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

    Fault : Websites do not load but the IP address pings -- DNS resolution failure
    Fix   : Point the machine at DNS servers it can actually reach
    Source: https://jbtecwiz.com/support/win-net-dns-only

    Run as     : Elevated PowerShell
    Expect     : 10 minutes
    Risk       : low
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    The configured servers do not answer at all -- most often a domain
    laptop off the corporate network.

    HOW TO UNDO IT
    Set-DnsClientServerAddress with the original list recorded in step one,
    or -ResetServerAddresses to return to DHCP.

    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 '  Websites do not load but the IP address pings -- DNS resolution failure' -ForegroundColor White
Write-Host '  Point the machine at DNS servers it can actually reach' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: low   Reversible   10 minutes'
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 'See what is set and where it came from.' -Command {
    Get-DnsClientServerAddress -AddressFamily IPv4 | Format-Table InterfaceAlias,ServerAddresses
}

Invoke-Step -Number 2 -Do 'Test each configured server before changing anything.' -Command {
    Test-NetConnection 10.0.0.10 -Port 53 -InformationLevel Detailed
}

Invoke-Step -Number 3 -Do 'If they came from a static entry that no longer applies, hand DNS back to DHCP.' -Why 'Resetting is better than typing in a public resolver on a domain machine -- a domain member that cannot resolve its own internal names loses Group Policy, shares and printers, which is a worse fault than the one being fixed.' -Command {
    Set-DnsClientServerAddress -InterfaceAlias 'Wi-Fi' -ResetServerAddresses
}

Invoke-Step -Number 4 -Do 'On a non-domain machine with no working local resolver, set a public one deliberately.' -Command {
    Set-DnsClientServerAddress -InterfaceAlias 'Wi-Fi' -ServerAddresses 1.1.1.1,8.8.8.8
}

Write-Rule "  Confirm it worked"
Show-Prose 'Names resolve and the internal ones still work if this is a domain machine.' 'White'
Write-Host ''
if (-not $DryRun) {
    Resolve-DnsName $env:USERDNSDOMAIN -Type SOA
}

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-dns-only' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Set-DnsClientServerAddress with the original list recorded in step one, or -ResetServerAddresses to return to DHCP.' 'DarkGray'
Write-Rule