using System.Text.RegularExpressions;

namespace SeaHaven.Services.Helpers
{
    public static class WorkOrderNumberNormalizer
    {
        private const int RequiredLength = 11;
        private const string ProvisionalPrefix = "SH";
        private const int MinimumProvisionalDigits = 5;

        public static bool TryNormalize(string? input, out string normalized, out string? error)
        {
            normalized = "";
            error = null;

            if (string.IsNullOrWhiteSpace(input))
            {
                error = "WO number is required.";
                return false;
            }

            var trimmed = input.Trim();
            if (WorkOrderNumberRules.IsProvisional(trimmed))
                return TryNormalizeProvisional(trimmed, out normalized, out error);

            var digits = Regex.Replace(trimmed, @"\D", "");
            if (digits.Length == 0)
            {
                error = "WO number must contain digits.";
                return false;
            }

            if (digits.Length > RequiredLength)
            {
                error = $"WO number cannot exceed {RequiredLength} digits.";
                return false;
            }

            normalized = digits.PadLeft(RequiredLength, '0');
            return true;
        }

        // SH-320: an SH-prefixed number is the documented placeholder for a WO still
        // awaiting its real APM number; keep the prefix instead of stripping it to digits.
        private static bool TryNormalizeProvisional(string trimmed, out string normalized, out string? error)
        {
            normalized = "";
            error = null;

            var digits = Regex.Replace(trimmed[ProvisionalPrefix.Length..], @"\D", "");
            if (digits.Length == 0)
            {
                error = "WO number must contain digits.";
                return false;
            }

            var candidate = ProvisionalPrefix + digits.PadLeft(MinimumProvisionalDigits, '0');
            if (candidate.Length > RequiredLength)
            {
                error = $"WO number cannot exceed {RequiredLength} characters.";
                return false;
            }

            normalized = candidate;
            return true;
        }
    }
}