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

# GroupMemberships.ps1 -GroupId "# Developer ADM"
# GroupMemberships.ps1 -GroupId "Domain Admins"
# GroupMemberships.ps1 -GroupId "# Developer"
# GroupMemberships.ps1 -GroupId "# Interne Automatisering Team-Assistent"
# GroupMemberships.ps1 -GroupId "# Interne Automatisering"

[string] $date = Get-Date -Format "yyyy-MM-dd HHmm"
[string] $OutputPath =  ".\$date ($GroupId) group members.csv" 
[string] $membershipOutputPath = ".\$date ($GroupId) group memberships - parent groups .csv"

# Connect to Microsoft Graph if not already connected
Write-Host "Connecting to Microsoft Graph..."
Connect-MgGraph -Scopes "Group.Read.All", "GroupMember.Read.All" -NoWelcome

# If GroupId is actually a group name, resolve it to the actual GroupId
if ($GroupId -notmatch '^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$') {
    Write-Host "Resolving group name '$GroupId' to GroupId..."
    try {
        $group = Get-MgGroup -Filter "displayName eq '$GroupId'" -ErrorAction Stop
        if ($group) {
            if ($group.Count -gt 1) {
                Write-Warning "Multiple groups found with name '$GroupId'. Using the first one."
                $GroupId = $group[0].Id
            } else {
                $GroupId = $group.Id
            }
            Write-Host "Resolved to GroupId: $GroupId"
        } else {
            Write-Error "Group with name '$GroupId' not found."
            exit 1
        }
    } catch {
        Write-Error "Error resolving group name: $($_.Exception.Message)"
        exit 1
    }
}

# Function to get groups that this group is a member of (reverse membership)
function Get-GroupMembershipRecursive {
    param(
        [string]$GroupId,
        [int]$Level = 0,
        [hashtable]$ProcessedMemberships = @{}
    )
    
    # Check for circular reference in membership chain
    if ($ProcessedMemberships.ContainsKey($GroupId)) {
        Write-Warning "Circular membership reference detected for group: $GroupId"
        return @()
    }
    
    # Check for maximum depth
    if ($Level -gt 50) {
        Write-Warning "Maximum membership recursion depth reached for group: $GroupId"
        return @()
    }
    
    # Mark group as being processed for membership
    $ProcessedMemberships[$GroupId] = $true
    $membershipResults = @()
    
    try {
        # Get groups that this group is a member of
        $memberOfGroups = Get-MgGroupMemberOf -GroupId $GroupId -All
        
        foreach ($parentGroup in $memberOfGroups) {
            if ($parentGroup.AdditionalProperties['@odata.type'] -eq '#microsoft.graph.group') {
                $parentGroupDetails = Get-MgGroup -GroupId $parentGroup.Id -Select "DisplayName,Mail,GroupTypes"
                
                $membershipObject = [PSCustomObject]@{
                    ChildGroupId = $GroupId
                    ParentGroupId = $parentGroup.Id
                    ParentGroupName = $parentGroupDetails.DisplayName
                    ParentGroupType = $parentGroupDetails.GroupTypes -join ","
                    ParentGroupEmail = $parentGroupDetails.Mail
                    MembershipLevel = $Level
                }
                
                $membershipResults += $membershipObject
                
                # Recursively get parent groups of this parent group
                if ($parentGroup.Id -ne $GroupId) {
                    $nestedMemberships = Get-GroupMembershipRecursive -GroupId $parentGroup.Id -Level ($Level + 1) -ProcessedMemberships $ProcessedMemberships
                    $membershipResults += $nestedMemberships
                }
            }
        }
    }
    catch {
        Write-Error "Error getting group memberships for $GroupId`: $($_.Exception.Message)"
    }
    finally {
        # Remove from processed memberships when done
        $ProcessedMemberships.Remove($GroupId)
    }
    
    return $membershipResults
}


# Initialize collections
$groupMembers = @()
$processedGroups = @{}
$groupStack = @()

# Function to get group members recursively
# This function will handle circular references and maximum recursion depth
function Get-GroupMembersRecursive {
    param(
        [string]$GroupId,
        [int]$Level = 0,
        [string]$ParentGroupName = ""
    )
    
    # Check for circular reference
    if ($processedGroups.ContainsKey($GroupId)) {
        Write-Warning "Circular reference detected for group: $GroupId"
        return
    }
    
