# Define a parameter for specifying replication groups (default is an empty array)
Param (
    [String[]]$ReplicationGroupList = ("")
)

# Get all DFS Replication Group configurations using WMI
$RGroups = Get-WmiObject -Namespace "root\MicrosoftDFS" -Query "SELECT * FROM DfsrReplicationGroupConfig"

# If replication groups are specified, filter the list based on the provided group names
if ($ReplicationGroupList) {
    $SelectedRGroups = @()
    foreach ($ReplicationGroup IN $ReplicationGroupList) {
        $SelectedRGroups += $RGroups | Where-Object { $_.ReplicationGroupName -eq $ReplicationGroup }
    }
    # If no matching groups are found, exit with an UNKNOWN status
    if ($SelectedRGroups.count -eq 0) {
        Write-Host "UNKNOWN: None of the group names specified were found."
        exit 3
    } else {
        $RGroups = $SelectedRGroups
    }
}

# Initialize counters for success, warning, and error
$Succ = 0
$Warn = 0
$Err = 0
# Initialize an array to store output messages
$Output = @()

# Iterate through each DFS Replication Group
foreach ($Group in $RGroups) {
    # Get DFS Replicated Folder configurations for the current group
    $RGFoldersWMIQ = "SELECT * FROM DfsrReplicatedFolderConfig WHERE ReplicationGroupGUID='" + $Group.ReplicationGroupGUID + "'"
    $RGFolders = Get-WmiObject -Namespace "root\MicrosoftDFS" -Query $RGFoldersWMIQ

    # Get DFS Replication Connection configurations for the current group
    $RGConnectionsWMIQ = "SELECT * FROM DfsrConnectionConfig WHERE ReplicationGroupGUID='" + $Group.ReplicationGroupGUID + "'"
    $RGConnections = Get-WmiObject -Namespace "root\MicrosoftDFS" -Query $RGConnectionsWMIQ

    # Iterate through each DFS Replication Connection for the current group
    foreach ($Connection in $RGConnections) {
        $ConnectionName = $Connection.PartnerName

        # Check if the connection is enabled
        if ($Connection.Enabled -eq $True) {
            # Iterate through each DFS Replicated Folder for the current connection
            foreach ($Folder in $RGFolders) {
                $RGName = $Group.ReplicationGroupName
                $RFName = $Folder.ReplicatedFolderName

                # Build and execute dfsrdiag command to get backlog information
                $BLCommand = "dfsrdiag Backlog /RGName:'" + $RGName + "' /RFName:'" + $RFName + "' /SendingMember:" + $ConnectionName + " /ReceivingMember:" + $env:ComputerName
                $Backlog = Invoke-Expression -Command $BLCommand

                $BacklogFileCount = 0
                # Parse the dfsrdiag output to get the backlog file count
                foreach ($item in $Backlog) {
                    if ($item -ilike "*Backlog File count*") {
                        $BacklogFileCount = [int]$Item.Split(":")[1].Trim()
                    }
                }

                # Based on the backlog file count, generate output messages and update counters
                if ($BacklogFileCount -eq 0) {
                    $Output += "OK: $BacklogFileCount files in backlog $ConnectionName->$env:ComputerName for $RGName"
                    $Succ++
                } elseif ($BacklogFileCount -lt 10) {
                    $Output += "WARNING: $BacklogFileCount files in backlog $ConnectionName->$env:ComputerName for $RGName"
                    $Warn++
                } else {
                    $Output += "CRITICAL: $BacklogFileCount files in backlog $ConnectionName->$env:ComputerName for $RGName"
                    $Err++
                }
            }
        }
    }
}

# Based on the counts of success, warning, and error, generate the final status and exit with the appropriate code
if ($Err -gt 0) {
    Write-Host "CRITICAL: $Err errors, $Warn warnings, and $Succ successful replications."
    Write-Host "$Output"
    exit 2
} elseif ($Warn -gt 0) {
    Write-Host "WARNING: $Warn warnings, and $Succ successful replications."
    Write-Host "$Output"
    exit 1
} else {
    Write-Host "OK: $Succ successful replications."
    Write-Host "$Output"
    exit 0
}