Getting all direct reports from Azure AD using the batch endpoint

function Get-AccessTokenFromGraphExplorerUrlOnClipboard
{
    [CmdletBinding()]
    [Alias()]
    Param
    ([String[]] $RequiredScopes = @())
  
    Process
    {
        $token = $null
        $first = $true
        do {
            if(!$first) {
                Sleep -Seconds 1   
            }
            $first = $false
  
            Write-Verbose "Trying to get Graph Explorer URL from clipboard"
            $url = Get-Clipboard
            if($url -ne $null -and $url.StartsWith("https://developer.microsoft.com/en-us/graph/graph-explorer#access_token=")) {
                $token = $url -split "[=&]" | Select -Index 1
            }
        } while($token -eq $null -or !$token.StartsWith("ey"))
  
        $token1 = $token.Split(".")[1]
        if(($token1.Length % 4) -gt 0) {
            $token1 = $token1.PadRight($token1.Length + (4 - ($token1.Length % 4)), "=")
        }
        $tokenAsObject = $token1 |ConvertFrom-Base64 | ConvertFrom-Json
        $RequiredScopes | Where{$_ -notin ($tokenAsObject.scp -split " ")} | Foreach {
            Write-Warning "Missing scope: $($_)"
        }

        $token
    }
}

function ConvertTo-Buckets
{
    [CmdletBinding()]
    [Alias()]
    [OutputType([int])]
    Param
    (
        # Total number of buckets, bucket size will vary
        [Parameter(Mandatory=$true,
                    Position=0,
                    ParameterSetName="NumberOfBuckets")]
        [ValidateRange(2, 9999)]
        [int] $NumberOfBuckets,
                   
        # Size of each bucket, last bucket will have different size of the rest
        [Parameter(Mandatory=$true,
                    Position=1,
                    ParameterSetName="BucketSize")]
        [ValidateRange(2, 99999)]
        [int]  $BucketSize,
 
        # Input object to put into bucket
        [Parameter(Mandatory=$true,
                    Position=2, ValueFromPipeline=$true)]
        $InputObject
    )
                   
    Begin
    {
        $Buckets = New-Object System.Collections.ArrayList<Object>
        if($NumberOfBuckets -gt 0) {
            # Add numberofbuckets number of array lists to create a multi dimensional array list
            1..$NumberOfBuckets | Foreach {
                $Buckets.Add((New-Object System.Collections.ArrayList<Object>)) | Out-Null
            }   
        } else {
            # Add a single bucket as our first bucket
            $Buckets.Add((New-Object System.Collections.ArrayList<Object>)) | Out-Null
        }
        $index = 0
    }
    Process
    {
        if($NumberOfBuckets -gt 0) {
            $index = ($index + 1) % $NumberOfBuckets
            $Buckets[$index].Add($InputObject) | Out-Null
        } else {
            $Buckets[$index].Add($InputObject) | Out-Null
            if($Buckets[$index].Count -ge $BucketSize) {
                $Buckets.Add((New-Object System.Collections.ArrayList<Object>)) | Out-Null
                $index += 1
            }
        }
         
    }
    End
    {
        $Buckets
    }
}

# Get the access token
Write-Host -ForegroundColor Green "Sign into graph explorer and copy the url with the access token - https://developer.microsoft.com/en-us/graph/graph-explorer"
$token = Get-AccessTokenFromGraphExplorerUrlOnClipboard -Verbose -RequiredScopes @("User.ReadWrite.All")
$restparams = @{headers = @{Authorization = "Bearer $token"}}

# Read all users
$users = @()
$uri = "https://graph.microsoft.com/v1.0/users?`$select=id&`$top=999"
do {
    $result = Invoke-RestMethod -Uri $uri @restparams
    $uri = $result.'@odata.nextLink'
    $users += $result.value
    Write-Verbose "User count: $($users.Count)" -Verbose
} while($uri -ne $null)

$report = $users | ConvertTo-Buckets -BucketSize 20 | Foreach {
    Write-Verbose "Processing bucket of 20 users" -Verbose
    
    # Generate request body
    $inc = 1
    $requestIdToObjectId = @{}
    $requestBody = @{
        requests = @($_ | Foreach {
            @{
                id = "$inc"
                method = "GET"
                url = "/users/$($_.id)/directReports?`$top=999&`$select=id"
            }
            $requestIdToObjectId["$inc"] = $_.id
            $inc += 1
        })
    } | ConvertTo-Json
    
    # Send request
    $result = Invoke-RestMethod -Uri "https://graph.microsoft.com/v1.0/`$batch" @restparams -ContentType "application/json" -Method Post -Body $requestBody
    $result.responses | Foreach {
        [PSCustomObject] @{
            Id = $requestIdToObjectId[$_.id]
            DirectReports = $_.body.value.id
        }
    }
}

# Just out gridview the whole thing
$report | Out-GridView