DocumentService/DocumentService.Application/AddAttachments/AddAttachmentsCommand.cs

using DocumentService.Application.Common.Interfaces;
using FluentValidation;
using MediatR;

namespace DocumentService.Application.AddAttachments;

/// <summary>
/// Command to add one or more attachments to a PDF document (supports PDF/A-3)
/// </summary>
public record AddAttachmentsCommand : IRequest<byte[]>
{
    /// <summary>
    /// PDF document stream. Must be positioned at the beginning (Position = 0).
    /// </summary>
    public required Stream PdfStream { get; init; }

    /// <summary>
    /// List of attachments to embed (filename, content, optional MIME type)
    /// </summary>
    public required IReadOnlyList<AttachmentFile> Attachments { get; init; }
}

/// <summary>
/// Represents a file to be attached to a PDF
/// </summary>
public record AttachmentFile
{
    /// <summary>
    /// File name (e.g., "invoice.xml", "document.pdf")
    /// </summary>
    public required string FileName { get; init; }

    /// <summary>
    /// File content as byte array
    /// </summary>
    public required byte[] Content { get; init; }

    /// <summary>
    /// MIME type (optional, e.g., "application/xml", "application/pdf")
    /// If not provided, will be inferred from file extension
    /// </summary>
    public string? MimeType { get; init; }
}

/// <summary>
/// Handler for AddAttachmentsCommand
/// </summary>
public class AddAttachmentsCommandHandler(IPdfProcessor pdfProcessor) 
    : IRequestHandler<AddAttachmentsCommand, byte[]>
{
    public async Task<byte[]> Handle(AddAttachmentsCommand request, CancellationToken cancellationToken)
    {
        // Convert to tuple list for IPdfProcessor
        var attachmentTuples = request.Attachments
            .Select(a => (a.FileName, a.Content, a.MimeType))
            .ToList();

        return await pdfProcessor.AddAttachmentsAsync(request.PdfStream, attachmentTuples);
    }
}

/// <summary>
/// Validator for AddAttachmentsCommand
/// </summary>
public class AddAttachmentsCommandValidator : AbstractValidator<AddAttachmentsCommand>
{
    public AddAttachmentsCommandValidator()
    {
        RuleFor(x => x.PdfStream)
            .NotNull()
            .WithMessage("PDF stream is required");

        RuleFor(x => x.Attachments)
            .NotNull()
            .NotEmpty()
            .WithMessage("At least one attachment is required");

        RuleForEach(x => x.Attachments).ChildRules(attachment =>
        {
            attachment.RuleFor(a => a.FileName)
                .NotEmpty()
                .WithMessage("Attachment file name is required");

            attachment.RuleFor(a => a.Content)
                .NotNull()
                .NotEmpty()
                .WithMessage("Attachment content is required");
        });
    }
}