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

namespace LehrerApp.Desktop.Tests;

/// Tests für 9.1 (heutige Stunden mit Uhrzeit und Raum im Dashboard) und 9.2 (Absprung von einer
/// Stunde), außerdem die Kalender-Sitzungsanzeige (3.3.4) und die Mindeststichprobe der
/// Fehlzeiten-Warnung (5.2.3). Deckt nicht die übrigen, unveränderten Dashboard-Bausteine
/// (offene Aufgaben, ...).
public sealed class DashboardViewModelTests
{
    [Fact]
    public void LeereHinweisbereiche_WerdenAusgeblendetUndZusammenfassungBleibtKompakt()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today });

        Assert.False(vm.ExcusesCard.EffectiveIsVisible);
        Assert.False(vm.CorrectionsCard.EffectiveIsVisible);
        Assert.False(vm.AlertsCard.EffectiveIsVisible);
        Assert.Equal("0 offene Punkte", vm.AttentionSummary);
        Assert.True(vm.TodayCard.EffectiveIsVisible);
        Assert.True(vm.CalendarCard.EffectiveIsVisible);
    }

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

    private static DashboardSettingsService NewDashboardSettings()
    {
        var tempPath = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-dashboardsettings-tests-{Guid.NewGuid():N}");
        Directory.CreateDirectory(tempPath);
        return new DashboardSettingsService(tempPath);
    }

    private static SchoolCalendarSettingsService NewCalendarSettings()
    {
        var tempPath = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-schoolcalendar-tests-{Guid.NewGuid():N}");
        Directory.CreateDirectory(tempPath);
        return new SchoolCalendarSettingsService(tempPath);
    }

    private static DashboardViewModel BuildVm(LearningGroup group, Lesson lesson,
        FakeTimetableSlots? slots = null, PeriodScheduleService? periodSchedule = null,
        FakeExams? exams = null, FakeResults? results = null, FakeGrades? grades = null,
        FakeReportGrades? reportGrades = null, FakeMemberships? memberships = null,
        FakeWorkTasks? tasks = null, FakeStudents? students = null, FakeDocumentation? documentation = null,
        DashboardSettingsService? dashboardSettings = null, FakeSchoolHolidays? schoolHolidays = null,
        FakeLessons? lessons = null, FakeSubstitutionEntries? substitutions = null,
        FakeSessions? sessions = null, FakeEntries? entries = null,
        FakeAnnualPlanEvents? annualPlanEvents = null, List<LearningGroup>? allGroups = null)
    {
        lessons ??= new FakeLessons();
        lessons.Add(lesson);
        return new DashboardViewModel(
            new FakeGroups(allGroups ?? [group]), new FakeSubjects([]), lessons,
            exams ?? new FakeExams([]), results ?? new FakeResults(), grades ?? new FakeGrades(),
            reportGrades ?? new FakeReportGrades(), memberships ?? new FakeMemberships([]),
            tasks ?? new FakeWorkTasks(), sessions ?? new FakeSessions([]), entries ?? new FakeEntries(),
            students ?? new FakeStudents([]), documentation ?? new FakeDocumentation(),
            slots ?? new FakeTimetableSlots(), periodSchedule ?? NewPeriodSchedule(),
            new AttendanceBalanceService(), new SchoolYearService(), dashboardSettings ?? NewDashboardSettings(),
            schoolHolidays ?? new FakeSchoolHolidays(), new PublicHolidayService(), NewCalendarSettings(),
            substitutions ?? new FakeSubstitutionEntries(), annualPlanEvents);
    }

    [Fact]
    public void TodaysLessons_LoestRaumUeberPassendenStundenplanSlotAuf()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 3, Room = "R204" });

        var vm = BuildVm(group, lesson, slots: slots);

        var item = Assert.Single(vm.TodaysLessons);
        Assert.Equal("R204", item.Room);
        Assert.True(item.HasRoom);
    }

    [Fact]
    public void TodaysLessons_OhnePassendenSlot_HatKeinenRaum()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox" };

        var vm = BuildVm(group, lesson);

        var item = Assert.Single(vm.TodaysLessons);
        Assert.False(item.HasRoom);
        Assert.Equal("", item.Room);
    }

    [Fact]
    public void TodaysLessons_ZeitKommtAusLessonStartTimeWennGesetzt()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var lesson = new Lesson
        {
            GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox",
            StartTime = new TimeOnly(9, 15),
        };
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 3, Start = new TimeOnly(10, 0), End = new TimeOnly(10, 45) }]);

        var vm = BuildVm(group, lesson, periodSchedule: periodSchedule);

