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

namespace LehrerApp.Desktop.Tests;

public sealed class StudentGroupGeneratorViewModelTests
{
    private static (StudentGroupGeneratorViewModel Vm, List<Student> Students, LearningGroup Group,
        FakeSessions Sessions, FakeEntries Entries) Build(int studentCount = 10,
            FakeStudentGroupPlans? savedPlans = null)
    {
        var group = new LearningGroup { Name = "8a", GradingSystem = GradingSystem.Grades1To6 };
        var students = Enumerable.Range(1, studentCount).Select(i => new Student
        {
            FirstName = $"Kind{i:00}", LastName = "Test",
        }).ToList();
        var memberships = students.Select(s => new GroupMembership
        {
            GroupId = group.Id, StudentId = s.Id,
        }).ToList();
        var sessions = new FakeSessions([]);
        var entries = new FakeEntries();
        var vm = new StudentGroupGeneratorViewModel(
            new FakeStudents(students), new FakeGroups([group]), new FakeMemberships(memberships),
            sessions, entries, new FakeGrades(), group.Id, new Random(7), savedPlans);
        return (vm, students, group, sessions, entries);
    }

    [Fact]
    public void ManuelleUmverteilung_WirdGespeichertUndSpaeterWiederGeladen()
    {
        var plans = new FakeStudentGroupPlans();
        var (vm, students, group, _, _) = Build(6, plans);
        vm.TargetGroupCount = 2;
        vm.CountPriority = 100;
        vm.GenerateCommand.Execute(null);
        var source = vm.GeneratedGroups[0];
        var target = vm.GeneratedGroups[1];
        var member = source.Members[0];

        Assert.True(vm.MoveStudent(member, target));
        Assert.False(vm.MoveStudent(member, target));
        Assert.DoesNotContain(member, source.Members);
        vm.PlanName = "Projektwoche";
        vm.SavePlanCommand.Execute(null);

        var saved = Assert.Single(plans.GetByGroup(group.Id));
        Assert.Equal("Projektwoche", saved.Name);
        Assert.Contains(member.Id, saved.Groups[1].StudentIds);
        Assert.False(vm.HasUnsavedChanges);

        vm.GenerateCommand.Execute(null);
        vm.SelectedSavedPlan = Assert.Single(vm.SavedPlans);
        vm.LoadSavedPlanCommand.Execute(null);
        Assert.Contains(vm.GeneratedGroups[1].Members, m => m.Id == member.Id);
        Assert.DoesNotContain(vm.GeneratedGroups[0].Members, m => m.Id == member.Id);
        Assert.False(vm.HasUnsavedChanges);
        Assert.Equal("Projektwoche", vm.PlanName);

        var reopened = new StudentGroupGeneratorViewModel(
            new FakeStudents(students), new FakeGroups([group]),
            new FakeMemberships(students.Select(s => new GroupMembership
            {
                GroupId = group.Id, StudentId = s.Id,
            }).ToList()),
            new FakeSessions([]), new FakeEntries(), new FakeGrades(), group.Id,
            savedPlans: plans);
        reopened.SelectedSavedPlan = Assert.Single(reopened.SavedPlans);
        reopened.LoadSavedPlanCommand.Execute(null);
        Assert.Contains(reopened.GeneratedGroups[1].Members, m => m.Id == member.Id);

        reopened.PlanName = "Projektwoche aktualisiert";
        reopened.SavePlanCommand.Execute(null);
        Assert.Equal("Projektwoche aktualisiert", Assert.Single(plans.GetByGroup(group.Id)).Name);
    }

    [Fact]
    public void SpeichernUeberschreibtAusgewaehltenPlanErstNachDemLaden()
    {
        var plans = new FakeStudentGroupPlans();
        var (vm, _, group, _, _) = Build(6, plans);
        vm.GenerateCommand.Execute(null);
        vm.PlanName = "Alter Plan";
        vm.SavePlanCommand.Execute(null);

        vm.GenerateCommand.Execute(null);
        vm.SelectedSavedPlan = Assert.Single(vm.SavedPlans);
        vm.PlanName = "Neuer Plan";
        vm.SavePlanCommand.Execute(null);

        Assert.Equal(2, plans.GetByGroup(group.Id).Count);
        Assert.Contains(plans.GetByGroup(group.Id), p => p.Name == "Alter Plan");
        Assert.Contains(plans.GetByGroup(group.Id), p => p.Name == "Neuer Plan");
    }

    [Fact]
    public void FesteZielgroesse_ErzeugtPassendeAnzahlMitKleinerAusnahme()
    {
        var (vm, _, _, _, _) = Build(10);
        vm.TargetGroupSize = 4;
        vm.TargetGroupCount = 2;
        vm.SizePriority = 100;
        vm.CountPriority = 20;

        vm.GenerateCommand.Execute(null);

        Assert.Equal(3, vm.GeneratedGroups.Count);
        Assert.Equal(new[] { 3, 3, 4 }, vm.GeneratedGroups.Select(g => g.Members.Count).OrderBy(x => x));
        Assert.Contains("nicht gleichzeitig", vm.WarningText);
    }

    [Fact]
    public void FesteGruppenanzahl_HatVorrangVorZielgroesse()
    {
        var (vm, _, _, _, _) = Build(10);
        vm.TargetGroupSize = 3;
        vm.TargetGroupCount = 2;
        vm.SizePriority = 20;
        vm.CountPriority = 100;

        vm.GenerateCommand.Execute(null);

        Assert.Equal(2, vm.GeneratedGroups.Count);
        Assert.All(vm.GeneratedGroups, group => Assert.Equal(5, group.Members.Count));
    }

