EnvelopeGenerator/EnvelopeGenerator.ServiceHost/Jobs/FinalizeDocument/PDFMerger.cs

using EnvelopeGenerator.ServiceHost.Exceptions;
using GdPicture14;
using Microsoft.Extensions.Options;

namespace EnvelopeGenerator.ServiceHost.Jobs.FinalizeDocument;

public class PDFMerger
{
    private readonly AnnotationManager _manager;
    private readonly LicenseManager _licenseManager;

    private const bool AllowRasterization = true;
    private const bool AllowVectorization = true;

    private readonly PdfConversionConformance _pdfaConformanceLevel = PdfConversionConformance.PDF_A_1b;

    public PDFMerger(LicenseManager licenseManager, AnnotationManager annotationManager)
    {
        _licenseManager = licenseManager;
        _manager = annotationManager;
    }

    public byte[] MergeDocuments(byte[] document, byte[] report)
    {
        using var documentStream = new MemoryStream(document);
        using var reportStream = new MemoryStream(report);
        using var finalStream = new MemoryStream();
        using var documentPdf = new GdPicturePDF();
        using var reportPdf = new GdPicturePDF();

        documentPdf.LoadFromStream(documentStream, true);
        var status = documentPdf.GetStat();
        if (status != GdPictureStatus.OK)
        {
            throw new MergeDocumentException($"Document could not be loaded: {status}");
        }

        reportPdf.LoadFromStream(reportStream, true);
        status = reportPdf.GetStat();
        if (status != GdPictureStatus.OK)
        {
            throw new MergeDocumentException($"Report could not be loaded: {status}");
        }

        var mergedPdf = documentPdf.Merge2Documents(documentPdf, reportPdf);
        status = mergedPdf.GetStat();
        if (status != GdPictureStatus.OK)
        {
            throw new MergeDocumentException($"Documents could not be merged: {status}");
        }

        mergedPdf.ConvertToPDFA(finalStream, _pdfaConformanceLevel, AllowVectorization, AllowRasterization);
        status = documentPdf.GetStat();
        if (status != GdPictureStatus.OK)
        {
            throw new MergeDocumentException($"Document could not be converted to PDF/A: {status}");
        }

        return finalStream.ToArray();
    }
}