using LehrerApp.Core.Models;
using LehrerApp.Core.Services;
using LehrerApp.Desktop.Services;
using LehrerApp.Desktop.ViewModels.Planning;
using LehrerApp.Desktop.ViewModels.Settings;
using Xunit;

namespace LehrerApp.Desktop.Tests;

public sealed class TimetableViewModelTests
{
    private static TimetableViewModel BuildViewModel(
        FakeTimetableSlots slots, FakeGroups groups, FakeSchoolHolidays? holidays = null,
        FakeSubjects? subjects = null, FakeLessons? lessons = null, FakeExams? exams = null,
        SchoolCalendarSettingsService? calendarSettings = null,
        FakeSupervisionDuties? supervisionDuties = null, FakeSubstitutionEntries? substitutions = null,
        FakeUntisSlotMappings? untisMappings = null, WebUntisSettingsService? untisSettings = null,
        PeriodScheduleService? periodSchedule = null)
    {
        // Bewusst kein "using": SchoolCalendarSettingsService/PeriodScheduleService lesen den Pfad
        // nur bei Bedarf, das Verzeichnis muss über die Lebensdauer des ViewModels bestehen bleiben.
        var tempPath = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-timetablevm-tests-{Guid.NewGuid():N}");
        Directory.CreateDirectory(tempPath);
        return new TimetableViewModel(
            slots, groups, subjects ?? new FakeSubjects([]),
            lessons ?? new FakeLessons(), exams ?? new FakeExams([]),
            holidays ?? new FakeSchoolHolidays(),
            calendarSettings ?? new SchoolCalendarSettingsService(tempPath),
            new PublicHolidayService(), new SchoolYearService(),
            supervisionDuties ?? new FakeSupervisionDuties(), substitutions ?? new FakeSubstitutionEntries(),
            untisMappings ?? new FakeUntisSlotMappings(), untisSettings ?? TestSupport.BuildWebUntisSettingsService(),
            periodSchedule ?? new PeriodScheduleService(tempPath));
    }

    /// Nächstes Datum ab (inkl.) <paramref name="from"/>, das auf einen Wochentag Mo-Fr fällt —
    /// nur diese Tage haben eine Spalte im Raster. Für Badge-Tests reicht ein beliebiger
    /// Mo-Fr-Wochentag: die Badges hängen nur am Wochentag (nicht am konkreten Kalenderdatum),
    /// da `TimetableSlot` ein wiederkehrendes Muster ohne Datum ist.
    private static DateOnly NextGridWeekday(DateOnly from)
    {
        var d = from;
        while (d.DayOfWeek is DayOfWeek.Saturday or DayOfWeek.Sunday) d = d.AddDays(1);
        return d;
    }

    /// Datum des angegebenen Wochentags in der laufenden Kalenderwoche — exakt wie
    /// `TimetableViewModel.BuildWeekOverview` es berechnet, für Tests der Wochenkachel-Inhalte
    /// (Thema, Klausur am Tag), die anders als die Badges an ein konkretes Datum gebunden sind.
    private static DateOnly DateInCurrentWeek(DayOfWeek weekday)
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var monday = today.AddDays(-((int)today.DayOfWeek + 6) % 7);
        return monday.AddDays((int)weekday - (int)DayOfWeek.Monday);
    }

    [Fact]
    public void Load_BautEineZelleProWochentagUndStundePlusKopfzeilen()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));

        // 1 Ecke + 5 Wochentage + 10 Stunden × (1 Label + 5 Zellen)
        Assert.Equal(6 + 10 * 6, vm.Cells.Count);
        Assert.Equal(6 + 10 * 6, vm.WeekItems.Count);
    }

    [Fact]
    public void Load_ZeigtZugewieseneGruppeInDerPassendenZelle()
    {
        var weekday = NextGridWeekday(DateOnly.FromDateTime(DateTime.Today));
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday.DayOfWeek, PeriodNumber = 1, Room = "R204" });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var cell = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == weekday.DayOfWeek && c.PeriodNumber == 1);

        Assert.True(cell.IsAssigned);
        Assert.Equal("Q1 Chemie · R204", cell.Text);
    }

    [Fact]
    public void HoursWarnings_WeichtDieZugewieseneStundenzahlAb_ZeigtWarnung()
    {
        var group = new LearningGroup { Name = "Q1 Chemie", SchoolYear = new SchoolYearService().CurrentSchoolYear(), HoursPerWeek = 3 };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        Assert.Single(vm.HoursWarnings);
        Assert.Contains("1 von 3", vm.HoursWarnings[0].Text);
    }

    [Fact]
    public void HoursWarnings_PassendeStundenzahl_KeineWarnung()
    {
        var group = new LearningGroup { Name = "Q1 Chemie", SchoolYear = new SchoolYearService().CurrentSchoolYear(), HoursPerWeek = 1 };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        Assert.Empty(vm.HoursWarnings);
    }

    // ── "Heute"-Ansicht: Tagesliste (Nutzer-Feedback: nicht-editierende Standardansicht) ────

    [Fact]
    public void Load_ZeigtHeutigeStundeMitGruppeUndRaum()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 3, Room = "R204" });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var item = Assert.Single(vm.TodayItems);
        Assert.Equal("Q1 Chemie", item.GroupName);
        Assert.Equal("R204", item.Room);
        Assert.Equal(3, item.PeriodNumber);
    }

    [Fact]
    public void Load_HeutigeStundeMitLektionUndKlausur_ZeigtBeides()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = today, Topic = "Redoxreaktionen" });
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = today, Title = "Klausur Nr. 2" }]);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons, exams: exams);

        var item = Assert.Single(vm.TodayItems);
        Assert.Equal("Redoxreaktionen", item.LessonTopic);
        Assert.Equal("Klausur Nr. 2", item.ExamTitle);
        Assert.True(item.HasExam);
    }

