using HSchool.Content;
using HSchool.People;
using HSchool.Protocol;
using HSchool.Schedule;
using HSchool.Server.Api;
using HSchool.Server.Net;
using HSchool.Simulation;
using Microsoft.Extensions.Options;

namespace HSchool.Server.Game;

/// <summary>
/// Thin supervisor: create/delete/load schools, route commands into per-school mailboxes, expose
/// published snapshots to the menu. It never touches a <see cref="School"/> or its <c>World</c>.
/// </summary>
internal sealed class GameLoopService(
    IOptions<SimulationOptions> options,
    GameCommandQueue commands,
    ClientRegistry clients,
    GameMetrics metrics,
    SchoolStore store,
    ModContent mods,
    SwarmUiSettingsStore swarmSettings,
    ILoggerFactory loggerFactory,
    ILogger<GameLoopService> logger) : BackgroundService
{
    private readonly SimulationOptions _options = options.Value;
    private readonly SchoolNameGenerator _names = new();
    private readonly Dictionary<int, SchoolWorker> _workers = [];
    private readonly Dictionary<int, SchoolState> _incompatible = [];
    private readonly List<int> _order = [];

    private SchoolWorker[] _publishedWorkers = [];
    private SchoolState[] _publishedIncompatible = [];
    private int _currentTick;
    private int _nextId = 1;

    public uint CurrentTick => (uint)Volatile.Read(ref _currentTick);

    public SimulationOptions Options => _options;

    /// <summary>
    /// Menu requests read this instead of blocking a worker. Each card's clock is whatever that
    /// school's worker last published.
    /// </summary>
    public SchoolsState SchoolsState
    {
        get
        {
            var workers = Volatile.Read(ref _publishedWorkers);
            var broken = Volatile.Read(ref _publishedIncompatible);
            var schools = new List<SchoolState>(workers.Length + broken.Length);
            for (var i = 0; i < workers.Length; i++)
            {
                schools.Add(workers[i].Snapshot);
            }

            schools.AddRange(broken);
            schools.Sort((left, right) => left.Id.CompareTo(right.Id));

            return new SchoolsState(_options.MaxSchools, schools);
        }
    }

    /// <summary>Create-time SwarmUI copy for this living school, or null on older saves.</summary>
    public SwarmUiConfigFile? PortraitSettingsOf(int schoolId)
    {
        foreach (var worker in Volatile.Read(ref _publishedWorkers))
        {
            if (worker.Id == schoolId)
            {
                return worker.PortraitSettings;
            }
        }

        return null;
    }

    /// <summary>
    /// Menu-style read of one school's published roster and frozen catalog. Does not post to the
    /// mailbox — the list is HTTP over a snapshot, the same way the menu reads clocks.
    /// </summary>
    public PublishedSchoolPeople? FindPeople(int schoolId)
    {
        foreach (var worker in Volatile.Read(ref _publishedWorkers))
        {
            if (worker.Id == schoolId)
            {
                return new PublishedSchoolPeople(
                    worker.Snapshot,
                    worker.RosterSnapshot,
                    worker.ApplicantSnapshot,
                    worker.CatalogSnapshot,
                    worker.TimetableSnapshot,
                    worker.MapSnapshot);
            }
        }

        return null;
    }

    public SchoolState? FindSchool(int schoolId)
    {
        foreach (var worker in Volatile.Read(ref _publishedWorkers))
        {
            if (worker.Id == schoolId)
            {
                return worker.Snapshot;
            }
        }

        if (_incompatible.TryGetValue(schoolId, out var broken))
        {
            return broken;
        }

        return null;
    }

    public int CountOwnedBy(string normalizedUserName)
    {
        var count = 0;
        foreach (var school in SchoolsState.Schools)
        {
            if (SchoolOwnership.IsOwner(school, normalizedUserName))
            {
                count++;
            }
        }

        return count;
    }

    public Task ReloadFromDiskAsync(CancellationToken cancellationToken)
    {
        var completion = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        commands.Enqueue(new GameCommand.ReloadSaves(completion));
        return completion.Task.WaitAsync(cancellationToken);
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        logger.LogInformation(
            "School supervisor starting at {TickRate} Hz, up to {MaxSchoolsTotal} schools ({MaxSchools} per player), saves in {Directory}.",
            _options.TickRate,
            _options.MaxSchoolsTotal,
            _options.MaxSchools,
            store.DirectoryPath);

