Parse an Amazon Resource Name (ARN) into its individual parts

Resolve-AmazonARN.ps1

function Resolve-AmazonArn {
<#
.SYNOPSIS
    Parse an Amazon Resource Name (ARN) into its individual parts.
.EXAMPLE
    'arn:aws:iam::111222333444:role/MyRole' | Resolve-AmazonArn
.EXAMPLE
    Resolve-AmazonArn arn:aws:s3:::MyBucket/MyFolder/*
.EXAMPLE
    Resolve-AmazonArn s3://MyBucket/MyFolder/MyFile.json

    This will error out, because the provided string is not a valid ARN.
.NOTES
    Author:   Panos Grigoriadis
    Date:     13-Jul-2025
    Version:  1.0
#>
[CmdletBinding()]
[OutputType([psobject])]   # <-- PSCustomObject with TypeName of "Amazon.ARN"
param (
    [Parameter(Mandatory,ValueFromPipeline)]
    [Alias('ARN')]
    [string]$InputString   # <-- the ARN string
)

# helper function to handle nullability for strings
function Try-NullString($string) {if ([string]::IsNullOrWhiteSpace($string)) {$null} else {$string}}

# regex pattern match for ARN strings
$Pattern = '^(?<FullName>arn:(?<Partition>[^:\n]*):(?<Service>[^:\n]*):(?<Region>[^:\n]*):(?<AccountID>[^:\n]*):(?<Ignore>(?<ResourceType>[^:\/\n]*)[:\/])?(?<Resource>.*))$'
$Regex   = [System.Text.RegularExpressions.Regex]::Match($InputString,$Pattern)

# assemble the output object
if ($Regex.Success) {
    $Grp = $Regex.Groups
    $out = [pscustomobject]@{
        PSTypeName   = 'Amazon.ARN'
        FullName     = $Grp['FullName'].Value
        Partition    = $Grp['Partition'].Value
        Service      = Try-NullString $Grp['Service'].Value
        Region       = Try-NullString $Grp['Region'].Value
        AccountID    = Try-NullString $Grp['AccountID'].Value
        ResourceType = Try-NullString $Grp['ResourceType'].Value
        Resource     = Try-NullString $Grp['Resource'].Value
    }
}
else {
  throw "Could not parse the provided ARN ($InputString)"
}

# add a method to get the AWS Region Endpoint object
$MethodValue = {
    if ([string]::IsNullOrWhiteSpace($this.Region) -or $this.Region -eq '*') {$null}
    elseif ('Amazon.RegionEndpoint' -as [type]) {
        try   {[Amazon.RegionEndpoint]::GetBySystemName($this.Region)}
        catch {[Amazon.RegionEndpoint]::GetBySystemName('Unknown')}
    }
    else {Write-Warning 'The [Amazon.RegionEndpoint] class was not found'}
}
$out | Add-Member -MemberType ScriptMethod -Name GetRegionEndpoint -Value $MethodValue

# add a method to get the AWS Service object
$MethodValue = {
    if ([string]::IsNullOrWhiteSpace($this.Service) -or $this.Service -eq '*') {$null}
    elseif (Get-Command -Name Get-AWSService -EA 0) {Get-AWSService -Service $this.Service}
    else {Write-Warning 'The Get-AWSService command was not found'}
}
$out | Add-Member -MemberType ScriptMethod -Name GetAwsService -Value $MethodValue

# overwrite the ToString() method
$out | Add-Member -MemberType ScriptMethod -Name ToString -Value {$this.FullName} -Force

Write-Output $out
}