using System.Globalization;

namespace SeaHaven.Services.Helpers
{
    /// <summary>
    /// The board's exact work-order id filter: comma-separated positive integers, deduplicated,
    /// at most <see cref="MaxCount"/> distinct ids.
    /// </summary>
    public static class WorkOrderIdSet
    {
        public const int MaxCount = 200;

        /// <summary>
        /// Null when <paramref name="raw"/> is absent or blank. Throws <see cref="ArgumentException"/>
        /// (a 400 on the board) for any token that is not a positive integer, or too many ids.
        /// </summary>
        public static IReadOnlyList<int>? ParseOrThrow(string? raw)
        {
            if (string.IsNullOrWhiteSpace(raw))
                return null;

            var ids = new List<int>();
            var seen = new HashSet<int>();
            foreach (var token in raw.Split(','))
            {
                if (!int.TryParse(token.Trim(), NumberStyles.None, CultureInfo.InvariantCulture, out var id) || id <= 0)
                    throw new ArgumentException("ids must be a comma-separated list of positive work order ids.");
                if (seen.Add(id))
                    ids.Add(id);
            }

            if (ids.Count > MaxCount)
                throw new ArgumentException($"ids accepts at most {MaxCount} work orders.");

            return ids;
        }
    }
}