EnvelopeGenerator/EnvelopeGenerator.Application/PdfSigning/SignPdfByElementCommand.cs

using DigitalData.Core.Exceptions;
using EnvelopeGenerator.Application.Common.Configurations;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Application.Common.Enums;
using EnvelopeGenerator.Application.Common.Interfaces.Doc;
using EnvelopeGenerator.Application.Common.Interfaces.Services;
using EnvelopeGenerator.Application.DocReceiverElements.Queries;
using MediatR;
using Microsoft.Extensions.Options;

namespace EnvelopeGenerator.Application.PdfSigning;

/// <summary>
/// 
/// </summary>
public record SignPdfByElementCommand : IRequest<Stream>
{
    /// <summary>
    /// 
    /// </summary>
    public DocReceiverElementDto? Element { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public int? ElementId { get; init; }

    /// <summary>
    /// Custom document 
    /// </summary>
    public Stream? Document { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public string? Phone { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public string? Reason { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public PdfSignatureCertificationLevel CertificationLevel { get; init; } = PdfSignatureCertificationLevel.NoChangesAllowed;
}

/// <summary>
/// 
/// </summary>
/// <param name="sender"></param>
/// <param name="signService"></param>
/// <param name="imgRenderer"></param>
/// <param name="options"></param>
public class SignPdfCommandHandler(ISender sender, IPdfDigitalSignatureService signService, IPdfPageImageRenderer imgRenderer, IOptionsMonitor<ESignParams> options) : IRequestHandler<SignPdfByElementCommand, Stream>
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public async Task<Stream> Handle(SignPdfByElementCommand request, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();

        // ensure element
        if (request.Element is null)
        {
            var elements = await sender.Send(new ReadDocReceiverElementQuery() 
            {
                Id = request.ElementId!,
                IncludeDocument = request.Document is null
            }, cancellationToken);
            
            request.Element = elements.FirstOrDefault() ?? throw new NotFoundException($"Element with ID {request.ElementId} not found."); ;
        }

        // ensure document
        if(request.Document is null)
        {
            if (request.Element?.Document?.ByteData is not { Length: > 0 })
                throw new NotFoundException("Document data is missing or empty.");

            request.Document = new MemoryStream(request.Element.Document.ByteData);
        }

        ValidateAfterDataIsComplete(request);

        // create signature image from element
        var img = imgRenderer.ComposeSignaturePreviewPng(request.Element);

        // sign pdf
        var outputPdf = new MemoryStream();

        await signService.SignPdfAsync(
            inputPdf: request.Document,
            outputPdf: outputPdf,
            options: new PdfSignOptionsDto
            {
                Name = request.Element.FullName!,
                Location = request.Element.Position!,
                Phone = request.Phone,
                Reason = request.Reason ?? options.CurrentValue.DefaultReason,
                Email = request.Element.Receiver!.EmailAddress,
                ApplicationName = options.CurrentValue.ApplicationName,
                DocumentElementId = request.Element.Id,

                CertificationLevel = request.CertificationLevel,
                Appearance = new PdfSignatureAppearanceDto(
                    PageNumber: request.Element.Page,
                    Left: request.Element.Left,
                    Bottom: request.Element.Y,
                    Width: request.Element.Width,
                    Height: request.Element.Height,
                    CoordinateUnit: PdfSignatureCoordinateUnit.Inch,
                    CoordinateOrigin: PdfSignatureCoordinateOrigin.TopLeft)
            },
            image: img,
            cancellationToken: cancellationToken);

        return outputPdf;
    }

    private static void ValidateAfterDataIsComplete(SignPdfByElementCommand request)
    {
        if(request.Element!.FullName is null)
            throw new BadRequestException($"Document is not signed. FullName is required. Element ID: {request.Element.Id}");
        else if(request.Element.Position is null)
            throw new BadRequestException($"Document is not signed. Position is required. Element ID: {request.Element.Id}");
    }
}