#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : 169.254.x.x address -- "Unidentified network, no internet"
    Fix   : Rebuild the TCP/IP stack and Winsock on this machine
    Source: https://jbtecwiz.com/support/win-net-apipa

    Run as     : Elevated Command Prompt
    Expect     : 20 minutes
    Risk       : medium
    Reversible : NO -- read the undo note below before running

    WHEN THIS IS THE RIGHT FIX
    One machine only, the service is running, and a renew still gets
    nothing. Usually follows a bad VPN client or security product uninstall.

    HOW TO UNDO IT
    netsh advfirewall reset clears custom firewall rules -- export them
    first with netsh advfirewall export if any are bespoke.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 4"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  169.254.x.x address -- "Unidentified network, no internet"' -ForegroundColor White
Write-Host '  Rebuild the TCP/IP stack and Winsock on this machine' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   NOT REVERSIBLE   20 minutes' -ForegroundColor Yellow
Write-Host ''
Show-Prose 'Undo: netsh advfirewall reset clears custom firewall rules -- export them first with netsh advfirewall export if any are bespoke.' 'Yellow'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Note the current configuration first -- this resets it.' -Command {
    cmd.exe /c 'ipconfig /all > %USERPROFILE%\Desktop\before-reset.txt'
}

Invoke-Step -Number 2 -Do 'Reset the two layers a broken filter driver sits between.' -Why 'Winsock reset removes third-party layered service providers; the IP reset rewrites the interface registry keys. A leftover VPN or antivirus filter driver breaks DHCP without breaking the link light, which is exactly what this looks like.' -Command {
    cmd.exe /c 'netsh winsock reset & netsh int ip reset'
}

Invoke-Step -Number 3 -Do 'Clear the resolver and re-register.' -Command {
    cmd.exe /c 'ipconfig /flushdns & nbtstat -R & netsh advfirewall reset'
}

Invoke-Step -Number 4 -Do 'Restart. This is not optional -- the stack is rebuilt at boot.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'After the restart the adapter picks up a proper lease within a few seconds.' 'White'
Write-Host ''
if (-not $DryRun) {
    cmd.exe /c 'ipconfig /all | findstr /i "DHCP Lease Gateway"'
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/win-net-apipa' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: netsh advfirewall reset clears custom firewall rules -- export them first with netsh advfirewall export if any are bespoke.' 'DarkGray'
Write-Rule