using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using System.Collections.ObjectModel;
using System.Collections.Generic;

namespace LehrerApp.Desktop.ViewModels.Groups;

// ── Tab-ViewModel ─────────────────────────────────────────────────────────────

public partial class ParticipationTabViewModel : ObservableObject
{
    private readonly IParticipationSessionRepository _sessions;
    private readonly IParticipationRepository        _entries;
    private readonly IParticipationAspectRepository  _aspects;
    private readonly IStudentRepository              _students;
    private readonly IGroupMembershipRepository      _memberships;
    private readonly IGroupRepository                _groups;
    private readonly ICompetencyDomainRepository     _competencyDomains;

    private Guid   _groupId;
    private string _schoolYear = "";
    private Guid?  _subjectId;
    private int    _gradeLevel;
    private GradingSystem _gradingSystem;

    public Guid GroupId => _groupId;
    public string SchoolYear => _schoolYear;
    public GradingSystem GradingSystem => _gradingSystem;
    public string GroupLabel { get; private set; } = "";

    [ObservableProperty] private ParticipationSessionItem? _selectedSession;
    [ObservableProperty] private string _noDataText = "Keine Bewertungssitzung ausgewählt.";
    [ObservableProperty] private bool   _competencyTagsVisible;
    [ObservableProperty] private bool   _hasCompetencyCatalog;
    [ObservableProperty] private bool   _studentCompetencyRatingsVisible;
    [ObservableProperty] private int    _rebuildColumnsSignal;

    public string SelectedSessionDisplay => SelectedSession?.Display ?? "";
    public List<string> ActiveCompetencyCodes { get; private set; } = [];

    public ObservableCollection<ParticipationSessionItem>  Sessions            { get; } = [];
    public ObservableCollection<ParticipationStudentRow>   StudentRows         { get; } = [];
    public ObservableCollection<AspectColumnDef>           Aspects             { get; } = [];
    public ObservableCollection<CompetencyTagGroup>        CompetencyTagGroups { get; } = [];

    public Func<Task<ParticipationSession?>>? OnAddSession   { get; set; }
    public Func<ParticipationTabViewModel, Task>? OnQuickInput { get; set; }
    public Func<ParticipationTabViewModel, Task>? OnStatusQuickInput { get; set; }
    public Func<ParticipationTabViewModel, Task>? OnComputeGrade { get; set; }
    public Func<ParticipationTabViewModel, Task>? OnOpenWizard { get; set; }

    public ParticipationTabViewModel(
        IParticipationSessionRepository sessions,
        IParticipationRepository entries,
        IParticipationAspectRepository aspects,
        IStudentRepository students,
        IGroupMembershipRepository memberships,
        IGroupRepository groups,
        ICompetencyDomainRepository competencyDomains)
    {
        _sessions         = sessions;    _entries     = entries;
        _aspects          = aspects;     _students    = students;
        _memberships      = memberships; _groups      = groups;
        _competencyDomains = competencyDomains;
    }

    public void Initialize(Guid groupId, string schoolYear)
    {
        _groupId    = groupId;
        _schoolYear = schoolYear;

        var group   = _groups.GetById(groupId);
        _subjectId  = group?.SubjectId;
        _gradeLevel = group?.GradeLevel ?? 0;
        _gradingSystem = group?.GradingSystem ?? GradingSystem.Grades1To6;
        GroupLabel = group?.Name ?? "";

        HasCompetencyCatalog = _subjectId.HasValue
            && _competencyDomains.GetBySubjectAndGrade(_subjectId.Value, _gradeLevel).Count > 0;

