# https://www.say-tech.co.jp/contents/blog/yamanxworld/2026vol169
# Add ConvertTo-Subnet function
param(
  [Parameter(Mandatory)]
  [string]$VMName
)

function ConvertTo-SubnetMask {
    param(
        [string]$PrefixLength
    )

    if ($PrefixLength -notmatch '^\d+$' -or
        [int]$PrefixLength -lt 0 -or
        [int]$PrefixLength -gt 32) {
        return $PrefixLength
    }

    $mask = [uint32]::MaxValue -shl (32 - [int]$PrefixLength)
    $bytes = [BitConverter]::GetBytes($mask)
    [Array]::Reverse($bytes)
    return ($bytes -join '.')
}

$vm  = Get-VM -Name $vmname
if($vm.State -ne "Running") {
    Write-Host "VM $($VMName) is not Running."
    exit
}
#$vmName = Read-Host "Specify the name of your virtual machine"
$ns = "root\virtualization\v2"
$vsvms = Get-WmiObject -Namespace $ns -Class Msvm_VirtualSystemManagementService 
$vmcs = Get-WmiObject -Namespace $ns -Class Msvm_ComputerSystem -Filter "ElementName='$vmName'"
if (-not $vmcs) {
  Write-Host "Error: VM $vmname is missing."
  exit 1;
}
$vs_settingdata = ($vmcs.GetRelated("Msvm_VirtualSystemSettingData", "Msvm_SettingsDefineState", $null, $null, "SettingData", "ManagedElement", $false, $null) | %{$_})
$et_settingdata = $vs_settingdata.GetRelated("Msvm_SyntheticEthernetPortSettingData")
$vm_netconf = ($et_settingdata.GetRelated("Msvm_GuestNetworkAdapterConfiguration", "Msvm_SettingDataComponent", $null, $null, "PartComponent", "GroupComponent", $false, $null) | % {$_})
$yesno = Read-Host "Enable DHCP? (y/n[n])"
if ($yesno.toLower() -eq "y") {
  $vm_netconf.DHCPEnabled = $true
  $vm_netconf.DNSServers = @()
} else {
  $vm_netconf.DHCPEnabled = $false
  $vm_netconf.IPAddresses = (Read-Host "Specify static ipv4 address")
  $vm_netconf.Subnets = (Read-Host "Specify subnetmask")
  $vm_netconf.Subnets = ConvertTo-SubnetMask $vm_netconf.Subnets 
  $vm_netconf.DefaultGateways = (Read-Host "Specify default gateway")
  $vm_netconf.DNSServers = @((Read-Host "Specify preferred dns server")) -split '\s*,\s*'
}
$ret = $vsvms.SetGuestNetworkAdapterConfiguration($vmcs.Path, $vm_netconf.GetText(1))
if ($ret.ReturnValue -ne 0) {
  Write-Host "Error: something went wrong"
} 

Get-CimInstance -Namespace $ns -ClassName Msvm_GuestNetworkAdapterConfiguration |
  Where { $_.InstanceID -like "*$($vm.vmId)*" }|Select DHCPEnabled,IPAddresses,Subnets,DefaultGateways,DNSServers