function ExitWithCode {
param
(
    $exitcode
)

$host.SetShouldExit($exitcode)
exit
}

function Write-Log {
<#
.SYNOPSIS
    Write-Log writes a message to a logfile

.DESCRIPTION
    The Write-Log function is designed to add logging capability to other scripts.
    In addition to writing output and/or verbose you can write to a log file for
    later debugging.
#>
[CmdletBinding()]
Param
(
    [Parameter(Mandatory = $true,ValueFromPipelineByPropertyName = $true)]
    [ValidateNotNullOrEmpty()]
    [Alias('LogContent')]
    [string]$Message,

    [Parameter(Mandatory = $false)]
    [ValidateSet("Error", "Info", "Status")]
    [string]$Level = "Info",

    [Parameter(Mandatory = $false)]
    [Alias('LogPath')]
    [string]$Path = 'C:dataloopADHealthCheck.log'

)

BEGIN {

    [string]$FormattedDate = Get-Date -Format "dd-MM-yyyy HH:mm"

    If (-NOT (Test-Path $path)) {
        Write-Verbose "Creating $Path"
        [System.IO.FileInfo]$LogFile = New-Item $Path -Force -ItemType file
    }
}
PROCESS {
    [string]$LogLine = "$FormattedDate - $Level - $message"
    $LogLine | Out-File -FilePath $Path -Append

    Switch ($Level) {

        "Info" {Write-Verbose $LogLine}
        "Status" {Write-Output $LogLine}
        "Error" {Write-Error $LogLine}
    }
}
END {}
}

function Get-ADHealthCheck {
    [CmdletBinding()]
        param()

        BEGIN {
        Write-Log "Beginning the AD Health Check..."
        }


        PROCESS {
        $DCs = Get-ADDomainController -Filter * |sort name

        Write-Log "$($DCs.Count) Domain Controllers found" -level Info

        $results = @()

        ForEach ($DC in $DCs) {

            Write-Log "Getting replication metadata for $($DC.HostName)" -level Status
            $ReplStatuses = Get-ADReplicationPartnerMetadata -target $DC.HostName -PartnerType Both -ErrorAction SilentlyContinue

            If ($ReplStatuses) {

                 Write-Log "$($ReplStatuses.Count) replication links found for $($DC.HostName)" -level Info

                ForEach ($ReplStatus in $ReplStatuses) {

                    $Partner = $ReplStatus.Partner.Split(",")[1].Replace("CN=","")

                    $results += [pscustomobject] @{
                        'Source DC' = $DC.HostName.ToUpper()
                        'Partner DC' = (Get-ADComputer $Partner).DNSHostName.ToUpper()
                        'Direction' = $ReplStatus.PartnerType
                        'Type' = $ReplStatus.IntersiteTransportType
                        'Last Attempt' = $ReplStatus.LastReplicationAttempt
                        'Last Success' = $ReplStatus.LastReplicationSuccess
                        'Last Result' = $ReplStatus.LastReplicationResult
                    }
                }
            }

            Else {

                Write-Log "Unable to get replication status for $($DC.HostName)" -level Error
                $results += [pscustomobject] @{
                    'Source DC' = $DC.HostName.ToUpper()
                    'Partner DC' = "N/A"
                    Direction = "N/A"
                    Type = "N/A"
                    'Last Attempt' = "N/A"
                    'Last Success' = "N/A"
                    'Last Result' = "N/A"
                }
             }
        }

        ForEach ($result in $results) {

            If ("$($results.'Last Result')" -eq "0") {

                Write-Log "There were no replication issues found" -Level Info
                ExitWithCode -exitcode 0
            }

            Else {

                Write-Log "These domain controllers have replication errors. Please review them..." -Level Error
                $error = $results | where {"$($_.'Last Result')" -ne "0"} | select 'Source DC','Partner DC','Direction' | ft -AutoSize
                Write-Log $error -Level Error
                ExitWithCode -exitcode 2
            }
        }
    }
}
Get-ADHealthCheck