        Assert.Equal("09:15", Assert.Single(vm.TodaysLessons).TimeDisplay);
    }

    [Fact]
    public void TodaysLessons_OhneStartTime_FaelltAufStundenrasterZurueck()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox" };
        var periodSchedule = NewPeriodSchedule();
        periodSchedule.SetPeriods([new PeriodTimeEntry { PeriodNumber = 3, Start = new TimeOnly(10, 0), End = new TimeOnly(10, 45) }]);

        var vm = BuildVm(group, lesson, periodSchedule: periodSchedule);

        Assert.Equal("10:00", Assert.Single(vm.TodaysLessons).TimeDisplay);
    }

    [Fact]
    public void OpenLesson_RuftNavigationMitGruppenIdAuf()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox" };
        var vm = BuildVm(group, lesson);

        Guid? navigatedTo = null;
        vm.OnNavigateToLesson = id => navigatedTo = id;

        vm.OpenLessonCommand.Execute(vm.TodaysLessons[0]);

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

    [Fact]
    public void UpcomingDates_BuendeltKlausurenFristenUndFoerderplanPruefungen()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var exams = new FakeExams([
            new Exam { GroupId = group.Id, Title = "Chemie-Test", Date = today.AddDays(5) },
        ]);
        var tasks = new FakeWorkTasks();
        tasks.Add(new WorkTask { Title = "Notenschluss", DueDate = today.AddDays(10) });
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        var documentation = new FakeDocumentation();
        documentation.Add(new Documentation
        {
            StudentId = student.Id, Type = DocumentationType.SupportPlan, Title = "Leseförderung",
            SupportData = new SupportData { Status = SupportStatus.Active, ReviewDate = today.AddDays(3) },
        });

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, exams: exams,
            tasks: tasks, students: new FakeStudents([student]), documentation: documentation);

        Assert.Contains(vm.UpcomingDates, i => i.Kind == UpcomingDateKind.Exam && i.Title == "Chemie-Test");
        Assert.Contains(vm.UpcomingDates, i => i.Kind == UpcomingDateKind.Deadline && i.Title == "Notenschluss");
        Assert.Contains(vm.UpcomingDates, i => i.Kind == UpcomingDateKind.SupportPlan && i.StudentId == student.Id);
    }

    [Fact]
    public void OpenCorrections_ZeigtBewertungsfortschrittJeKlausur()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var exam = new Exam
            { GroupId = group.Id, Title = "Klausur 1", Date = today.AddDays(-2), Status = ExamStatus.Conducted };
        var anna = new Student { FirstName = "Anna", LastName = "A" };
        var ben = new Student { FirstName = "Ben", LastName = "B" };
        var memberships = new FakeMemberships([
            new GroupMembership { GroupId = group.Id, StudentId = anna.Id },
            new GroupMembership { GroupId = group.Id, StudentId = ben.Id },
        ]);
        var results = new FakeResults();
        results.Add(new ExamResult { ExamId = exam.Id, StudentId = anna.Id, Grade = "2" });

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today },
            exams: new FakeExams([exam]), results: results, memberships: memberships,
            students: new FakeStudents([anna, ben]));

        var correction = Assert.Single(vm.OpenCorrections);
        Assert.Equal(1, correction.Completed);
        Assert.Equal(2, correction.Total);
        Assert.Equal(50, correction.Percent);
    }

    [Fact]
    public void Alerts_ErkenntDeutlichenNotenabfall()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c", GradingSystem = GradingSystem.Grades1To6 };
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        var memberships = new FakeMemberships([
            new GroupMembership { GroupId = group.Id, StudentId = student.Id },
        ]);
        var grades = new FakeGrades();
        grades.Add(new Grade { GroupId = group.Id, StudentId = student.Id, Date = today.AddDays(-20), Value = "2" });
        grades.Add(new Grade { GroupId = group.Id, StudentId = student.Id, Date = today.AddDays(-15), Value = "2" });
        grades.Add(new Grade { GroupId = group.Id, StudentId = student.Id, Date = today.AddDays(-10), Value = "4" });
        grades.Add(new Grade { GroupId = group.Id, StudentId = student.Id, Date = today.AddDays(-5), Value = "4" });

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, grades: grades,
            memberships: memberships, students: new FakeStudents([student]));

        Assert.Contains(vm.Alerts, a => a.StudentId == student.Id && a.KindLabel == "Notenabfall");
    }

    [Fact]
    public void Kalenderauswahl_ZeigtTermineDesGeklicktenTages()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var examDate = today.AddDays(2);
        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today },
            exams: new FakeExams([new Exam { GroupId = group.Id, Title = "Test", Date = examDate }]));
        var day = vm.CalendarDays.Single(d => d.Date == examDate);

        vm.SelectCalendarDayCommand.Execute(day);

