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

namespace DocumentService.Application.ConvertToPdfA;

/// <summary>
/// Command to convert a standard PDF to PDF/A format
/// </summary>
public record ConvertToPdfACommand : IRequest<byte[]>
{
    /// <summary>
    /// PDF document stream. Must be positioned at the beginning (Position = 0).
    /// </summary>
    public required Stream PdfStream { get; init; }

    /// <summary>
    /// Target PDF/A level (e.g., "PDF/A-1b", "PDF/A-2b", "PDF/A-3b")
    /// </summary>
    public required string PdfALevel { get; init; }
}

/// <summary>
/// Handler for ConvertToPdfACommand
/// </summary>
public class ConvertToPdfACommandHandler(IPdfProcessor pdfProcessor) 
    : IRequestHandler<ConvertToPdfACommand, byte[]>
{
    public async Task<byte[]> Handle(ConvertToPdfACommand request, CancellationToken cancellationToken)
    {
        return await pdfProcessor.ConvertToPdfAAsync(request.PdfStream, request.PdfALevel);
    }
}

/// <summary>
/// Validator for ConvertToPdfACommand
/// </summary>
public class ConvertToPdfACommandValidator : AbstractValidator<ConvertToPdfACommand>
{
    private static readonly string[] ValidPdfALevels = 
    {
        "PDF/A-1b", "PDF/A-1a",
        "PDF/A-2b", "PDF/A-2u", "PDF/A-2a",
        "PDF/A-3b", "PDF/A-3u", "PDF/A-3a"
    };

    public ConvertToPdfACommandValidator()
    {
        RuleFor(x => x.PdfStream)
            .NotNull()
            .WithMessage("PDF stream is required");

        RuleFor(x => x.PdfALevel)
            .NotEmpty()
            .WithMessage("PDF/A level is required")
            .Must(level => ValidPdfALevels.Contains(level, StringComparer.OrdinalIgnoreCase))
            .WithMessage($"Invalid PDF/A level. Valid values: {string.Join(", ", ValidPdfALevels)}");
    }
}