param (
    [Parameter(Mandatory=$true)]
    [string]
    $UserId
)

$VerbosePreference = 'Continue'

Connect-MgGraph -NoWelcome -Scopes User.ReadWrite.All,Organization.Read.All

$User = Get-MgUser -UserId $UserId -Property DisplayName,UserPrincipalName,Id,OnPremisesImmutableId | Select-Object -Property DisplayName,UserPrincipalName,Id,OnPremisesImmutableId

Write-Host "User identified to remove is '$($User.DisplayName) ($($User.UserPrincipalName))'"
do {
    $Decision = Read-Host "Continue? (y/n)"
    if ($Decision -cmatch '[Nn](?:o)?') { exit }
} while ($Decision -cnotmatch '[Yy](?:es)?')

Write-Host "Removing OnPremisesImmutableId..."
Invoke-MgGraphRequest -Method PATCH -Uri "https://graph.microsoft.com/v1.0/Users/$($User.Id)" -Body @{OnPremisesImmutableId = $null}
Write-Verbose "OnPremisesImmutableId: '$($User.OnPremisesImmutableId)' -> '$((Get-MgUser -UserId $UserId -Property OnPremisesImmutableId).OnPremisesImmutableId)'"

Write-Host "Starting ADSync Delta sync... " -NoNewline
try {
   if ($Configuration.RemoteAdSync) {
      Invoke-Command -ComputerName $Configuration.RemoteAdSyncComputerName -ScriptBlock { (Start-AdSyncSyncCycle -PolicyType Delta).Result }
   } else {
      (Start-AdSyncSyncCycle -PolicyType Delta).Result
   }
} catch {
   Write-Host -ForegroundColor Red "Failed: $_"
   break
}