        LoadAspects();
        LoadSessions();
    }

    private void LoadAspects()
    {
        Aspects.Clear();
        var defaults = _aspects.GetDefaults();
        var specific = _aspects.GetByGroup(_groupId);
        var all = defaults.Concat(specific).ToList();

        if (!all.Any())
        {
            foreach (var a in DefaultParticipationAspects.All)
                Aspects.Add(new AspectColumnDef(a));
        }
        else
        {
            foreach (var a in all) Aspects.Add(new AspectColumnDef(a));
        }
    }

    public void LoadSessions()
    {
        Sessions.Clear();
        foreach (var s in _sessions.GetByGroup(_groupId))
            Sessions.Add(new ParticipationSessionItem(s));
        if (SelectedSession is null && Sessions.Any())
            SelectedSession = Sessions[0];
    }

    partial void OnSelectedSessionChanged(ParticipationSessionItem? value)
    {
        OnPropertyChanged(nameof(SelectedSessionDisplay));
        if (value is null)
        {
            StudentRows.Clear();
            CompetencyTagGroups.Clear();
            ActiveCompetencyCodes = [];
            QuickInputCommand.NotifyCanExecuteChanged();
            StatusQuickInputCommand.NotifyCanExecuteChanged();
            RebuildColumnsSignal++;
            return;
        }
        LoadCompetencyTags(value.Id);  // sets ActiveCompetencyCodes first
        LoadGrid(value.Id);            // uses ActiveCompetencyCodes, fires RebuildColumnsSignal++
    }

    private void LoadGrid(Guid sessionId)
    {
        StudentRows.Clear();
        var session     = _sessions.GetById(sessionId);
        var sessionDate = session?.Date ?? DateOnly.FromDateTime(DateTime.Today);
        var students    = _students.GetByGroup(_groupId);
        var memberships = _memberships.GetByGroup(_groupId);
        var entries     = _entries.GetBySession(sessionId);

        foreach (var s in students)
        {
            var membership = memberships.FirstOrDefault(e => e.StudentId == s.Id);
            if (membership is not null && !IsMemberAtDate(membership, sessionDate))
                continue;

            var entry = entries.FirstOrDefault(e => e.StudentId == s.Id)
                        ?? new ParticipationEntry { SessionId = sessionId, StudentId = s.Id };
            var row = new ParticipationStudentRow(s.Id, s.FullName, entry, Aspects.ToList(), ActiveCompetencyCodes);
            row.OnRatingChanged           = (sid, key, val)  => SaveRating(sessionId, sid, key, val);
            row.OnCompetencyRatingChanged = (sid, code, val) => SaveCompetencyRating(sessionId, sid, code, val);
            row.HomeworkChangedCallback         = (sid, val) => SaveHomework(sessionId, sid, val);
            row.AttendanceChangedCallback       = (sid, val) => SaveAttendance(sessionId, sid, val);
            StudentRows.Add(row);
        }
        QuickInputCommand.NotifyCanExecuteChanged();
        StatusQuickInputCommand.NotifyCanExecuteChanged();
        RebuildColumnsSignal++;
    }

    private static bool IsMemberAtDate(GroupMembership membership, DateOnly date) => membership.Period switch
    {
        MembershipPeriod.H1Only => date.Month >= 8 || date.Month <= 1,
        MembershipPeriod.H2Only => date.Month >= 2 && date.Month <= 7,
        MembershipPeriod.Custom => (membership.JoinedAt is null || date >= membership.JoinedAt.Value)
                                && (membership.LeftAt  is null || date <= membership.LeftAt.Value),
        _                       => true,
    };

    private void SaveRating(Guid sessionId, Guid studentId, string key, int? value)
    {
        var entry = _entries.GetBySessionAndStudent(sessionId, studentId)
                      ?? new ParticipationEntry
                      {
                          SessionId = sessionId,
                          StudentId = studentId,
                      };

        var existing = entry.Ratings.FirstOrDefault(r => r.Key == key);
        if (value is null)
        {
            if (existing is not null) entry.Ratings.Remove(existing);
        }
        else
        {
            if (existing is null) entry.Ratings.Add(new AspectRating { Key = key, Value = value.Value });
            else                  existing.Value = value.Value;
        }
        _entries.Save(entry);
    }

    public void RefreshCurrentGrid()
    {
        if (SelectedSession is not null) LoadGrid(SelectedSession.Id);
    }

    private void SaveHomework(Guid sessionId, Guid studentId, HomeworkStatus? value)
    {
        var entry = _entries.GetBySessionAndStudent(sessionId, studentId)
                    ?? new ParticipationEntry { SessionId = sessionId, StudentId = studentId };
        entry.Homework = value;
        entry.HomeworkMissing = HomeworkDisplay.CountsAsMissing(value);
        _entries.Save(entry);
    }

    private void SaveAttendance(Guid sessionId, Guid studentId, AttendanceStatus? value)
    {
        var entry = _entries.GetBySessionAndStudent(sessionId, studentId)
                    ?? new ParticipationEntry { SessionId = sessionId, StudentId = studentId };
        entry.Attendance = value;
        _entries.Save(entry);
    }