        await StartWorkersFromDiskAsync().ConfigureAwait(false);
        _ = HeartbeatAsync(stoppingToken);

        try
        {
            while (await commands.Reader.WaitToReadAsync(stoppingToken).ConfigureAwait(false))
            {
                while (commands.Reader.TryRead(out var command))
                {
                    await DispatchAsync(command).ConfigureAwait(false);
                }
            }
        }
        catch (OperationCanceledException)
        {
            // Normal shutdown.
        }
        finally
        {
            await StopAllWorkersAsync(persist: true).ConfigureAwait(false);
            logger.LogInformation("School supervisor stopped at tick {Tick}.", CurrentTick);
        }
    }

    private async Task HeartbeatAsync(CancellationToken cancellationToken)
    {
        using var timer = new PeriodicTimer(_options.TickInterval);

        try
        {
            while (await timer.WaitForNextTickAsync(cancellationToken).ConfigureAwait(false))
            {
                Interlocked.Increment(ref _currentTick);
            }
        }
        catch (OperationCanceledException)
        {
            // Normal shutdown.
        }
    }

    private async Task DispatchAsync(GameCommand command)
    {
        switch (command)
        {
            case GameCommand.CreateSchool create:
                await HandleCreateAsync(create).ConfigureAwait(false);
                break;

            case GameCommand.DeleteSchool delete:
                await HandleDeleteAsync(delete).ConfigureAwait(false);
                break;

            case GameCommand.SuggestName suggest:
                Complete(suggest.Result, () => SuggestName(suggest.Language));
                break;

            case GameCommand.OpenSchool open:
                HandleOpen(open);
                break;

            case GameCommand.CloseSchool close:
                StopWatching(close.PlayerId, close.SchoolId);
                Route(close.SchoolId, new WorkerCommand.Close(close.PlayerId));
                break;

            case GameCommand.SetRunning setRunning:
                HandleClockCommand(setRunning.PlayerId, setRunning.NormalizedUserName, new WorkerCommand.SetRunning(setRunning.Running));
                break;

            case GameCommand.SetSpeed setSpeed:
                HandleClockCommand(setSpeed.PlayerId, setSpeed.NormalizedUserName, new WorkerCommand.SetSpeed(setSpeed.SpeedIndex));
                break;

            case GameCommand.SkipEmpty skipEmpty:
                HandleClockCommand(skipEmpty.PlayerId, skipEmpty.NormalizedUserName, new WorkerCommand.SkipEmpty());
                break;

            case GameCommand.DismissNotice dismiss:
                HandleClockCommand(dismiss.PlayerId, dismiss.NormalizedUserName, new WorkerCommand.DismissNotice(dismiss.NoticeId));
                break;

            case GameCommand.DismissSchoolNotice dismissHttp:
                HandleDismissHttp(dismissHttp);
                break;

            case GameCommand.PostSchoolNotice postNotice:
                HandlePostNotice(postNotice);
                break;

            case GameCommand.GetNoticePortraitTarget getTarget:
                HandleGetNoticePortraitTarget(getTarget);
                break;

            case GameCommand.ReloadSaves reload:
                await HandleReloadAsync(reload).ConfigureAwait(false);
                break;

            case GameCommand.WorkerFailed failed:
                HandleWorkerFailed(failed.SchoolId);
                break;

            case GameCommand.DumpSchool dump:
                HandleDump(dump);
                break;

            case GameCommand.GetPerson getPerson:
                HandleGetPerson(getPerson);
                break;

            case GameCommand.GetPortraitBuildInput getBuild:
                HandleGetPortraitBuildInput(getBuild);
                break;

            case GameCommand.GetPersonLog getLog:
                HandleGetPersonLog(getLog);
                break;

            case GameCommand.HireStaff hire:
                HandleStaffing(
                    hire.SchoolId,
                    new WorkerCommand.HireStaff(hire.PersonId, hire.Position, hire.Result),
                    hire.Result);
                break;

