shoc-backend/SeaHaven.Services/Helpers/WorkOrderNumberRules.cs

using System.Globalization;

namespace SeaHaven.Services.Helpers
{
    public static class WorkOrderNumberRules
    {
        private const int MaximumLength = 11;
        private const int MinimumProvisionalDigits = 5;

        public static bool IsProvisional(string? woNumber)
            => !string.IsNullOrWhiteSpace(woNumber)
               && woNumber.Trim().StartsWith("SH", StringComparison.OrdinalIgnoreCase);

        public static string FormatProvisional(long seed)
        {
            if (seed < 1)
                throw new ArgumentOutOfRangeException(nameof(seed), "Provisional WO number seed must be positive.");

            var digits = seed.ToString(CultureInfo.InvariantCulture)
                .PadLeft(MinimumProvisionalDigits, '0');
            var provisional = $"SH{digits}";

            if (provisional.Length > MaximumLength)
                throw new ArgumentOutOfRangeException(nameof(seed), "Provisional WO number exceeds the supported length.");

            return provisional;
        }
    }
}