    [Fact]
    public void Load_HeutigeStunde_VorherigeUnkontrollierteHausaufgabe_ZeigtBadge()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = today.AddDays(-3), Homework = "S. 42, Aufgabe 3" });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var item = Assert.Single(vm.TodayItems);
        Assert.True(item.HasUnhandledHomework);
    }

    [Fact]
    public void Load_HeutigeStunde_HausaufgabeKontrolliert_KeinBadge()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson
        {
            GroupId = group.Id, Date = today.AddDays(-3), Homework = "S. 42, Aufgabe 3", HomeworkChecked = true,
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var item = Assert.Single(vm.TodayItems);
        Assert.False(item.HasUnhandledHomework);
    }

    [Fact]
    public void Load_HeutigeStunde_HausaufgabenKontrolleBewusstAbgeschaltet_KeinBadge()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson
        {
            GroupId = group.Id, Date = today.AddDays(-3), Homework = "S. 42, Aufgabe 3",
            HomeworkCheckDismissed = true,
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var item = Assert.Single(vm.TodayItems);
        Assert.False(item.HasUnhandledHomework);
    }

    [Fact]
    public void Load_HeutigeStunde_VorherigeStundeOhneHausaufgabe_KeinBadge()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = today.AddDays(-3) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var item = Assert.Single(vm.TodayItems);
        Assert.False(item.HasUnhandledHomework);
    }

    [Fact]
    public void Load_Wochenkachel_VorherigeUnkontrollierteHausaufgabe_ZeigtBadge()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Wednesday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Wednesday, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = date.AddDays(-2), Homework = "Vokabeln lernen" });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Wednesday && c.PeriodNumber == 1);
        Assert.True(cell.HasUnhandledHomework);
    }

    [Fact]
    public void OpenGroup_RuftOnNavigateToGroupMitDerGroupIdAuf()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));
        Guid? navigatedTo = null;
        vm.OnNavigateToGroup = id => navigatedTo = id;

        vm.OpenGroupCommand.Execute(vm.TodayItems[0].GroupId);

        Assert.Equal(group.Id, navigatedTo);
    }

    // ── Direktsprung in den Verlaufsplan-Viewer (4.5.2) ──────────────────────────

    [Fact]
    public async Task OpenTodayLesson_MitVorhandenerLesson_OeffnetDenViewerStattZurGruppeZuNavigieren()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 1, Topic = "Redox" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);
        Lesson? openedLesson = null;
        Guid? navigatedTo = null;
        vm.OnOpenLessonViewer = l => { openedLesson = l; return Task.CompletedTask; };
        vm.OnNavigateToGroup = id => navigatedTo = id;

        await vm.OpenTodayLessonCommand.ExecuteAsync(vm.TodayItems[0]);

        Assert.Equal(lesson.Id, openedLesson?.Id);
        Assert.Null(navigatedTo);
        Assert.Equal("Verlaufsplan ansehen", vm.TodayItems[0].OpenButtonLabel);
    }

    [Fact]
    public async Task OpenTodayLesson_OhneVorhandeneLesson_NavigiertWieBisherZurGruppe()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));
        Guid? navigatedTo = null;
        var viewerOpened = false;
        vm.OnOpenLessonViewer = _ => { viewerOpened = true; return Task.CompletedTask; };
        vm.OnNavigateToGroup = id => navigatedTo = id;

        await vm.OpenTodayLessonCommand.ExecuteAsync(vm.TodayItems[0]);

        Assert.Equal(group.Id, navigatedTo);
        Assert.False(viewerOpened);
        Assert.Equal("Stunde anlegen", vm.TodayItems[0].OpenButtonLabel);
    }

    [Fact]
    public async Task OpenTodayLesson_OhneLesson_StartetDirektanlageMitExaktemTermin()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 4 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));
        TimetableLessonRequest? requested = null;
        vm.OnCreateLesson = request => { requested = request; return Task.CompletedTask; };

        await vm.OpenTodayLessonCommand.ExecuteAsync(vm.TodayItems[0]);

        Assert.Equal(new TimetableLessonRequest(group.Id, today, 4), requested);
    }

    // ── Unterrichtsmodus (14.x) ────────────────────────────────────────────────

    [Fact]
    public async Task StartTeachingMode_MitVorhandenerLesson_OeffnetDenUnterrichtsmodus()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 1, Topic = "Redox" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);
        Lesson? openedLesson = null;
        vm.OnOpenTeachingMode = l => { openedLesson = l; return Task.CompletedTask; };

        await vm.StartTeachingModeCommand.ExecuteAsync(vm.TodayItems[0]);

        Assert.Equal(lesson.Id, openedLesson?.Id);
    }

    [Fact]
    public async Task StartTeachingMode_OhneVorhandeneLesson_TutNichts()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));
        var opened = false;
        vm.OnOpenTeachingMode = _ => { opened = true; return Task.CompletedTask; };

        await vm.StartTeachingModeCommand.ExecuteAsync(vm.TodayItems[0]);

        Assert.False(opened);
        Assert.False(vm.TodayItems[0].HasLesson);
    }

    [Fact]
    public async Task OpenWeekCell_MitVorhandenerLesson_OeffnetDenViewer()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var lesson = new Lesson { GroupId = group.Id, Date = date, LessonNumber = 1, Topic = "Redox" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);
        Lesson? openedLesson = null;
        vm.OnOpenLessonViewer = l => { openedLesson = l; return Task.CompletedTask; };

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        await vm.OpenWeekCellCommand.ExecuteAsync(cell);

