# This script will rename all the VMs hosted by the current host based
# on their Nova instance GUID (stored within VM notes).
#
# If the VM is clustered, the according cluster group/resources will be
# renamed as well.

function is_guid($string){
    $pattern = "^[0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-" +
               "[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-" +
               "[0-9a-fA-F]{12}$"
    $string -match $pattern
}

write-host "Renaming Nova instances using their GUID."

$cluster = get-cluster -ErrorAction SilentlyContinue

if (!(cluster)){
    write-host "Could not retrieve any failover cluster. "`
               "Assuming the instances are not clustered."
}
else {
    write-host "Retrieved failover cluster. Any cluster VM resources "`
               "created by Nova will be renamed."
}

$vms = get-vm

foreach($vm in $vms) {
    $vmName = $vm.Name
    $vmGUID = $vm.Notes

    # Nova stores the instance GUID within the instance notes field.
    if (!(is_guid $vmGUID)) {
        write-host "Skipping renaming instance '$vmName' as the "`
                   "instance notes '$vmGUID' do not contain a GUID."`
                   "Assuming it's not created by Nova."
        continue
    }

    # Check the VM name
    if ($vmName -eq $vmGUID) {
        write-host "Instance '$vmName' is already named using its GUID."
    }
    else {
        write-host "Renaming Nova instance '$vmName' to '$vmGUID'."
        set-vm $vm -NewVMName $vmGUID
    }

    # Rename the VM cluster group/resources, if found.
    if (!($cluster)) {
        continue
    }

    $group = get-clustergroup $vmName -ErrorAction SilentlyContinue
    if ($group) {
        write-host "Renaming cluster group '$vmName' to '$vmGUID'"
        $group.Name = $vmGUID
    }
    else {
        write-host "Could not find cluster group '$vmName'. "`
                   "Assuming the instance is not clustered."
        continue
    }

    $vmClusResName = "Virtual Machine $vmName"
    $vmConfigClusResName = "Virtual Machine Configuration $vmName"

    $newVmClusResName = "Virtual Machine $vmGUID"
    $newVmConfigClusResName = "Virtual Machine Configuration $vmGUID"

    $vmClusRes = get-clusterresource $vmClusResName
    if ($vmClusRes) {
        write-host "Renaming cluster resource $vmClusResName to "`
                   "$newVmClusResName"
        $vmClusRes.Name = $newVmClusResName
    }
    else {
        write-error "Could not find cluster resource $vmClusResName, "`
                    "although the according cluster group was found."
    }

    $vmConfigClusRes = get-clusterresource $vmConfigClusResName
    if ($vmConfigClusRes) {
        write-host "Renaming cluster resource $vmClusResName to "`
                   "$newVmClusResName"
        $vmConfigClusRes.Name = $newVmConfigClusResName
    }
    else {
        write-error "Could not find cluster resource $vmConfigClusRes, "`
                    "although the according cluster group was found."
    }
}