using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;

namespace LehrerApp.Data.Repositories;

internal static class ArchivedGroupWriteGuard
{
    public const string Message =
        "Diese Lerngruppe ist archiviert. Bitte reaktiviere sie, bevor du Änderungen vornimmst.";

    public static void EnsureActive(LiteDbContext db, Guid groupId)
    {
        if (db.Groups.FindById(groupId) is { IsActive: false })
            throw new InvalidOperationException(Message);
    }
}

public class StudentRepository(LiteDbContext db) : IStudentRepository
{
    public Student? GetById(Guid id) => db.Students.FindById(id);
    public List<Student> GetAll(bool includeInactive = false) =>
        (includeInactive ? db.Students.FindAll() : db.Students.Find(s => s.IsActive))
        .OrderBy(s => s.LastName).ToList();
    public List<Student> GetByGroup(Guid groupId)
    {
        var ids = db.Memberships
            .Find(e => e.GroupId == groupId)
            .Select(e => e.StudentId).ToHashSet();
        return db.Students.Find(s => ids.Contains(s.Id)).OrderBy(s => s.LastName).ToList();
    }
    public StudentReferenceSummary GetReferenceSummary(Guid studentId) => new(
        db.Memberships.Count(m => m.StudentId == studentId),
        db.ExamResults.Count(r => r.StudentId == studentId),
        db.Grades.Count(g => g.StudentId == studentId),
        db.ReportGrades.Count(g => g.StudentId == studentId),
        db.ParticipationEntries.Count(e => e.StudentId == studentId),
        db.Documentation.Count(d => d.StudentId == studentId));
    public void Save(Student s)
    {
        s.ExternalIds ??= [];
        s.Contacts ??= [];
        s.UpdatedAt = DateTime.UtcNow;
        db.Students.Upsert(s);
        db.OnChange?.Invoke(nameof(Student), s.Id.ToString(), "Save", s);
    }
    public void Delete(Guid id)
    {
        var references = GetReferenceSummary(id);
        if (references.HasReferences)
            throw new InvalidOperationException(
                "Der Schüler besitzt verknüpfte Daten und kann nur deaktiviert werden.");
        db.Students.Delete(id);
        db.OnChange?.Invoke(nameof(Student), id.ToString(), "Delete", null);
    }
}

public class GroupRepository(LiteDbContext db) : IGroupRepository
{
    public LearningGroup? GetById(Guid id) => db.Groups.FindById(id);
    public List<LearningGroup> GetAll(bool includeInactive = false) =>
        (includeInactive ? db.Groups.FindAll() : db.Groups.Find(g => g.IsActive))
        .OrderBy(g => g.SchoolYear).ThenBy(g => g.Name).ToList();
    public List<LearningGroup> GetBySchoolYear(string schoolYear, bool includeInactive = false) =>
        (includeInactive
            ? db.Groups.Find(g => g.SchoolYear == schoolYear)
            : db.Groups.Find(g => g.SchoolYear == schoolYear && g.IsActive))
        .OrderBy(g => g.Name).ToList();
    public void Save(LearningGroup g)
    {
        var existing = db.Groups.FindById(g.Id);
        if (existing is { IsActive: false } && !g.IsActive)
            throw new InvalidOperationException(ArchivedGroupWriteGuard.Message);
        if (existing is { IsActive: false } && g.IsActive
            && (existing.Name != g.Name || existing.Type != g.Type || existing.SubjectId != g.SubjectId
                || existing.SchoolYear != g.SchoolYear || existing.GradeLevel != g.GradeLevel
                || existing.GradingSystem != g.GradingSystem || existing.HoursPerWeek != g.HoursPerWeek
                || existing.IsOwnClass != g.IsOwnClass || existing.IsDifferentiated != g.IsDifferentiated))
            throw new InvalidOperationException(
                "Bitte reaktiviere die Lerngruppe zuerst und nimm die Änderungen anschließend vor.");
        if (g.SubjectId is Guid subjectId && db.Subjects.FindById(subjectId) is null)
            throw new InvalidOperationException("Das gewählte Fach existiert nicht mehr.");
        g.UpdatedAt = DateTime.UtcNow;
        db.Groups.Upsert(g);
        db.OnChange?.Invoke(nameof(LearningGroup), g.Id.ToString(), "Save", g);
    }
    public void Delete(Guid id)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, id);
        db.CascadeDeleteGroup(id);
        db.OnChange?.Invoke(nameof(LearningGroup), id.ToString(), "Delete", null);
    }
}

public class SeatingPlanRepository(LiteDbContext db) : ISeatingPlanRepository
{
    public SeatingPlan? GetById(Guid id) => db.SeatingPlans.FindById(id);

    public List<SeatingPlan> GetByGroup(Guid groupId) =>
        db.SeatingPlans.Find(p => p.GroupId == groupId)
            .OrderBy(p => p.Name).ThenBy(p => p.Room).ToList();

    public void Save(SeatingPlan plan)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, plan.GroupId);
        // LiteDB can deserialize missing/legacy optional string fields as null even
        // though the current model initializes them with an empty string.
        plan.Name = plan.Name?.Trim() ?? "";
        plan.Room = plan.Room?.Trim() ?? "";
        plan.Assignments ??= [];
        plan.ColumnGapWidths ??= [];
        plan.HiddenSeats ??= [];
        if (plan.Name.Length == 0)
            throw new ArgumentException("Der Name des Sitzplans darf nicht leer sein.");
        if (plan.Rows is < 1 or > 10 || plan.Columns is < 1 or > 10)
            throw new ArgumentOutOfRangeException(nameof(plan), "Ein Sitzplan muss zwischen 1 und 10 Reihen und Spalten haben.");
        if (db.Groups.FindById(plan.GroupId) is null)
            throw new InvalidOperationException("Die zugehörige Lerngruppe existiert nicht.");

