using FluentValidation;

namespace DocumentOperator.Application.ValidatePdfA.Validators;

/// <summary>
/// Validator for ValidatePdfAQuery
/// Ensures exactly ONE input format is provided (PdfBytes XOR Base64Pdf)
/// </summary>
public class ValidatePdfAQueryValidator : AbstractValidator<Queries.ValidatePdfAQuery>
{
    public ValidatePdfAQueryValidator()
    {
        RuleFor(x => x)
            .Must(x => (x.PdfBytes != null && x.PdfBytes.Length > 0) ^ 
                       !string.IsNullOrWhiteSpace(x.Base64Pdf))
            .WithMessage("Either PdfBytes or Base64Pdf must be provided, but not both");

        When(x => !string.IsNullOrWhiteSpace(x.Base64Pdf), () =>
        {
            RuleFor(x => x.Base64Pdf!)
                .Must(BeValidBase64)
                .WithMessage("Base64Pdf must be a valid Base64 string");
        });

        When(x => x.PdfBytes != null, () =>
        {
            RuleFor(x => x.PdfBytes!)
                .Must(bytes => bytes.Length > 0)
                .WithMessage("PdfBytes cannot be empty");
        });
    }

    private static bool BeValidBase64(string base64)
    {
        if (string.IsNullOrWhiteSpace(base64))
            return false;

        try
        {
            Convert.FromBase64String(base64);
            return true;
        }
        catch (FormatException)
        {
            return false;
        }
    }
}