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

namespace LehrerApp.Desktop.Tests;

/// Tests für die reinen (nur Repository-Lesezugriff, kein Netzwerk) Teile von AiPlanningService:
/// BuildContext (Export) und ApplyResponse (Import). Login/GetBalanceAsync/RequestPlanAsync
/// brauchen einen echten HTTP-Endpunkt und sind nicht Teil dieser Tests (siehe Planungsdokument,
/// Abschnitt "Nicht ohne echtes Deployment ... verifizierbar").
public sealed class AiPlanningServiceTests
{
    private static AiPlanningService Build(FakeLessons lessons, FakeGroups groups, FakeSubjects subjects,
        FakeCompetencyDomains competencyDomains, FakeAlternativeLessonPaths altPaths) =>
        new(new HttpClient(), lessons, groups, subjects, competencyDomains, altPaths);

    [Fact]
    public void BuildContext_FuelltGruppenUndFachKontext()
    {
        var subject = new Subject { Name = "Chemie" };
        var group = new LearningGroup { Name = "9c", SubjectId = subject.Id, GradeLevel = 9 };
        var unit = new Unit { GroupId = group.Id, Title = "Redoxreaktionen" };

        var service = Build(new FakeLessons(), new FakeGroups([group]), new FakeSubjects([subject]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var context = service.BuildContext(unit, "Testanweisung");

        Assert.Equal(unit.Id, context.Id);
        Assert.Equal("Redoxreaktionen", context.Title);
        Assert.Equal("Chemie", context.SubjectName);
        Assert.Equal(9, context.GradeLevel);
        Assert.Equal("9c", context.GroupName);
    }

    [Fact]
    public void BuildContext_FiltertKompetenzkatalogNachFachUndStufe()
    {
        var subject = new Subject { Name = "Chemie" };
        var group = new LearningGroup { SubjectId = subject.Id, GradeLevel = 9 };
        var unit = new Unit { GroupId = group.Id, Title = "T" };

        var domains = new FakeCompetencyDomains();
        domains.Add(new CompetencyDomain
        {
            SubjectId = subject.Id, GradeLevel = 9, Name = "Chemische Reaktionen",
            Items = [new CompetencyItem { Code = "C1", Description = "Redoxreaktionen erklären" }],
        });

        var service = Build(new FakeLessons(), new FakeGroups([group]), new FakeSubjects([subject]),
            domains, new FakeAlternativeLessonPaths([]));

        var context = service.BuildContext(unit, "");

        var catalogDomain = Assert.Single(context.CompetencyCatalog);
        Assert.Equal("Chemische Reaktionen", catalogDomain.Name);
        var item = Assert.Single(catalogDomain.Items);
        Assert.Equal("C1", item.Code);
        Assert.Equal("Redoxreaktionen erklären", item.Description);
    }

    [Fact]
    public void BuildContext_EnthaeltVorhandeneLessonsMitEchtenIds()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var lesson = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Erste Stunde" };
        var lessons = new FakeLessons();
        lessons.Add(lesson);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var context = service.BuildContext(unit, "");

        var aiLesson = Assert.Single(context.Lessons);
        Assert.Equal(lesson.Id, aiLesson.Id);
        Assert.Equal("Erste Stunde", aiLesson.Topic);
    }

    [Fact]
    public void BuildContext_LoestAlternativePathNameAuf()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var path = new AlternativeLessonPath { Name = "Vertiefung" };
        var lesson = new Lesson
        {
            UnitId = unit.Id, GroupId = group.Id, Topic = "Stunde",
            Phases = [new LessonPhaseStep { Name = "Erarbeitung", AlternativePathId = path.Id }],
        };
        var lessons = new FakeLessons();
        lessons.Add(lesson);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([path]));

        var context = service.BuildContext(unit, "");

        var phase = Assert.Single(Assert.Single(context.Lessons).Phases);
        Assert.Equal("Vertiefung", phase.AlternativePathName);
        Assert.Contains(context.AlternativePathCatalog, p => p.Name == "Vertiefung" && p.Id == path.Id);
    }

    [Fact]
    public void BuildContext_DraftOverride_ErsetztBestehendeLessonMitGleicherId()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Alter Titel" };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var draft = new List<AiLesson> { new() { Id = existing.Id, Topic = "Neuer Entwurfstitel", Phases = [] } };
        var context = service.BuildContext(unit, "", draft);

        var aiLesson = Assert.Single(context.Lessons);
        Assert.Equal(existing.Id, aiLesson.Id);
        Assert.Equal("Neuer Entwurfstitel", aiLesson.Topic);
    }

    [Fact]
    public void BuildContext_DraftOverride_HaengtNeueEntwurfLessonsOhneIdAn()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Bestehend" };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var draft = new List<AiLesson> { new() { Id = null, Topic = "Neu aus Runde 1", Phases = [] } };
        var context = service.BuildContext(unit, "", draft);

        Assert.Equal(2, context.Lessons.Count);
        Assert.Contains(context.Lessons, l => l.Topic == "Bestehend");
        Assert.Contains(context.Lessons, l => l.Topic == "Neu aus Runde 1" && l.Id == null);
    }

