Radicade/Server/Players/UsernameRules.cs

namespace RadicadeServer.Utils
{
		public static class UsernameRules
	{
		public const int MinLength = 3;
		public const int MaxLength = 24;

				private static readonly string[] ReservedNames =
		[
			"me", "you", "recroom", "recnet", "radicade", "againstgravity",
			"system", "admin", "administrator", "moderator", "mod", "support",
			"staff", "official", "developer", "owner", "root"
		];

				public static string? Normalize(string? posted)
		{
			if (string.IsNullOrWhiteSpace(posted)) return null;

			var name = posted.Trim().TrimStart('@').Trim();
			return name.Length == 0 ? null : name;
		}

				public static string? Parse(string? posted, out string? rejection)
		{
			rejection = null;

			var name = Normalize(posted);
			if (name == null) return null;

			rejection = Rejection(name);
			return rejection == null ? name : null;
		}

				public static string? Rejection(string name)
		{
			if (name.Length < MinLength)
				return $"Names must be at least {MinLength} characters.";
			if (name.Length > MaxLength)
				return $"Names must be {MaxLength} characters or fewer.";

			bool hasLetter = false;
			foreach (var character in name)
			{
				if (char.IsAsciiLetter(character)) { hasLetter = true; continue; }
				if (char.IsAsciiDigit(character)) continue;
				return "Names can only use letters and numbers.";
			}

			if (!hasLetter)
				return "Names must contain at least one letter.";

			if (ReservedNames.Any(reserved => string.Equals(reserved, name, StringComparison.OrdinalIgnoreCase)))
				return "That name is reserved. Please pick another one.";

			if (!name.IsPure())
				return "That name is not allowed. Please pick another one.";

			return null;
		}

				public static string ComparisonKey(string name) => name.ToUpperInvariant();

				public static string Generate() => RecNet.Generators.GenerateUsername();
	}
}