using FluentValidation;

namespace DocumentOperator.Application.CheckPdfAttachments.Queries;

/// <summary>
/// Validator for CheckPdfAttachmentsQuery
/// Ensures exactly one input type (PdfBytes OR Base64Pdf) is provided
/// </summary>
public class CheckPdfAttachmentsQueryValidator : AbstractValidator<CheckPdfAttachmentsQuery>
{
    public CheckPdfAttachmentsQueryValidator()
    {
        // Rule 1: Exactly ONE input must be provided (XOR logic)
        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");

        // Rule 2: Base64 format validation (if provided)
        RuleFor(x => x.Base64Pdf)
            .Must(BeValidBase64)
            .When(x => !string.IsNullOrWhiteSpace(x.Base64Pdf))
            .WithMessage("Base64Pdf must be a valid Base64 string");
    }

    /// <summary>
    /// Validates if a string is a valid Base64 format
    /// </summary>
    private bool BeValidBase64(string? base64)
    {
        if (string.IsNullOrWhiteSpace(base64))
            return true; // Skip validation if null/empty (handled by Rule 1)

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