        plan.ColumnGapWidths = Enumerable.Range(0, Math.Max(0, plan.Columns - 1))
            .Select(i => i < plan.ColumnGapWidths.Count && double.IsFinite(plan.ColumnGapWidths[i])
                ? Math.Clamp(plan.ColumnGapWidths[i], 0, 300)
                : 0)
            .ToList();

        var duplicateName = db.SeatingPlans.Find(p => p.GroupId == plan.GroupId)
            .FirstOrDefault(p => p.Id != plan.Id
                && string.Equals(p.Name, plan.Name, StringComparison.OrdinalIgnoreCase)
                && string.Equals(p.Room, plan.Room, StringComparison.OrdinalIgnoreCase));
        if (duplicateName is not null)
            throw new InvalidOperationException("Für diese Lerngruppe existiert bereits ein gleichnamiger Sitzplan in diesem Raum.");

        plan.Assignments = plan.Assignments
            .Where(a => a.Row >= 0 && a.Row < plan.Rows && a.Column >= 0 && a.Column < plan.Columns)
            .ToList();
        if (plan.Assignments.GroupBy(a => (a.Row, a.Column)).Any(g => g.Count() > 1))
            throw new InvalidOperationException("Ein Sitzplatz darf nur einmal belegt werden.");
        if (plan.Assignments.GroupBy(a => a.StudentId).Any(g => g.Count() > 1))
            throw new InvalidOperationException("Ein Schüler darf in einem Sitzplan nur einmal vorkommen.");

        var memberIds = db.Memberships.Find(m => m.GroupId == plan.GroupId)
            .Select(m => m.StudentId).ToHashSet();
        if (plan.Assignments.Any(a => !memberIds.Contains(a.StudentId)))
            throw new InvalidOperationException("Der Sitzplan enthält einen Schüler, der nicht zur Lerngruppe gehört.");

        // Ein ausgeblendeter Platz darf nie belegt sein - die Zuordnung eines Schülers ist
        // wertvoller als das Ausblenden, deshalb wird hier stillschweigend wieder eingeblendet
        // statt die Zuordnung zu verwerfen. Sollte über die UI (SeatingPlanTabViewModel verhindert
        // das Belegen ausgeblendeter Plätze) nie vorkommen - reine Absicherung bei fehlerhaften
        // oder von einem älteren Client synchronisierten Daten.
        var assignedPositions = plan.Assignments.Select(a => (a.Row, a.Column)).ToHashSet();
        plan.HiddenSeats = plan.HiddenSeats
            .Where(h => h.Row >= 0 && h.Row < plan.Rows && h.Column >= 0 && h.Column < plan.Columns)
            .Where(h => !assignedPositions.Contains((h.Row, h.Column)))
            .DistinctBy(h => (h.Row, h.Column))
            .ToList();

        plan.UpdatedAt = DateTime.UtcNow;
        db.SeatingPlans.Upsert(plan);
        db.OnChange?.Invoke(nameof(SeatingPlan), plan.Id.ToString(), "Save", plan);
    }

    public void Delete(Guid id)
    {
        if (db.SeatingPlans.FindById(id) is not { } plan) return;
        ArchivedGroupWriteGuard.EnsureActive(db, plan.GroupId);
        db.MoveToTrash(nameof(SeatingPlan), id, plan,
            string.IsNullOrWhiteSpace(plan.Room) ? plan.Name : $"{plan.Name} (Raum {plan.Room})");
        db.SeatingPlans.Delete(id);
        db.OnChange?.Invoke(nameof(SeatingPlan), id.ToString(), "Delete", null);
    }

    public void Restore(Guid trashId)
    {
        if (db.RestoreFromTrash<SeatingPlan>(trashId) is { } plan) Save(plan);
    }
}

public class GroupMembershipRepository(LiteDbContext db) : IGroupMembershipRepository
{
    public List<GroupMembership> GetByStudent(Guid id) =>
        db.Memberships.Find(e => e.StudentId == id).ToList();
    public List<GroupMembership> GetByGroup(Guid id) =>
        db.Memberships.Find(e => e.GroupId == id).ToList();
    public GroupMembership? GetByStudentAndGroup(Guid studentId, Guid groupId) =>
        db.Memberships.FindOne(e => e.StudentId == studentId && e.GroupId == groupId);
    public void Save(GroupMembership membership)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, membership.GroupId);
        var existing = GetByStudentAndGroup(membership.StudentId, membership.GroupId);
        if (existing is not null && existing.Id != membership.Id)
            throw new InvalidOperationException("Der Schüler ist dieser Lerngruppe bereits zugeordnet.");
        db.Memberships.Upsert(membership);
        db.OnChange?.Invoke(nameof(GroupMembership), membership.Id.ToString(), "Save", membership);
    }
    public void Delete(Guid id)
    {
        if (db.Memberships.FindById(id) is { } membership)
            ArchivedGroupWriteGuard.EnsureActive(db, membership.GroupId);
        db.Memberships.Delete(id);
        db.OnChange?.Invoke(nameof(GroupMembership), id.ToString(), "Delete", null);
    }
}

