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

namespace LehrerApp.Desktop.Tests;

/// Tests für die Mitarbeits-Aggregation (3.2): ParticipationGradeDialogViewModel
/// verrechnet die Sitzungsbewertungen eines Zeitraums zu einer Mitarbeitsnote je Schüler.
public class ParticipationGradeAggregationTests
{
    private static (ParticipationGradeDialogViewModel Vm, Guid AnnaId, Guid BenId, Guid CoraId, Guid GroupId, FakeGrades Grades)
        BuildScenario()
    {
        var groupId = Guid.NewGuid();
        var anna = new Student { Id = Guid.NewGuid(), FirstName = "Anna", LastName = "Beispiel" };
        var ben = new Student { Id = Guid.NewGuid(), FirstName = "Ben", LastName = "Muster" };
        var cora = new Student { Id = Guid.NewGuid(), FirstName = "Cora", LastName = "Ohne" }; // nie bewertet

        var students = new FakeStudents([anna, ben, cora]);
        var memberships = new FakeMemberships([]);
        var aspects = new FakeAspects();

        var sess1 = new ParticipationSession { GroupId = groupId, Date = new DateOnly(2025, 9, 1) };
        var sess2 = new ParticipationSession { GroupId = groupId, Date = new DateOnly(2025, 9, 15) };
        var sess3 = new ParticipationSession { GroupId = groupId, Date = new DateOnly(2025, 9, 29) };
        var sessions = new FakeSessions([sess1, sess2, sess3]);

        var entries = new FakeEntries();
        // Anna: −1, 0, +2 → steigender Trend, beide Standardaspekte gleich bewertet.
        entries.Add(new ParticipationEntry
        {
            SessionId = sess1.Id, StudentId = anna.Id,
            Ratings = [new() { Key = "quality", Value = -1 }, new() { Key = "quantity", Value = -1 }],
        });
        entries.Add(new ParticipationEntry
        {
            SessionId = sess2.Id, StudentId = anna.Id,
            Ratings = [new() { Key = "quality", Value = 0 }, new() { Key = "quantity", Value = 0 }],
        });
        entries.Add(new ParticipationEntry
        {
            SessionId = sess3.Id, StudentId = anna.Id,
            Ratings = [new() { Key = "quality", Value = 2 }, new() { Key = "quantity", Value = 2 }],
        });
        // Ben: nur einmal bewertet.
        entries.Add(new ParticipationEntry
        {
            SessionId = sess1.Id, StudentId = ben.Id,
            Ratings = [new() { Key = "quality", Value = 0 }],
        });
        // Cora: nie bewertet.

        var grades = new FakeGrades();
        var grading = new GradingService();

        var vm = new ParticipationGradeDialogViewModel(sessions, entries, aspects, students, memberships,
            grades, grading, groupId, "2025/26", GradingSystem.Grades1To6);

        return (vm, anna.Id, ben.Id, cora.Id, groupId, grades);
    }

    [Fact]
    public void Recompute_MittelBerechnungGewichtetAlleSitzungenGleich()
    {
        var (vm, annaId, _, _, _, _) = BuildScenario();

        var anna = vm.Rows.Single(r => r.StudentId == annaId);

        Assert.Equal(3, anna.SessionCount);
        Assert.Equal((-1.0 + 0.0 + 2.0) / 3.0, double.Parse(anna.AverageDisplay.Replace(',', '.'),
            System.Globalization.CultureInfo.InvariantCulture), precision: 2);
    }

    [Fact]
    public void Recompute_NichtBewerteterSchueler_HatKeineNoteStattSchlechterNote()
    {
        var (vm, _, _, coraId, _, _) = BuildScenario();

        var cora = vm.Rows.Single(r => r.StudentId == coraId);

        Assert.Equal(0, cora.SessionCount);
        Assert.Null(cora.Grade);
        Assert.Equal("nicht bewertet", cora.GradeDisplay);
    }

    [Fact]
    public void Recompute_EinzelneBewertung_ErgibtTrotzdemEineNote()
    {
        var (vm, _, benId, _, _, _) = BuildScenario();

        var ben = vm.Rows.Single(r => r.StudentId == benId);

        Assert.Equal(1, ben.SessionCount);
        Assert.NotNull(ben.Grade);
    }

    [Fact]
    public void Recompute_SteigendeBewertungen_ZeigenAufwaertstrend()
    {
        var (vm, annaId, _, _, _, _) = BuildScenario();

        var anna = vm.Rows.Single(r => r.StudentId == annaId);