        Assert.Equal(lesson.Id, openedLesson?.Id);
    }

    /// Nutzer-Feedback (zweite Runde): der Direktklick auf eine Wochenraster-Kachel soll
    /// "einheitlicher" springen — bei einer Lesson HEUTE, während gerade Unterrichtszeit ist,
    /// direkt in den Unterrichtsmodus statt in den (schreibgeschützten) Planungsviewer.
    [Fact]
    public async Task OpenWeekCell_LessonHeuteWaehrendUnterrichtszeit_OeffnetUnterrichtsmodus()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        // Bewusst nicht der reale DateTime.Today-Wochentag: an einem Sa/So gäbe es dafür keine
        // Kachel im Mo-Fr-Raster. Stattdessen ein beliebiger Wochentag der laufenden Kalenderwoche
        // (Kachel existiert immer), dessen Datum per VM.Clock als "heute" simuliert wird (siehe
        // TimetableViewModel.Clock - genau für solche Tests eingeführt).
        var weekday = DayOfWeek.Monday;
        var lessonDate = DateInCurrentWeek(weekday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday, PeriodNumber = 1 });
        var lesson = new Lesson { GroupId = group.Id, Date = lessonDate, LessonNumber = 1, Topic = "Redox" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);
        var periodSchedule = BuildPeriodSchedule(1);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons, periodSchedule: periodSchedule);
        // Gleiche Uhrzeit wie BuildPeriodSchedule (reales DateTime.Now), aber am simulierten
        // "heutigen" Datum - die Stundenzeit-Prüfung (Uhrzeit) bleibt so unabhängig vom Datum.
        vm.Clock = () => lessonDate.ToDateTime(TimeOnly.FromDateTime(DateTime.Now));
        Lesson? teachingModeLesson = null;
        Lesson? viewerLesson = null;
        vm.OnOpenTeachingMode = l => { teachingModeLesson = l; return Task.CompletedTask; };
        vm.OnOpenLessonViewer = l => { viewerLesson = l; return Task.CompletedTask; };

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == weekday && c.PeriodNumber == 1);
        await vm.OpenWeekCellCommand.ExecuteAsync(cell);

        Assert.Equal(lesson.Id, teachingModeLesson?.Id);
        Assert.Null(viewerLesson);
    }

    /// Dieselbe Stundenzeit passt, die Lesson liegt aber nicht heute — bleibt beim Viewer.
    [Fact]
    public async Task OpenWeekCell_LessonNichtHeuteTrotzPassenderUhrzeit_OeffnetViewer()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var otherWeekday = today.DayOfWeek == DayOfWeek.Monday ? DayOfWeek.Tuesday : DayOfWeek.Monday;
        var otherDate = DateInCurrentWeek(otherWeekday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = otherWeekday, PeriodNumber = 1 });
        var lesson = new Lesson { GroupId = group.Id, Date = otherDate, LessonNumber = 1, Topic = "Redox" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);
        var periodSchedule = BuildPeriodSchedule(1);
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons, periodSchedule: periodSchedule);
        Lesson? teachingModeLesson = null;
        Lesson? viewerLesson = null;
        vm.OnOpenTeachingMode = l => { teachingModeLesson = l; return Task.CompletedTask; };
        vm.OnOpenLessonViewer = l => { viewerLesson = l; return Task.CompletedTask; };

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == otherWeekday && c.PeriodNumber == 1);
        await vm.OpenWeekCellCommand.ExecuteAsync(cell);

        Assert.Equal(lesson.Id, viewerLesson?.Id);
        Assert.Null(teachingModeLesson);
    }

    /// Weites Zeitfenster um <paramref name="around"/> herum (±2 Stunden), damit der Test nicht an
    /// die exakte Toleranz von TimetableViewModel.TeachingTimeTolerance gebunden ist.
    /// Start UND Ende exakt auf "jetzt" statt eines künstlich breiteren Fensters (z.B. ganzer Tag
    /// via TimeOnly.MinValue/MaxValue): TimetableViewModel.IsAroundTeachingTime addiert selbst
    /// noch ±10 Minuten Toleranz (TeachingTimeTolerance) auf Start/Ende — ein zusätzliches, vom
    /// Test vorgegebenes Fenster würde nahe Mitternacht durch die TimeOnly-Arithmetik (wrappt bei
    /// 24 Uhr) selbst kippen. "Jetzt" als Start/Ende bleibt nur dann riskant, wenn der Test
    /// zufällig innerhalb der letzten/ersten 10 Minuten des Tages läuft — dasselbe inhärente
    /// Randproblem hätte dann auch die Produktion, kein Testartefakt.
    private static PeriodScheduleService BuildPeriodSchedule(int periodNumber)
    {
        var tempPath = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-periodschedule-tests-{Guid.NewGuid():N}");
        Directory.CreateDirectory(tempPath);
        var service = new PeriodScheduleService(tempPath);
        var now = TimeOnly.FromDateTime(DateTime.Now);
        service.SetPeriods([new PeriodTimeEntry { PeriodNumber = periodNumber, Start = now, End = now }]);
        return service;
    }

    [Fact]
    public void OpenSettings_RuftOnNavigateToSettingsAuf()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));
        SettingsTab? navigatedTab = null;
        vm.OnNavigateToSettings = tab => navigatedTab = tab;

        vm.OpenSettingsCommand.Execute(null);

        Assert.Equal(SettingsTab.Holidays, navigatedTab);
    }

    // ── "Heute"-Ansicht: Wochenraster (Nutzer-Feedback, zweite Iteration) ────────────────────

    [Fact]
    public void Load_Wochenkachel_ZeigtFachKlasseRaumUndThema()
    {
        var subject = new Subject { Name = "Chemie", ShortName = "Ch" };
        var group = new LearningGroup { Name = "Q1 Chemie", SubjectId = subject.Id };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1, Room = "R204" });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = date, Topic = "Redoxreaktionen" });
        var vm = BuildViewModel(slots, new FakeGroups([group]), subjects: new FakeSubjects([subject]), lessons: lessons);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.Equal("Ch", cell.SubjectLabel);
        Assert.Equal("Q1 Chemie", cell.GroupName);
        Assert.Equal("R204", cell.Room);
        Assert.Equal("Redoxreaktionen", cell.Topic);
    }

