<#
.SYNOPSIS
    Gets unique user logins from AD groups with their group membership
.DESCRIPTION
    Processes security groups from input file, recursively expands all members,
    and exports users with their source groups
.PARAMETER InputFile
    Path to file containing group names (one per line)
.PARAMETER OutputFile
    Path to result file (default: Get-UsersFromGroups_Output.csv)
#>
param(
    [Parameter(Mandatory=$true)]
    [string]$InputFile,
    
    [string]$OutputFile = "Get-UsersFromGroups_Output.csv"
)

# Get unique groups from input file
$groups = Get-Content $InputFile | 
          Where-Object { $_ -match '\S' } | 
          Select-Object -Unique

# Initialize result storage: user -> groups
$results = @{}

foreach ($group in $groups) {
    try {
        # Get AD group object
        $adGroup = Get-ADGroup -Identity $group -ErrorAction Stop
        
        # Recursively get all user members
        $users = Get-ADGroupMember -Identity $adGroup -Recursive -ErrorAction Stop | 
                 Where-Object { $_.objectClass -eq 'user' }
        
        # Add group to each user's membership list
        foreach ($user in $users) {
            $login = $user.SamAccountName
            if (-not $results.ContainsKey($login)) {
                $results[$login] = [System.Collections.Generic.List[string]]::new()
            }
            $results[$login].Add($group)
        }
    }
    catch {
        Write-Warning "Error processing group '$group': $_"
    }
}

# Convert to sorted object array
$output = $results.GetEnumerator() | 
          ForEach-Object {
              [PSCustomObject]@{
                  User  = $_.Key
                  Groups = ($_.Value -join "; ")
              }
          } | 
          Sort-Object User

# Export to CSV
$output | Export-Csv -Path $OutputFile -NoTypeInformation -Encoding UTF8

# Console output
$output | Format-Table -AutoSize