192.168.0.1'
# Set this to the cloudflare zone name.
DOMAIN='slap.com'
# Set this to the A record name.
RECORD_NAME='forward.slap.com'
# Set this to your account e-mail address.
EMAIL='mongoose@whatever.tld'
# Set this to your CloudFlare API key.
API_KEY='1d10ab0dd09abfda6cc3dd0a92ca75de75671'

###########################################################################
##                               INTERNALS                               ##
###########################################################################

AIRPORT_EXTERNAL_ADDRRESS=`snmpwalk \
    -v1 \
    -c public $AIRPORT_LOCAL_ADDRESS \
    -m AIRPORT-BASESTATION-3-MIB \
        RFC1213-MIB::ipAdEntAddr | \
        head -1 | \
        awk '{ print $4 }'`

#echo $AIRPORT_EXTERNAL_ADDRRESS

if [ -z $AIRPORT_EXTERNAL_ADDRRESS ]; then
    echo "Unable to retrieve Airport external address."
    echo "Please check that the Airport has SNMP enabled."
    exit 1
fi

FLARE=$(curl -s https://www.cloudflare.com/api_json.html \
    -d 'a=rec_load_all' \
    -d "tkn=$API_KEY" \
    -d "email=$EMAIL" \
    -d "z=$DOMAIN")

if [ -z $FLARE ]; then
    echo "Unable to retrieve CloudFlare zone."
    echo "Please check the API key."
    exit 1
fi

ZONE_ADDRESS=`echo $FLARE | sed -E "s/.*,\"name\":\"$RECORD_NAME\",[^}]*?,\"type\":\"A\",[^}]*?,\"content\":\"([0-9\.]+?)\",.*/\1/"`
if [ -z $ZONE_ADDRESS ]; then
    echo "Unable to retrieve the CloudFlare zone IP address."
    exit 1
fi

# if the airport external address matches the zone address terminate
if [ $AIRPORT_EXTERNAL_ADDRRESS = $ZONE_ADDRESS ]; then
    exit 0
fi

RECORD_ID=`echo $FLARE | sed -E "s/.*\"rec_id\":\"([0-9]+?)\",[^}]*?,\"name\":\"$RECORD_NAME\",[^}]*?,\"type\":\"A\",.*/\1/"`
if [ -z $RECORD_ID ]; then
    echo "Unable to retrieve CloudFlare record ID for the zone."
    exit 1
fi

FLARE=$(curl -s https://www.cloudflare.com/api_json.html \
    -d 'a=rec_edit' \
    -d "tkn=$API_KEY" \
    -d "id=$RECORD_ID" \
    -d "email=$EMAIL" \
    -d "z=$DOMAIN" \
    -d 'type=A' \
    -d "name=$RECORD_NAME" \
    -d "content=$AIRPORT_EXTERNAL_ADDRRESS" \
    -d 'service_mode=0' \
    -d 'ttl=1')

RESULT=`echo $FLARE | sed -E "s/.*,\"result\":\"([^\,]*?)\",.*/\1/"`
if [ $RESULT = "success" ]; then
    echo "$RECORD_NAME now points to $AIRPORT_EXTERNAL_ADDRRESS"
    exit 0
fi
exit 1