    [Fact]
    public void Load_Wochenkachel_UnbelegteZelle_IstNichtZugewiesen()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.False(cell.IsAssigned);
    }

    [Fact]
    public void Load_Wochenkachel_KlausurAmTag_ZeigtKlausurIcon()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = date, Title = "Klausur" }]);
        var vm = BuildViewModel(slots, new FakeGroups([group]), exams: exams);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.HasExam);
    }

    [Fact]
    public void Load_Wochenkachel_TagInSchulferien_WirdAusgegraut()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var holidays = new FakeSchoolHolidays();
        holidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = date, EndDate = date.AddDays(5) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), holidays);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.IsHoliday);
        Assert.Equal("#BDBDBD", cell.ColorHex);
    }

    [Fact]
    public void Load_Wochenkachel_TagAusserhalbVonFerien_WirdNichtAusgegraut()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.False(cell.IsHoliday);
    }

    [Fact]
    public void Load_Wochenkachel_ExperimentInPhaseGeplant_ZeigtExperimentIcon()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = date, Phases = [new LessonPhaseStep { Activity = "Experiment: Redoxreihe" }] });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.HasExperiment);
    }

    [Fact]
    public void Load_Wochenkachel_OhneExperimentErwaehnung_KeinExperimentIcon()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = group.Id, Date = date, Phases = [new LessonPhaseStep { Activity = "Stillarbeit" }] });
        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.False(cell.HasExperiment);
    }

    [Fact]
    public void Load_Wochenkachel_UnvollstaendigePhasendaten_VerursachenKeinenFehler()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var lessons = new FakeLessons();
        lessons.Add(new Lesson
        {
            GroupId = group.Id,
            Date = date,
            Phases = [new LessonPhaseStep { Name = null!, Activity = null!, Material = "Experimentiermaterial" }],
        });

        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.HasExperiment);
    }

    [Fact]
    public void Load_Wochenkachel_LetzteStundeVorKlausur_ZeigtIcon()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = date.AddDays(1), Title = "Klausur" }]);
        var vm = BuildViewModel(slots, new FakeGroups([group]), exams: exams);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.IsLastBeforeExam);
    }

    [Fact]
    public void Load_Wochenkachel_KeineAnstehendeKlausur_KeinIcon()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.False(cell.IsLastBeforeExam);
    }

    [Fact]
    public void PreviousWeek_ZeigtVorherigeKalenderwoche()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));
        var initialLabel = vm.WeekRangeLabel;

        vm.PreviousWeekCommand.Execute(null);

        Assert.NotEqual(initialLabel, vm.WeekRangeLabel);
        Assert.False(vm.IsCurrentWeek);
    }

    [Fact]
    public void NextWeek_GefolgtVonCurrentWeek_KehrtZurLaufendenWocheZurueck()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));
        var initialLabel = vm.WeekRangeLabel;

        vm.NextWeekCommand.Execute(null);
        Assert.NotEqual(initialLabel, vm.WeekRangeLabel);

        vm.CurrentWeekCommand.Execute(null);
        Assert.Equal(initialLabel, vm.WeekRangeLabel);
        Assert.True(vm.IsCurrentWeek);
    }

    [Fact]
    public void NextWeek_BadgeGehoertZurAngezeigtenWoche_NichtZuHeute()
    {
        // Klausur liegt in der übernächsten Woche relativ zu "heute" — im Wochenraster einer
        // Woche dahinter (also der übernächsten Woche selbst) muss "letzte Stunde vor Klausur"
        // erscheinen, nicht bereits in der aktuellen Woche.
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var currentWeekMonday = DateInCurrentWeek(DayOfWeek.Monday);
        var examWeekMonday = currentWeekMonday.AddDays(14);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = examWeekMonday.AddDays(1), Title = "Klausur" }]);
        var vm = BuildViewModel(slots, new FakeGroups([group]), exams: exams);

        var currentWeekCell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.False(currentWeekCell.IsLastBeforeExam);

        vm.NextWeekCommand.Execute(null);
        vm.NextWeekCommand.Execute(null);
        var examWeekCell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(examWeekCell.IsLastBeforeExam);
    }

    // ── Badge: letzte/vorletzte Stunde vor Ferien (Bearbeiten-Raster) ────────────────────────

    [Fact]
    public void Load_LetzteStundeVorFerien_ZeigtBadge1()
    {
        var weekday = NextGridWeekday(DateOnly.FromDateTime(DateTime.Today));
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday.DayOfWeek, PeriodNumber = 1 });
        var holidays = new FakeSchoolHolidays();
        holidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = weekday.AddDays(1), EndDate = weekday.AddDays(10) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), holidays);

        var cell = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == weekday.DayOfWeek && c.PeriodNumber == 1);
        Assert.Equal("1", cell.BadgeText);
    }

    [Fact]
    public void Load_Wochenkachel_LetzteStundeVorFerien_ZeigtBadge1()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var holidays = new FakeSchoolHolidays();
        holidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = date.AddDays(1), EndDate = date.AddDays(10) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), holidays);

        var weekCell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.Equal("1", weekCell.HolidayBadge);
    }

    [Fact]
    public void Load_VorletzteStundeVorFerien_ZeigtBadge2()
    {
        var firstOccurrence = NextGridWeekday(DateOnly.FromDateTime(DateTime.Today));
        var secondOccurrence = firstOccurrence.AddDays(7);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = firstOccurrence.DayOfWeek, PeriodNumber = 1 });
        var holidays = new FakeSchoolHolidays();
        holidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = secondOccurrence.AddDays(1), EndDate = secondOccurrence.AddDays(10) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), holidays);

        var cell = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == firstOccurrence.DayOfWeek && c.PeriodNumber == 1);
        Assert.Equal("2", cell.BadgeText);
    }