    # Check for stack overflow (max depth)
    if ($Level -gt 50) {
        Write-Warning "Maximum recursion depth reached for group: $GroupId"
        return
    }
    
    # Mark group as being processed
    $processedGroups[$GroupId] = $true
    $groupStack += $GroupId
    
    try {
        # Get the group information
        $group = Get-MgGroup -GroupId $GroupId -ErrorAction Stop
        
        # Get group members
        $members = Get-MgGroupMember -GroupId $GroupId -All
        
        foreach ($member in $members) {
            # Create custom object for the result
            $memberObject = [PSCustomObject]@{
                ParentGroupId = $GroupId
                ParentGroupName = $group.DisplayName
                ParentGroupType = $group.GroupTypes -join ","
                MemberId = $member.Id
                MemberType = $member.AdditionalProperties['@odata.type'] -replace '#microsoft.graph.', ''
                Level = $Level
                Path = ($groupStack -join " -> ") + " -> " + $member.Id
            }
            
            # Get member details based on type
            switch ($member.AdditionalProperties['@odata.type']) {
                '#microsoft.graph.user' {
                    $user = Get-MgUser -UserId $member.Id -Select "DisplayName,UserPrincipalName,Mail"
                    $memberObject | Add-Member -NotePropertyName "MemberName" -NotePropertyValue $user.DisplayName
                    $memberObject | Add-Member -NotePropertyName "MemberUPN" -NotePropertyValue $user.UserPrincipalName
                    $memberObject | Add-Member -NotePropertyName "MemberEmail" -NotePropertyValue $user.Mail
                }
                '#microsoft.graph.group' {
                    $memberGroup = Get-MgGroup -GroupId $member.Id -Select "DisplayName,Mail,GroupTypes"
                    $memberObject | Add-Member -NotePropertyName "MemberName" -NotePropertyValue $memberGroup.DisplayName
                    $memberObject | Add-Member -NotePropertyName "MemberUPN" -NotePropertyValue ""
                    $memberObject | Add-Member -NotePropertyName "MemberEmail" -NotePropertyValue $memberGroup.Mail
                    $memberObject | Add-Member -NotePropertyName "MemberGroupTypes" -NotePropertyValue ($memberGroup.GroupTypes -join ",")
                }
                default {
                    $memberObject | Add-Member -NotePropertyName "MemberName" -NotePropertyValue "Unknown"
                    $memberObject | Add-Member -NotePropertyName "MemberUPN" -NotePropertyValue ""
                    $memberObject | Add-Member -NotePropertyName "MemberEmail" -NotePropertyValue ""
                }
            }
            
            $script:groupMembers += $memberObject
            
            # If member is a group, recurse into it
            if ($member.AdditionalProperties['@odata.type'] -eq '#microsoft.graph.group') {
                # Check if this group is already in the current path to prevent immediate loops
                if ($member.Id -notin $groupStack) {
                    Get-GroupMembersRecursive -GroupId $member.Id -Level ($Level + 1) -ParentGroupName $group.DisplayName
                } else {
                    Write-Warning "Immediate circular reference detected. Skipping group: $($memberGroup.DisplayName)"
                }
            }
        }
    }
    catch {
        Write-Error "Error processing group $GroupId`: $($_.Exception.Message)"
    }
    finally {
        # Remove from stack and processed groups when done
        $groupStack = $groupStack[0..($groupStack.Length-2)]
        $processedGroups.Remove($GroupId)
    }
}

# Start the recursive process
Write-Host "Starting recursive group membership scan for group: $GroupId"
Get-GroupMembersRecursive -GroupId $GroupId

# Export results to CSV
if ($groupMembers.Count -gt 0) {
    $groupMembers | Export-Csv -Path $OutputPath -NoTypeInformation
    Write-Host "Results exported to: $OutputPath"
    Write-Host "Total members found: $($groupMembers.Count)"
} else {
    Write-Host "No members found in the specified group."
}

# Get group memberships (groups this group belongs to)
Write-Host "Getting group memberships for group: $GroupId"
$groupMemberships = Get-GroupMembershipRecursive -GroupId $GroupId

# Export group memberships to separate CSV if any found
if ($groupMemberships.Count -gt 0) {
    $groupMemberships | Export-Csv -Path $membershipOutputPath -NoTypeInformation
    Write-Host "Group memberships exported to: $membershipOutputPath"
    Write-Host "Total parent groups found: $($groupMemberships.Count)"
} else {
    Write-Host "No group memberships found for the specified group."
}