using DigitalData.Core.Exceptions;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Application.Common.Interfaces.Doc;
using EnvelopeGenerator.Application.Common.Interfaces.Services;
using EnvelopeGenerator.Application.DocReceiverElements.Queries;
using MediatR;

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>
/// 
/// </summary>
/// <param name="signService"></param>
public class SignPdfCommandHandler(ISender sender, IPdfDigitalSignatureService signService, IPdfPageImageRenderer imgRenderer) : IRequestHandler<SignPdfByElementCommand, Stream>
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public async Task<Stream> Handle(SignPdfByElementCommand request, CancellationToken cancellationToken)
    {
        // ensure element
        if(request.Element is null)
        {
            var elements = await sender.Send(new ReadDocReceiverElementQuery() 
            {
                Id = request.ElementId!,
                IncludeDocument= true
            }, cancellationToken);
            
            if (!elements.Any())
                throw new NotFoundException($"Element with ID {request.ElementId} not found.");

            request.Element = elements.FirstOrDefault();
        }

        // ensure document
        var doc = request.Element!.Document;

        if(doc is null || doc.ByteData is null || doc.ByteData.Length == 0)
            throw new NotFoundException("Document data is missing or empty.");

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

        // sign pdf
        var inputPdf = new MemoryStream(doc.ByteData);
        var outputPdf = new MemoryStream();

        await signService.SignPdfAsync(
            inputPdf: inputPdf,
            outputPdf: outputPdf,
            options: new PdfSignOptionsDto
            {
                Appearance = new PdfSignatureAppearanceDto(
                    PageNumber: request.Element.Page,
                    Left: request.Element.Left,
                    Bottom: request.Element.Y,
                    Width: request.Element.Width,
                    Height: request.Element.Height)
            },
            image: img,
            cancellationToken: cancellationToken);

        return outputPdf;
    }
}