    [RelayCommand]
    private void ToggleCompetencyTags() => CompetencyTagsVisible = !CompetencyTagsVisible;

    partial void OnStudentCompetencyRatingsVisibleChanged(bool value) => RebuildColumnsSignal++;

    private void LoadCompetencyTags(Guid sessionId)
    {
        CompetencyTagGroups.Clear();
        var session = _sessions.GetById(sessionId);
        ActiveCompetencyCodes = session?.CompetencyCodes?.ToList() ?? [];

        if (!_subjectId.HasValue) return;
        var active = ActiveCompetencyCodes.ToHashSet();

        foreach (var domain in _competencyDomains.GetBySubjectAndGrade(_subjectId.Value, _gradeLevel))
        {
            var group = new CompetencyTagGroup(domain.Name, domain.Code);
            foreach (var item in domain.Items.OrderBy(i => i.SortOrder))
            {
                var tag = new CompetencyTag(item.Code, item.Description, active.Contains(item.Code));
                tag.OnChanged = (code, sel) => OnTagToggled(code, sel);
                group.Items.Add(tag);
            }
            if (group.Items.Count > 0)
                CompetencyTagGroups.Add(group);
        }
    }

    private void OnTagToggled(string code, bool selected)
    {
        if (SelectedSession is null) return;
        var session = _sessions.GetById(SelectedSession.Id);
        if (session is null) return;
        if (selected) { if (!session.CompetencyCodes.Contains(code)) session.CompetencyCodes.Add(code); }
        else          { session.CompetencyCodes.Remove(code); }
        _sessions.Save(session);

        ActiveCompetencyCodes = session.CompetencyCodes.ToList();
        if (StudentCompetencyRatingsVisible)
            LoadGrid(SelectedSession.Id);  // reloads rows with updated cells, fires RebuildColumnsSignal++
    }

    [RelayCommand]
    private async Task AddSession()
    {
        if (OnAddSession is null) return;
        var session = await OnAddSession();
        if (session is null) return;
        session.GroupId = _groupId;
        _sessions.Save(session);

        Sessions.Clear();
        foreach (var s in _sessions.GetByGroup(_groupId))
            Sessions.Add(new ParticipationSessionItem(s));
        SelectedSession = Sessions.FirstOrDefault(s => s.Id == session.Id);
    }

    [RelayCommand(CanExecute = nameof(CanQuickInput))]
    private async Task QuickInput()
    {
        if (OnQuickInput is null) return;
        await OnQuickInput(this);
        if (SelectedSession is not null) LoadGrid(SelectedSession.Id);
    }

    private bool CanQuickInput() => SelectedSession is not null && StudentRows.Count > 0;

    [RelayCommand(CanExecute = nameof(CanQuickInput))]
    private async Task StatusQuickInput()
    {
        if (OnStatusQuickInput is null) return;
        await OnStatusQuickInput(this);
        if (SelectedSession is not null) LoadGrid(SelectedSession.Id);
    }

    [RelayCommand]
    private async Task ComputeGrade()
    {
        if (OnComputeGrade is null) return;
        await OnComputeGrade(this);
    }

    [RelayCommand]
    private async Task OpenWizard()
    {
        if (OnOpenWizard is null) return;
        await OnOpenWizard(this);
    }

