param(
  [Parameter(Mandatory)] [string] $InputPdf,
  [Parameter(Mandatory)] [string] $OutputPdf,
  [Parameter(Mandatory)] [string] $WatermarkPdf,
  [Parameter(Mandatory)] [string] $ITextDllDir,
  [Parameter(Mandatory)] [string] $LogFile,
  [Parameter(Mandatory)] [string] $AddDebugMarker
)

Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"

$AddDebugMarkerBool = ($AddDebugMarker -eq "True")

function Write-Log([string]$msg) {
  $line = "[{0}] {1}`r`n" -f (Get-Date), $msg
  try {
    [System.IO.File]::AppendAllText($LogFile, $line)
  } catch {
    # Fallback, falls LogFile kaputt/leer/nicht schreibbar ist
    $fallback = Join-Path $env:TEMP "pdf_worker_fallback.log"
    [System.IO.File]::AppendAllText($fallback, $line)
  }
}

function Import-IText7 {
  param([Parameter(Mandatory)] [string] $DllDir)

  if (-not (Test-Path $DllDir)) { throw "IText-DLL-Verzeichnis existiert nicht: $DllDir" }

  # PS7 / .NET: sauberes Laden über AssemblyLoadContext, ohne Resolve-Handler
  Add-Type -AssemblyName "System.Runtime.Loader" -ErrorAction Stop
  $alc = [System.Runtime.Loader.AssemblyLoadContext]::Default

  # Lade alle DLLs aus dem Ordner. Wichtig: erst commons/io, dann kernel/layout etc.
  $preferredOrder = @(
    "itext.commons.dll",
    "itext.io.dll",
    "itext.kernel.dll",
    "itext.layout.dll",
    "itext.barcodes.dll"
  )

  # 1) bevorzugte zuerst (wenn vorhanden)
  foreach ($name in $preferredOrder) {
    $p = Join-Path $DllDir $name
    if (Test-Path $p) {
      $full = (Resolve-Path $p).Path
      [void]$alc.LoadFromAssemblyPath($full)
    }
  }

  # 2) dann alle übrigen DLLs (z.B. BouncyCastle Adapter/Abhängigkeiten), die noch nicht geladen sind
  $dlls = Get-ChildItem -LiteralPath $DllDir -Filter "*.dll" -File | Sort-Object Name
  foreach ($dll in $dlls) {
    try {
      $full = $dll.FullName
      # Wenn bereits geladen, skip (heuristisch über Name)
      $already = [AppDomain]::CurrentDomain.GetAssemblies() |
        Where-Object { $_.GetName().Name -ieq [IO.Path]::GetFileNameWithoutExtension($dll.Name) }
      if ($already) { continue }

      [void]$alc.LoadFromAssemblyPath($full)
    } catch {
      # absichtlich leise: manche DLLs sind evtl. native/inkompatibel, wir wollen nicht hier abbrechen
    }
  }
}



function Add-StationeryWatermark {
  param(
    [Parameter(Mandatory)] [string] $InputPdf,
    [Parameter(Mandatory)] [string] $OutputPdf,
    [Parameter(Mandatory)] [string] $WatermarkPdf,
    [bool] $AddDebugMarker
  )

  $PdfReaderType  = [iText.Kernel.Pdf.PdfReader]
  $PdfWriterType  = [iText.Kernel.Pdf.PdfWriter]
  $PdfDocType     = [iText.Kernel.Pdf.PdfDocument]
  $PdfCanvasType  = [iText.Kernel.Pdf.Canvas.PdfCanvas]

  $reader=$null; $writer=$null; $pdf=$null
  $wmReader=$null; $wmDoc=$null

  try {
    $reader = New-Object $PdfReaderType($InputPdf)
    $writer = New-Object $PdfWriterType($OutputPdf)
    $pdf    = New-Object $PdfDocType($reader, $writer)
    $pages  = $pdf.GetNumberOfPages()

    $wmReader = New-Object $PdfReaderType($WatermarkPdf)
    $wmDoc    = New-Object $PdfDocType($wmReader)
    $wmPages  = $wmDoc.GetNumberOfPages()

    Write-Log ("INFO InputPages={0} WatermarkPages={1} WM={2}" -f $pages, $wmPages, $WatermarkPdf)

    if ($wmPages -lt 1) { throw "Wasserzeichen-PDF hat keine Seiten: $WatermarkPdf" }

    $wmFirstXObj = $wmDoc.GetPage(1).CopyAsFormXObject($pdf)
    $wmNextXObj  = if ($wmPages -ge 2) { $wmDoc.GetPage(2).CopyAsFormXObject($pdf) } else { $wmFirstXObj }

    for ($p=1; $p -le $pages; $p++) {
      $page = $pdf.GetPage($p)
      $canvas = New-Object $PdfCanvasType($page.NewContentStreamBefore(), $page.GetResources(), $pdf)

      $use = if ($pages -eq 1 -or $p -eq 1) { 1 } else { 2 }
      if ($use -eq 1) { $canvas.AddXObjectAt($wmFirstXObj, 0, 0) | Out-Null }
      else            { $canvas.AddXObjectAt($wmNextXObj,  0, 0) | Out-Null }

      # Debug-Marker: macht sofort sichtbar, ob Seite 2 wirklich benutzt wird
      if ($AddDebugMarker) {
        $canvas2 = New-Object $PdfCanvasType($page.NewContentStreamAfter(), $page.GetResources(), $pdf)
        $canvas2.BeginText() | Out-Null
        $canvas2.SetFontAndSize([iText.Kernel.Font.PdfFontFactory]::CreateFont(), 8) | Out-Null
        $canvas2.MoveText(10, 10) | Out-Null
        $canvas2.ShowText(("WM{0}" -f $use)) | Out-Null
        $canvas2.EndText() | Out-Null
        $canvas2.Release()
      }

      $canvas.Release()
    }
  }
  finally {
    foreach ($o in @($wmDoc,$pdf,$wmReader,$reader,$writer)) {
      try { if ($null -ne $o) { $o.Close() } } catch {}
    }
  }
}

try {
  Write-Log ("START Input={0} Out={1}" -f $InputPdf, $OutputPdf)

  if (-not (Test-Path $InputPdf))     { throw "Input-PDF nicht gefunden: $InputPdf" }
  if (-not (Test-Path $WatermarkPdf)) { throw "Wasserzeichen nicht gefunden: $WatermarkPdf" }
  if (-not (Test-Path $ITextDllDir))  { throw "ITextDllDir nicht gefunden: $ITextDllDir" }

  Import-IText7 -DllDir $ITextDllDir

  Add-StationeryWatermark -InputPdf $InputPdf -OutputPdf $OutputPdf -WatermarkPdf $WatermarkPdf -AddDebugMarker:$AddDebugMarkerBool

  Write-Log "OK"
  exit 0
}
catch {
  Write-Log ("FAIL :: {0}" -f $_.Exception.Message)
  $e = $_.Exception
  while ($e) {
    Write-Log ("EX: {0}: {1}" -f $e.GetType().FullName, $e.Message)
    $e = $e.InnerException
  }
  exit 2
}