public class ExamRepository(LiteDbContext db) : IExamRepository
{
    public Exam? GetById(Guid id) => db.Exams.FindById(id);
    public List<Exam> GetAll() => db.Exams.FindAll().OrderBy(e => e.Date).ToList();
    public List<Exam> GetByGroup(Guid groupId) =>
        db.Exams.Find(e => e.GroupId == groupId).OrderByDescending(e => e.Date).ToList();
    public void Save(Exam e)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, e.GroupId);
        e.UpdatedAt = DateTime.UtcNow;
        db.Exams.Upsert(e);
        db.OnChange?.Invoke(nameof(Exam), e.Id.ToString(), "Save", e);
    }
    public void Delete(Guid id)
    {
        if (db.Exams.FindById(id) is { } exam)
            ArchivedGroupWriteGuard.EnsureActive(db, exam.GroupId);
        db.CascadeDeleteExam(id);
        db.OnChange?.Invoke(nameof(Exam), id.ToString(), "Delete", null);
    }
}

public class ExamResultRepository(LiteDbContext db) : IExamResultRepository
{
    public List<ExamResult> GetByExam(Guid id) =>
        db.ExamResults.Find(r => r.ExamId == id).ToList();
    public List<ExamResult> GetByStudent(Guid id) =>
        db.ExamResults.Find(r => r.StudentId == id).ToList();
    public ExamResult? GetByExamAndStudent(Guid examId, Guid studentId) =>
        db.ExamResults.FindOne(r => r.ExamId == examId && r.StudentId == studentId);
    public void Save(ExamResult r)
    {
        if (db.Exams.FindById(r.ExamId) is { } exam)
            ArchivedGroupWriteGuard.EnsureActive(db, exam.GroupId);
        r.UpdatedAt = DateTime.UtcNow;
        db.ExamResults.Upsert(r);
        db.OnChange?.Invoke(nameof(ExamResult), r.Id.ToString(), "Save", r);
    }
    public void SaveMany(List<ExamResult> results)
    {
        foreach (var examId in results.Select(r => r.ExamId).Distinct())
            if (db.Exams.FindById(examId) is { } exam)
                ArchivedGroupWriteGuard.EnsureActive(db, exam.GroupId);
        var now = DateTime.UtcNow;
        foreach (var r in results) r.UpdatedAt = now;
        db.ExamResults.Upsert(results);
        foreach (var r in results)
            db.OnChange?.Invoke(nameof(ExamResult), r.Id.ToString(), "Save", r);
    }
}

public class GradingKeyTemplateRepository(LiteDbContext db) : IGradingKeyTemplateRepository
{
    public List<GradingKeyTemplate> GetAll() =>
        db.GradingKeyTemplates.FindAll().OrderBy(t => t.Name).ToList();
    public List<GradingKeyTemplate> GetByGradingSystem(GradingSystem system) =>
        db.GradingKeyTemplates.Find(t => t.GradingSystem == system).OrderBy(t => t.Name).ToList();
    public GradingKeyTemplate? GetById(Guid id) => db.GradingKeyTemplates.FindById(id);
    public void Save(GradingKeyTemplate t)
    {
        t.UpdatedAt = DateTime.UtcNow;
        db.GradingKeyTemplates.Upsert(t);
        db.OnChange?.Invoke(nameof(GradingKeyTemplate), t.Id.ToString(), "Save", t);
    }
    public void Delete(Guid id)
    {
        if (db.GradingKeyTemplates.FindById(id) is { } template)
            db.MoveToTrash(nameof(GradingKeyTemplate), id, template, template.Name);
        db.GradingKeyTemplates.Delete(id);
        db.OnChange?.Invoke(nameof(GradingKeyTemplate), id.ToString(), "Delete", null);
    }

    public void Restore(Guid trashId)
    {
        if (db.RestoreFromTrash<GradingKeyTemplate>(trashId) is { } template) Save(template);
    }
}

public class GradeRepository(LiteDbContext db) : IGradeRepository
{
    public List<Grade> GetByStudentAndGroup(Guid sid, Guid gid) =>
        db.Grades.Find(g => g.StudentId == sid && g.GroupId == gid).OrderBy(g => g.Date).ToList();
    public List<Grade> GetByGroup(Guid id) =>
        db.Grades.Find(g => g.GroupId == id).OrderBy(g => g.Date).ToList();
    public void Save(Grade g)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, g.GroupId);
        db.Grades.Upsert(g);
        db.OnChange?.Invoke(nameof(Grade), g.Id.ToString(), "Save", g);
    }
    public void Delete(Guid id)
    {
        if (db.Grades.FindById(id) is not { } grade) return;
        ArchivedGroupWriteGuard.EnsureActive(db, grade.GroupId);
        db.MoveToTrash(nameof(Grade), id, grade,
            $"Note {grade.Value} ({grade.Date:dd.MM.yyyy})");
        db.Grades.Delete(id);
        db.OnChange?.Invoke(nameof(Grade), id.ToString(), "Delete", null);
    }

    public void Restore(Guid trashId)
    {
        if (db.RestoreFromTrash<Grade>(trashId) is { } grade) Save(grade);
    }
}