    [Fact]
    public void Load_Doppelstunde_BeideStundenZeigenDasselbeBadge()
    {
        var weekday = NextGridWeekday(DateOnly.FromDateTime(DateTime.Today));
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday.DayOfWeek, PeriodNumber = 1 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday.DayOfWeek, PeriodNumber = 2 });
        var holidays = new FakeSchoolHolidays();
        holidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = weekday.AddDays(1), EndDate = weekday.AddDays(10) });
        var vm = BuildViewModel(slots, new FakeGroups([group]), holidays);

        var period1 = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == weekday.DayOfWeek && c.PeriodNumber == 1);
        var period2 = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == weekday.DayOfWeek && c.PeriodNumber == 2);
        Assert.Equal("1", period1.BadgeText);
        Assert.Equal("1", period2.BadgeText);
    }

    [Fact]
    public void Load_Doppelstunde_ZeigtLessonThemaInBeidenKacheln_AuchOhnePhasenUndStundenraster()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var group = new LearningGroup { Name = "10c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = date.DayOfWeek, PeriodNumber = 3 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = date.DayOfWeek, PeriodNumber = 4 });
        var lesson = new Lesson
        {
            GroupId = group.Id, Date = date, LessonNumber = 3, Topic = "Werkstoffprüfung",
            Phases = [],
        };
        var lessons = new FakeLessons();
        lessons.Add(lesson);

        var vm = BuildViewModel(slots, new FakeGroups([group]), lessons: lessons);

        var first = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == date.DayOfWeek && c.PeriodNumber == 3);
        var second = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == date.DayOfWeek && c.PeriodNumber == 4);
        Assert.Equal("Werkstoffprüfung", first.Topic);
        Assert.Equal("Werkstoffprüfung", second.Topic);
        Assert.Equal(lesson.Id, second.Lesson?.Id);
    }

    [Fact]
    public void Load_KeineAnstehendenFerien_KeinBadge()
    {
        var weekday = NextGridWeekday(DateOnly.FromDateTime(DateTime.Today));
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = weekday.DayOfWeek, PeriodNumber = 1 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var cell = vm.Cells.Single(c => c.IsSlotCell && c.Weekday == weekday.DayOfWeek && c.PeriodNumber == 1);
        Assert.False(cell.HasBadge);
    }

    // ── Aufsicht: wiederkehrend (Bearbeiten-Raster) ──────────────────────────

    [Fact]
    public void Load_AufsichtEingetragen_ZeigtSupervisionRowMitOrt()
    {
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = DayOfWeek.Monday, AfterPeriod = 2, Location = "Pausenhof" });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), supervisionDuties: duties);

        var label = vm.Cells.Single(c => c.IsSupervisionRow && c.Text.Contains("n. 2."));
        Assert.NotNull(label);
        var mondayCell = vm.Cells
            .SkipWhile(c => c != label).Skip(1) // erste Zelle nach dem Label = Montag
            .First();
        Assert.True(mondayCell.IsSupervisionCell);
        Assert.Equal("Pausenhof", mondayCell.SupervisionLocation);
    }

    [Fact]
    public void Load_KeineAufsichtEingetragen_KeineSupervisionRow()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));

        Assert.DoesNotContain(vm.Cells, c => c.IsSupervisionRow);
    }

    [Fact]
    public void Load_AufsichtEingetragen_BekommtSchmalereZeilenhoeheAlsStundenzeilen()
    {
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = DayOfWeek.Monday, AfterPeriod = 2, Location = "Pausenhof" });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), supervisionDuties: duties);

        var row = vm.GridRows.Single(r => r.Cells.Any(c => c.IsSupervisionRow && c.Text.Contains("n. 2.")));

        Assert.Equal(22, row.RowHeight);
        Assert.Contains(vm.GridRows, r => r.RowHeight == 46); // normale Stundenzeilen bleiben unverändert
    }

    // ── Aufsicht + Vertretung im Wochenraster ────────────────────────────────

    [Fact]
    public void Load_Wochenraster_ZeigtWiederkehrendeAufsicht()
    {
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = DayOfWeek.Monday, AfterPeriod = 2, Location = "Pausenhof" });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), supervisionDuties: duties);

        var label = vm.WeekItems.Single(c => c.IsSupervisionRow && c.Text.Contains("n. 2."));
        var mondayCell = vm.WeekItems.SkipWhile(c => c != label).Skip(1).First();
        Assert.Equal("Pausenhof", mondayCell.SupervisionLocation);
        Assert.False(mondayCell.IsSubstitutionSupervision);
    }

    [Fact]
    public void Load_Wochenraster_AufsichtBekommtSchmalereZeilenhoeheAlsStundenzeilen()
    {
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = DayOfWeek.Monday, AfterPeriod = 2, Location = "Pausenhof" });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), supervisionDuties: duties);

        var row = vm.WeekRows.Single(r => r.Cells.Any(c => c.IsSupervisionRow && c.Text.Contains("n. 2.")));

        Assert.Equal(22, row.RowHeight);
        Assert.Contains(vm.WeekRows, r => r.RowHeight == 76);
    }

    [Fact]
    public void Load_Wochenraster_VertretungsaufsichtUeberschreibtRegulaereAnzeige()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = DayOfWeek.Monday, AfterPeriod = 2, Location = "Pausenhof" });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.Supervision, AfterPeriod = 2,
            Description = "Vertretung für Hr. Müller",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]),
            supervisionDuties: duties, substitutions: substitutions);

        var label = vm.WeekItems.Single(c => c.IsSupervisionRow && c.Text.Contains("n. 2."));
        var mondayCell = vm.WeekItems.SkipWhile(c => c != label).Skip(1).First();
        Assert.Equal("Vertretung für Hr. Müller", mondayCell.SupervisionLocation);
        Assert.True(mondayCell.IsSubstitutionSupervision);
    }

