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

    Fault : Websites do not load but the IP address pings -- DNS resolution failure
    Fix   : Clear the resolver cache and the poisoned entries in it
    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
    Resolution works for some names and not others, or a name resolves to an
    address that was correct last week.

    HOW TO UNDO IT
    None needed. If you removed a hosts entry, it was recorded above before
    deleting.

    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 '  Clear the resolver cache and the poisoned entries in it' -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 'Look at what is actually cached before clearing it -- this often names the culprit.' -Command {
    Get-DnsClientCache | Where-Object Entry -notlike '*.local' | Select-Object -First 30 Entry,Data,TimeToLive
}

Invoke-Step -Number 2 -Do 'Check the hosts file. An entry here beats DNS entirely and survives every cache flush.' -Why 'Old testing entries and adware both live here, and nothing in the network stack will tell you they exist.' -Command {
    Get-Content $env:WINDIR\System32\drivers\etc\hosts | Where-Object { $_ -notmatch '^\s*#' -and $_.Trim() }
}

Invoke-Step -Number 3 -Do 'Flush and re-register.' -Command {
    Clear-DnsClientCache
    ipconfig /registerdns
}

Invoke-Step -Number 4 -Do 'Ask the configured server directly, then ask a public one, and compare.' -Command {
    Resolve-DnsName jbtecwiz.com
    Resolve-DnsName jbtecwiz.com -Server 1.1.1.1
}

Write-Rule "  Confirm it worked"
Show-Prose 'Both queries return the same address and browsing works.' 'White'
Write-Host ''
if (-not $DryRun) {
    Resolve-DnsName outlook.office365.com | Select-Object -First 3 Name,Type,IPAddress
}

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: None needed. If you removed a hosts entry, it was recorded above before deleting.' 'DarkGray'
Write-Rule