using System.Text.RegularExpressions;

namespace OnlyPrompt.Backend.Utils
{
	public static class SlugHelper
	{
		private static readonly Regex InvalidCharacters = new(@"[^a-z0-9\-]", RegexOptions.Compiled);
		private static readonly Regex MultipleDashes = new(@"-+", RegexOptions.Compiled);

		public static string GenerateSlug(string input, int? maxLength = null)
		{
			if (string.IsNullOrWhiteSpace(input))
				return string.Empty;

			var slug = input.ToLowerInvariant().Replace(" ", "-").Replace("_", "-");
			slug = InvalidCharacters.Replace(slug, string.Empty);
			slug = MultipleDashes.Replace(slug, "-");
			slug = slug.Trim('-');
			if (maxLength.HasValue)
				slug = slug.Limit(maxLength.Value);

			return slug;
		}

		private const string SuffixChars = "abcdefghijklmnopqrstuvwxyz0123456789";
		public static async Task<string> GenerateUniqueSlugAsync(string input, Func<string, Task<bool>> existsFunc, int? maxLenght)
		{
			var slug = GenerateSlug(input);
			var exists = await existsFunc(slug);
			if (exists)
			{
				var suffix = Random.Shared.GetString(8, SuffixChars);
				if (maxLenght.HasValue)
					slug = slug.Limit(maxLenght.Value - 9);

				slug = $"{slug}-{suffix}";
			}

			return slug;
		}
	}
}