            case GameCommand.AssignSubject assign:
                HandleStaffing(
                    assign.SchoolId,
                    new WorkerCommand.AssignSubject(assign.PersonId, assign.Subject, assign.Result),
                    assign.Result);
                break;

            case GameCommand.UnassignSubject unassign:
                HandleStaffing(
                    unassign.SchoolId,
                    new WorkerCommand.UnassignSubject(unassign.PersonId, unassign.Subject, unassign.Result),
                    unassign.Result);
                break;

            case GameCommand.AssignClassTeacher assignClassTeacher:
                HandleClassTeacher(
                    assignClassTeacher.SchoolId,
                    new WorkerCommand.AssignClassTeacher(
                        assignClassTeacher.ClassId,
                        assignClassTeacher.PersonId,
                        assignClassTeacher.Result),
                    assignClassTeacher.Result);
                break;

            case GameCommand.ClearClassTeacher clearClassTeacher:
                HandleClassTeacher(
                    clearClassTeacher.SchoolId,
                    new WorkerCommand.ClearClassTeacher(clearClassTeacher.ClassId, clearClassTeacher.Result),
                    clearClassTeacher.Result);
                break;

            case GameCommand.PinLesson pin:
                HandleTimetable(
                    pin.SchoolId,
                    new WorkerCommand.PinLesson(pin.ClassId, pin.Subject, pin.RoomId, pin.Day, pin.Period, pin.Result),
                    pin.Result);
                break;

            case GameCommand.UnpinLesson unpin:
                HandleTimetable(
                    unpin.SchoolId,
                    new WorkerCommand.UnpinLesson(unpin.ClassId, unpin.Subject, unpin.Day, unpin.Period, unpin.Result),
                    unpin.Result);
                break;

            case GameCommand.GetDressRules getRules:
                HandleDressRules(getRules.SchoolId, new WorkerCommand.GetDressRules(getRules.Result), getRules.Result);
                break;

            case GameCommand.SetDressRules setRules:
                HandleDressRules(
                    setRules.SchoolId,
                    new WorkerCommand.SetDressRules(setRules.PendingStudents, setRules.PendingStaff, setRules.Result),
                    setRules.Result);
                break;

            case GameCommand.GetSpeechRules getSpeech:
                HandleSpeechRules(getSpeech.SchoolId, new WorkerCommand.GetSpeechRules(getSpeech.Result), getSpeech.Result);
                break;

            case GameCommand.SetSpeechRules setSpeech:
                HandleSpeechRules(
                    setSpeech.SchoolId,
                    new WorkerCommand.SetSpeechRules(setSpeech.PendingStudents, setSpeech.PendingStaff, setSpeech.Result),
                    setSpeech.Result);
                break;
        }
    }

    private void HandleDump(GameCommand.DumpSchool command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.Dump(command.Result)))
        {
            command.Result.TrySetResult(null);
        }
    }

    private void HandleGetPerson(GameCommand.GetPerson command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.GetPerson(command.PersonId, command.Locale, command.Result)))
        {
            command.Result.TrySetResult(new PersonCardResult(null, PersonLookupError.UnknownSchool));
        }
    }

    private void HandleGetPortraitBuildInput(GameCommand.GetPortraitBuildInput command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.GetPortraitBuildInput(command.PersonId, command.Locale, command.Result)))
        {
            command.Result.TrySetResult(
                new PortraitBuildInputResult(null, PortraitScene.Empty, PersonLookupError.UnknownSchool));
        }
    }

    private void HandleGetPersonLog(GameCommand.GetPersonLog command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.GetPersonLog(command.PersonId, command.Locale, command.Query, command.Result)))
        {
            command.Result.TrySetResult(new PersonLogResult(null, PersonLookupError.UnknownSchool));
        }
    }

    private void HandleDressRules(int schoolId, WorkerCommand command, TaskCompletionSource<DressRulesOutcome> result)
    {
        if (!_workers.TryGetValue(schoolId, out var worker) || !worker.Post(command))
        {
            result.TrySetResult(DressRulesOutcome.Fail(DressRulesError.UnknownSchool));
        }
    }