        Assert.True(day.IsSelected);
        Assert.Contains(vm.SelectedDayEvents, e => e.Kind == CalendarEventKind.Exam && e.Title == "Test");
    }

    [Fact]
    public void Kalenderauswahl_SortiertKurseDesTagesVorDenAlphabetischenRest()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var selectedDate = today.AddDays(1);
        var alphabeticallyFirst = new LearningGroup { Name = "10a" };
        var selectedDayGroup = new LearningGroup { Name = "WAT 10c" };
        var lessons = new FakeLessons();
        lessons.Add(new Lesson { GroupId = selectedDayGroup.Id, Date = selectedDate });
        var vm = BuildVm(alphabeticallyFirst,
            new Lesson { GroupId = alphabeticallyFirst.Id, Date = today }, lessons: lessons,
            allGroups: [alphabeticallyFirst, selectedDayGroup]);

        vm.SelectCalendarDayCommand.Execute(vm.CalendarDays.Single(d => d.Date == selectedDate));

        Assert.Equal(selectedDayGroup.Id, vm.CurrentGroups[0].GroupId);
        Assert.True(vm.CurrentGroups[0].IsOnSelectedDay);
        Assert.Equal(alphabeticallyFirst.Id, vm.CurrentGroups[1].GroupId);
    }

    [Fact]
    public void Kalender_ZeigtMitarbeitssitzungenAlsEigenenTermintyp()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var sessionDate = today.AddDays(3);
        var session = new ParticipationSession { GroupId = group.Id, Date = sessionDate, Comment = "Aufsatz" };
        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today },
            sessions: new FakeSessions([session]));

        var day = vm.CalendarDays.Single(d => d.Date == sessionDate);
        Assert.True(day.HasSession);

        vm.SelectCalendarDayCommand.Execute(day);

        Assert.Contains(vm.SelectedDayEvents,
            e => e.Kind == CalendarEventKind.ParticipationSession && e.Subtitle == "Aufsatz");
    }

    [Fact]
    public void Kalender_ZeigtMehrtaegigenJahresplanParallelZumUnterrichtAn()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var annualPlan = new FakeAnnualPlanEvents();
        annualPlan.Add(new AnnualPlanEvent
        {
            ExternalId = "fahrt", Title = "Klassenfahrt 6a",
            Description = "Aushang beachten", Location = "Jugendherberge",
            CalendarGroup = "Lehrkräfte", StartDate = today, EndDate = today.AddDays(2),
            StartTime = new TimeOnly(13, 30), EndTime = new TimeOnly(15, 0), IsAllDay = false,
        });

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today, Topic = "Redox" },
            annualPlanEvents: annualPlan);

        var day = vm.CalendarDays.Single(d => d.Date == today);
        Assert.True(day.HasLesson);
        Assert.True(day.HasAnnualPlanEvent);

        vm.SelectCalendarDayCommand.Execute(day);

        Assert.Contains(vm.SelectedDayEvents, e => e.Kind == CalendarEventKind.Lesson);
        var annual = Assert.Single(vm.SelectedDayEvents, e => e.Kind == CalendarEventKind.AnnualPlan);
        Assert.Equal("Klassenfahrt 6a", annual.Title);
        Assert.Equal("Aushang beachten", annual.Description);
        Assert.Contains("13:30", annual.Subtitle);
        Assert.Null(annual.GroupId);
    }

    [Fact]
    public void Kalender_AusStundeErzeugteSitzungErzeugtKeinenDoppelteintrag()
    {
        // Regressionstest (Nutzer-Feedback): "Sitzung erzeugen" (3.3.1) verknüpft die Sitzung über
        // LessonId mit der Stunde — dieselbe Unterrichtsstunde darf im Kalender nicht zusätzlich
        // als eigener Sitzungstermin auftauchen.
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var lesson = new Lesson { GroupId = group.Id, Date = today, Topic = "Brechung" };
        var session = new ParticipationSession { GroupId = group.Id, Date = today, LessonId = lesson.Id, Comment = "Brechung" };
        var vm = BuildVm(group, lesson, sessions: new FakeSessions([session]));

        var day = vm.CalendarDays.Single(d => d.Date == today);
        Assert.True(day.HasLesson);
        Assert.False(day.HasSession);

        vm.SelectCalendarDayCommand.Execute(day);

        Assert.Single(vm.SelectedDayEvents);
        Assert.DoesNotContain(vm.SelectedDayEvents, e => e.Kind == CalendarEventKind.ParticipationSession);
    }

