Simplify user validation messages and add user logged-in check function

Scripts/Helpers/TestIfUserIsLoggedIn.ps1

@@ -0,0 +1,42 @@
+function TestIfUserIsLoggedIn {
+    param(
+        [Parameter(Mandatory)]
+        [string]$Username
+    )
+
+    try {
+        $quserOutput = @(& quser 2>$null)
+        if ($LASTEXITCODE -ne 0 -or -not $quserOutput) {
+            return $false
+        }
+
+        foreach ($line in ($quserOutput | Select-Object -Skip 1)) {
+            if ([string]::IsNullOrWhiteSpace($line)) { continue }
+
+            # Remove current-session marker and split columns.
+            $normalizedLine = $line.TrimStart('>', ' ')
+            $parts = $normalizedLine -split '\s+'
+            if ($parts.Count -eq 0) { continue }
+
+            $sessionUser = $parts[0]
+            if ([string]::IsNullOrWhiteSpace($sessionUser)) { continue }
+
+            # Normalize possible DOMAIN\user or user@domain formats.
+            if ($sessionUser.Contains('\')) {
+                $sessionUser = ($sessionUser -split '\\')[-1]
+            }
+            if ($sessionUser.Contains('@')) {
+                $sessionUser = ($sessionUser -split '@')[0]
+            }
+
+            if ($sessionUser.Equals($Username, [System.StringComparison]::OrdinalIgnoreCase)) {
+                return $true
+            }
+        }
+    }
+    catch {
+        return $false
+    }
+
+    return $false
+}