    [RelayCommand]
    private void DeleteSession()
    {
        if (SelectedSession is null) return;
        _sessions.Delete(SelectedSession.Id);
        LoadSessions();
    }

    public void SaveNote(Guid sessionId, Guid studentId, string note)
    {
        var entry = _entries.GetBySessionAndStudent(sessionId, studentId);
        if (entry is null) return;
        entry.Note = note;
        _entries.Save(entry);
    }

    private void SaveCompetencyRating(Guid sessionId, Guid studentId, string code, int? value)
    {
        var entry = _entries.GetBySessionAndStudent(sessionId, studentId)
                      ?? new ParticipationEntry
                      {
                          SessionId = sessionId,
                          StudentId = studentId,
                      };
        var existing = entry.CompetencyRatings.FirstOrDefault(r => r.Code == code);
        if (value is null)
        {
            if (existing is not null) entry.CompetencyRatings.Remove(existing);
        }
        else
        {
            if (existing is null) entry.CompetencyRatings.Add(new CompetencyRating { Code = code, Value = value.Value });
            else                  existing.Value = value.Value;
        }
        _entries.Save(entry);
    }
}

// ── Zeilendaten für das Bewertungsraster ─────────────────────────────────────

public partial class ParticipationStudentRow : ObservableObject
{
    public Guid   StudentId { get; }
    public string Name      { get; }

    private readonly ParticipationEntry             _entry;
    private readonly IReadOnlyList<AspectColumnDef> _aspectDefs;

    public ObservableCollection<RatingCell> Cells            { get; } = [];
    public ObservableCollection<RatingCell> CompetencyCells  { get; } = [];

    [ObservableProperty] private HomeworkStatus? _homework;
    [ObservableProperty] private AttendanceStatus? _attendance;

    public string AttendanceLabel => AttendanceDisplay.ShortLabel(Attendance);
    public string AttendanceTooltip => AttendanceDisplay.Label(Attendance);
    public string HomeworkSymbol => HomeworkDisplay.Symbol(Homework);
    public string HomeworkTooltip => HomeworkDisplay.Label(Homework);

    public Action<Guid, string, int?>? OnRatingChanged           { get; set; }
    public Action<Guid, string, int?>? OnCompetencyRatingChanged { get; set; }
    public Action<Guid, HomeworkStatus?>?  HomeworkChangedCallback   { get; set; }
    public Action<Guid, AttendanceStatus?>? AttendanceChangedCallback { get; set; }

    public ParticipationStudentRow(Guid id, string name, ParticipationEntry entry,
        List<AspectColumnDef> aspects, List<string> competencyCodes)
    {
        StudentId   = id;
        Name        = name;
        _entry      = entry;
        _aspectDefs = aspects;
        _homework = HomeworkDisplay.Effective(entry);
        _attendance       = entry.Attendance;

        foreach (var a in aspects)
        {
            var existing = entry.Ratings.FirstOrDefault(r => r.Key == a.Key);
            var cell = new RatingCell(id, a.Key, existing?.Value);
            cell.OnChanged = (sid, key, val) => OnRatingChanged?.Invoke(sid, key, val);
            Cells.Add(cell);
        }

        foreach (var code in competencyCodes)
        {
            var existing = entry.CompetencyRatings.FirstOrDefault(r => r.Code == code);
            var cell = new RatingCell(id, code, existing?.Value);
            cell.OnChanged = (sid, key, val) => OnCompetencyRatingChanged?.Invoke(sid, key, val);
            CompetencyCells.Add(cell);
        }
    }

    public int? GetRating(string key) =>
        _entry.Ratings.FirstOrDefault(r => r.Key == key)?.Value;

    public void SetRating(string key, int? value)
    {
        var cell = Cells.FirstOrDefault(c => c.AspectKey == key);
        cell?.SetValue(value);
        OnRatingChanged?.Invoke(StudentId, key, value);
    }

    [RelayCommand]
    private void ToggleHomework()
    {
        Homework = HomeworkDisplay.Next(Homework);
        OnPropertyChanged(nameof(HomeworkSymbol));
        OnPropertyChanged(nameof(HomeworkTooltip));
        HomeworkChangedCallback?.Invoke(StudentId, Homework);
    }

    public void SetHomework(HomeworkStatus? value)
    {
        Homework = value;
        OnPropertyChanged(nameof(HomeworkSymbol));
        OnPropertyChanged(nameof(HomeworkTooltip));
        HomeworkChangedCallback?.Invoke(StudentId, value);
    }

