using FluentValidation;

namespace cuqmbr.TravelGuide.Application.Common.FluentValidation;

public static class CustomValidators
{
    public static IRuleBuilderOptions<T, string> IsUsername<T>(
        this IRuleBuilder<T, string> ruleBuilder)
    {
        return
            ruleBuilder
                .Matches(@"^[a-z0-9-_.]*$");
    }

    // According to RFC 5321.
    public static IRuleBuilderOptions<T, string> IsEmail<T>(
        this IRuleBuilder<T, string> ruleBuilder)
    {
        return
            ruleBuilder
                .Matches(@"^[\w\.-]{1,64}@[\w\.-]{1,251}\.\w{2,4}$");
    }

    // According to ITU-T E.164, no spaces.
    public static IRuleBuilderOptions<T, string> IsPhoneNumber<T>(
        this IRuleBuilder<T, string> ruleBuilder)
    {
        return
            ruleBuilder
                .Matches(@"^\+[0-9]{7,15}$");
    }

    public static IRuleBuilderOptions<T, ICollection<TSource>>
        IsUnique<T, TSource, TResult>(
            this IRuleBuilder<T, ICollection<TSource>> ruleBuilder,
            Func<TSource, TResult> selector)
    {
        if (selector == null)
        {
            throw new ArgumentNullException(
                nameof(selector),
                "Cannot pass a null selector.");
        }

        return
            ruleBuilder
                .Must(x => x.IsDistinct(selector));
    }

    public static bool IsDistinct<TSource, TResult>(
        this IEnumerable<TSource> elements, Func<TSource, TResult> selector)
    {
        var hashSet = new HashSet<TResult>();
        foreach (var element in elements.Select(selector))
        {
            if (!hashSet.Contains(element))
                hashSet.Add(element);
            else
                return false;
        }
        return true;
    }
}