ErsatzTV/ErsatzTV.Application/Validators/StringValidation.cs

using System;
using System.Linq.Expressions;
using ErsatzTV.Core;
using LanguageExt;
using static LanguageExt.Prelude;

namespace ErsatzTV
{
    public static partial class Validators
    {
        public static Func<Expression<Func<T, string>>, Validation<BaseError, string>> NotLongerThan<T>(
            this T input,
            int maxLength) =>
            expression => Optional(expression)
                .Map(exp => exp.Compile()(input))
                .Where(s => s.Length <= maxLength)
                .ToValidation<BaseError>($"[{GetMemberName(expression)}] must not be longer than {maxLength}");

        public static Validation<BaseError, string> NotEmpty<T>(this T input, Expression<Func<T, string>> expression) =>
            Optional(expression.Compile()(input))
                .Where(s => !string.IsNullOrWhiteSpace(s))
                .ToValidation<BaseError>($"[{GetMemberName(expression)}] is an empty string");
    }
}