Public/Network/Expand-IPv6.ps1

function Expand-IPV6 {
  <#
.SYNOPSIS
    Takes an abbreviated IPv6 string and expands it fully
.DESCRIPTION
    Takes an abbreviated IPv6 string and expands it fully
.PARAMETER IPv6
    A string parameter that represents an IPv6 address. Aliased to 'Address'
.PARAMETER IncludeInput
    Switch that will display the input parameter along with the result
.EXAMPLE
    Expand-IPV6 'fe98::726d:daad:2afc:5393%18'
 
    Would return:
    FE98:0000:0000:0000:726D:DAAD:2AFC:0000
.EXAMPLE
    Expand-IPV6 'fe98::726d:daad:2afc:5393'
 
    Would return:
    FE98:0000:0000:0000:726D:DAAD:2AFC:5393
.EXAMPLE
    Expand-IPV6 -IPv6 '::1'
 
    Would return:
    0000:0000:0000:0000:0000:0000:0000:0001
.EXAMPLE
    '::1', 'fe98::726d:daad:2afc:5393' | Expand-IPV6 -IncludeInput
 
    OriginalIPv6 ExpandedIPv6
    ------------ ------------
    ::1 0000:0000:0000:0000:0000:0000:0000:0001
    fe98::726d:daad:2afc:5393 FE98:0000:0000:0000:726D:DAAD:2AFC:5393
.NOTES
    Source: https://badflyer.com/powershell-ipv4-to-ipv6/
 
    Changes:
    - added comment help
    - minor formatting changes
    - change IPv6 to string array
    - added IncludeInput parameter
#>


  [CmdletBinding()]
  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseDeclaredVarsMoreThanAssignments', '')]
  param
  (
    [Parameter(Mandatory, HelpMessage = 'Enter an IPv6 address', Position = 0, ValueFromPipeline, ValueFromPipelineByPropertyName)]
    [Alias('Address')]
    [string[]] $IPv6,

    [switch] $IncludeInput
  )

  begin {
    Write-Invocation $MyInvocation
  }

  process {
    foreach ($curIPv6 in $IPv6) {
      $count = 0
      $loc = -1
      # Count the number of colons, and keep track of the double colon
      for ($i = 0; $i -lt $curIPv6.Length; $i++) {
        if ($curIPv6[$i] -eq ':') {
          $count++
          if (($i - 1) -ge 0 -and $curIPv6[$i - 1] -eq ':') {
            $loc = $i
          }
        }
      }
      # If we didnt find a double colon and the count isn't 7, then throw an exception
      if ($loc -lt 0 -and $count -ne 7) {
        throw 'Invalid IPv6 Address'
      }
      # Add in any missing colons if we had a double
      $cleaned = $curIPv6
      if ($count -lt 7) {
        $cleaned = $curIPv6.Substring(0, $loc) + (':' * (7 - $count)) + $curIPv6.Substring($loc)
      }
      # Parse current values in fill in new IP with hex numbers padded to 4 digits
      $result = @()
      foreach ($splt in $cleaned -split ':') {
        $val = 0
        $r = [int]::TryParse($splt, [System.Globalization.NumberStyles]::HexNumber, [System.Globalization.CultureInfo]::InvariantCulture, [ref]$val)
        $result += ('{0:X4}' -f $val)
      }
      $result = $result -join ':'
      if ($IncludeInput) {
        New-Object -TypeName psobject -Property ([ordered] @{
            OriginalIPv6 = $curIPv6
            ExpandedIPv6 = $result
          })
      } else {
        Write-Output -InputObject $result
      }
    }
  }

  end {
    Out-Verbose $fxn "Complete."
  }
}