#Requires –Version 3

#Get WindowsUpdate List for offline patch
function Get-WindowsUpdateFileList
{
param(
    [Parameter(Mandatory=$True)]
    [string] $Filter
)
    $objSession = New-Object -ComObject "Microsoft.Update.Session"
    $objSearcher = $objSession.CreateUpdateSearcher()
    $results = $objSearcher.Search($Filter)
   
    $downloadList =@()
    foreach($update in $results.Updates)
    {
        $title = $update.Title
        $date  = $update.LastDeploymentChangeTime
        $isInstalled  = $update.IsInstalled
        $rebootRequired = $update.RebootRequired
        
        foreach($bundledUpdate in $update.BundledUpdates)
        {
            foreach($content in $bundledUpdate.DownloadContents)
            {
                #if($url.Contains("-express_") -or $url.Contains("-delta_") -or $url.EndsWith(".psf"))
                if($content.IsDeltaCompressedContent)
                {
                    #Skip express package(Delta Compressed Package) and .psf file
                    continue
                }

                #Append to download list
                $url = $content.DownloadURL
                $fileName = [IO.Path]::GetFileName($url)
                $downloadList += [pscustomobject]@{Title=$title;LastDeploymentChangeTime=$date ;DownloadURL=$url;IsInstalled=$isInstalled;RebootRequired=$rebootRequired;FileName=$fileName}
            }
        }
    }
    return $downloadList
}

function Start-DownloadWindowsUpdateFile
{
[Cmdletbinding()]
param(
    [string] $TargetComputer,
    $Credential,
    [string] $DownloadFolder,
    [string] $WindowsUpdateFilter
)
    if(!(Test-Path $DownloadFolder))
    {
        Write-Error "Destination folder not found!"
    }
   
    
    if($TargetComputer -eq $env:ComputerName)
    {
        Write-Verbose ("Search WindowsUpdate for local computer...")
        $results = Get-WindowsUpdateFileList $WindowsUpdateFilter
    }
    else
    {
        Write-Verbose ("Search WindowsUpdate for remote computer({0})..." -f $TargetComputer)
        $results = Invoke-Command -Computer $TargetComputer -Credential $Credential -ScriptBlock ${function:Get-WindowsUpdateFileList} -ArgumentList $WindowsUpdateFilter
    }

    Write-Verbose ("WindowsUpdate check completed: {0} files found" -f $results.Count) 

    #$results | select Title,FileName, LastDeploymentChangeTime | Format-List

    #Start Download Files
    Write-Verbose ("Download files started...")
    foreach($update in $results)
    {
        $fileName = [IO.Path]::GetFileName($update.DownloadURL)
        $filePath = Join-Path $DownloadFolder $fileName
        if(Test-Path $filePath)
        {
            Write-Verbose  "`tSkip already exists patch: $fileName"
            continue
        }
        
        Write-Verbose  "`tStart download patch: $fileName"
        $params = @{
            Source      = $update.DownloadURL
            DisplayName = $update.Title
            Description = $update.DownloadURL
            Destination = $DownloadFolder
        }
        Start-BitsTransfer @params
    }
    Write-Verbose ("Download files completed...")
}