LehrerApp/LehrerApp.Desktop/ViewModels/Planning/TimetableSlotDialogViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Core.Services;

namespace LehrerApp.Desktop.ViewModels.Planning;

/// <summary>Zuweisen/Bearbeiten/Entfernen eines Stundenplan-Termins (4.3.3).</summary>
public partial class TimetableSlotDialogViewModel : ObservableObject
{
    private readonly ITimetableSlotRepository _slots;
    private readonly Dictionary<string, Guid> _groupIdsByName;
    private readonly TimetableSlot? _editing;

    public DayOfWeek Weekday { get; }
    public int PeriodNumber { get; }
    public string WeekdayLabel { get; }
    public string DialogTitle { get; }
    public bool IsEditing => _editing is not null;

    [ObservableProperty] private string _selectedGroupName = "";
    [ObservableProperty] private string _room = "";
    [ObservableProperty] private string _groupError = "";

    public string[] GroupOptions { get; }

    /// null = unverändert/Abbruch, sonst das neue/aktualisierte Ergebnis.
    public TimetableSlot? Result { get; private set; }
    public bool Deleted { get; private set; }

    public TimetableSlotDialogViewModel(ITimetableSlotRepository slots, IGroupRepository groups,
        SchoolYearService schoolYear, DayOfWeek weekday, int periodNumber, TimetableSlot? editing)
    {
        _slots = slots;
        _editing = editing;
        Weekday = weekday;
        PeriodNumber = periodNumber;
        WeekdayLabel = weekday switch
        {
            DayOfWeek.Monday => "Montag", DayOfWeek.Tuesday => "Dienstag",
            DayOfWeek.Wednesday => "Mittwoch", DayOfWeek.Thursday => "Donnerstag",
            DayOfWeek.Friday => "Freitag", _ => weekday.ToString(),
        };
        DialogTitle = $"{WeekdayLabel}, {periodNumber}. Stunde";

        var availableGroups = groups.GetBySchoolYear(schoolYear.CurrentSchoolYear()).OrderBy(g => g.Name).ToList();
        _groupIdsByName = availableGroups.ToDictionary(g => g.Name, g => g.Id);
        GroupOptions = availableGroups.Select(g => g.Name).ToArray();

        if (editing is not null)
        {
            SelectedGroupName = availableGroups.FirstOrDefault(g => g.Id == editing.GroupId)?.Name ?? "";
            Room = editing.Room ?? "";
        }
    }

    [RelayCommand]
    private void Save()
    {
        GroupError = "";
        if (string.IsNullOrWhiteSpace(SelectedGroupName) || !_groupIdsByName.TryGetValue(SelectedGroupName, out var groupId))
        {
            GroupError = "Bitte eine Gruppe auswählen.";
            return;
        }

        var slot = _editing ?? new TimetableSlot { Weekday = Weekday, PeriodNumber = PeriodNumber };
        slot.GroupId = groupId;
        slot.Room = string.IsNullOrWhiteSpace(Room) ? null : Room.Trim();

        try
        {
            _slots.Save(slot);
            Result = slot;
        }
        catch (InvalidOperationException ex)
        {
            GroupError = ex.Message;
        }
    }

    [RelayCommand]
    private void Delete()
    {
        if (_editing is null) return;
        _slots.Delete(_editing.Id);
        Deleted = true;
    }
}