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

namespace HSchool.Server.Game;

/// <summary>
/// Overlays the current lesson onto map-tree nodes. Occupancy is derived from the timetable and
/// the clock; it is not stored on the map.
/// </summary>
internal static class MapOccupancy
{
    public static void Apply(
        MapSnapshotNode[] nodes,
        School school,
        int weekDays,
        string locale)
    {
        if (school.Timetable is null || school.Roster is null || school.Catalog is null)
        {
            return;
        }

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

        var catalog = school.Catalog;
        var classes = school.Roster.Classes.ToDictionary(item => item.Id, StringComparer.Ordinal);
        var people = school.Roster.People.ToDictionary(person => person.Id, StringComparer.Ordinal);
        var byRoom = occurring.ToDictionary(lesson => lesson.RoomId, StringComparer.Ordinal);

        for (var i = 0; i < nodes.Length; i++)
        {
            if (!byRoom.TryGetValue(nodes[i].Id, out var lesson))
            {
                continue;
            }

            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}";

            nodes[i] = nodes[i] with
            {
                ActivitySubject = subjectLabel,
                ActivityClass = classLabel,
                Characters = NamesOf(lesson, schoolClass, people),
            };
        }
    }

    private static string[] NamesOf(
        LessonPlacement lesson,
        SchoolClass? schoolClass,
        IReadOnlyDictionary<string, Person> people)
    {
        var names = new List<string>();
        if (people.TryGetValue(lesson.TeacherId, out var teacher))
        {
            names.Add(teacher.Name.Full);
        }
        else if (lesson.TeacherId.Length > 0)
        {
            names.Add(lesson.TeacherId);
        }

        if (schoolClass is not null)
        {
            foreach (var pupilId in schoolClass.PupilIds)
            {
                if (people.TryGetValue(pupilId, out var pupil))
                {
                    names.Add(pupil.Name.Full);
                }
            }
        }

        return names.Count > byte.MaxValue ? [.. names.Take(byte.MaxValue)] : [.. names];
    }
}