    [Fact]
    public void Load_Wochenraster_VertretungsaufsichtOhneRegulaereAufsicht_ZeigtEigeneRow()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.Supervision, AfterPeriod = 3,
            Description = "Vertretung für Fr. Schmidt",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var label = vm.WeekItems.Single(c => c.IsSupervisionRow && c.Text.Contains("n. 3."));
        var mondayCell = vm.WeekItems.SkipWhile(c => c != label).Skip(1).First();
        Assert.Equal("Vertretung für Fr. Schmidt", mondayCell.SupervisionLocation);
    }

    [Fact]
    public void Load_ZusaetzlicheAufsichtInDerFolgewoche_ErscheintImWochenrasterNachNavigation()
    {
        // Nutzer-Feedback: "Auch die Extra-Aufsicht ist dann nicht im Plan [...] So macht doch der
        // Sync nur so halb Sinn" - dieselbe Anzeige-Infrastruktur wie beim Ausfall oben, hier für
        // eine automatisch erkannte zusätzliche Aufsicht ohne reguläre SupervisionDuty.
        var dateNextWeek = DateInCurrentWeek(DayOfWeek.Monday).AddDays(7);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = dateNextWeek, Kind = SubstitutionKind.Supervision, AfterPeriod = 1,
            Description = "Automatisch über WebUntis-Abgleich erkannt: Zusätzliche Aufsicht laut WebUntis.",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        Assert.DoesNotContain(vm.WeekItems, c => c.IsSupervisionRow && c.Text.Contains("n. 1."));

        vm.NextWeekCommand.Execute(null);

        var label = vm.WeekItems.Single(c => c.IsSupervisionRow && c.Text.Contains("n. 1."));
        var mondayCell = vm.WeekItems.SkipWhile(c => c != label).Skip(1).First();
        Assert.True(mondayCell.IsSubstitutionSupervision);
        Assert.Contains("Zusätzliche Aufsicht", mondayCell.SupervisionLocation);
    }

    [Fact]
    public void Load_Wochenraster_VertretungsstundeUeberschreibtNormaleAnzeige()
    {
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.Lesson, PeriodNumber = 1,
            GroupLabel = "8a", Description = "Vertretung Erdkunde",
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), substitutions: substitutions);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.True(cell.IsSubstitutionLesson);
        Assert.Equal("8a", cell.GroupName);
        Assert.Equal("Vertretung Erdkunde", cell.Topic);
    }

    [Fact]
    public void Load_Wochenraster_VertretungsstundeOhnePassendenSlot_ErscheintTrotzdem()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.Lesson, PeriodNumber = 5,
            GroupLabel = "8a", Description = "Vertretung Erdkunde",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 5);
        Assert.True(cell.IsSubstitutionLesson);
        Assert.True(cell.IsAssigned);
    }

    // ── Aufsicht + Vertretung in der Tagesliste ("Heute") ────────────────────

    [Fact]
    public void Load_Heute_ZeigtHeutigeAufsicht()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var duties = new FakeSupervisionDuties();
        duties.Add(new SupervisionDuty { Weekday = today.DayOfWeek, AfterPeriod = 2, Location = "Pausenhof" });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), supervisionDuties: duties);

        var item = Assert.Single(vm.TodaySupervisions);
        Assert.Equal("Pausenhof", item.Description);
        Assert.False(item.IsSubstitution);
    }

    [Fact]
    public void Load_Heute_VertretungsstundeErsetztNormaleStundenanzeige()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = today, Kind = SubstitutionKind.Lesson, PeriodNumber = 1,
            GroupLabel = "8a", Description = "Vertretung Erdkunde",
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), substitutions: substitutions);

        var item = Assert.Single(vm.TodayItems);
        Assert.True(item.IsSubstitution);
        Assert.Equal("8a", item.GroupName);
        Assert.Equal("Vertretung Erdkunde", item.LessonTopic);
    }

    [Fact]
    public void OpenGroup_MitLeererGroupId_RuftDelegateNichtAuf()
    {
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]));
        var called = false;
        vm.OnNavigateToGroup = _ => called = true;

        vm.OpenGroupCommand.Execute(Guid.Empty);

        Assert.False(called);
    }

    // ── Sondereinsätze (Ausflüge, Berufsmessen, ...) ─────────────────────────

    [Fact]
    public void Load_Wochenraster_GanztaegigerSondereinsatz_UeberdecktAllePeriodenDesTages()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.SpecialAssignment, IsAllDay = true,
            GroupLabel = "8a", Description = "Ausflug ins Museum",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var period1 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        var period7 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 7);
        Assert.True(period1.IsSpecialAssignment);
        Assert.True(period7.IsSpecialAssignment);
        Assert.Equal("Ausflug ins Museum", period1.Topic);
        Assert.Equal("8a", period1.GroupName);
    }

    [Fact]
    public void Load_Wochenraster_SondereinsatzMitStundenbereich_NurDortSichtbar()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.SpecialAssignment, IsAllDay = false,
            FromPeriod = 3, ToPeriod = 4, Description = "Berufsmesse",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var period2 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 2);
        var period3 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 3);
        var period4 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 4);
        var period5 = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 5);
        Assert.False(period2.IsSpecialAssignment);
        Assert.True(period3.IsSpecialAssignment);
        Assert.True(period4.IsSpecialAssignment);
        Assert.False(period5.IsSpecialAssignment);
    }

    [Fact]
    public void Load_Wochenraster_SondereinsatzOhneGruppe_ZeigtLeeresGroupName()
    {
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.SpecialAssignment, IsAllDay = true, Description = "Berufsmesse",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 1);
        Assert.Equal("", cell.GroupName);
    }

    [Fact]
    public void Load_Heute_ZeigtGanztaegigenSondereinsatz()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = today, Kind = SubstitutionKind.SpecialAssignment, IsAllDay = true,
            GroupLabel = "8a", Description = "Ausflug ins Museum",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var item = Assert.Single(vm.TodaySpecialAssignments);
        Assert.Equal("Ganztägig", item.PeriodLabel);
        Assert.Equal("Ausflug ins Museum", item.Description);
        Assert.Equal("8a", item.GroupLabel);
    }