public class GradingSchemeRepository(LiteDbContext db) : IGradingSchemeRepository
{
    public GradingScheme? GetByGroup(Guid groupId) => db.GradingSchemes.FindOne(s => s.GroupId == groupId);
    public GradingScheme? GetDefaultForType(GroupType type) =>
        db.GradingSchemes.FindOne(s => s.GroupId == null && s.GroupType == type);
    public void Save(GradingScheme s)
    {
        if (s.GroupId is Guid groupId) ArchivedGroupWriteGuard.EnsureActive(db, groupId);
        s.UpdatedAt = DateTime.UtcNow;
        db.GradingSchemes.Upsert(s);
        db.OnChange?.Invoke(nameof(GradingScheme), s.Id.ToString(), "Save", s);
    }
    public void Delete(Guid id)
    {
        if (db.GradingSchemes.FindById(id)?.GroupId is Guid groupId)
            ArchivedGroupWriteGuard.EnsureActive(db, groupId);
        db.GradingSchemes.Delete(id);
        db.OnChange?.Invoke(nameof(GradingScheme), id.ToString(), "Delete", null);
    }
}

public class ReportGradeRepository(LiteDbContext db) : IReportGradeRepository
{
    public List<ReportGrade> GetByGroup(Guid groupId) => db.ReportGrades.Find(r => r.GroupId == groupId).ToList();
    public ReportGrade? GetByStudentGroupPeriod(Guid studentId, Guid groupId, string period) =>
        db.ReportGrades.FindOne(r => r.StudentId == studentId && r.GroupId == groupId && r.Period == period);
    public void Save(ReportGrade r)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, r.GroupId);
        r.UpdatedAt = DateTime.UtcNow;
        db.ReportGrades.Upsert(r);
        db.OnChange?.Invoke(nameof(ReportGrade), r.Id.ToString(), "Save", r);
    }
    public void Delete(Guid id)
    {
        if (db.ReportGrades.FindById(id) is { } grade)
            ArchivedGroupWriteGuard.EnsureActive(db, grade.GroupId);
        db.ReportGrades.Delete(id);
        db.OnChange?.Invoke(nameof(ReportGrade), id.ToString(), "Delete", null);
    }
}

public class UnitRepository(LiteDbContext db) : IUnitRepository
{
    public Unit? GetById(Guid id) => db.Units.FindById(id);
    public List<Unit> GetByGroup(Guid id) =>
        db.Units.Find(u => u.GroupId == id).OrderBy(u => u.StartDate).ToList();
    public void Save(Unit u)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, u.GroupId);
        u.UpdatedAt = DateTime.UtcNow;
        db.Units.Upsert(u);
        db.OnChange?.Invoke(nameof(Unit), u.Id.ToString(), "Save", u);
    }
    public void Delete(Guid id)
    {
        if (db.Units.FindById(id) is { } unit)
            ArchivedGroupWriteGuard.EnsureActive(db, unit.GroupId);
        db.Units.Delete(id);
        db.OnChange?.Invoke(nameof(Unit), id.ToString(), "Delete", null);
    }
}

public class LessonRepository(LiteDbContext db) : ILessonRepository
{
    public List<Lesson> GetByUnit(Guid id) =>
        db.Lessons.Find(l => l.UnitId == id).OrderBy(l => l.Date).ThenBy(l => l.LessonNumber).ToList();
    public List<Lesson> GetByGroupAndDate(Guid gid, DateOnly date) =>
        db.Lessons.Find(l => l.GroupId == gid && l.Date == date).ToList();
    public List<Lesson> GetByGroupAndRange(Guid gid, DateOnly from, DateOnly to) =>
        db.Lessons.Find(l => l.GroupId == gid && l.Date >= from && l.Date <= to)
            .OrderBy(l => l.Date).ToList();
    public void Save(Lesson l)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, l.GroupId);
        l.UpdatedAt = DateTime.UtcNow;
        db.Lessons.Upsert(l);
        db.OnChange?.Invoke(nameof(Lesson), l.Id.ToString(), "Save", l);
    }
    public void Delete(Guid id)
    {
        if (db.Lessons.FindById(id) is { } lesson)
        {
            ArchivedGroupWriteGuard.EnsureActive(db, lesson.GroupId);
            foreach (var attachment in lesson.Attachments) db.Attachments.Delete(attachment.StorageId);
        }
        db.Lessons.Delete(id);
        db.OnChange?.Invoke(nameof(Lesson), id.ToString(), "Delete", null);
    }
}

public class DocumentationRepository(LiteDbContext db) : IDocumentationRepository
{
    public List<Documentation> GetByStudent(Guid id) =>
        db.Documentation.Find(d => d.StudentId == id && !d.IsDeleted).OrderByDescending(d => d.Date).ToList();
    public List<Documentation> GetByStudentAndType(Guid sid, DocumentationType type) =>
        db.Documentation.Find(d => d.StudentId == sid && d.Type == type && !d.IsDeleted)
            .OrderByDescending(d => d.Date).ToList();
    public List<Documentation> GetAll() =>
        db.Documentation.Find(d => !d.IsDeleted).OrderByDescending(d => d.Date).ToList();
    public void Save(Documentation d)
    {
        d.UpdatedAt = DateTime.UtcNow;
        db.Documentation.Upsert(d);
        db.OnChange?.Invoke(nameof(Documentation), d.Id.ToString(), "Save", d);
    }
    public void Delete(Guid id)
    {
        var doc = db.Documentation.FindById(id);
        if (doc is null) return;
        doc.IsDeleted = true;
        doc.DeletedAt = DateTime.UtcNow;
        db.Documentation.Update(doc);
        // Weiches Löschen ist inhaltlich eine Änderung, kein Entfernen -> "Save", damit ein
        // anwendendes Gerät den IsDeleted-Stand einfach übernimmt statt den Datensatz zu entfernen.
        db.OnChange?.Invoke(nameof(Documentation), id.ToString(), "Save", doc);
    }
    public void HardDelete(Guid id)
    {
        db.CascadeHardDeleteDocumentation(id);
        db.OnChange?.Invoke(nameof(Documentation), id.ToString(), "Delete", null);
    }
}

