LehrerApp/LehrerApp.Desktop.Tests/LessonDialogViewModelTests.cs

using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Core.Services;
using LehrerApp.Desktop.ViewModels.Groups;
using Xunit;

namespace LehrerApp.Desktop.Tests;

public sealed class LessonDialogViewModelTests
{
    private static PeriodScheduleService NewPeriodSchedule()
    {
        var tempPath = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-lessondialogvm-tests-{Guid.NewGuid():N}");
        Directory.CreateDirectory(tempPath);
        return new PeriodScheduleService(tempPath);
    }

    private static LessonDialogViewModel BuildVm(Guid unitId, Guid groupId, Lesson? editing = null,
        FakeTimetableSlots? slots = null, PeriodScheduleService? periodSchedule = null) =>
        new(new FakeLessons(), new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            slots ?? new FakeTimetableSlots(), periodSchedule ?? NewPeriodSchedule(), new FakeAttachmentStorage(),
            unitId, groupId, "10c", "Chemie", [], [], editing);

    /// Nutzer-Feedback: bei einer Klasse, die in mehreren Fächern unterrichtet wird (mehrere
    /// LearningGroup-Datensätze mit gleichem Namen), war im Stunden-Dialog nicht erkennbar,
    /// welche der beiden Stunden man gerade bearbeitet.
    [Fact]
    public void GroupSubjectDisplay_ZeigtGruppeUndFachZusammen()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        Assert.Equal("10c · Chemie", vm.GroupSubjectDisplay);
    }

    [Fact]
    public void AddPhase_FuegtZeileMitStandardwertenHinzu()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());

        vm.AddPhaseCommand.Execute(null);

        Assert.Single(vm.Phases);
        Assert.Equal(5, vm.Phases[0].DurationMinutes);
        Assert.False(vm.Phases[0].HasAlternativePath);
    }

    [Fact]
    public void RemovePhase_EntferntZeileUndAktualisiertGesamtdauer()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 20;

        vm.Phases[0].RemoveCommand.Execute(null);

        Assert.Empty(vm.Phases);
        Assert.Equal("0 Minuten gesamt", vm.TotalDurationDisplay);
    }

    [Fact]
    public void MoveDown_VertauschtReihenfolgeDerPhasen()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].Name = "Einstieg";
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[1].Name = "Erarbeitung";

        vm.Phases[0].MoveDownCommand.Execute(null);

        Assert.Equal("Erarbeitung", vm.Phases[0].Name);
        Assert.Equal("Einstieg", vm.Phases[1].Name);
    }

    [Fact]
    public void Shorthand_IstFreitextOhneErzwungeneVonNachStruktur()
    {
        // Kurzsymbol muss nicht immer ein Materialfluss-Pfeil sein — manchmal nur eine
        // Sozialform ohne Pfeil (z.B. "Plenum", "LDE").
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.AddPhaseCommand.Execute(null);
        var phase = vm.Phases[0];

        phase.Shorthand = "Plenum";
        Assert.Equal("Plenum", phase.Shorthand);

        phase.Shorthand = "AB001->S";
        Assert.Equal("AB001->S", phase.Shorthand);
    }

    [Fact]
    public void ShorthandSuggestions_KombiniertKatalogUndBisherigeStundenwerte()
    {
        var codes = new FakeShorthandCodes([new ShorthandCode { Code = "Tb" }, new ShorthandCode { Code = "SH" }]);
        var vm = new LessonDialogViewModel(new FakeLessons(), codes, new FakeAlternativeLessonPaths([]),
            new FakeTimetableSlots(), NewPeriodSchedule(), new FakeAttachmentStorage(),
            Guid.NewGuid(), Guid.NewGuid(), "10c", "Chemie", [], ["Plenum", "LDE", "Tb"], null); // "Tb" doppelt (Katalog + Historie), soll nur einmal erscheinen

        Assert.Equal(["LDE", "Plenum", "SH", "Tb"], vm.ShorthandSuggestions);
    }

    [Fact]
    public void RecomputeTimes_LeitetUhrzeitJePhaseAusBeginnUndKumulierterDauerAb()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.StartTimeText = "12:00";
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 15;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[1].DurationMinutes = 10;

        Assert.Equal("ab 12:00", vm.Phases[0].ComputedTimeDisplay);
        Assert.Equal("ab 12:15", vm.Phases[1].ComputedTimeDisplay);
        Assert.Equal("25 Minuten gesamt", vm.TotalDurationDisplay);
    }

    [Fact]
    public void RecomputeTimes_OhneBeginnBleibtDieUhrzeitanzeigeLeer()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 15;