    [Fact]
    public void AdHoc_SchliesstHeuteAbwesendeAus()
    {
        var (vm, students, group, sessions, entries) = Build(6);
        var session = new ParticipationSession { GroupId = group.Id, Date = DateOnly.FromDateTime(DateTime.Today) };
        sessions.Save(session);
        entries.Add(new ParticipationEntry
        {
            SessionId = session.Id, StudentId = students[0].Id, Attendance = AttendanceStatus.Excused,
        });
        vm.ParticipantModeName = StudentGroupGeneratorViewModel.AdHocModeLabel;
        vm.TargetGroupCount = 2;
        vm.CountPriority = 100;

        vm.GenerateCommand.Execute(null);

        var names = vm.GeneratedGroups.SelectMany(g => g.Members).Select(m => m.Name).ToList();
        Assert.Equal(5, names.Count);
        Assert.DoesNotContain(students[0].FullName, names);
        Assert.Contains("fehlt heute", vm.WarningText);
    }

    [Fact]
    public void AdHoc_OhneHeutigeErfassung_WarntUndNutztAlleAktiven()
    {
        var (vm, students, _, _, _) = Build(6);
        vm.ParticipantModeName = StudentGroupGeneratorViewModel.AdHocModeLabel;

        vm.GenerateCommand.Execute(null);

        Assert.Equal(students.Count, vm.GeneratedGroups.SelectMany(g => g.Members).Count());
        Assert.Contains("keine Anwesenheit", vm.WarningText);
    }

    [Fact]
    public void Leistungsverteilung_UnterscheidetHomogeneUndHeterogeneGruppen()
    {
        var group = new LearningGroup { Name = "Kurs", GradingSystem = GradingSystem.Grades1To6 };
        var students = new[] { "A", "B", "C", "D" }.Select(name => new Student
        {
            FirstName = name, LastName = "Test",
        }).ToList();
        var memberships = students.Select(s => new GroupMembership { GroupId = group.Id, StudentId = s.Id }).ToList();
        var grades = new FakeGrades();
        var values = new[] { "1", "2", "5", "6" };
        for (var i = 0; i < students.Count; i++)
            grades.Add(new Grade { GroupId = group.Id, StudentId = students[i].Id, Value = values[i] });
        var vm = new StudentGroupGeneratorViewModel(
            new FakeStudents(students), new FakeGroups([group]), new FakeMemberships(memberships),
            new FakeSessions([]), new FakeEntries(), grades, group.Id, new Random(3))
        {
            TargetGroupCount = 2,
            CountPriority = 100,
            PerformanceDistribution = -100,
        };

        vm.GenerateCommand.Execute(null);
        var homogeneousFirst = vm.GeneratedGroups[0].Members.Select(m => m.Name).ToHashSet();
        Assert.Contains(students[0].FullName, homogeneousFirst);
        Assert.Contains(students[1].FullName, homogeneousFirst);

        vm.PerformanceDistribution = 100;
        vm.GenerateCommand.Execute(null);
        Assert.All(vm.GeneratedGroups, generated =>
        {
            var names = generated.Members.Select(m => m.Name).ToHashSet();
            Assert.True(names.Overlaps([students[0].FullName, students[1].FullName]));
            Assert.True(names.Overlaps([students[2].FullName, students[3].FullName]));
        });
    }

    [Fact]
    public void Paarregeln_ErzwingenZusammenUndTrennenMitHoherPrioritaet()
    {
        var (vm, students, _, _, _) = Build(6);
        vm.TargetGroupCount = 2;
        vm.CountPriority = 100;
        vm.PerformanceDistribution = 0;
        vm.ForcedPairPriority = 100;
        vm.SelectedPairStudentA = vm.PairCandidates.Single(s => s.Id == students[0].Id);
        vm.SelectedPairStudentB = vm.PairCandidates.Single(s => s.Id == students[1].Id);
        vm.AddForcedPairCommand.Execute(null);
        vm.SelectedPairStudentA = vm.PairCandidates.Single(s => s.Id == students[2].Id);
        vm.SelectedPairStudentB = vm.PairCandidates.Single(s => s.Id == students[3].Id);
        vm.AddExcludedPairCommand.Execute(null);

        vm.GenerateCommand.Execute(null);

        var groupByName = vm.GeneratedGroups.SelectMany((group, index) =>
                group.Members.Select(member => (member.Name, index)))
            .ToDictionary(x => x.Name, x => x.index);
        Assert.Equal(groupByName[students[0].FullName], groupByName[students[1].FullName]);
        Assert.NotEqual(groupByName[students[2].FullName], groupByName[students[3].FullName]);
    }

    [Fact]
    public void FoerderschuelerWerdenMoeglichstGleichmaessigVerteilt()
    {
        var group = new LearningGroup { Name = "Kurs" };
        var students = Enumerable.Range(1, 8).Select(i => new Student
        {
            FirstName = $"Kind{i}", LastName = "Test",
        }).ToList();
        var memberships = students.Select((student, index) => new GroupMembership
        {
            GroupId = group.Id,
            StudentId = student.Id,
            Niveau = index < 4 ? Niveau.Foerder : null,
        }).ToList();
        var vm = new StudentGroupGeneratorViewModel(
            new FakeStudents(students), new FakeGroups([group]), new FakeMemberships(memberships),
            new FakeSessions([]), new FakeEntries(), new FakeGrades(), group.Id, new Random(4))
        {
            TargetGroupCount = 2,
            CountPriority = 100,
            PerformanceDistribution = -100,
            DistributeSupportStudents = true,
        };

        vm.GenerateCommand.Execute(null);

        var supportNames = students.Take(4).Select(s => s.FullName).ToHashSet();
        Assert.All(vm.GeneratedGroups, generated =>
            Assert.Equal(2, generated.Members.Count(member => supportNames.Contains(member.Name))));
    }
}