public class WorkTaskRepository(LiteDbContext db) : IWorkTaskRepository
{
    public List<WorkTask> GetByStatus(WorkTaskStatus s) =>
        db.Tasks.Find(t => t.Status == s).OrderBy(t => t.DueDate).ToList();
    public List<WorkTask> GetAll() =>
        db.Tasks.FindAll().OrderBy(t => t.Status).ThenBy(t => t.DueDate).ToList();
    public List<WorkTask> GetByGroup(Guid groupId) =>
        db.Tasks.Find(t => t.GroupId == groupId).OrderBy(t => t.Status).ThenBy(t => t.DueDate).ToList();
    public void Save(WorkTask t)
    {
        t.UpdatedAt = DateTime.UtcNow;
        db.Tasks.Upsert(t);
        db.OnChange?.Invoke(nameof(WorkTask), t.Id.ToString(), "Save", t);
    }
    public void Delete(Guid id)
    {
        if (db.Tasks.FindById(id) is { } task)
            db.MoveToTrash(nameof(WorkTask), id, task, task.Title);
        db.Tasks.Delete(id);
        db.OnChange?.Invoke(nameof(WorkTask), id.ToString(), "Delete", null);
    }

    public void Restore(Guid trashId)
    {
        if (db.RestoreFromTrash<WorkTask>(trashId) is { } task) Save(task);
    }
}

public class TimeEntryRepository(LiteDbContext db) : ITimeEntryRepository
{
    public List<TimeEntry> GetByDate(DateOnly date) =>
        db.TimeEntries.Find(e => e.Date == date).OrderBy(e => e.StartTime).ToList();
    public List<TimeEntry> GetByDateRange(DateOnly from, DateOnly to) =>
        db.TimeEntries.Find(e => e.Date >= from && e.Date <= to).OrderBy(e => e.Date).ToList();
    public List<TimeEntry> GetByTask(Guid id) =>
        db.TimeEntries.Find(e => e.TaskId == id).ToList();
    public void Save(TimeEntry e)
    {
        db.TimeEntries.Upsert(e);
        db.OnChange?.Invoke(nameof(TimeEntry), e.Id.ToString(), "Save", e);
    }
    public void Delete(Guid id)
    {
        if (db.TimeEntries.FindById(id) is { } entry)
            db.MoveToTrash(nameof(TimeEntry), id, entry,
                $"{entry.DurationMinutes} Min. {entry.Category} ({entry.Date:dd.MM.yyyy})");
        db.TimeEntries.Delete(id);
        db.OnChange?.Invoke(nameof(TimeEntry), id.ToString(), "Delete", null);
    }

    public void Restore(Guid trashId)
    {
        if (db.RestoreFromTrash<TimeEntry>(trashId) is { } entry) Save(entry);
    }
}

public class ParticipationSessionRepository(LiteDbContext db) : IParticipationSessionRepository
{
    public List<ParticipationSession> GetByGroup(Guid groupId) =>
        db.ParticipationSessions.Find(s => s.GroupId == groupId).OrderByDescending(s => s.Date).ToList();
    public ParticipationSession? GetById(Guid id) => db.ParticipationSessions.FindById(id);
    public void Save(ParticipationSession s)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, s.GroupId);
        s.UpdatedAt = DateTime.UtcNow;
        db.ParticipationSessions.Upsert(s);
        db.OnChange?.Invoke(nameof(ParticipationSession), s.Id.ToString(), "Save", s);
    }
    public void Delete(Guid id)
    {
        if (db.ParticipationSessions.FindById(id) is { } session)
            ArchivedGroupWriteGuard.EnsureActive(db, session.GroupId);
        db.CascadeDeleteParticipationSession(id);
        db.OnChange?.Invoke(nameof(ParticipationSession), id.ToString(), "Delete", null);
    }
}

