using SeaHaven.Services.DTOs;

namespace SeaHaven.Services.Helpers
{
    public static class NotificationFeedOrdering
    {
        /// <summary>
        /// Drops empty sections, orders items by severity then recency, and orders sections by
        /// their highest severity with the fixed reason order breaking ties.
        /// </summary>
        public static IReadOnlyList<NotificationSectionDto> Order(
            IEnumerable<(string Reason, int Count, IReadOnlyList<NotificationItemDto> Items)> sections)
        {
            return sections
                .Where(section => section.Items.Count > 0)
                .Select(section =>
                {
                    var items = section.Items
                        .OrderByDescending(item => NotificationSeverities.Rank(item.Severity))
                        .ThenByDescending(item => item.TriggeredAt)
                        .ThenBy(item => item.Id, StringComparer.Ordinal)
                        .ToList();
                    return new NotificationSectionDto
                    {
                        Reason = section.Reason,
                        Label = NotificationReasons.Labels[section.Reason],
                        Severity = items[0].Severity,
                        Count = section.Count,
                        Items = items
                    };
                })
                .OrderByDescending(section => NotificationSeverities.Rank(section.Severity))
                .ThenBy(section => ReasonIndex(section.Reason))
                .ToList();
        }

        private static int ReasonIndex(string reason)
        {
            for (var index = 0; index < NotificationReasons.Order.Count; index++)
            {
                if (NotificationReasons.Order[index] == reason)
                    return index;
            }
            return NotificationReasons.Order.Count;
        }
    }

    public static class NotificationBusinessTime
    {
        /// <summary>Business-calendar date of <paramref name="utcNow"/> in the dashboard's time zone.</summary>
        public static DateOnly Today(DateTime utcNow)
        {
            var timezone = TimeZoneInfo.FindSystemTimeZoneById(DashboardBusinessTime.TimeZoneId);
            return DateOnly.FromDateTime(TimeZoneInfo.ConvertTimeFromUtc(utcNow, timezone));
        }
    }
}