Create Azure mg/subscription hierarchy Mermaid diagram

Get-SubscriptionHierarchyDiagram.ps1

<#
.SYNOPSIS
	Create a Mermaid diagram (https://mermaidjs.github.io/)
	that reflects the Azure management group and subscription hierarchy.

.DESCRIPTION
	This script assumes prerequisites:
	1) The Az module is installed (https://docs.microsoft.com/en-us/powershell/azure/new-azureps-module-az)
	2) Azure sign-in is completed (Connect-AzAccount)
	3) The signed-in user has the required permissions to enumerate the management groups and subscriptions

.NOTES
	Author: Reuben Cabrera
 	Script birth date: 2019-02-22
 
.EXAMPLE
	Get-SubscriptionHierarchyDiagram.ps1 | Out-File diagram.mmd
#>

Param(
	# The name of the root management group from which to begin
	[Parameter(Mandatory=$true)]
	[String]
	$RootGroupName,
	# Orient the tree diagram to be Top-Down (instead of Left-Right)
	[Parameter(Mandatory=$false)]
	[switch]
	$OrientTopDown
)

# retrieve all the data
$m = Get-AzManagementGroup -GroupName $RootGroupName -Expand -Recurse

function WalkTree {
	param (
		$parent,
		$entity
	)
	$entity | Select-Object `
		@{Name="Type"; Expression={$entity.Type.split('/')[-1]}}, `
		DisplayName, `
		@{Name="FancyName"; Expression={
			$prefix = "fa:fa-group"
			if ($entity.Type -eq "/subscriptions") {
				$prefix = "fa:fa-key"
			}
			$prefix + " " + $entity.DisplayName
		}}, `
		@{Name="Id"; Expression={$entity.Id -replace '[/]'}}, `
		@{Name="ParentId"; Expression={
			if ($null -eq $parent) {
				$null
			}
			else {
				$parent.Id -replace '[/]'
			}
		}}

	foreach ($child in $entity.Children) {
		WalkTree $entity $child
	}
}

$orientation = If ($OrientTopDown) { "graph TD" } else { "graph LR" }

# unroll into dependency pairs
$list = WalkTree $null $m
$orientation
$list | ForEach-Object -Process {"     $($_.Id)[$($_.FancyName)]"}
$list | Where-Object ParentId -NE $null | ForEach-Object -Process {"     $($_.ParentId) --> $($_.Id)"}
"     classDef managementGroups fill:#0ff"
"     classDef subscriptions fill:#ff0"
$list | ForEach-Object -Process {"     class $($_.Id) $($_.Type)"}