    private void HandleSpeechRules(int schoolId, WorkerCommand command, TaskCompletionSource<SpeechRulesOutcome> result)
    {
        if (!_workers.TryGetValue(schoolId, out var worker) || !worker.Post(command))
        {
            result.TrySetResult(SpeechRulesOutcome.Fail(SpeechRulesError.UnknownSchool));
        }
    }

    private void HandleStaffing(int schoolId, WorkerCommand command, TaskCompletionSource<StaffingOutcome> result)
    {
        if (!_workers.TryGetValue(schoolId, out var worker) || !worker.Post(command))
        {
            result.TrySetResult(Staffing.UnknownSchool());
        }
    }

    private void HandleClassTeacher(int schoolId, WorkerCommand command, TaskCompletionSource<ClassTeacherOutcome> result)
    {
        if (!_workers.TryGetValue(schoolId, out var worker) || !worker.Post(command))
        {
            result.TrySetResult(ClassTeachers.UnknownSchool());
        }
    }

    private void HandleTimetable(int schoolId, WorkerCommand command, TaskCompletionSource<TimetableOutcome> result)
    {
        if (!_workers.TryGetValue(schoolId, out var worker) || !worker.Post(command))
        {
            result.TrySetResult(TimetableOutcome.Fail(TimetableError.UnknownSchool));
        }
    }

    /// <summary>
    /// A school's thread died. Keep a menu card so the player can delete the file instead of
    /// opening a school that no longer ticks.
    /// </summary>
    private void HandleWorkerFailed(int schoolId)
    {
        if (!_workers.TryGetValue(schoolId, out var worker))
        {
            return;
        }

        RememberIncompatible(worker.Snapshot with { Incompatible = true, Running = false });
        Untrack(schoolId);

        foreach (var client in clients.All)
        {
            if (client.OpenSchoolId == schoolId)
            {
                client.OpenSchoolId = null;
                SendSchoolGone(client, schoolId);
            }
        }

        logger.LogError("School {SchoolId} stopped after a worker failure; its save file is unchanged.", schoolId);
    }

    private async Task HandleCreateAsync(GameCommand.CreateSchool command)
    {
        try
        {
            if (_workers.Count >= _options.MaxSchoolsTotal)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.ServerFull));
                return;
            }

            if (CountOwnedBy(command.Owner) >= _options.MaxSchools)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.LimitReached));
                return;
            }

            if (!SchoolNames.TryNormalize(command.Name, out var normalized))
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidName));
                return;
            }

            if (!GameClock.IsValidStartDate(command.StartDate))
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidStartDate));
                return;
            }

            var extras = command.ExtraModIds ?? [];
            foreach (var packId in extras)
            {
                if (!ModContent.IsSafePackId(packId) || !mods.PackExists(packId))
                {
                    command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.UnknownMod));
                    return;
                }
            }

            IReadOnlyList<string> packIds;
            try
            {
                packIds = mods.ResolveSelectedPacks(extras);
            }
            catch (PackDependencyException ex) when (ex.Code == PackDependencyException.MissingCode)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(
                    null,
                    SchoolCreationError.MissingMod,
                    ex.MissingPackId));
                return;
            }
            catch (PackDependencyException)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.ModCycle));
                return;
            }
            catch (ContentLoadException)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));
                return;
            }

            if (!mods.PackExists(CatalogLoader.CorePackId))
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));
                return;
            }

            DefCatalog catalog;
            try
            {
                catalog = mods.LoadCatalog(packIds);
            }
            catch (Exception ex) when (ex is ContentLoadException or SchoolContentUnavailableException)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));
                return;
            }

            var countryId = ResolveCountryId(catalog, command.CountryId);
            if (countryId is null || !catalog.Countries.TryGetValue(countryId, out var country) || country.Abstract)
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.UnknownCountry));
                return;
            }

            if (!string.IsNullOrWhiteSpace(command.NativeLanguage) && !NativeLanguages.Allows(country.Names, command.NativeLanguage))
            {
                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.UnknownNativeLanguage));
                return;
            }

            var id = _nextId++;
            store.WriteNextId(_nextId);
            var seed = command.Seed ?? Random.Shared.Next();
            var nativeLanguage = NativeLanguages.Pick(country.Names, seed, command.NativeLanguage, rollIfOmitted: true);
            var climatePresetId = CountryClimate.Pick(country, seed, rollIfOmitted: true);