    [Fact]
    public void Kalender_EigeneKlasseAmStundenplanTagOhneLessonZeigtDenRingTrotzdem()
    {
        // Regressionstest (Nutzer-Feedback): der "Meine Klasse"-Ring soll schon laut Stundenplan
        // gelten, nicht erst, sobald für den Tag eine Lesson angelegt wurde.
        var today = DateOnly.FromDateTime(DateTime.Today);
        var tomorrow = today.AddDays(1);
        var group = new LearningGroup { Name = "9c", IsOwnClass = true };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = tomorrow.DayOfWeek, PeriodNumber = 3 });

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, slots: slots);

        var day = vm.CalendarDays.Single(d => d.Date == tomorrow);
        Assert.True(day.IsOwnClassDay);
    }

    [Fact]
    public void DashboardKacheln_SichtbarkeitUndReihenfolgeWerdenGespeichert()
    {
        var settings = NewDashboardSettings();
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, dashboardSettings: settings);
        vm.TodayCard.IsVisible = false;
        vm.MoveCardDownCommand.Execute(vm.TasksCard);

        var saved = settings.Load();

        Assert.False(saved.Single(c => c.Key == "today").IsVisible);
        Assert.True(saved.FindIndex(c => c.Key == "tasks") > 1);
    }

    // ── Ungeplante Stunden (Nutzer-Feedback) ──────────────────────────────────

    [Fact]
    public void UnplannedLessons_StundeplanSlotOhneLessonMitThema_ErscheintInDerListe()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        // "lesson" liegt bewusst weit in der Vergangenheit, damit sie nicht in den heute/morgen-
        // Vorgriff fällt und den Test verfälscht.
        var pastLesson = new Lesson { GroupId = group.Id, Date = today.AddYears(-1), LessonNumber = 1, Topic = "Alt" };

        var vm = BuildVm(group, pastLesson, slots: slots);

        var item = Assert.Single(vm.UnplannedLessons);
        Assert.Equal(group.Id, item.GroupId);
        Assert.Equal(1, item.PeriodNumber);
        Assert.Equal("Heute", item.DateDisplay);
    }

    [Fact]
    public void UnplannedLessons_LessonMitThemaVorhanden_ErscheintNicht()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        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 = "Redoxreaktionen" };

        var vm = BuildVm(group, lesson, slots: slots);

        Assert.Empty(vm.UnplannedLessons);
    }

    [Fact]
    public void UnplannedLessons_GruppeOhnePlanungsbedarf_WirdIgnoriert()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "Klassenrat", RequiresLessonPlanning = false };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var pastLesson = new Lesson { GroupId = group.Id, Date = today.AddYears(-1), LessonNumber = 1, Topic = "Alt" };

        var vm = BuildVm(group, pastLesson, slots: slots);

        Assert.Empty(vm.UnplannedLessons);
    }

    [Fact]
    public void UnplannedLessons_Feiertag_WirdUebersprungen()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 1 });
        var pastLesson = new Lesson { GroupId = group.Id, Date = today.AddYears(-1), LessonNumber = 1, Topic = "Alt" };
        var schoolHolidays = new FakeSchoolHolidays();
        schoolHolidays.Add(new SchoolHoliday { Name = "Ferien", StartDate = today, EndDate = today.AddDays(1) });

        var vm = BuildVm(group, pastLesson, slots: slots, schoolHolidays: schoolHolidays);

        Assert.Empty(vm.UnplannedLessons);
    }

    [Fact]
    public void UnplannedLessons_DoppelstundeMitThemaAmErstenSlot_ZweiterSlotWirdNichtGemeldet()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 3 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 4 });
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "Redox" };

        var vm = BuildVm(group, lesson, slots: slots);

        Assert.Empty(vm.UnplannedLessons);
    }

    [Fact]
    public void UnplannedLessons_DoppelstundeOhneThema_BeideSlotsWerdenGemeldet()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 3 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 4 });
        var lesson = new Lesson { GroupId = group.Id, Date = today, LessonNumber = 3, Topic = "" };

        var vm = BuildVm(group, lesson, slots: slots);

        Assert.Equal(2, vm.UnplannedLessons.Count);
        Assert.Contains(vm.UnplannedLessons, i => i.PeriodNumber == 3);
        Assert.Contains(vm.UnplannedLessons, i => i.PeriodNumber == 4);
    }

