namespace SeaHaven.Services.Helpers
{
    /// <summary>
    /// Server-side Add-On cutoff: Saturday 23:59:59 UTC of the week prior to the schedule week.
    /// SH-184: recalculated whenever scheduling is set, changed, or cleared; audited on change.
    /// At creation the WO arrives when it is created; on a reschedule it arrives when it is moved.
    /// Create may accept a client hint when unscheduled; schedule present ignores override.
    /// </summary>
    public static class WorkOrderAddonCutoff
    {
        /// <summary>
        /// Cutoff = Monday-of(anchor) − 2 days, end of day UTC (prior-week Saturday 23:59:59).
        /// </summary>
        public static DateTime GetAddonCutoffUtc(DateTime anchor)
        {
            var monday = WorkOrderBoardMutationRules.GetWeekStartMonday(anchor);
            var saturday = monday.Date.AddDays(-2);
            return DateTime.SpecifyKind(
                saturday.AddHours(23).AddMinutes(59).AddSeconds(59),
                DateTimeKind.Utc);
        }

        public static DateTime GetAddonCutoffUtc(DateOnly anchor)
            => GetAddonCutoffUtc(anchor.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc));

        /// <summary>
        /// With schedule (ScheduledDate or TargetWeek): IsAddOn when createdAtUtc is after cutoff.
        /// Without schedule: client <paramref name="manualOverride"/> (default false).
        /// </summary>
        public static bool ComputeIsAddOnAtCreation(
            DateTime createdAtUtc,
            DateTime? scheduledDate,
            DateOnly? targetWeek,
            bool? manualOverride)
        {
            return ComputeFromScheduleAnchor(createdAtUtc, scheduledDate, targetWeek, manualOverride);
        }

        /// <summary>
        /// SH-412: a reschedule into another week makes the WO arrive in that week at the moment
        /// of the reschedule, so Add-On compares <paramref name="rescheduledAtUtc"/> (not the
        /// creation time) with the new week's cutoff. A move within the same week keeps the
        /// current value; a cleared schedule yields false. Matches the prototype's reschedule rule.
        /// </summary>
        public static bool RecalculateIsAddOnOnReschedule(
            bool currentIsAddOn,
            DateTime? previousScheduledDate,
            DateOnly? previousTargetWeek,
            DateTime? scheduledDate,
            DateOnly? targetWeek,
            DateTime rescheduledAtUtc)
        {
            var anchor = ScheduleAnchor(scheduledDate, targetWeek);
            if (!anchor.HasValue)
                return false;

            var previousAnchor = ScheduleAnchor(previousScheduledDate, previousTargetWeek);
            if (previousAnchor.HasValue
                && WorkOrderBoardMutationRules.GetWeekStartMonday(previousAnchor.Value)
                    == WorkOrderBoardMutationRules.GetWeekStartMonday(anchor.Value))
                return currentIsAddOn;

            return NormalizeUtc(rescheduledAtUtc) > GetAddonCutoffUtc(anchor.Value);
        }

        private static DateTime? ScheduleAnchor(DateTime? scheduledDate, DateOnly? targetWeek)
        {
            if (scheduledDate.HasValue)
                return scheduledDate.Value;
            if (targetWeek.HasValue)
                return targetWeek.Value.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc);
            return null;
        }

        private static bool ComputeFromScheduleAnchor(
            DateTime createdAtUtc,
            DateTime? scheduledDate,
            DateOnly? targetWeek,
            bool? manualOverride)
        {
            var anchor = ScheduleAnchor(scheduledDate, targetWeek);
            if (!anchor.HasValue)
                return manualOverride ?? false;

            var cutoff = GetAddonCutoffUtc(anchor.Value);
            var created = NormalizeUtc(createdAtUtc);
            return created > cutoff;
        }

        private static DateTime NormalizeUtc(DateTime value)
        {
            if (value.Kind == DateTimeKind.Utc)
                return value;
            if (value.Kind == DateTimeKind.Local)
                return value.ToUniversalTime();
            return DateTime.SpecifyKind(value, DateTimeKind.Utc);
        }
    }
}