            var portrait = SwarmUiConfigFile.Clone(command.PortraitSettings ?? swarmSettings.Current);
            var worker = SpawnWorker(
                id,
                normalized,
                command.StartDate,
                running: true,
                ClockSpeed.DefaultIndex,
                isNew: true,
                packIds,
                command.Map,
                countryId,
                climatePresetId,
                nativeLanguage,
                seed,
                owner: command.Owner,
                portraitSettings: portrait);
            Track(worker);
            worker.Start();

            try
            {
                await worker.Started.ConfigureAwait(false);
            }
            catch (SchoolContentUnavailableException ex)
            {
                Untrack(id);
                await worker.StopAsync(persist: false).ConfigureAwait(false);
                command.Result.TrySetResult(new SchoolCreationOutcome(null, ContentError(ex)));
                return;
            }
            catch
            {
                Untrack(id);
                await worker.StopAsync(persist: false).ConfigureAwait(false);
                throw;
            }

            logger.LogInformation("School {SchoolId} \"{Name}\" created with seed {Seed}.", id, normalized, seed);
            command.Result.TrySetResult(new SchoolCreationOutcome(worker.Snapshot, SchoolCreationError.None));
        }
        catch (Exception ex)
        {
            command.Result.TrySetException(ex);
        }
    }

    private async Task HandleDeleteAsync(GameCommand.DeleteSchool command)
    {
        try
        {
            if (!_workers.TryGetValue(command.SchoolId, out var worker))
            {
                if (_incompatible.Remove(command.SchoolId))
                {
                    store.Delete(command.SchoolId);
                    PublishWorkers();
                    logger.LogInformation("Incompatible school {SchoolId} deleted.", command.SchoolId);
                    command.Result.TrySetResult(true);
                    return;
                }

                command.Result.TrySetResult(false);
                return;
            }

            Untrack(command.SchoolId);

            foreach (var client in clients.All)
            {
                if (client.OpenSchoolId == command.SchoolId)
                {
                    client.OpenSchoolId = null;
                    SendSchoolGone(client, command.SchoolId);
                }
            }

            await worker.StopAsync(persist: false).ConfigureAwait(false);
            store.Delete(command.SchoolId);

            logger.LogInformation("School {SchoolId} deleted.", command.SchoolId);
            command.Result.TrySetResult(true);
        }
        catch (Exception ex)
        {
            command.Result.TrySetException(ex);
        }
    }

    private async Task HandleReloadAsync(GameCommand.ReloadSaves command)
    {
        try
        {
            await StopAllWorkersAsync(persist: true).ConfigureAwait(false);
            await StartWorkersFromDiskAsync().ConfigureAwait(false);
            command.Result.TrySetResult();
        }
        catch (Exception ex)
        {
            command.Result.TrySetException(ex);
        }
    }

    private void HandleOpen(GameCommand.OpenSchool command)
    {
        var client = clients.Find(command.PlayerId);
        if (client is null)
        {
            return;
        }

        if (!_workers.TryGetValue(command.SchoolId, out var worker))
        {
            SendSchoolGone(client, command.SchoolId);
            return;
        }

        client.OpenSchoolId = command.SchoolId;
        worker.Post(new WorkerCommand.Open(client));
        logger.LogInformation("Client {PlayerId} opened school {SchoolId}.", command.PlayerId, command.SchoolId);
    }

    /// <summary>
    /// The connection stops receiving clock frames for that school. The calendar keeps running —
    /// schools live whether or not somebody is looking at them.
    /// </summary>
    private void StopWatching(uint playerId, int schoolId)
    {
        var client = clients.Find(playerId);
        if (client?.OpenSchoolId == schoolId)
        {
            client.OpenSchoolId = null;
        }
    }

    private string SuggestName(SchoolNameLanguage language)
    {
        var taken = SchoolsState.Schools.Select(school => school.Name);
        return _names.Next(taken, language);
    }

    private void Route(int schoolId, WorkerCommand command)
    {
        if (_workers.TryGetValue(schoolId, out var worker))
        {
            worker.Post(command);
        }
    }

    private void HandleClockCommand(uint playerId, string normalizedUserName, WorkerCommand command)
    {
        var client = clients.Find(playerId);
        if (client?.OpenSchoolId is not { } schoolId)
        {
            return;
        }

        if (!_workers.TryGetValue(schoolId, out var worker)
            || !SchoolOwnership.CanManage(worker.Snapshot, normalizedUserName))
        {
            return;
        }