    [Fact]
    public void UnplannedLessons_StundenausfallEingetragen_WirdNichtGemeldet()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var slots = new FakeTimetableSlots();
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 5 });
        slots.Add(new TimetableSlot { GroupId = group.Id, Weekday = today.DayOfWeek, PeriodNumber = 6 });
        var pastLesson = new Lesson { GroupId = group.Id, Date = today.AddYears(-1), LessonNumber = 5, Topic = "Alt" };
        var substitutions = new FakeSubstitutionEntries();
        substitutions.Add(new SubstitutionEntry { Date = today, Kind = SubstitutionKind.Cancelled, PeriodNumber = 5 });
        substitutions.Add(new SubstitutionEntry { Date = today, Kind = SubstitutionKind.Cancelled, PeriodNumber = 6 });

        var vm = BuildVm(group, pastLesson, slots: slots, substitutions: substitutions);

        Assert.Empty(vm.UnplannedLessons);
    }

    [Fact]
    public void AttendanceWarnings_KleineStichprobeMitHoherQuoteWirdNichtGemeldet()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        var sessions = new FakeSessions([]);
        var entries = new FakeEntries();

        // Nur 3 erfasste Termine, alle unentschuldigt (100 %) — Stichprobe zu klein für eine Meldung.
        for (var i = 0; i < 3; i++)
        {
            var session = new ParticipationSession { GroupId = group.Id, Date = today.AddDays(-i - 1) };
            sessions.Save(session);
            entries.Add(new ParticipationEntry { SessionId = session.Id, StudentId = student.Id, Attendance = AttendanceStatus.Unexcused });
        }

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today },
            students: new FakeStudents([student]), sessions: sessions, entries: entries);

        Assert.Empty(vm.AttendanceWarnings);
    }

    [Fact]
    public void AttendanceWarnings_MeldetHoheQuoteAbMindeststichprobe()
    {
        var today = DateOnly.FromDateTime(DateTime.Today);
        var group = new LearningGroup { Name = "9c" };
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        var sessions = new FakeSessions([]);
        var entries = new FakeEntries();

        // 10 erfasste Termine, 3 davon unentschuldigt (30 % > 20 % Schwelle) — genug Stichprobe.
        for (var i = 0; i < 10; i++)
        {
            var session = new ParticipationSession { GroupId = group.Id, Date = today.AddDays(-i - 1) };
            sessions.Save(session);
            var status = i < 3 ? AttendanceStatus.Unexcused : AttendanceStatus.Present;
            entries.Add(new ParticipationEntry { SessionId = session.Id, StudentId = student.Id, Attendance = status });
        }

        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today },
            students: new FakeStudents([student]), sessions: sessions, entries: entries);

        var item = Assert.Single(vm.AttendanceWarnings);
        Assert.Equal(student.FullName, item.StudentName);
        Assert.Equal(30.0, item.AbsenceRatePercent);
    }

    [Fact]
    public async Task AddTask_SpeichertErgebnisUndAktualisiertOffeneAufgaben()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var tasks = new FakeWorkTasks();
        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, tasks: tasks);
        vm.OnAddTask = startAsReminder => Task.FromResult<WorkTask?>(
            new WorkTask { Title = "Ansage an die Klasse", Kind = startAsReminder ? TaskKind.Reminder : TaskKind.WorkItem });

        await vm.AddReminderCommand.ExecuteAsync(null);

        Assert.Single(tasks.GetAll());
        Assert.Contains(vm.OpenTasks, t => t.Title == "Ansage an die Klasse" && t.IsReminder);
    }

    [Fact]
    public async Task AddTask_OhneDelegatMachtNichts()
    {
        var group = new LearningGroup { Name = "9c" };
        var today = DateOnly.FromDateTime(DateTime.Today);
        var tasks = new FakeWorkTasks();
        var vm = BuildVm(group, new Lesson { GroupId = group.Id, Date = today }, tasks: tasks);

        await vm.AddTaskCommand.ExecuteAsync(null);

        Assert.Empty(tasks.GetAll());
    }

    [Fact]
    public void WeatherWarningItem_BereitetAmtlicheWarnungFuerDashboardAuf()
    {
        var warning = new WeatherWarning
        {
            Event = "GEWITTER", Headline = "Amtliche Warnung vor Gewitter",
            Description = "Es treten Gewitter auf.", Instruction = "Gebäude aufsuchen.",
            Severity = "Severe", Onset = new DateTime(2026, 8, 23, 16, 0, 0, DateTimeKind.Utc),
            Expires = new DateTime(2026, 8, 23, 18, 0, 0, DateTimeKind.Utc),
        };

        var item = new DashboardWeatherWarningItem(warning);

        Assert.Equal("Amtliche Warnung vor Gewitter", item.Headline);
        Assert.Equal("#D32F2F", item.SeverityColor);
        Assert.Contains("Uhr", item.PeriodDisplay);
    }
}