        Assert.Equal("", vm.Phases[0].ComputedTimeDisplay);
    }

    [Fact]
    public void Save_ErfordertThemaUndGueltigesDatum()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.Topic = ""; vm.DateText = "keinDatum";

        vm.SaveCommand.Execute(null);

        Assert.Null(vm.Result);
        Assert.NotEqual("", vm.TopicError);
        Assert.NotEqual("", vm.DateTextError);
    }

    [Fact]
    public void Save_UngueltigesBeginnFormatWirdAbgelehnt()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.Topic = "Thema"; vm.DateText = "01.09.2025"; vm.StartTimeText = "nicht-uhrzeit";

        vm.SaveCommand.Execute(null);

        Assert.Null(vm.Result);
        Assert.NotEqual("", vm.StartTimeTextError);
    }

    [Fact]
    public void Save_SetztUnitIdGroupIdUndUebernimmtPhasenUndBeginn()
    {
        var unitId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        var lessons = new FakeLessons();
        var vm = new LessonDialogViewModel(lessons, new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            new FakeTimetableSlots(), NewPeriodSchedule(), new FakeAttachmentStorage(), unitId, groupId, "10c", "Chemie", [], [], null)
        {
            Topic = "Brechung", DateText = "01.09.2025", StartTimeText = "11:45",
        };
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].Name = "Einstieg";
        vm.Phases[0].DurationMinutes = 10;
        vm.Phases[0].Activity = "Begrüßung";
        vm.Phases[0].Material = "AB01";
        vm.Phases[0].Shorthand = "L->AB01";

        vm.SaveCommand.Execute(null);

        Assert.NotNull(vm.Result);
        Assert.Equal(unitId, vm.Result!.UnitId);
        Assert.Equal(groupId, vm.Result.GroupId);
        Assert.Equal(new TimeOnly(11, 45), vm.Result.StartTime);
        Assert.Single(vm.Result.Phases);
        Assert.Equal("Einstieg", vm.Result.Phases[0].Name);
        Assert.Equal(10, vm.Result.Phases[0].DurationMinutes);
        Assert.Equal("L->AB01", vm.Result.Phases[0].Shorthand);
        Assert.Single(lessons.GetByUnit(unitId));
    }

    [Fact]
    public void AddAttachment_LaedtHochUndSaveUebernimmtIhnInDasErgebnis()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.Topic = "Thema"; vm.DateText = "01.09.2025";

        vm.AddAttachment("gbu-natrium.pdf", new MemoryStream([1, 2, 3]));
        vm.SaveCommand.Execute(null);

        Assert.NotNull(vm.Result);
        var attachment = Assert.Single(vm.Result!.Attachments);
        Assert.Equal("gbu-natrium.pdf", attachment.FileName);
        Assert.Equal(3, attachment.SizeBytes);
    }

    [Fact]
    public void AddAttachment_ZuGrosseDateiWirdAbgelehnt()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());

        vm.AddAttachment("riesig.pdf", new MemoryStream(new byte[IAttachmentStorage.MaxSizeBytes + 1]));

        Assert.Empty(vm.Attachments);
        Assert.NotEqual("", vm.AttachmentError);
    }

    [Fact]
    public void RemoveAttachmentCommand_EntferntDenAnhangAusDerListe()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.AddAttachment("gbu-natrium.pdf", new MemoryStream([1, 2, 3]));
        var item = vm.Attachments[0];

        vm.RemoveAttachmentCommand.Execute(item);

        Assert.Empty(vm.Attachments);
    }

    [Fact]
    public void BearbeiteteStunde_LaedtVorhandeneAnhaengeVor()
    {
        var editing = new Lesson
        {
            Attachments = [new DocumentAttachment { StorageId = "abc", FileName = "gbu.pdf", SizeBytes = 42 }],
        };

        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), editing);

        var attachment = Assert.Single(vm.Attachments);
        Assert.Equal("gbu.pdf", attachment.FileName);
    }

    [Fact]
    public void HasHomeworkText_OhneHausaufgabe_IstFalse()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        Assert.False(vm.HasHomeworkText);

        vm.Homework = "   ";
        Assert.False(vm.HasHomeworkText);

        vm.Homework = "S. 42";
        Assert.True(vm.HasHomeworkText);
    }

    [Fact]
    public void Save_UebernimmtHomeworkCheckedUndDismissed()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.Topic = "Brechung"; vm.DateText = "01.09.2025";
        vm.Homework = "S. 42"; vm.HomeworkChecked = true;

        vm.SaveCommand.Execute(null);