        Route(schoolId, command);
    }

    private void HandleDismissHttp(GameCommand.DismissSchoolNotice command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.DismissNoticeHttp(command.NoticeId, command.Result)))
        {
            command.Result.TrySetResult();
        }
    }

    private void HandlePostNotice(GameCommand.PostSchoolNotice command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.PostNotice(command.DefName, command.PersonKey, command.Kind, command.Result)))
        {
            command.Result.TrySetResult(null);
        }
    }

    private void HandleGetNoticePortraitTarget(GameCommand.GetNoticePortraitTarget command)
    {
        if (!_workers.TryGetValue(command.SchoolId, out var worker)
            || !worker.Post(new WorkerCommand.GetNoticePortraitTarget(command.NoticeId, command.Result)))
        {
            command.Result.TrySetResult(NoticePortraitTarget.UnknownSchool);
        }
    }

    private async Task StartWorkersFromDiskAsync()
    {
        var saves = store.LoadAll();
        var nextId = Math.Max(store.ReadNextId(), 1);
        if (saves.Count > 0)
        {
            nextId = Math.Max(nextId, saves.Max(save => save.Id) + 1);
        }

        _nextId = nextId;

        var startable = new List<SchoolSave>();
        foreach (var save in saves)
        {
            if (SchoolStore.CanStart(save))
            {
                startable.Add(save);
            }
            else
            {
                RememberIncompatible(FromSave(save));
            }
        }

        if (startable.Count > _options.MaxSchoolsTotal)
        {
            logger.LogWarning(
                "Found {Count} runnable school saves but the limit is {Max}; starting the first {Max}.",
                startable.Count,
                _options.MaxSchoolsTotal,
                _options.MaxSchoolsTotal);
            foreach (var extra in startable.Skip(_options.MaxSchoolsTotal))
            {
                RememberIncompatible(FromSave(extra));
            }

            startable = [.. startable.Take(_options.MaxSchoolsTotal)];
        }

        foreach (var save in startable)
        {
            var worker = SpawnWorker(
                save.Id,
                save.Name,
                save.GameTime,
                save.Running,
                save.SpeedIndex,
                isNew: false,
                save.ModIds,
                save.Map,
                save.CountryId,
                save.ClimatePresetId,
                save.NativeLanguage,
                createSeed: null,
                save.Presence,
                save.DressRules,
                save.SpeechRules,
                save.Owner,
                save.PortraitSettings is null ? null : SwarmUiConfigFile.Clone(save.PortraitSettings),
                save.Notices);
            worker.Start();

            try
            {
                await worker.Started.ConfigureAwait(false);
                Track(worker);
            }
            catch (Exception ex)
            {
                logger.LogWarning(
                    ex,
                    "School {SchoolId} \"{Name}\" was not started; the save file is unchanged.",
                    save.Id,
                    save.Name);
                await worker.StopAsync(persist: false).ConfigureAwait(false);
                RememberIncompatible(FromSave(save));
            }
        }

        PublishWorkers();

        if (_workers.Count > 0)
        {
            logger.LogInformation("Restored {Count} school(s) from disk.", _workers.Count);
        }
    }

    private async Task StopAllWorkersAsync(bool persist)
    {
        var stopping = _workers.Values.Select(worker => worker.StopAsync(persist)).ToArray();
        _workers.Clear();
        _order.Clear();
        _incompatible.Clear();
        PublishWorkers();

        if (stopping.Length > 0)
        {
            await Task.WhenAll(stopping).ConfigureAwait(false);
        }
    }

