using HSchool.Content;
using HSchool.People;
using HSchool.Protocol;
using HSchool.Schedule;
using HSchool.Simulation;

namespace HSchool.Server.Game;

/// <summary>
/// Builds a presence frame from stored places plus the current lesson. Occupancy is state;
/// the lesson labels are still derived from the timetable so an empty classroom during a period
/// still shows what should be happening there.
/// </summary>
internal static class PresenceFrame
{
    public static ServerPresenceMessage Build(School school, int weekDays, string locale)
    {
        var people = new List<PresencePerson>();
        var counts = new Dictionary<string, int>(StringComparer.Ordinal);
        foreach (var row in school.CapturePresence())
        {
            if (row.NodeId is null)
            {
                continue;
            }

            var walking = row.Path.Count > 0 || row.RemainingMinutes > 0;
            var circle = school.TalkCircleOf(row.PersonId);
            var summonPhase = school.DirectorSummonPresencePhase(row.PersonId);
            people.Add(new PresencePerson(
                row.PersonId,
                row.NodeId,
                walking ? PresenceState.Walking : PresenceState.Here,
                circle?.MemberIds ?? [],
                circle?.TopicId ?? "",
                summonPhase));
            counts[row.NodeId] = counts.GetValueOrDefault(row.NodeId) + 1;
        }

        people.Sort((left, right) => StringComparer.Ordinal.Compare(left.Id, right.Id));

        var activity = ActivityByRoom(school, weekDays, locale);
        var nodeIds = counts.Keys
            .Concat(activity.Keys)
            .Distinct(StringComparer.Ordinal)
            .OrderBy(id => id, StringComparer.Ordinal);

        var nodes = new List<PresenceNode>();
        foreach (var id in nodeIds)
        {
            var count = (ushort)Math.Min(counts.GetValueOrDefault(id), ushort.MaxValue);
            var subject = "";
            var classLabel = "";
            if (activity.TryGetValue(id, out var labels))
            {
                subject = labels.Subject;
                classLabel = labels.Class;
            }

            nodes.Add(new PresenceNode(id, count, subject, classLabel));
        }

        return new ServerPresenceMessage(school.Id, nodes, people);
    }

    private static Dictionary<string, (string Subject, string Class)> ActivityByRoom(
        School school,
        int weekDays,
        string locale)
    {
        var labels = new Dictionary<string, (string Subject, string Class)>(StringComparer.Ordinal);
        if (school.Timetable is null || school.Roster is null || school.Catalog is null)
        {
            return labels;
        }

        var occurring = TimetableClock.OccurringAt(
            school.Timetable,
            school.Catalog,
            school.Clock.Time,
            weekDays);
        if (occurring.Count == 0)
        {
            return labels;
        }

        var catalog = school.Catalog;
        var classes = school.Roster.Classes.ToDictionary(item => item.Id, StringComparer.Ordinal);
        foreach (var lesson in occurring)
        {
            classes.TryGetValue(lesson.ClassId, out var schoolClass);
            var subjectLabel = catalog.Subjects.TryGetValue(lesson.Subject, out var subject)
                ? catalog.Label(locale, subject)
                : lesson.Subject;
            var classLabel = schoolClass is null
                ? lesson.ClassId
                : $"{schoolClass.Year}{schoolClass.Letter}";
            labels[lesson.RoomId] = (subjectLabel, classLabel);
        }

        return labels;
    }
}