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('-');
			return slug;
		}

		private const string SuffixChars = "abcdefghijklmnopqrstuvwxyz0123456789";
		public static async Task<string> GenerateUniqueSlugAsync(string input, Func<string, Task<bool>> existsFunc, int? maxLenght)
		{
			var baseSlug = GenerateSlug(input, maxLenght - 9); 
			var slug = baseSlug;
			var suffix = Random.Shared.GetString(8, SuffixChars);	
			return $"{slug}-{suffix}";
		}
	}
}