public class ParticipationRepository(LiteDbContext db) : IParticipationRepository
{
    public List<ParticipationEntry> GetBySession(Guid sessionId) =>
        db.ParticipationEntries.Find(e => e.SessionId == sessionId).ToList();
    public List<ParticipationEntry> GetByStudent(Guid studentId) =>
        db.ParticipationEntries.Find(e => e.StudentId == studentId).ToList();
    public ParticipationEntry? GetBySessionAndStudent(Guid sessionId, Guid studentId) =>
        db.ParticipationEntries.FindOne(e => e.SessionId == sessionId && e.StudentId == studentId);
    public void Save(ParticipationEntry e)
    {
        if (db.ParticipationSessions.FindById(e.SessionId) is { } session)
            ArchivedGroupWriteGuard.EnsureActive(db, session.GroupId);
        e.UpdatedAt = DateTime.UtcNow;
        db.ParticipationEntries.Upsert(e);
        db.OnChange?.Invoke(nameof(ParticipationEntry), e.Id.ToString(), "Save", e);
    }
    public void SaveMany(List<ParticipationEntry> entries)
    {
        foreach (var sessionId in entries.Select(e => e.SessionId).Distinct())
            if (db.ParticipationSessions.FindById(sessionId) is { } session)
                ArchivedGroupWriteGuard.EnsureActive(db, session.GroupId);
        var now = DateTime.UtcNow;
        foreach (var e in entries) e.UpdatedAt = now;
        db.ParticipationEntries.Upsert(entries);
        foreach (var e in entries)
            db.OnChange?.Invoke(nameof(ParticipationEntry), e.Id.ToString(), "Save", e);
    }
    public void DeleteBySession(Guid sessionId)
    {
        if (db.ParticipationSessions.FindById(sessionId) is { } session)
            ArchivedGroupWriteGuard.EnsureActive(db, session.GroupId);
        foreach (var e in db.ParticipationEntries.Find(e => e.SessionId == sessionId).ToList())
        {
            db.ParticipationEntries.Delete(e.Id);
            db.OnChange?.Invoke(nameof(ParticipationEntry), e.Id.ToString(), "Delete", null);
        }
    }
}

public class ParticipationAspectRepository(LiteDbContext db) : IParticipationAspectRepository
{
    public List<ParticipationAspect> GetDefaults() =>
        db.ParticipationAspects.Find(a => a.GroupId == null && a.IsActive).OrderBy(a => a.SortOrder).ToList();
    public List<ParticipationAspect> GetByGroup(Guid groupId) =>
        db.ParticipationAspects.Find(a => a.GroupId == groupId && a.IsActive).OrderBy(a => a.SortOrder).ToList();
    public List<ParticipationAspect> GetAllByGroup(Guid groupId) =>
        db.ParticipationAspects.Find(a => a.GroupId == groupId).OrderBy(a => a.SortOrder).ToList();
    public void Save(ParticipationAspect a)
    {
        if (a.GroupId is Guid groupId) ArchivedGroupWriteGuard.EnsureActive(db, groupId);
        a.Key = a.Key.Trim();
        a.Label = a.Label.Trim();
        if (a.Key.Length == 0) throw new ArgumentException("Der Schlüssel darf nicht leer sein.");
        if (a.Label.Length == 0) throw new ArgumentException("Die Bezeichnung darf nicht leer sein.");
        // Ein Schlüssel muss innerhalb dessen, was für eine Gruppe tatsächlich gilt, eindeutig
        // sein — das sind die globalen Standardaspekte UND die gruppenspezifischen zusammen
        // (siehe ParticipationTabViewModel.LoadAspects, das beide konkateniert). Sonst entstünde
        // in der Bewertungsübersicht eine mehrdeutige Spalte mit identischem Schlüssel.
        var relevant = db.ParticipationAspects.Find(x => x.GroupId == null || x.GroupId == a.GroupId);
        var duplicate = relevant.FirstOrDefault(x =>
            x.Id != a.Id && string.Equals(x.Key, a.Key, StringComparison.OrdinalIgnoreCase));
        if (duplicate is not null)
            throw new InvalidOperationException("Ein Aspekt mit diesem Schlüssel existiert für diese Gruppe bereits.");
        a.UpdatedAt = DateTime.UtcNow;
        db.ParticipationAspects.Upsert(a);
        db.OnChange?.Invoke(nameof(ParticipationAspect), a.Id.ToString(), "Save", a);
    }
    public void Delete(Guid id)
    {
        if (db.ParticipationAspects.FindById(id)?.GroupId is Guid groupId)
            ArchivedGroupWriteGuard.EnsureActive(db, groupId);
        db.ParticipationAspects.Delete(id);
        db.OnChange?.Invoke(nameof(ParticipationAspect), id.ToString(), "Delete", null);
    }
}

public class ParticipationSectionRepository(LiteDbContext db) : IParticipationSectionRepository
{
    public List<ParticipationSection> GetByGroup(Guid groupId) =>
        db.ParticipationSections.Find(s => s.GroupId == groupId).OrderBy(s => s.StartDate).ToList();
    public void Save(ParticipationSection s)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, s.GroupId);
        db.ParticipationSections.Upsert(s);
        db.OnChange?.Invoke(nameof(ParticipationSection), s.Id.ToString(), "Save", s);
    }
    public void Delete(Guid id)
    {
        if (db.ParticipationSections.FindById(id) is { } section)
            ArchivedGroupWriteGuard.EnsureActive(db, section.GroupId);
        db.ParticipationSections.Delete(id);
        db.OnChange?.Invoke(nameof(ParticipationSection), id.ToString(), "Delete", null);
    }
}