    [RelayCommand]
    private void CycleAttendance()
    {
        Attendance = Attendance switch
        {
            null                              => AttendanceStatus.Present,
            AttendanceStatus.Present          => AttendanceStatus.ExcusePending,
            AttendanceStatus.ExcusePending    => AttendanceStatus.Excused,
            AttendanceStatus.Excused          => AttendanceStatus.Unexcused,
            AttendanceStatus.Unexcused        => AttendanceStatus.Truant,
            AttendanceStatus.Truant           => AttendanceStatus.OtherSchoolEvent,
            AttendanceStatus.OtherSchoolEvent => null,
            _                                 => null,
        };
        OnPropertyChanged(nameof(AttendanceLabel));
        OnPropertyChanged(nameof(AttendanceTooltip));
        AttendanceChangedCallback?.Invoke(StudentId, Attendance);
    }

    // Direktes Setzen (z.B. aus dem Grading-Wizard heraus), ohne den Zyklus zu durchlaufen.
    public void SetAttendance(AttendanceStatus? value)
    {
        Attendance = value;
        OnPropertyChanged(nameof(AttendanceLabel));
        OnPropertyChanged(nameof(AttendanceTooltip));
        AttendanceChangedCallback?.Invoke(StudentId, value);
    }
}

// ── Hausaufgaben-Anzeige ─────────────────────────────────────────────────────

public static class HomeworkDisplay
{
    public static HomeworkStatus? Effective(ParticipationEntry entry) =>
        entry.Homework ?? (entry.HomeworkMissing ? HomeworkStatus.MissingOpen : null);

    public static HomeworkStatus? Next(HomeworkStatus? status) => status switch
    {
        null                            => HomeworkStatus.Completed,
        HomeworkStatus.Completed        => HomeworkStatus.PartiallyCompleted,
        HomeworkStatus.PartiallyCompleted => HomeworkStatus.PartialSubmittedLate,
        HomeworkStatus.PartialSubmittedLate => HomeworkStatus.PartialMissingOverdue,
        HomeworkStatus.PartialMissingOverdue => HomeworkStatus.MissingOpen,
        HomeworkStatus.MissingOpen      => HomeworkStatus.MissingOverdue,
        HomeworkStatus.MissingOverdue   => HomeworkStatus.SubmittedLate,
        HomeworkStatus.SubmittedLate    => null,
        _                               => null,
    };

    public static string Label(HomeworkStatus? status) => status switch
    {
        null                            => "Keine Hausaufgabe aufgegeben",
        HomeworkStatus.Completed        => "Hausaufgabe gemacht",
        HomeworkStatus.PartiallyCompleted => "Teilweise angefertigt – Rest offen",
        HomeworkStatus.PartialSubmittedLate => "Teilweise angefertigt – Rest nachgereicht",
        HomeworkStatus.PartialMissingOverdue => "Teilweise angefertigt – Rest nicht nachgereicht",
        HomeworkStatus.MissingOpen      => "Nicht gemacht – Nachreichen offen",
        HomeworkStatus.MissingOverdue   => "Nicht gemacht – nicht mehr nachgereicht",
        HomeworkStatus.SubmittedLate    => "Hausaufgabe nachgereicht",
        _                               => "Keine Hausaufgabe aufgegeben",
    };

    public static string Symbol(HomeworkStatus? status) => status switch
    {
        null                            => "·",
        HomeworkStatus.Completed        => "✓",
        HomeworkStatus.PartiallyCompleted => "◐",
        HomeworkStatus.PartialSubmittedLate => "◕",
        HomeworkStatus.PartialMissingOverdue => "◒",
        HomeworkStatus.MissingOpen      => "!",
        HomeworkStatus.MissingOverdue   => "✕",
        HomeworkStatus.SubmittedLate    => "↺",
        _                               => "·",
    };

    public static string Color(HomeworkStatus? status) => status switch
    {
        HomeworkStatus.Completed        => "#2E9D57",
        HomeworkStatus.PartiallyCompleted => "#D98200",
        HomeworkStatus.PartialSubmittedLate => "#7F77DD",
        HomeworkStatus.PartialMissingOverdue => "#D64545",
        HomeworkStatus.MissingOpen      => "#D98200",
        HomeworkStatus.MissingOverdue   => "#D64545",
        HomeworkStatus.SubmittedLate    => "#7F77DD",
        _                               => "",
    };

    public static bool CountsAsMissing(HomeworkStatus? status) => status is
        HomeworkStatus.MissingOpen or
        HomeworkStatus.MissingOverdue or
        HomeworkStatus.PartiallyCompleted or
        HomeworkStatus.PartialMissingOverdue;
}

