LehrerApp/LehrerApp.Desktop.Tests/TimetableViewModelTests.cs

using LehrerApp.Core.Models;
using LehrerApp.Core.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)
    {
        // Bewusst kein "using": SchoolCalendarSettingsService liest den Pfad nur bei Bedarf
        // (SetState), 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());
    }

    /// 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 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);
    }

    [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_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_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);
    }

    // ── 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_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_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_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);
    }
}