"Connecting to Graph API."
Connect-MgGraph -NoWelcome -Scopes "AuditLog.Read.All"

"Connecting to Exchange On-line"
Connect-ExchangeOnline -ShowBanner:$false

"Fetching list of SKUs."
# Note that SKU product names are documented at:
# https://learn.microsoft.com/en-us/azure/active-directory/enterprise-users/licensing-service-plan-reference
$SKUs = Get-MgSubscribedSku

"Fetching list of all users."
$Users = Get-MgUser -All -Property Id, UserPrincipalName, DisplayName, SignInActivity, UserType

# Define an empty list for our results.
$StaleUsers = @()

# Determine the cutoff date for users to be considered stale:
$CutoffDate = $(Get-Date).AddDays(-90)

"Processing users."
ForEach($User in $Users) {
    # If the user is a guest user, skip it.
    If($User.UserType -like "Guest") {
        Continue
    }
    
    # If the user has signed in in the last 30 days, skip it.
    If($User.SignInActivity.LastSignInDateTime) {
        $LastSignInDateTime =  [datetime]::parseexact($User.SignInActivity.LastSignInDateTime,'MM/dd/yyyy HH:mm:ss',$Null)
        If($LastSignInDateTime -gt $CutoffDate) {
            Continue
        }
    } Else {
        $LastSignInDateTime = "Never"
    }
    
    # Get the recipient type from Exchange, if a mailbox exists.
    $OldPref = $global:ErrorActionPreference
    try {
        $global:ErrorActionPreference = 'Stop'
        $Type = (Get-EXOMailbox -Identity $User.UserPrincipalName).RecipientTypeDetails
    } catch {
        $Type = "No Mailbox"
    }
    finally {
        $global:ErrorActionPreference = $OldPref
    }

    # Create a record to add to the results.
    $UserRecord = [PSCustomObject]@{
        Id = $User.Id
        UserPrincipalName = $User.UserPrincipalName
        DisplayName = $User.DisplayName
        LastSignInDateTime = $LastSignInDateTime
        AnyLicenseAssigned = $False
        Type = $Type
    }

    ForEach($SKU in $SKUs) {
        Add-Member -InputObject $UserRecord -MemberType NoteProperty -Name $SKU.SkuPartNumber -Value $False
    }
    
    $LicenseDetails = Get-MgUserLicenseDetail -UserId $User.UserPrincipalName
    
    ForEach($LicenseDetail in $LicenseDetails) {
        $UserRecord.$($LicenseDetail.SkuPartNumber) = $True
        $UserRecord.AnyLicenseAssigned = $True
    }

$StaleUsers += ,$UserRecord

}

"Exporting results to CSV file."
$StaleUsers | Sort-Object LastSignInDateTime | Select UserPrincipalName, DisplayName, Type, LastSignInDateTime, AnyLicenseAssigned, SPE_E3, SPE_E5 | Export-Csv -Path "stale_licensed_users.csv"

Disconnect-MgGraph