param(
  [ValidateSet('DHCP','STATIC','INFO')] [string]$Mode,
  [string]$Interface = 'Ethernet',
  [string]$IP,
  [string]$Mask,
  [string]$Gateway,
  [string[]]$Dns
)

function MaskToPrefix($m){
  $b = ($m -split '\.') | ForEach-Object {[Convert]::ToString([int]$_,2).PadLeft(8,'0')}
  ($b -join '').ToCharArray() | Where-Object {$_ -eq '1'} | Measure-Object | Select-Object -ExpandProperty Count
}

function EnsureInterface($alias){
  $a = Get-NetAdapter -InterfaceAlias $alias -ErrorAction SilentlyContinue
  if(-not $a){ throw "Interface not found: $alias" }
}

function ConfigureDhcp($alias){
  EnsureInterface $alias
  Set-NetIPInterface -InterfaceAlias $alias -AddressFamily IPv4 -Dhcp Enabled
  Set-DnsClientServerAddress -InterfaceAlias $alias -ResetServerAddresses
  ipconfig /flushdns | Out-Null
}

function ConfigureStatic($alias,$ip,$mask,$gw,$dns){
  EnsureInterface $alias
  $prefix = MaskToPrefix $mask
  Get-NetIPConfiguration -InterfaceAlias $alias | Get-NetIPAddress -AddressFamily IPv4 -ErrorAction SilentlyContinue | Remove-NetIPAddress -Confirm:$false -ErrorAction SilentlyContinue
  Get-NetIPConfiguration -InterfaceAlias $alias | Get-DnsClientServerAddress -AddressFamily IPv4 -ErrorAction SilentlyContinue | ForEach-Object { Set-DnsClientServerAddress -InterfaceAlias $alias -ResetServerAddresses }
  New-NetIPAddress -InterfaceAlias $alias -IPAddress $ip -PrefixLength $prefix -DefaultGateway $gw | Out-Null
  if($dns){ Set-DnsClientServerAddress -InterfaceAlias $alias -ServerAddresses $dns }
  ipconfig /flushdns | Out-Null
}

function ShowNicInfo($alias){
  $na = Get-NetAdapter -InterfaceAlias $alias -ErrorAction SilentlyContinue
  if(-not $na){ throw "Interface not found: $alias" }
  $adv = Get-NetAdapterAdvancedProperty -InterfaceDescription $na.InterfaceDescription -ErrorAction SilentlyContinue | Where-Object { $_.DisplayName -match 'Duplex|Speed' }
  [pscustomobject]@{
    Name                 = $na.Name
    InterfaceAlias       = $na.InterfaceAlias
    InterfaceDescription = $na.InterfaceDescription
    Status               = $na.Status
    MediaConnection      = $na.MediaConnectionState
    LinkSpeed            = $na.LinkSpeed
    DuplexSetting        = ($adv | Where-Object { $_.DisplayName -match 'Duplex' } | Select-Object -First 1 -ExpandProperty DisplayValue)
  }
}

if(-not $Mode){
  Write-Host "1) DHCP  2) STATIC  3) INFO"
  $sel = Read-Host "Select mode [1/2/3]"
  if($sel -eq '1'){ $Mode='DHCP' }
  elseif($sel -eq '2'){ $Mode='STATIC' }
  elseif($sel -eq '3'){ $Mode='INFO' }
}

if($Mode -eq 'DHCP'){
  if(-not $PSBoundParameters.ContainsKey('Interface')){
    $Interface = Read-Host "Interface alias (default: Ethernet)"
    if([string]::IsNullOrWhiteSpace($Interface)){ $Interface='Ethernet' }
  }
  ConfigureDhcp -alias $Interface
  Get-NetIPConfiguration -InterfaceAlias $Interface
  exit
}

if($Mode -eq 'STATIC'){
  if(-not $PSBoundParameters.ContainsKey('Interface')){
    $Interface = Read-Host "Interface alias (default: Ethernet)"
    if([string]::IsNullOrWhiteSpace($Interface)){ $Interface='Ethernet' }
  }
  if(-not $IP){ $IP = Read-Host "IPv4 address" }
  if(-not $Mask){ $Mask = Read-Host "Subnet mask" }
  if(-not $Gateway){ $Gateway = Read-Host "Gateway" }
  if(-not $Dns){
    $DnsStr = Read-Host "DNS (comma-separated, optional)"
    if($DnsStr){ $Dns = $DnsStr -split '\s*,\s*' }
  }
  ConfigureStatic -alias $Interface -ip $IP -mask $Mask -gw $Gateway -dns $Dns
  Get-NetIPConfiguration -InterfaceAlias $Interface
  exit
}

if($Mode -eq 'INFO'){
  if(-not $PSBoundParameters.ContainsKey('Interface')){
    $Interface = Read-Host "Interface alias (default: Ethernet)"
    if([string]::IsNullOrWhiteSpace($Interface)){ $Interface='Ethernet' }
  }
  ShowNicInfo -alias $Interface | Format-List
  exit
}