    [Fact]
    public void ApplyResponse_BekannteId_WirdAlsUpdateBehandelt()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Alt" };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var accepted = new List<AiLesson> { new() { Id = existing.Id, Topic = "Neu formuliert" } };
        var result = service.ApplyResponse(unit, accepted);

        var lesson = Assert.Single(result);
        Assert.Equal(existing.Id, lesson.Id);
        Assert.Equal("Neu formuliert", lesson.Topic);
        Assert.Equal(unit.Id, lesson.UnitId);
        Assert.Equal(group.Id, lesson.GroupId);
    }

    /// Die KI kennt/liefert keinen Status — ohne diese Absicherung würde eine bereits gehaltene
    /// Stunde durch eine übernommene KI-Änderung stillschweigend auf "Geplant" zurückgesetzt.
    [Fact]
    public void ApplyResponse_BekannteId_BehaeltStatusDerBestehendenLessonBei()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Alt", Status = LessonStatus.Conducted };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var accepted = new List<AiLesson> { new() { Id = existing.Id, Topic = "Nachträglich präzisiert" } };
        var result = service.ApplyResponse(unit, accepted);

        Assert.Equal(LessonStatus.Conducted, Assert.Single(result).Status);
    }

    /// Umfangs-Umschalter (Nutzer-Nachtrag): "Einheit umplanen ohne Stunden zu ändern" muss auch
    /// dann greifen, wenn die KI die Anweisung im Systemprompt ignoriert und trotzdem eine
    /// bestehende Id zurückgibt — client-seitig hart durchgesetzt, nicht nur per Prompt erbeten.
    [Fact]
    public void ApplyResponse_AenderungVerboten_VerwirftUpdateBestehenderLesson()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Alt" };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var accepted = new List<AiLesson>
        {
            new() { Id = existing.Id, Topic = "Sollte verworfen werden" },
            new() { Id = null, Topic = "Neue Stunde bleibt erlaubt" },
        };
        var result = service.ApplyResponse(unit, accepted, allowModifyingExistingLessons: false);

        var lesson = Assert.Single(result);
        Assert.Equal("Neue Stunde bleibt erlaubt", lesson.Topic);
    }

    [Fact]
    public void ApplyResponse_NullId_WirdAlsNeueLessonBehandelt()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };

        var service = Build(new FakeLessons(), new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var accepted = new List<AiLesson> { new() { Id = null, Topic = "Ganz neu" } };
        var result = service.ApplyResponse(unit, accepted);

        var lesson = Assert.Single(result);
        Assert.NotEqual(Guid.Empty, lesson.Id);
        Assert.Equal("Ganz neu", lesson.Topic);
    }

    /// Zentraler Sicherheitstest (siehe Planungsdokument): eine von der KI zurückgegebene Id, die
    /// zu keiner tatsächlich zur Einheit gehörenden Lesson passt, darf NIE als Update interpretiert
    /// werden — sonst könnte eine halluzinierte/fremde Id im schlimmsten Fall eine fremde Lesson
    /// überschreiben. Sie muss stattdessen wie eine neue Lesson behandelt werden (frische Id).
    [Fact]
    public void ApplyResponse_UnbekannteFremdeId_WirdNieAlsUpdateUebernommen()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var existing = new Lesson { UnitId = unit.Id, GroupId = group.Id, Topic = "Bestehende Stunde" };
        var lessons = new FakeLessons();
        lessons.Add(existing);

        var service = Build(lessons, new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([]));

        var foreignId = Guid.NewGuid(); // gehört zu keiner Lesson dieser Einheit
        var accepted = new List<AiLesson> { new() { Id = foreignId, Topic = "Verdächtig" } };
        var result = service.ApplyResponse(unit, accepted);

        var lesson = Assert.Single(result);
        Assert.NotEqual(foreignId, lesson.Id);
        Assert.NotEqual(existing.Id, lesson.Id);
    }

    [Fact]
    public void ApplyResponse_LoestAlternativePathNameZurueckZuId_KeinTrefferBleibtNull()
    {
        var group = new LearningGroup();
        var unit = new Unit { GroupId = group.Id, Title = "T" };
        var path = new AlternativeLessonPath { Name = "Förderung" };

        var service = Build(new FakeLessons(), new FakeGroups([group]), new FakeSubjects([]),
            new FakeCompetencyDomains(), new FakeAlternativeLessonPaths([path]));

        var accepted = new List<AiLesson>
        {
            new()
            {
                Topic = "T", Phases =
                [
                    new AiPhaseStep { Name = "A", AlternativePathName = "Förderung" },
                    new AiPhaseStep { Name = "B", AlternativePathName = "Unbekannter Pfad" },
                ],
            },
        };
        var result = service.ApplyResponse(unit, accepted);

        var phases = Assert.Single(result).Phases;
        Assert.Equal(path.Id, phases[0].AlternativePathId);
        Assert.Null(phases[1].AlternativePathId);
    }
}