    private SchoolWorker SpawnWorker(
        int id,
        string name,
        DateTime time,
        bool running,
        int speedIndex,
        bool isNew,
        IReadOnlyList<string>? modIds,
        MapLayout? map,
        string? countryId,
        string? climatePresetId,
        string? nativeLanguage,
        int? createSeed = null,
        IReadOnlyList<PresenceSnapshot>? presence = null,
        SchoolDressRules? dressRules = null,
        SchoolSpeechRules? speechRules = null,
        string? owner = null,
        SwarmUiConfigFile? portraitSettings = null,
        IReadOnlyList<StickyNoticeSave>? notices = null) =>
        new(
            id,
            name,
            time,
            running,
            speedIndex,
            isNew,
            modIds,
            map,
            countryId,
            climatePresetId,
            nativeLanguage,
            createSeed,
            presence,
            dressRules,
            speechRules,
            owner,
            portraitSettings,
            notices,
            _options,
            clients,
            metrics,
            store,
            mods,
            onFailed: schoolId => commands.Enqueue(new GameCommand.WorkerFailed(schoolId)),
            loggerFactory.CreateLogger($"HSchool.Server.Game.SchoolWorker.{id}"));

    /// <summary>
    /// Empty request uses the first placeable country (core's Russia). A named id must exist in
    /// the catalog already loaded for this pack list — unknown extras were rejected above.
    /// </summary>
    internal static string? ResolveCountryId(DefCatalog catalog, string? requested)
    {
        var available = catalog.Countries.Values
            .Where(def => !def.Abstract)
            .Select(def => def.DefName)
            .OrderBy(name => name, StringComparer.Ordinal)
            .ToArray();
        if (available.Length == 0)
        {
            return null;
        }

        if (string.IsNullOrWhiteSpace(requested))
        {
            return available[0];
        }

        return available.Contains(requested, StringComparer.Ordinal) ? requested : null;
    }

    private void Track(SchoolWorker worker)
    {
        _workers[worker.Id] = worker;
        _order.Add(worker.Id);
        PublishWorkers();
    }

    private void Untrack(int id)
    {
        _workers.Remove(id);
        _order.Remove(id);
        PublishWorkers();
    }

    private void PublishWorkers()
    {
        var snapshot = new SchoolWorker[_order.Count];
        for (var i = 0; i < _order.Count; i++)
        {
            snapshot[i] = _workers[_order[i]];
        }

        Volatile.Write(ref _publishedWorkers, snapshot);
        metrics.SchoolsChanged(snapshot.Length);
        Volatile.Write(
            ref _publishedIncompatible,
            [.. _incompatible.Values.OrderBy(school => school.Id)]);
    }

    private void RememberIncompatible(SchoolState school)
    {
        _incompatible[school.Id] = school with { Incompatible = true, Running = false };
    }

    private SchoolState FromSave(SchoolSave save) =>
        new(
            save.Id,
            save.Name,
            save.GameTime,
            Running: false,
            (byte)Math.Clamp(save.SpeedIndex, 0, 255),
            save.ModIds ?? [],
            SeedOf(save.Id),
            Owner: string.IsNullOrWhiteSpace(save.Owner) ? null : save.Owner,
            Incompatible: true);

    private int SeedOf(int schoolId)
    {
        try
        {
            return store.TryReadPeople(schoolId)?.Seed ?? 0;
        }
        catch (Exception)
        {
            return 0;
        }
    }

    private static void SendSchoolGone(GameClient client, int schoolId)
    {
        var frame = new byte[ProtocolCodec.MaxFrameSize];
        var length = ProtocolCodec.WriteSchoolGone(frame, new ServerSchoolGoneMessage(schoolId));
        client.TrySend(frame.AsMemory(0, length));
    }

    private static SchoolCreationError ContentError(SchoolContentUnavailableException ex) =>
        ex.InnerException switch
        {
            MapValidationException => SchoolCreationError.InvalidMap,
            ContentLoadException => SchoolCreationError.InvalidCatalog,
            _ => SchoolCreationError.InvalidCatalog,
        };

    /// <summary>Runs work for a waiting request thread without letting an exception kill the supervisor.</summary>
    private static void Complete<T>(TaskCompletionSource<T> completion, Func<T> work)
    {
        try
        {
            completion.TrySetResult(work());
        }
        catch (Exception ex)
        {
            completion.TrySetException(ex);
        }
    }
}

internal sealed record PublishedSchoolPeople(
    SchoolState School,
    Roster? Roster,
    ApplicantPool? Applicants,
    DefCatalog? Catalog,
    Timetable? Timetable,
    MapLayout? Map);