<#
    .SYNOPSIS
    Simple script to safely assign AWS Elastic IPs (EIPs) at Windows Boot.
    
    .DESCRIPTION
    Script first checks to see if the IP is already assigned, and if so aborts
    returning a non-zero code.  If assginement is successful, zero (0) is returned.
    
    NOTE:  Script must be updated to include instanceID, EIP, security credentials,
        and ServiceURL for your particular Region.
    
    .NOTES
        File Name :  AWS-EIP.ps1
        Author    :  Nick Webb - nickw@redwireservices.com
        Version   :  0.2 - 02/21/2012
        
    .LINK
        http://www.redwireservices.com
    
    .EXAMPLE
    
    AWS-EIP.ps1
#>


# User modifyable items: #################################################

# Update to the AWS SDK Path on your system, if not default
Add-Type -Path "C:\Program Files (x86)\AWS SDK for .NET\bin\AWSSDK.dll"

# Update the following lines, as needed:
$accessKeyID="your access key ID"
$secretAccessKey="your secret access key"
$instanceID="i-your instance id"
$instanceEIP="x.x.x.x"

# Uncomment ONE of the following, which applies to your region
# US-West N. California:
$ServiceURL="https://ec2.us-west-1.amazonaws.com"

# US-West Oregon
#$ServiceURL="https://ec2.us-west-2.amazonaws.com"

# US-East (Standard)
#$ServiceURL="https://ec2.us-east-1.amazonaws.com"
# END User configurable options ##########################################

$config=New-Object Amazon.EC2.AmazonEC2Config
$config.ServiceURL = $ServiceURL
$client=[Amazon.AWSClientFactory]::CreateAmazonEC2Client($accessKeyID,$secretAccessKey,$config)

# See if the IP is already assigned somewhere
$request = New-Object -TypeName Amazon.EC2.Model.DescribeAddressesRequest
[void]$request.WithPublicIp($instanceEIP)

$result = New-Object -TypeName Amazon.EC2.Model.DescribeAddressesResponse
try {
    $result = $client.DescribeAddresses($request)
} 
catch {
    echo "Failed to validate EIP $instanceEIP, ensure that it is allocated and associated with your account.  Aborting."
    exit 2
}

# See if an instanceID is already assigned to this EIP
$xml=[xml]$result.ToXML()
$assignedInstanceID = [string]($xml.DescribeAddressesResponse.DescribeAddressesResult.Address.InstanceId)

# Run this block if an Instance already has this EIP associated to it... just in case changes would 
# result in downtime (i.e. if we are launching a test system from a cloned production one).
if ($assignedInstanceID) {
  echo "Address $instanceEIP already assigned to: $assignedInstanceID, aborting."
  exit 1
}

# If we get here, the IP is free and clear, go ahead and associate it.
$request = New-Object -TypeName Amazon.EC2.Model.AssociateAddressRequest
[void]$request.WithInstanceId($instanceID)
[void]$request.WithPublicIp($instanceEIP)

$result = $client.AssociateAddress($request)
if ($result) {
  echo "Address $instanceEIP assigned to $instanceID successfully."
  exit 0
}
else {
  echo "Failed to assign $instanceEIP to $instanceID."
  exit 3
}