#!/bin/bash
 
# Hosted Zone ID e.g. BJBK35SKMM9OE
ZONEID="Z49JKEQC08KW8"
 
# The CNAME you want to update e.g. hello.example.com
RECORDSET="aws.monkeybox.org"
 
# More advanced options below
# The Time-To-Live of this recordset
TTL=300
# Change this if you want
COMMENT="Auto updating @ `date`"
# Change to AAAA if using an IPv6 address
TYPE="AAAA"
 
# Get the external IP address
IP=`curl -ss http://ipv6.icanhazip.com/`

# IPv6 Validation:
WORD="[0-9A-Fa-f]\{1,4\}"
# flat address, no compressed words
FLAT="^${WORD}\(:${WORD}\)\{7\}$"
# ::'s compressions excluding beginning and end edge cases
COMP2="^\(${WORD}:\)\{1,1\}\(:${WORD}\)\{1,6\}$"
COMP3="^\(${WORD}:\)\{1,2\}\(:${WORD}\)\{1,5\}$"
COMP4="^\(${WORD}:\)\{1,3\}\(:${WORD}\)\{1,4\}$"
COMP5="^\(${WORD}:\)\{1,4\}\(:${WORD}\)\{1,3\}$"
COMP6="^\(${WORD}:\)\{1,5\}\(:${WORD}\)\{1,2\}$"
COMP7="^\(${WORD}:\)\{1,6\}\(:${WORD}\)\{1,1\}$"
# trailing :: edge case, includes case of only :: (all 0's)
EDGE_TAIL="^\(\(${WORD}:\)\{1,7\}\|:\):$"
# leading :: edge case
EDGE_LEAD="^:\(:${WORD}\)\{1,7\}$"

function valid_ip()
{
    # Returns 0 on a good IP, 1 on a bad IP
    local  ip=$1

    echo $ip | grep --silent "\(${FLAT}\)\|\(${COMP2}\)\|\(${COMP3}\)\|\(${COMP4}\)\|\(${COMP5}\)\|\(${COMP6}\)\|\(${COMP7}\)\|\(${EDGE_TAIL}\)\|\(${EDGE_LEAD}\)"
    if [ $? -eq 0 ]; then
        return 0
    fi
    return 1
}
 
# Get current dir (stolen from http://stackoverflow.com/a/246128/920350)
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
LOGFILE="$DIR/update-route53.ipv6.log"
IPFILE="$DIR/update-route53.ipv6.ip"
 
if ! valid_ip $IP; then
    echo "Invalid IP address: $IP" >> "$LOGFILE"
    exit 1
fi
 
# Check if the IP has changed
if [ ! -f "$IPFILE" ]
    then
    touch "$IPFILE"
fi
 
if grep -Fxq "$IP" "$IPFILE"; then
    # code if found
    echo "IP is still $IP. Exiting" >> "$LOGFILE"
    exit 0
else
    echo "IP has changed to $IP" >> "$LOGFILE"
    # Fill a temp file with valid JSON
    TMPFILE=$(mktemp /tmp/temporary-file.XXXXXXXX)
    cat > ${TMPFILE} << EOF
    {
      "Comment":"$COMMENT",
      "Changes":[
        {
          "Action":"UPSERT",
          "ResourceRecordSet":{
            "ResourceRecords":[
              {
                "Value":"$IP"
              }
            ],
            "Name":"$RECORDSET",
            "Type":"$TYPE",
            "TTL":$TTL
          }
        }
      ]
    }
EOF
 
    # Update the Hosted Zone record
    aws route53 change-resource-record-sets \
        --hosted-zone-id $ZONEID \
        --change-batch file://"$TMPFILE" >> "$LOGFILE"
    echo "" >> "$LOGFILE"
 
    # Clean up
    rm $TMPFILE
fi
 
# All Done - cache the IP address for next time
echo "$IP" > "$IPFILE"