    [Fact]
    public void Load_Heute_ZeigtSondereinsatzMitStundenbereich()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = today, Kind = SubstitutionKind.SpecialAssignment, IsAllDay = false,
            FromPeriod = 3, ToPeriod = 4, Description = "Berufsmesse",
        });
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([]), substitutions: substitutions);

        var item = Assert.Single(vm.TodaySpecialAssignments);
        Assert.Equal("3.–4. Stunde", item.PeriodLabel);
    }

    // ── Stundenausfall ────────────────────────────────────────────────────────

    [Fact]
    public void Load_Wochenraster_Ausfall_ZeigtGruppeUndFachAusDemStundenplan()
    {
        var subject = new Subject { Name = "Naturwissenschaften", ShortName = "NAT" };
        var group = new LearningGroup { Name = "6a", SubjectId = subject.Id };
        var date = DateInCurrentWeek(DayOfWeek.Monday);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 2 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = date, Kind = SubstitutionKind.Cancelled, PeriodNumber = 2, Description = "6a auf Klassenfahrt",
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), subjects: new FakeSubjects([subject]), substitutions: substitutions);

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 2);
        Assert.True(cell.IsCancelled);
        Assert.Equal("NAT", cell.SubjectLabel);
        Assert.Equal("6a", cell.GroupName);
        Assert.Equal("6a auf Klassenfahrt", cell.Topic);
    }

    [Fact]
    public void Load_AusfallInDerFolgewoche_ErscheintImWochenrasterNachNavigation()
    {
        // Nutzer-Feedback: "Nächste Woche habe ich eine Stunde Ausfall [...] wäre es doch auch
        // schön, wenn das im Stundenplan für die nächste Woche irgendwie erkenntlich ist" - genau
        // der Weg, den ein automatisch von WebUntis erkannter Ausfall nimmt (derselbe
        // SubstitutionEntry-Mechanismus wie bei Handeinträgen), hier erstmals mit WeekOffset != 0
        // geprüft.
        var subject = new Subject { Name = "Naturwissenschaften", ShortName = "NAT" };
        var group = new LearningGroup { Name = "6a", SubjectId = subject.Id };
        var dateNextWeek = DateInCurrentWeek(DayOfWeek.Thursday).AddDays(7);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Thursday, PeriodNumber = 3 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = dateNextWeek, Kind = SubstitutionKind.Cancelled, PeriodNumber = 3,
            Description = "Automatisch über WebUntis-Abgleich erkannt.",
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), subjects: new FakeSubjects([subject]), substitutions: substitutions);

        // Aktuelle Woche: an dieser Stelle regulär, noch kein Ausfall sichtbar.
        var currentWeekCell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Thursday && c.PeriodNumber == 3);
        Assert.False(currentWeekCell.IsCancelled);

        vm.NextWeekCommand.Execute(null);

        var nextWeekCell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Thursday && c.PeriodNumber == 3);
        Assert.True(nextWeekCell.IsCancelled);
        Assert.Equal("Automatisch über WebUntis-Abgleich erkannt.", nextWeekCell.Topic);
    }

    [Fact]
    public void Load_Wochenraster_KeinAusfall_ZeigtNormaleStunde()
    {
        var group = new LearningGroup { Name = "6a" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 2 });
        var vm = BuildViewModel(slots, new FakeGroups([group]));

        var cell = vm.WeekItems.Single(c => c.IsSlotCell && c.Weekday == DayOfWeek.Monday && c.PeriodNumber == 2);
        Assert.False(cell.IsCancelled);
    }

    [Fact]
    public void Load_Heute_Ausfall_ErsetztNormaleStundenanzeige()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "6a" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 2 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry
        {
            Date = today, Kind = SubstitutionKind.Cancelled, PeriodNumber = 2, Description = "6a auf Klassenfahrt",
        });
        var vm = BuildViewModel(slots, new FakeGroups([group]), substitutions: substitutions);

        var item = Assert.Single(vm.TodayItems);
        Assert.True(item.IsCancelled);
        Assert.Equal("6a", item.GroupName);
        Assert.Equal("6a auf Klassenfahrt", item.LessonTopic);
        Assert.Equal(group.Id, item.GroupId);
    }

    [Fact]
    public void Load_Heute_AusfallOhneGrund_LessonTopicBleibtLeer()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "6a" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 2 });
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry { Date = today, Kind = SubstitutionKind.Cancelled, PeriodNumber = 2 });
        var vm = BuildViewModel(slots, new FakeGroups([group]), substitutions: substitutions);

        var item = Assert.Single(vm.TodayItems);
        Assert.False(item.HasLessonTopic);
    }

    // ── Anstehende Klausurtermine (4.4.3) ────────────────────────────────────

    [Fact]
    public void Load_ZeigtKlausurInnerhalbDesVorausblicks()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = today.AddDays(10), Title = "Klausur Nr. 2" }]);
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([group]), exams: exams);

        var item = Assert.Single(vm.UpcomingExams);
        Assert.Equal("Q1 Chemie", item.GroupName);
        Assert.Equal("Klausur Nr. 2", item.Title);
        Assert.Equal(today.AddDays(10), item.Date);
    }

    [Fact]
    public void Load_KlausurAusserhalbDesVorausblicks_WirdNichtGezeigt()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = today.AddDays(30), Title = "Klausur Nr. 3" }]);
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([group]), exams: exams);

        Assert.Empty(vm.UpcomingExams);
    }

    [Fact]
    public void Load_VergangeneKlausur_WirdNichtGezeigt()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = today.AddDays(-1), Title = "Alte Klausur" }]);
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([group]), exams: exams);

