Script to balance AD group membership.

# Define the AD groups
$groupNames = @(
    "Group1",  # Replace with actual group names
    "Group2",
    "Group3"
    # Add more groups as needed
)

# Function to get members of each group
function Get-GroupMembers {
    param (
        [string]$groupName
    )
    return Get-ADGroupMember -Identity $groupName | Where-Object { $_.ObjectClass -eq "user" }
}

# Function to distribute members
function Distribute-Members {
    param (
        [array]$groupNames
    )

    # Create an array to store members and group sizes
    $groupMembers = @{}
    $totalMembers = 0

    # Get the current members of each group
    foreach ($groupName in $groupNames) {
        $members = Get-GroupMembers -groupName $groupName
        $groupMembers[$groupName] = $members
        $totalMembers += $members.Count
    }

    # Calculate the target number of members per group
    $numGroups = $groupNames.Count
    $targetMembersPerGroup = [math]::Ceiling($totalMembers / $numGroups)

    # Create an array to store the excess members to redistribute
    $excessMembers = @()

    # Loop through each group and identify excess members
    foreach ($groupName in $groupNames) {
        $currentGroupSize = $groupMembers[$groupName].Count
        if ($currentGroupSize > $targetMembersPerGroup) {
            $excessMembers += $groupMembers[$groupName] | Select-Object -First ($currentGroupSize - $targetMembersPerGroup)
            $groupMembers[$groupName] = $groupMembers[$groupName] | Select-Object -Skip ($currentGroupSize - $targetMembersPerGroup)
        }
    }

    # Now redistribute the excess members to the groups with fewer members
    foreach ($groupName in $groupNames) {
        $currentGroupSize = $groupMembers[$groupName].Count
        while ($currentGroupSize < $targetMembersPerGroup -and $excessMembers.Count -gt 0) {
            $groupMembers[$groupName] += $excessMembers[0]
            $excessMembers = $excessMembers[1..($excessMembers.Count - 1)]
            $currentGroupSize++
        }
    }

    # Add the redistributed members back to the AD groups
    foreach ($groupName in $groupNames) {
        $membersToAdd = $groupMembers[$groupName]
        $existingMembers = Get-GroupMembers -groupName $groupName

        # Filter out existing members to avoid duplicates
        $membersToAdd = $membersToAdd | Where-Object { $_.DistinguishedName -notin $existingMembers.DistinguishedName }

        if ($membersToAdd.Count -gt 0) {
            # Add the members to the group
            Add-ADGroupMember -Identity $groupName -Members $membersToAdd
            Write-Host "Added $($membersToAdd.Count) members to $groupName"
        }
    }
}

# Execute the function to redistribute the members
Distribute-Members -groupNames $groupNames