Radarr/src/NzbDrone.Core/Organizer/FileNameValidation.cs

using System.IO;
using System.Linq;
using FluentValidation;
using FluentValidation.Validators;
using NzbDrone.Common.Extensions;

namespace NzbDrone.Core.Organizer
{
    public static class FileNameValidation
    {
        public static IRuleBuilderOptions<T, string> ValidMovieFolderFormat<T>(this IRuleBuilder<T, string> ruleBuilder)
        {
            ruleBuilder.SetValidator(new NotEmptyValidator(null));
            ruleBuilder.SetValidator(new IllegalCharactersValidator());

            return ruleBuilder.SetValidator(new RegularExpressionValidator(FileNameBuilder.MovieTitleRegex)).WithMessage("Must contain movie title");
        }

        public static IRuleBuilderOptions<T, string> ValidMovieFormat<T>(this IRuleBuilder<T, string> ruleBuilder)
        {
            ruleBuilder.SetValidator(new NotEmptyValidator(null));
            ruleBuilder.SetValidator(new IllegalCharactersValidator());

            return ruleBuilder.SetValidator(new RegularExpressionValidator(FileNameBuilder.MovieTitleRegex)).WithMessage("Must contain movie title");
        }
    }

    public class IllegalCharactersValidator : PropertyValidator
    {
        private static readonly char[] InvalidPathChars = Path.GetInvalidPathChars();

        protected override string GetDefaultMessageTemplate() => "Contains illegal characters: {InvalidCharacters}";

        protected override bool IsValid(PropertyValidatorContext context)
        {
            var value = context.PropertyValue as string;
            if (value.IsNullOrWhiteSpace())
            {
                return true;
            }

            var invalidCharacters = InvalidPathChars.Where(i => value!.IndexOf(i) >= 0).ToList();
            if (invalidCharacters.Any())
            {
                context.MessageFormatter.AppendArgument("InvalidCharacters", string.Join("", invalidCharacters));
                return false;
            }

            return true;
        }
    }
}