        Assert.True(vm.Result!.HomeworkChecked);
        Assert.False(vm.Result.HomeworkCheckDismissed);
    }

    [Fact]
    public void HomeworkChecked_UndHomeworkCheckDismissed_SchliessenSichGegenseitigAus()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());

        vm.HomeworkChecked = true;
        Assert.False(vm.HomeworkCheckDismissed);

        vm.HomeworkCheckDismissed = true;
        Assert.False(vm.HomeworkChecked);
    }

    [Fact]
    public void Bearbeiten_UebernimmtGespeicherteHomeworkFlags()
    {
        var editing = new Lesson
        {
            Topic = "Alt", Date = new DateOnly(2025, 9, 1), Homework = "S. 42",
            HomeworkCheckDismissed = true,
        };

        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), editing);

        Assert.True(vm.HomeworkCheckDismissed);
        Assert.False(vm.HomeworkChecked);
    }

    [Fact]
    public void HasAlternativePath_AngehaktOeffnetZuweisungUndUebernimmtErgebnis()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        var path = new AlternativeLessonPath { Name = "Kurzversion" };
        vm.OnPickAlternativePath = _ => Task.FromResult<AlternativeLessonPath?>(path);
        vm.AddPhaseCommand.Execute(null);

        vm.Phases[0].HasAlternativePath = true;

        Assert.True(vm.Phases[0].HasAlternativePath);
        Assert.Equal("Kurzversion", vm.Phases[0].AlternativePathName);
        Assert.Equal(path.Id, vm.Phases[0].AlternativePathId);
    }

    [Fact]
    public void HasAlternativePath_AbbruchDerZuweisungLaesstEsUnangehakt()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        vm.OnPickAlternativePath = _ => Task.FromResult<AlternativeLessonPath?>(null); // abgebrochen
        vm.AddPhaseCommand.Execute(null);

        vm.Phases[0].HasAlternativePath = true;

        Assert.False(vm.Phases[0].HasAlternativePath);
        Assert.Null(vm.Phases[0].AlternativePathId);
    }

    [Fact]
    public void HasAlternativePath_AbwaehlenEntferntZuordnungOhneDialogZuOeffnen()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        var path = new AlternativeLessonPath { Name = "Kurzversion" };
        var dialogCalls = 0;
        vm.OnPickAlternativePath = _ => { dialogCalls++; return Task.FromResult<AlternativeLessonPath?>(path); };
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].HasAlternativePath = true; // zuweisen -> 1 Dialogaufruf

        vm.Phases[0].HasAlternativePath = false; // abwählen -> kein weiterer Dialogaufruf

        Assert.Equal(1, dialogCalls);
        Assert.False(vm.Phases[0].HasAlternativePath);
        Assert.Equal("", vm.Phases[0].AlternativePathName);
        Assert.Null(vm.Phases[0].AlternativePathId);
    }

    [Fact]
    public void Save_UebernimmtZugewiesenenAlternativePfad()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid());
        var path = new AlternativeLessonPath { Name = "Kurzversion" };
        vm.OnPickAlternativePath = _ => Task.FromResult<AlternativeLessonPath?>(path);
        vm.Topic = "Thema"; vm.DateText = "01.09.2025";
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].HasAlternativePath = true;

        vm.SaveCommand.Execute(null);

        Assert.Equal(path.Id, vm.Result!.Phases[0].AlternativePathId);
    }

    [Fact]
    public void AddPhaseInternal_LoestBestehendeZuordnungBeimBearbeitenAuf()
    {
        var path = new AlternativeLessonPath { Name = "Kurzversion" };
        var alternativePaths = new FakeAlternativeLessonPaths([path]);
        var editing = new Lesson
        {
            Topic = "Thema", Date = new DateOnly(2025, 9, 1),
            Phases = [new LessonPhaseStep { Name = "Einstieg", AlternativePathId = path.Id }],
        };

        var vm = new LessonDialogViewModel(new FakeLessons(), new FakeShorthandCodes([]), alternativePaths,
            new FakeTimetableSlots(), NewPeriodSchedule(), new FakeAttachmentStorage(), Guid.NewGuid(), Guid.NewGuid(), "10c", "Chemie", [], [], editing);

        Assert.True(vm.Phases[0].HasAlternativePath);
        Assert.Equal("Kurzversion", vm.Phases[0].AlternativePathName);
    }