public class SubjectRepository(LiteDbContext db) : ISubjectRepository
{
    public List<Subject> GetAll() => db.Subjects.FindAll().OrderBy(s => s.Name).ToList();
    public Subject? GetById(Guid id) => db.Subjects.FindById(id);
    public Subject? GetByName(string name) => db.Subjects.FindAll().FirstOrDefault(s =>
        string.Equals(s.Name.Trim(), name.Trim(), StringComparison.OrdinalIgnoreCase));
    public void Save(Subject s)
    {
        s.Name = s.Name.Trim();
        s.ShortName = s.ShortName.Trim();
        if (s.Name.Length == 0) throw new ArgumentException("Der Fachname darf nicht leer sein.");
        var duplicate = GetByName(s.Name);
        if (duplicate is not null && duplicate.Id != s.Id)
            throw new InvalidOperationException("Ein Fach mit diesem Namen existiert bereits.");
        s.UpdatedAt = DateTime.UtcNow;
        db.Subjects.Upsert(s);
        db.OnChange?.Invoke(nameof(Subject), s.Id.ToString(), "Save", s);
    }
    public void Delete(Guid id)
    {
        if (db.Groups.Exists(g => g.SubjectId == id) || db.CompetencyDomains.Exists(d => d.SubjectId == id))
            throw new InvalidOperationException("Das Fach wird noch von einer Lerngruppe oder einem Kompetenzkatalog verwendet.");
        db.Subjects.Delete(id);
        db.OnChange?.Invoke(nameof(Subject), id.ToString(), "Delete", null);
    }
}

public class ShorthandCodeRepository(LiteDbContext db) : IShorthandCodeRepository
{
    public List<ShorthandCode> GetAll() => db.ShorthandCodes.FindAll().OrderBy(c => c.Code).ToList();
    public void Save(ShorthandCode c)
    {
        c.Code = c.Code.Trim();
        c.Label = c.Label.Trim();
        if (c.Code.Length == 0) throw new ArgumentException("Das Kürzel darf nicht leer sein.");
        var duplicate = db.ShorthandCodes.FindAll()
            .FirstOrDefault(x => string.Equals(x.Code, c.Code, StringComparison.OrdinalIgnoreCase));
        if (duplicate is not null && duplicate.Id != c.Id)
            throw new InvalidOperationException("Ein Kürzel mit diesem Code existiert bereits.");
        c.UpdatedAt = DateTime.UtcNow;
        db.ShorthandCodes.Upsert(c);
        db.OnChange?.Invoke(nameof(ShorthandCode), c.Id.ToString(), "Save", c);
    }
    public void Delete(Guid id)
    {
        db.ShorthandCodes.Delete(id);
        db.OnChange?.Invoke(nameof(ShorthandCode), id.ToString(), "Delete", null);
    }
}

public class AlternativeLessonPathRepository(LiteDbContext db) : IAlternativeLessonPathRepository
{
    public List<AlternativeLessonPath> GetAll() => db.AlternativeLessonPaths.FindAll().OrderBy(p => p.Name).ToList();
    public AlternativeLessonPath? GetById(Guid id) => db.AlternativeLessonPaths.FindById(id);
    public void Save(AlternativeLessonPath p)
    {
        p.Name = p.Name.Trim();
        p.Description = string.IsNullOrWhiteSpace(p.Description) ? null : p.Description.Trim();
        if (p.Name.Length == 0) throw new ArgumentException("Der Name darf nicht leer sein.");
        var duplicate = db.AlternativeLessonPaths.FindAll()
            .FirstOrDefault(x => string.Equals(x.Name, p.Name, StringComparison.OrdinalIgnoreCase));
        if (duplicate is not null && duplicate.Id != p.Id)
            throw new InvalidOperationException("Ein alternativer Ablauf mit diesem Namen existiert bereits.");
        p.UpdatedAt = DateTime.UtcNow;
        db.AlternativeLessonPaths.Upsert(p);
        db.OnChange?.Invoke(nameof(AlternativeLessonPath), p.Id.ToString(), "Save", p);
    }
    public void Delete(Guid id)
    {
        db.AlternativeLessonPaths.Delete(id);
        db.OnChange?.Invoke(nameof(AlternativeLessonPath), id.ToString(), "Delete", null);
    }
}

public class TimetableSlotRepository(LiteDbContext db) : ITimetableSlotRepository
{
    public List<TimetableSlot> GetAll() =>
        db.TimetableSlots.FindAll().OrderBy(s => s.Weekday).ThenBy(s => s.PeriodNumber).ToList();
    public List<TimetableSlot> GetByGroup(Guid groupId) =>
        db.TimetableSlots.Find(s => s.GroupId == groupId).OrderBy(s => s.Weekday).ThenBy(s => s.PeriodNumber).ToList();
    public void Save(TimetableSlot slot)
    {
        ArchivedGroupWriteGuard.EnsureActive(db, slot.GroupId);
        var occupied = db.TimetableSlots.FindAll()
            .FirstOrDefault(s => s.Weekday == slot.Weekday && s.PeriodNumber == slot.PeriodNumber);
        if (occupied is not null && occupied.Id != slot.Id)
            throw new InvalidOperationException("Diese Stunde ist bereits belegt.");
        db.TimetableSlots.Upsert(slot);
        db.OnChange?.Invoke(nameof(TimetableSlot), slot.Id.ToString(), "Save", slot);
    }
    public void Delete(Guid id)
    {
        if (db.TimetableSlots.FindById(id) is { } slot)
            ArchivedGroupWriteGuard.EnsureActive(db, slot.GroupId);
        db.TimetableSlots.Delete(id);
        db.OnChange?.Invoke(nameof(TimetableSlot), id.ToString(), "Delete", null);
    }
}

public class SchoolHolidayRepository(LiteDbContext db) : ISchoolHolidayRepository
{
    public List<SchoolHoliday> GetAll() => db.SchoolHolidays.FindAll().OrderBy(h => h.StartDate).ToList();
    public void Save(SchoolHoliday holiday)
    {
        db.SchoolHolidays.Upsert(holiday);
        db.OnChange?.Invoke(nameof(SchoolHoliday), holiday.Id.ToString(), "Save", holiday);
    }
    public void Delete(Guid id)
    {
        db.SchoolHolidays.Delete(id);
        db.OnChange?.Invoke(nameof(SchoolHoliday), id.ToString(), "Delete", null);
    }
}

