param(
    [Parameter(Mandatory)]
    [string]$Interface,

    [Parameter(Mandatory)]
    [string]$IPAddress,

    [Parameter(Mandatory)]
    [int]$PrefixLength,

    [Parameter(Mandatory)]
    [string]$Gateway,

    [string]$DnsServers = @("8.8.8.8", "1.1.1.1")
)

$ErrorActionPreference = "Stop"

# check root
if ((id -u) -ne 0) {
    throw "You have to run 'sudo pwsh'!"
}

# check NIC
$NicExists = Test-Path "/sys/class/net/$Interface"
if (-not $NicExists) {
    throw "NIC interface '$Interface' does not exist."
}

# Netplan conf
$NetplanFile = "/etc/netplan/99-static-ip.yaml"

# DNSList to yaml
$DnsServersArray = @(
    $DnsServers -split ',' |
    ForEach-Object { $_.Trim() } |
    Where-Object { $_ -ne "" }
)

$DnsList = ($DnsServersArray | ForEach-Object {
    '"' + $_ + '"'
}) -join ', '

Write-Host "DnsServers raw: $DnsServers"
Write-Host "DnsServersArray:"
$DnsServersArray | ForEach-Object { Write-Host "  [$_]" }
Write-Host "DnsList: $DnsList"

$Yaml = @"
network:
  version: 2
  renderer: networkd
  ethernets:
    ${Interface}:
      dhcp4: false
      addresses:
        - $IPAddress/$PrefixLength
      routes:
        - to: default
          via: $Gateway
      nameservers:
        addresses: [$DnsList]
"@

Write-Host "=== Current configuration ==="
& ip -br addr show $Interface
& ip route

Write-Host ""
Write-Host "Writing: $NetplanFile"

$Yaml | Set-Content `
    -Path $NetplanFile `
    -Encoding utf8NoBOM

# Only rootc can view
& chmod 600 $NetplanFile

Write-Host ""
Write-Host "=== Netplan configuration ==="
Get-Content $NetplanFile

# Check Netplan conf
Write-Host ""
Write-Host "Validating Netplan..."
& netplan generate

if ($LASTEXITCODE -ne 0) {
    throw "Failed: netplan generate."
}

# Apply Netplan
#Write-Host "Applying Netplan..."
#& netplan apply
#
#if ($LASTEXITCODE -ne 0) {
#    throw "Failed: netplan apply."
#}
Write-Host "Scheduling netplan apply..."

& /usr/bin/systemd-run `
    --unit=netplan-apply-once `
    --on-active=2s `
    /usr/sbin/netplan apply

if ($LASTEXITCODE -ne 0) {
    throw "Failed to schedule netplan apply."
}

Write-Host "Netplan apply scheduled. Disconnecting..."
exit 0