    // ── Zeitbedarf-Rückmeldung (4.2.2 Nachtrag: Stundenraster) ───────────────────

    [Fact]
    public void RecomputeTimeBudget_EinzelneStunde_ZeigtVerfuegbareZeitAusStundenraster()
    {
        var groupId = Guid.NewGuid();
        var date = new DateOnly(2025, 9, 1);
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 3, Start = new TimeOnly(9, 45), End = new TimeOnly(10, 30) }]);
        var vm = BuildVm(Guid.NewGuid(), groupId, periodSchedule: periodSchedule);
        vm.DateText = date.ToString("dd.MM.yyyy");
        vm.LessonNumber = 3;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 40;

        Assert.True(vm.HasTimeBudgetInfo);
        Assert.Contains("40 von 45 Minuten geplant", vm.TimeBudgetLabel);
    }

    [Fact]
    public void RecomputeTimeBudget_Doppelstunde_AddiertBeidePerioden()
    {
        var groupId = Guid.NewGuid();
        var date = new DateOnly(2025, 9, 1);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = date.DayOfWeek, PeriodNumber = 3 });
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = date.DayOfWeek, PeriodNumber = 4 });
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([
            new PeriodTimeEntry { PeriodNumber = 3, Start = new TimeOnly(9, 45), End = new TimeOnly(10, 30) },
            new PeriodTimeEntry { PeriodNumber = 4, Start = new TimeOnly(10, 30), End = new TimeOnly(11, 15) },
        ]);
        var vm = BuildVm(Guid.NewGuid(), groupId, slots: slots, periodSchedule: periodSchedule);
        vm.DateText = date.ToString("dd.MM.yyyy");
        vm.LessonNumber = 3;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 84;

        Assert.True(vm.HasTimeBudgetInfo);
        Assert.Contains("84 von 90 Minuten geplant", vm.TimeBudgetLabel);
    }

    [Fact]
    public void RecomputeTimeBudget_FolgeperiodeGehoertAndererGruppe_WirdNichtMitgezaehlt()
    {
        var groupId = Guid.NewGuid();
        var otherGroupId = Guid.NewGuid();
        var date = new DateOnly(2025, 9, 1);
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = date.DayOfWeek, PeriodNumber = 3 });
        slots.Add(new TimetableSlot { GroupId = otherGroupId, Weekday = date.DayOfWeek, PeriodNumber = 4 });
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([
            new PeriodTimeEntry { PeriodNumber = 3, Start = new TimeOnly(9, 45), End = new TimeOnly(10, 30) },
            new PeriodTimeEntry { PeriodNumber = 4, Start = new TimeOnly(10, 30), End = new TimeOnly(11, 15) },
        ]);
        var vm = BuildVm(Guid.NewGuid(), groupId, slots: slots, periodSchedule: periodSchedule);
        vm.DateText = date.ToString("dd.MM.yyyy");
        vm.LessonNumber = 3;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 40;

        Assert.Contains("40 von 45 Minuten geplant", vm.TimeBudgetLabel);
    }

    [Fact]
    public void RecomputeTimeBudget_FarbeGruenImZielbereich()
    {
        var date = new DateOnly(2025, 9, 1);
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 1, Start = new TimeOnly(8, 0), End = new TimeOnly(8, 45) }]);
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), periodSchedule: periodSchedule);
        vm.DateText = date.ToString("dd.MM.yyyy");
        vm.LessonNumber = 1;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 42; // 42/45 ≈ 93 % — Zielbereich

        Assert.Equal("#43A047", vm.TimeBudgetColorHex);
    }

    [Fact]
    public void RecomputeTimeBudget_FarbeDunkelrotBeiDeutlicherUeberplanung()
    {
        var date = new DateOnly(2025, 9, 1);
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 1, Start = new TimeOnly(8, 0), End = new TimeOnly(8, 45) }]);
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), periodSchedule: periodSchedule);
        vm.DateText = date.ToString("dd.MM.yyyy");
        vm.LessonNumber = 1;
        vm.AddPhaseCommand.Execute(null);
        vm.Phases[0].DurationMinutes = 60; // 60/45 ≈ 133 % — deutlich überplant

        Assert.Equal("#B71C1C", vm.TimeBudgetColorHex);
    }

    [Fact]
    public void LessonNumberGeaendert_UebernimmtBeginnAusStundenraster_WennNochKeinerEingetragen()
    {
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 5, Start = new TimeOnly(11, 45), End = new TimeOnly(12, 30) }]);
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), periodSchedule: periodSchedule);

        vm.LessonNumber = 5;

        Assert.Equal("11:45", vm.StartTimeText);
    }

    [Fact]
    public void LessonNumberGeaendert_UeberschreibtBereitsEingetragenenBeginnNicht()
    {
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 5, Start = new TimeOnly(11, 45), End = new TimeOnly(12, 30) }]);
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid(), periodSchedule: periodSchedule);
        vm.StartTimeText = "09:00";

        vm.LessonNumber = 5;