// ── Anwesenheits-Anzeige ──────────────────────────────────────────────────────

public static class AttendanceDisplay
{
    public static string Label(AttendanceStatus? s) => s switch
    {
        null                            => "Noch nicht kontrolliert",
        AttendanceStatus.Present        => "Anwesend",
        AttendanceStatus.ExcusePending  => "Krank (Entschuldigung offen)",
        AttendanceStatus.Excused        => "Krank, entschuldigt",
        AttendanceStatus.Unexcused      => "Krank, unentschuldigt",
        AttendanceStatus.Truant         => "Geschwänzt",
        AttendanceStatus.OtherSchoolEvent => "Andere Schulveranstaltung",
        _                                => "Anwesend",
    };

    public static string ShortLabel(AttendanceStatus? s) => s switch
    {
        null                            => "",
        AttendanceStatus.Present        => "✓",
        AttendanceStatus.ExcusePending  => "?",
        AttendanceStatus.Excused        => "⊘",
        AttendanceStatus.Unexcused      => "!",
        AttendanceStatus.Truant         => "✕",
        AttendanceStatus.OtherSchoolEvent => "◇",
        _                                => "",
    };

    public static string Color(AttendanceStatus? s) => s switch
    {
        AttendanceStatus.Present          => "#2E9D57",
        AttendanceStatus.ExcusePending    => "#D98200",
        AttendanceStatus.Excused          => "#4C86A8",
        AttendanceStatus.Unexcused        => "#D96C00",
        AttendanceStatus.Truant           => "#D64545",
        AttendanceStatus.OtherSchoolEvent => "#5277C3",
        _                                 => "",
    };
}

// ── Eine Bewertungszelle ──────────────────────────────────────────────────────

public partial class RatingCell : ObservableObject
{
    public Guid   StudentId { get; }
    public string AspectKey { get; }

    [ObservableProperty] private int? _value;
    [ObservableProperty] private string _displayLabel = "";

    public Action<Guid, string, int?>? OnChanged { get; set; }

    public RatingCell(Guid studentId, string key, int? value)
    {
        StudentId = studentId;
        AspectKey = key;
        _value    = value;
        UpdateLabel();
    }

    public void SetValue(int? value)
    {
        Value = value;
        UpdateLabel();
        OnChanged?.Invoke(StudentId, AspectKey, value);
    }

    [RelayCommand]
    private void CycleUp()
    {
        var next = Value is null ? -2 : Math.Min(2, Value.Value + 1);
        SetValue(next);
    }

    [RelayCommand]
    private void CycleDown()
    {
        var next = Value is null ? 2 : Math.Max(-2, Value.Value - 1);
        SetValue(next);
    }

    [RelayCommand]
    private void Clear() => SetValue(null);

    private void UpdateLabel() => DisplayLabel = Value switch
    {
        2  => "++",
        1  => "+",
        0  => "~",
        -1 => "−",
        -2 => "−−",
        _  => "",
    };
}

// ── Kompetenz-Tags ────────────────────────────────────────────────────────────

public class CompetencyTagGroup(string name, string code)
{
    public string Name        { get; } = name;
    public string Code        { get; } = code;
    public string DisplayName { get; } = string.IsNullOrEmpty(code) ? name : $"{name}  ({code})";
    public List<CompetencyTag> Items { get; } = [];
}

public partial class CompetencyTag : ObservableObject
{
    public string Code        { get; }
    public string Description { get; }
    public string Display     { get; }

    [ObservableProperty] private bool _isSelected;

    public Action<string, bool>? OnChanged { get; set; }

    public CompetencyTag(string code, string description, bool isSelected)
    {
        Code        = code;
        Description = description;
        Display     = string.IsNullOrEmpty(code) ? description : $"[{code}]  {description}";
        _isSelected = isSelected;
    }

    partial void OnIsSelectedChanged(bool value) => OnChanged?.Invoke(Code, value);
}

