param(
  [string]$CIDR = ""
)

function Get-DefaultCIDR {
  $ipObj = Get-NetIPAddress -AddressFamily IPv4 |
    Where-Object { $_.IPAddress -notlike "169.254*" -and $_.IPAddress -ne "127.0.0.1" -and $_.PrefixOrigin -ne "WellKnown" } |
    Sort-Object -Property InterfaceMetric |
    Select-Object -First 1

  if (-not $ipObj) { return "192.168.1.0/24" }

  $ip = $ipObj.IPAddress
  $prefix = $ipObj.PrefixLength

  # Netzadresse grob berechnen
  $bytes = $ip.Split(".") | ForEach-Object { [int]$_ }
  $maskBits = $prefix
  $mask = @(0,0,0,0)
  for ($i=0; $i -lt 4; $i++) {
    $b = [Math]::Min(8, $maskBits)
    $maskBits -= $b
    $mask[$i] = if ($b -le 0) { 0 } else { (0xFF -shl (8-$b)) -band 0xFF }
  }
  $net = @()
  for ($i=0; $i -lt 4; $i++) { $net += ($bytes[$i] -band $mask[$i]) }
  return ("{0}.{1}.{2}.{3}/{4}" -f $net[0],$net[1],$net[2],$net[3],$prefix)
}

if (-not $CIDR -or $CIDR.Trim() -eq "") {
  $CIDR = Get-DefaultCIDR
}

# Check nmap
$nmap = (Get-Command nmap -ErrorAction SilentlyContinue)
if (-not $nmap) {
  Write-Host "FEHLER: nmap ist nicht installiert. Bitte installieren: https://nmap.org/download.html" -ForegroundColor Red
  exit 1
}

$OutDir = Join-Path $PSScriptRoot ("lan-scan-" + (Get-Date -Format "yyyy-MM-dd_HH-mm-ss"))
New-Item -ItemType Directory -Force -Path $OutDir | Out-Null

$XmlPath = Join-Path $OutDir "scan.xml"
$JsonPath = Join-Path $OutDir "scan.json"
$CsvPath  = Join-Path $OutDir "scan.csv"

Write-Host "Scan läuft: $CIDR"
& nmap -sn -n $CIDR -oX $XmlPath | Out-Null

[xml]$xml = Get-Content $XmlPath

$hosts = @()
foreach ($h in $xml.nmaprun.host) {
  $status = $h.status.state
  if ($status -ne "up") { continue }

  $ip = ""
  $mac = ""
  $vendor = ""
  foreach ($a in $h.address) {
    if ($a.addrtype -eq "ipv4") { $ip = $a.addr }
    if ($a.addrtype -eq "mac") { $mac = $a.addr; $vendor = $a.vendor }
  }

  $name = ""
  if ($h.hostnames -and $h.hostnames.hostname) {
    $name = $h.hostnames.hostname[0].name
  }

  $hosts += [pscustomobject]@{
    ip = $ip
    name = $name
    mac = $mac
    vendor = $vendor
  }
}

$payload = [pscustomobject]@{
  ok = $true
  cidr = $CIDR
  scanned_at = (Get-Date).ToString("s")
  count = $hosts.Count
  hosts = $hosts
}

$payload | ConvertTo-Json -Depth 5 | Out-File -Encoding UTF8 $JsonPath
$hosts | Export-Csv -NoTypeInformation -Encoding UTF8 -Delimiter ";" -Path $CsvPath

Write-Host "Fertig. Dateien:"
Write-Host "  $JsonPath"
Write-Host "  $CsvPath"