        Assert.Equal("09:00", vm.StartTimeText);
    }

    [Fact]
    public void RecomputeTimeBudget_OhneStundenrasterEintrag_KeineRueckmeldung()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid()); // leeres PeriodScheduleService
        vm.DateText = "01.09.2025";
        vm.LessonNumber = 1;
        vm.AddPhaseCommand.Execute(null);

        Assert.False(vm.HasTimeBudgetInfo);
    }

    // ── Datumsvorschlag für eine neue Stunde (Nutzer-Feedback: Feld stand sonst immer auf
    // "heute", was die Doppelstunden-Erkennung stillschweigend auf eine Einzelperiode
    // zurückfallen ließ, wenn heute zufällig nicht der Unterrichtstag ist) ────────────────────

    [Fact]
    public void NeueStunde_OhneStundenplanEintraege_BleibtBeimHeutigenDatum()
    {
        var vm = BuildVm(Guid.NewGuid(), Guid.NewGuid()); // FakeTimetableSlots leer

        Assert.Equal(DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy"), vm.DateText);
    }

    [Fact]
    public void NeueStunde_LetzteStundeInDerZukunft_SchlaegtNaechstenPassendenWochentagDanachVor()
    {
        var unitId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        var futureLessonDate = new DateOnly(2099, 1, 6); // Dienstag
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { UnitId = unitId, GroupId = groupId, Date = futureLessonDate, LessonNumber = 3 });
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = DayOfWeek.Tuesday, PeriodNumber = 3 });

        var vm = new LessonDialogViewModel(lessons, new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            slots, NewPeriodSchedule(), new FakeAttachmentStorage(), unitId, groupId, "10c", "Chemie", [], [], null);

        // Nächster Dienstag nach dem 06.01.2099 (einem Dienstag) ist der 13.01.2099.
        Assert.Equal("13.01.2099", vm.DateText);
        Assert.Equal(3, vm.LessonNumber);
    }

    [Fact]
    public void NeueStunde_LetzteStundeInDerVergangenheit_SchlaegtNaechstenPassendenWochentagAbHeuteVor()
    {
        var unitId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { UnitId = unitId, GroupId = groupId, Date = new DateOnly(2000, 1, 1), LessonNumber = 3 });
        var weekday = DateTime.Today.DayOfWeek; // garantiert am selben oder folgenden Tag erreichbar
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = weekday, PeriodNumber = 3 });

        var vm = new LessonDialogViewModel(lessons, new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            slots, NewPeriodSchedule(), new FakeAttachmentStorage(), unitId, groupId, "10c", "Chemie", [], [], null);

        var suggested = DateOnly.ParseExact(vm.DateText, "dd.MM.yyyy");
        Assert.True(suggested >= DateOnly.FromDateTime(DateTime.Today));
        Assert.Equal(weekday, suggested.DayOfWeek);
        Assert.Equal(3, vm.LessonNumber);
    }

    [Fact]
    public void NeueStunde_Doppelstunde_SchlaegtDieErstePeriodeAlsStundennummerVor()
    {
        var unitId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        var futureLessonDate = new DateOnly(2099, 1, 6); // Dienstag
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { UnitId = unitId, GroupId = groupId, Date = futureLessonDate, LessonNumber = 3 });
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = DayOfWeek.Tuesday, PeriodNumber = 4 });
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = DayOfWeek.Tuesday, PeriodNumber = 3 });

        var vm = new LessonDialogViewModel(lessons, new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            slots, NewPeriodSchedule(), new FakeAttachmentStorage(), unitId, groupId, "10c", "Chemie", [], [], null);

        Assert.Equal(3, vm.LessonNumber); // frühere Periode, nicht 4
    }

    [Fact]
    public void NeueStunde_MitStundenvorschlag_UebernimmtBeginnAusStundenraster()
    {
        var unitId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        var weekday = DateTime.Today.DayOfWeek;
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = groupId, Weekday = weekday, PeriodNumber = 2 });
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 2, Start = new TimeOnly(8, 50), End = new TimeOnly(9, 35) }]);

        var vm = new LessonDialogViewModel(new FakeLessons(), new FakeShorthandCodes([]), new FakeAlternativeLessonPaths([]),
            slots, periodSchedule, new FakeAttachmentStorage(), unitId, groupId, "10c", "Chemie", [], [], null);

        Assert.Equal(2, vm.LessonNumber);
        Assert.Equal("08:50", vm.StartTimeText);
    }
}