// ── Hilfsklassen ──────────────────────────────────────────────────────────────

public class AspectColumnDef
{
    public string Key   { get; }
    public string Label { get; }
    public AspectColumnDef(ParticipationAspect a) { Key = a.Key; Label = a.Label; }
}

public class ParticipationSessionItem
{
    public Guid   Id      { get; }
    public string Display { get; }
    public string Comment { get; }
    public DateOnly Date  { get; }

    public ParticipationSessionItem(ParticipationSession s)
    {
        Id      = s.Id;
        Date    = s.Date;
        Comment = s.Comment ?? "";
        Display = s.Comment is { Length: > 0 }
            ? $"{s.Date:dd.MM.yyyy}  –  {s.Comment}"
            : s.Date.ToString("dd.MM.yyyy");
    }
}

// ── Dialog: Sitzung anlegen ───────────────────────────────────────────────────

public partial class AddSessionDialogViewModel : ObservableObject
{
    [ObservableProperty] private DateOnly _date = DateOnly.FromDateTime(DateTime.Today);
    [ObservableProperty] private string   _comment = "";
    [ObservableProperty] private string   _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
    [ObservableProperty] private string   _dateTextError = "";

    public ParticipationSession? Result { get; private set; }

    [RelayCommand]
    private void Save()
    {
        if (!DateOnly.TryParseExact(DateText, "dd.MM.yyyy", null,
                System.Globalization.DateTimeStyles.None, out var date))
        {
            DateTextError = "Format TT.MM.JJJJ.";
            return;
        }
        DateTextError = "";
        Result = new ParticipationSession { Date = date, Comment = Comment.Trim() };
    }
}

// ── Dialog: Schnelleingabe ────────────────────────────────────────────────────

public partial class QuickInputViewModel : ObservableObject
{
    private readonly List<ParticipationStudentRow> _rows;
    private readonly List<AspectColumnDef>         _aspects;

    [ObservableProperty] private int    _studentIndex;
    [ObservableProperty] private int    _aspectIndex;
    [ObservableProperty] private string _studentName = "";
    [ObservableProperty] private string _currentAspectLabel = "";
    [ObservableProperty] private string _currentValueLabel  = "";
    [ObservableProperty] private string _progressText = "";

    public ObservableCollection<QuickAspectRow> AspectRows { get; } = [];

    public QuickInputViewModel(List<ParticipationStudentRow> rows, List<AspectColumnDef> aspects)
    {
        _rows    = rows;
        _aspects = aspects;
        if (rows.Any()) ShowStudent(0);
    }

    private void ShowStudent(int index)
    {
        if (index < 0 || index >= _rows.Count) return;
        StudentIndex = index;
        var row = _rows[index];
        StudentName  = row.Name;
        ProgressText = $"{index + 1} / {_rows.Count}";

        AspectRows.Clear();
        foreach (var (a, i) in _aspects.Select((a, i) => (a, i)))
        {
            var val = row.GetRating(a.Key);
            AspectRows.Add(new QuickAspectRow(i, a.Label, val, i == AspectIndex));
        }
        UpdateCurrentAspect();
    }

    private void UpdateCurrentAspect()
    {
        if (!_aspects.Any()) return;
        var safeIdx = Math.Clamp(AspectIndex, 0, _aspects.Count - 1);
        CurrentAspectLabel = _aspects[safeIdx].Label;
        var row = AspectRows.ElementAtOrDefault(safeIdx);
        CurrentValueLabel  = row?.DisplayLabel ?? "";
        foreach (var r in AspectRows) r.IsActive = r.Index == safeIdx;
    }

    public void SetRatingByNumber(int num)
    {
        // 1=−−, 2=−, 3=~, 4=+, 5=++
        var val = num switch { 1 => -2, 2 => -1, 3 => 0, 4 => 1, 5 => 2, _ => (int?)null };
        if (val is null) return;
        ApplyRating(val.Value);
    }

    public void IncrementRating()
    {
        var cell = GetCurrentCell();
        if (cell is null) return;
        var next = cell.Value is null ? -2 : Math.Min(2, cell.Value.Value + 1);
        ApplyRating(next);
    }