        Assert.Equal("↑", anna.TrendSymbol);
    }

    [Fact]
    public void AspektGewicht_AufNullGesetzt_NimmtAspektAusDerBerechnungHeraus()
    {
        var (vm, annaId, _, _, _, _) = BuildScenario();
        var quantity = vm.AspectWeights.First(a => a.Key == "quantity");

        quantity.Weight = 0;

        // Nur noch "quality" zählt: (-1 + 0 + 2) / 3 = 0.33 — identisch zum Gesamtmittel,
        // da beide Aspekte bei Anna durchgehend gleich bewertet wurden.
        var anna = vm.Rows.Single(r => r.StudentId == annaId);
        var average = double.Parse(anna.AverageDisplay.Replace(',', '.'), System.Globalization.CultureInfo.InvariantCulture);
        Assert.Equal(1.0 / 3.0, average, precision: 2);
    }

    [Fact]
    public void SelectedPeriod_H1_SchliesstSitzungenAusserhalbAus()
    {
        var (vm, _, _, _, _, _) = BuildScenario();

        vm.SelectedPeriod = vm.PeriodOptions.First(p => p.Period == ParticipationPeriod.H2);

        // Alle Testsitzungen liegen im September (H1) -> im H2-Zeitraum bleibt niemand bewertet.
        Assert.All(vm.Rows, r => Assert.Equal(0, r.SessionCount));
    }

    [Fact]
    public void Apply_SpeichertEineNoteJeBewertetemSchueler()
    {
        var (vm, annaId, benId, coraId, groupId, grades) = BuildScenario();

        vm.ApplyCommand.Execute(null);

        Assert.NotNull(grades.GetByStudentAndGroup(annaId, groupId)
            .SingleOrDefault(g => g.Category == GradeCategory.Participation));
        Assert.NotNull(grades.GetByStudentAndGroup(benId, groupId)
            .SingleOrDefault(g => g.Category == GradeCategory.Participation));
        Assert.Empty(grades.GetByStudentAndGroup(coraId, groupId));
    }

    [Fact]
    public void Apply_ZweitesMal_AktualisiertBestehendeNoteStattZuDuplizieren()
    {
        var (vm, annaId, _, _, groupId, grades) = BuildScenario();

        vm.ApplyCommand.Execute(null);
        vm.ApplyCommand.Execute(null);

        var annaGrades = grades.GetByStudentAndGroup(annaId, groupId)
            .Where(g => g.Category == GradeCategory.Participation).ToList();
        Assert.Single(annaGrades);
    }

    /// 3.1.3: ein Punkte-Aspekt darf nicht als roher Zahlenwert in die Mittelwertbildung
    /// einfließen (z.B. "4 Punkte" wäre auf der -2..+2-Achse ein Extremwert weit über +2) —
    /// er muss vorher auf dieselbe Achse normiert werden wie Scale5/Scale3/Binary.
    [Fact]
    public void Recompute_PunkteAspekt_WirdVorDerMittelungAufMinus2Bis2AchseNormiert()
    {
        var groupId = Guid.NewGuid();
        var anna = new Student { FirstName = "Anna", LastName = "Beispiel" };
        var students = new FakeStudents([anna]);
        var memberships = new FakeMemberships([]);

        var aspects = new FakeAspects();
        aspects.Save(new ParticipationAspect
        {
            GroupId = groupId, Key = "raised_hand", Label = "Meldungen",
            ValueType = AspectValueType.Points, MaxPoints = 4,
        });

        var session = new ParticipationSession { GroupId = groupId, Date = new DateOnly(2025, 9, 1) };
        var sessions = new FakeSessions([session]);

        var entries = new FakeEntries();
        // 2 von 4 Punkten -> Mitte der Skala, normiert genau auf 0.
        entries.Add(new ParticipationEntry
        {
            SessionId = session.Id, StudentId = anna.Id,
            Ratings = [new() { Key = "raised_hand", Value = 2 }],
        });

        var grades = new FakeGrades();
        var grading = new GradingService();
        var vm = new ParticipationGradeDialogViewModel(sessions, entries, aspects, students, memberships,
            grades, grading, groupId, "2025/26", GradingSystem.Grades1To6);

        var row = Assert.Single(vm.Rows);
        Assert.Equal(0.0, double.Parse(row.AverageDisplay.Replace(',', '.'),
            System.Globalization.CultureInfo.InvariantCulture), precision: 2);
    }
}