public class SupervisionDutyRepository(LiteDbContext db) : ISupervisionDutyRepository
{
    public List<SupervisionDuty> GetAll() =>
        db.SupervisionDuties.FindAll().OrderBy(d => d.Weekday).ThenBy(d => d.AfterPeriod).ToList();
    public void Save(SupervisionDuty duty)
    {
        var occupied = db.SupervisionDuties.FindAll()
            .FirstOrDefault(d => d.Weekday == duty.Weekday && d.AfterPeriod == duty.AfterPeriod);
        if (occupied is not null && occupied.Id != duty.Id)
            throw new InvalidOperationException("Für diese Pause ist bereits eine Aufsicht eingetragen.");
        db.SupervisionDuties.Upsert(duty);
        db.OnChange?.Invoke(nameof(SupervisionDuty), duty.Id.ToString(), "Save", duty);
    }
    public void Delete(Guid id)
    {
        db.SupervisionDuties.Delete(id);
        db.OnChange?.Invoke(nameof(SupervisionDuty), id.ToString(), "Delete", null);
    }
}

public class SubstitutionEntryRepository(LiteDbContext db) : ISubstitutionEntryRepository
{
    public List<SubstitutionEntry> GetAll() => db.SubstitutionEntries.FindAll().OrderBy(e => e.Date).ToList();
    public List<SubstitutionEntry> GetByDate(DateOnly date) =>
        db.SubstitutionEntries.Find(e => e.Date == date).ToList();
    public void Save(SubstitutionEntry entry)
    {
        db.SubstitutionEntries.Upsert(entry);
        db.OnChange?.Invoke(nameof(SubstitutionEntry), entry.Id.ToString(), "Save", entry);
    }
    public void Delete(Guid id)
    {
        db.SubstitutionEntries.Delete(id);
        db.OnChange?.Invoke(nameof(SubstitutionEntry), id.ToString(), "Delete", null);
    }
}

public class CompetencyDomainRepository(LiteDbContext db) : ICompetencyDomainRepository
{
    public List<CompetencyDomain> GetBySubjectAndGrade(Guid subjectId, int gradeLevel) =>
        db.CompetencyDomains
          .Find(d => d.SubjectId == subjectId && d.GradeLevel == gradeLevel)
          .OrderBy(d => d.SortOrder)
          .ToList();
    public CompetencyDomain? GetById(Guid id) => db.CompetencyDomains.FindById(id);
    public void Save(CompetencyDomain d)
    {
        d.UpdatedAt = DateTime.UtcNow;
        db.CompetencyDomains.Upsert(d);
        db.OnChange?.Invoke(nameof(CompetencyDomain), d.Id.ToString(), "Save", d);
    }
    public void Delete(Guid id)
    {
        db.CompetencyDomains.Delete(id);
        db.OnChange?.Invoke(nameof(CompetencyDomain), id.ToString(), "Delete", null);
    }
    public void DeleteBySubjectAndGrade(Guid subjectId, int gradeLevel)
    {
        foreach (var d in db.CompetencyDomains
                             .Find(d => d.SubjectId == subjectId && d.GradeLevel == gradeLevel)
                             .ToList())
        {
            db.CompetencyDomains.Delete(d.Id);
            db.OnChange?.Invoke(nameof(CompetencyDomain), d.Id.ToString(), "Delete", null);
        }
    }
    public void ReplaceForSubjectAndGrade(Guid subjectId, int gradeLevel, List<CompetencyDomain> domains)
    {
        db.ExecuteInTransaction(() =>
        {
            foreach (var domain in db.CompetencyDomains
                         .Find(d => d.SubjectId == subjectId && d.GradeLevel == gradeLevel).ToList())
            {
                db.CompetencyDomains.Delete(domain.Id);
                db.OnChange?.Invoke(nameof(CompetencyDomain), domain.Id.ToString(), "Delete", null);
            }
            var now = DateTime.UtcNow;
            foreach (var domain in domains)
            {
                domain.SubjectId = subjectId;
                domain.GradeLevel = gradeLevel;
                domain.UpdatedAt = now;
                db.CompetencyDomains.Upsert(domain);
                db.OnChange?.Invoke(nameof(CompetencyDomain), domain.Id.ToString(), "Save", domain);
            }
        });
    }
}

/// <summary>Papierkorb (14.3) — bewusst nicht sync-fähig: TrashedItem wird nie über
/// db.OnChange gemeldet, bleibt also rein lokal auf dem Gerät, auf dem gelöscht wurde. Ein
/// "Fehlklick sofort rückgängig machen"-Werkzeug, kein geräteübergreifendes Archiv.</summary>
public class TrashRepository(LiteDbContext db) : ITrashRepository
{
    public List<TrashedItem> GetAll() =>
        db.TrashedItems.FindAll().OrderByDescending(t => t.DeletedAt).ToList();

    public void PurgeOlderThan(DateTime cutoffUtc)
    {
        foreach (var item in db.TrashedItems.Find(t => t.DeletedAt < cutoffUtc).ToList())
            db.TrashedItems.Delete(item.Id);
    }
}