    public void DecrementRating()
    {
        var cell = GetCurrentCell();
        if (cell is null) return;
        var next = cell.Value is null ? 2 : Math.Max(-2, cell.Value.Value - 1);
        ApplyRating(next);
    }

    private void ApplyRating(int val)
    {
        if (_rows.Count == 0 || !_aspects.Any()) return;
        var key = _aspects[Math.Clamp(AspectIndex, 0, _aspects.Count - 1)].Key;
        _rows[StudentIndex].SetRating(key, val);
        var row = AspectRows.ElementAtOrDefault(AspectIndex);
        if (row is not null)
        {
            row.Value = val;
            row.UpdateLabel();
        }
        CurrentValueLabel = RatingLabel(val);
    }

    public void SelectAspect(int index)
    {
        if (index < 0 || index >= _aspects.Count) return;
        AspectIndex = index;
        UpdateCurrentAspect();
    }

    public void NextAspect()
    {
        AspectIndex = (AspectIndex + 1) % _aspects.Count;
        UpdateCurrentAspect();
    }

    public void NextStudent()
    {
        if (StudentIndex >= _rows.Count - 1) return;
        AspectIndex = 0;
        ShowStudent(StudentIndex + 1);
    }

    public void PreviousStudent()
    {
        if (StudentIndex <= 0) return;
        AspectIndex = 0;
        ShowStudent(StudentIndex - 1);
    }

    public bool IsLastStudent => StudentIndex >= _rows.Count - 1;

    private RatingCell? GetCurrentCell()
    {
        if (_rows.Count == 0 || !_aspects.Any()) return null;
        var key = _aspects[Math.Clamp(AspectIndex, 0, _aspects.Count - 1)].Key;
        return _rows[StudentIndex].Cells.FirstOrDefault(c => c.AspectKey == key);
    }

    private static string RatingLabel(int? v) => v switch
    {
        2 => "++", 1 => "+", 0 => "~", -1 => "−", -2 => "−−", _ => "",
    };
}

public partial class QuickAspectRow : ObservableObject
{
    public int    Index { get; }
    public string Label { get; }
    [ObservableProperty] private bool   _isActive;
    [ObservableProperty] private string _displayLabel = "";
    public int? Value { get; set; }

    public QuickAspectRow(int index, string label, int? value, bool isActive)
    {
        Index    = index;
        Label    = label;
        Value    = value;
        IsActive = isActive;
        UpdateLabel();
    }

    public void UpdateLabel() => DisplayLabel = Value switch
    {
        2 => "++", 1 => "+", 0 => "~", -1 => "−", -2 => "−−", _ => "·",
    };
}

// ── Schnelleingabe Anwesenheit / Hausaufgaben ────────────────────────────────

public partial class AttendanceHomeworkQuickInputViewModel : ObservableObject
{
    public List<ParticipationStudentRow> Rows { get; }
    public string SessionLabel { get; }

    [ObservableProperty] private ParticipationStudentRow? _selectedRow;
    [ObservableProperty] private bool _advanceAfterInput = true;

    public AttendanceHomeworkQuickInputViewModel(
        IEnumerable<ParticipationStudentRow> rows, string sessionLabel)
    {
        Rows = rows.ToList();
        SessionLabel = sessionLabel;
        SelectedRow = Rows.FirstOrDefault();
    }

    public void ApplyAttendance(ParticipationStudentRow row, AttendanceStatus? status)
    {
        SelectedRow = row;
        row.SetAttendance(status);
        AdvanceIfRequested();
    }

    public void ApplyHomework(ParticipationStudentRow row, HomeworkStatus? status)
    {
        SelectedRow = row;
        row.SetHomework(status);
        AdvanceIfRequested();
    }

    public void MoveSelection(int delta)
    {
        if (Rows.Count == 0) return;
        var current = SelectedRow is null ? 0 : Rows.IndexOf(SelectedRow);
        SelectedRow = Rows[Math.Clamp(current + delta, 0, Rows.Count - 1)];
    }

    private void AdvanceIfRequested()
    {
        if (AdvanceAfterInput) MoveSelection(1);
    }
}