        Assert.Empty(vm.UpcomingExams);
    }

    [Fact]
    public void Load_MehrereKlausuren_SindNachDatumSortiert()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var exams = new FakeExams(
        [
            new Exam { GroupId = group.Id, Date = today.AddDays(15), Title = "Später" },
            new Exam { GroupId = group.Id, Date = today.AddDays(3), Title = "Früher" },
        ]);
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([group]), exams: exams);

        Assert.Equal(["Früher", "Später"], vm.UpcomingExams.Select(e => e.Title));
    }

    [Fact]
    public void Load_HeutigeKlausur_IstImVorausblickEnthalten()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Q1 Chemie" };
        var exams = new FakeExams([new Exam { GroupId = group.Id, Date = today, Title = "Heute" }]);
        var vm = BuildViewModel(new FakeTimetableSlots(), new FakeGroups([group]), exams: exams);

        Assert.Single(vm.UpcomingExams);
    }

    // ── WebUntis-Abweichung ───────────────────────────────────────────────────

    [Fact]
    public void Load_UntisAbgleichNichtAktiviert_ZeigtKeineAbweichung()
    {
        var group = new LearningGroup { Name = "10c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });

        var vm = BuildViewModel(slots, new FakeGroups([group]));

        Assert.False(vm.HasUntisMismatch);
    }

    [Fact]
    public void Load_UntisAktivSlotOhneBestaetigteZuordnung_ZeigtAbweichung()
    {
        var group = new LearningGroup { Name = "10c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var untisSettings = TestSupport.BuildWebUntisSettingsService();
        untisSettings.SetIcalUrl("https://example.org/ical");
        untisSettings.SetEnabled(true);

        var vm = BuildViewModel(slots, new FakeGroups([group]), untisSettings: untisSettings);

        Assert.True(vm.HasUntisMismatch);
        Assert.Contains("1 Stundenplan-Eintrag", vm.UntisMismatchLabel);
    }

    [Fact]
    public void Load_UntisAktivMitBestaetigterZuordnung_ZeigtKeineAbweichung()
    {
        var group = new LearningGroup { Name = "10c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        var mappings = new FakeUntisSlotMappings();
        mappings.Add(new UntisSlotMapping
        {
            Weekday = DayOfWeek.Monday, PeriodNumber = 1, GroupId = group.Id, Confirmed = true,
        });
        var untisSettings = TestSupport.BuildWebUntisSettingsService();
        untisSettings.SetIcalUrl("https://example.org/ical");
        untisSettings.SetEnabled(true);

        var vm = BuildViewModel(slots, new FakeGroups([group]), untisMappings: mappings, untisSettings: untisSettings);

        Assert.False(vm.HasUntisMismatch);
    }

    [Fact]
    public void Load_DoppelstundenZuordnungBestaetigtBeideTimetableSlots()
    {
        // Regression: "ich habe aber jetzt alles zugeordnet, und trotzdem erhalte ich die
        // Warnung, dass 16 Stunden ohne Untis-Zuordnung sind" - eine WebUntis-Doppelstunde
        // bestätigt beide zugehörigen TimetableSlots, nicht nur den ersten.
        var group = new LearningGroup { Name = "10c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 1 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = DayOfWeek.Monday, PeriodNumber = 2 });
        var mappings = new FakeUntisSlotMappings();
        mappings.Add(new UntisSlotMapping
        {
            Weekday = DayOfWeek.Monday, PeriodNumber = 1, CoveredPeriods = [1, 2],
            GroupId = group.Id, Confirmed = true,
        });
        var untisSettings = TestSupport.BuildWebUntisSettingsService();
        untisSettings.SetIcalUrl("https://example.org/ical");
        untisSettings.SetEnabled(true);

        var vm = BuildViewModel(slots, new FakeGroups([group]), untisMappings: mappings, untisSettings: untisSettings);

        Assert.False(vm.HasUntisMismatch);
    }
}

/// Nutzer-Feedback (zweite Runde): das Popup-Menü je Wochenraster-Kachel (TimetableView.axaml,
/// MenuFlyout) blendet "Unterrichtsansicht"/"Planungsviewer" per IsVisible="{Binding HasLesson}"
/// aus, wenn für den Slot noch keine Lesson existiert, und den ganzen Menü-Trigger per
/// IsVisible="{Binding HasGroupId}", wenn die Kachel gar keiner Gruppe zugeordnet ist (z.B. eine
/// GroupId-lose Vertretung). Diese beiden Properties sind die Grundlage dafür.
public sealed class WeekCellItemMenuVisibilityTests
{
    [Fact]
    public void ForSlot_MitLesson_HatHasLessonUndHasGroupId()
    {
        var lesson = new Lesson { Topic = "Redox" };
        var cell = WeekCellItem.ForSlot(DayOfWeek.Monday, 3, isToday: true, "Che", "Q1 Chemie",
            "R204", "Redox", "#4C8DFF", "", hasExam: false, isLastBeforeExam: false,
            hasExperiment: false, Guid.NewGuid(), isHoliday: false, lesson: lesson);

        Assert.True(cell.HasLesson);
        Assert.True(cell.HasGroupId);
    }

    [Fact]
    public void ForSlot_OhneLesson_HatKeinHasLesson()
    {
        var cell = WeekCellItem.ForSlot(DayOfWeek.Monday, 3, isToday: true, "Che", "Q1 Chemie",
            "R204", "", "#4C8DFF", "", hasExam: false, isLastBeforeExam: false,
            hasExperiment: false, Guid.NewGuid(), isHoliday: false);

        Assert.False(cell.HasLesson);
        Assert.True(cell.HasGroupId);
    }

    [Fact]
    public void ForSubstitutionLesson_OhneGroupId_HatKeinHasGroupId()
    {
        var cell = WeekCellItem.ForSubstitutionLesson(DayOfWeek.Monday, 3, isToday: true,
            new SubstitutionEntry { GroupId = null, GroupLabel = "Fremde Klasse", Description = "Vertretung" });

        Assert.False(cell.HasGroupId);
    }
}