namespace MeetingAssistant.MeetingNotes;

internal static class OutlookMeetingCandidateSelector
{
    private static readonly TimeSpan MinimumRemainingOverlap = TimeSpan.FromMinutes(5);
    private static readonly TimeSpan UpcomingStartWindow = TimeSpan.FromMinutes(5);

    public static T? Select<T>(
        IReadOnlyList<T> candidates,
        DateTime startedAt,
        Func<T, DateTime> getStart,
        Func<T, DateTime> getEnd)
        where T : class
    {
        var goodOverlaps = candidates
            .Where(candidate =>
                getStart(candidate) <= startedAt &&
                getEnd(candidate) >= startedAt.Add(MinimumRemainingOverlap))
            .ToList();
        if (goodOverlaps.Count == 1)
        {
            return goodOverlaps[0];
        }

        if (goodOverlaps.Count > 1)
        {
            return null;
        }

        var upcoming = candidates
            .Where(candidate =>
                getStart(candidate) > startedAt &&
                getStart(candidate) <= startedAt.Add(UpcomingStartWindow))
            .OrderBy(getStart)
            .ToList();
        return upcoming.Count == 1 ? upcoming[0] : null;
    }
}