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

namespace LehrerApp.Desktop.ViewModels.Planning;

public sealed class TimetableUnitOption(Unit unit)
{
    public Unit Model { get; } = unit;
    public string Label { get; } = unit.Title;
    public string Detail { get; } = unit.Status switch
    {
        UnitStatus.Active => "Laufende Einheit",
        UnitStatus.Completed => "Abgeschlossene Einheit",
        _ => "Geplante Einheit",
    };
}

/// <summary>Ordnet eine direkt aus dem Stundenplan angelegte Stunde einer Einheit zu.</summary>
public partial class TimetableUnitPickerViewModel : ObservableObject
{
    private readonly IUnitRepository _units;
    private readonly Guid _groupId;
    private readonly DateOnly _date;

    public string ContextLabel { get; }
    public ObservableCollection<TimetableUnitOption> Units { get; } = [];
    [ObservableProperty] private TimetableUnitOption? _selectedUnit;
    [ObservableProperty] private string _newUnitTitle = "";
    [ObservableProperty] private string _error = "";
    public Unit? Result { get; private set; }
    public bool ResultIsNew { get; private set; }
    public bool HasUnits => Units.Count > 0;

    public TimetableUnitPickerViewModel(IUnitRepository units, Guid groupId, string groupName,
        DateOnly date, int period)
    {
        _units = units;
        _groupId = groupId;
        _date = date;
        ContextLabel = $"{groupName} · {date:dd.MM.yyyy} · {period}. Stunde";

        foreach (var unit in units.GetByGroup(groupId)
                     .OrderBy(u => u.Status == UnitStatus.Active ? 0 : u.Status == UnitStatus.Planned ? 1 : 2)
                     .ThenByDescending(u => u.StartDate)
                     .ThenBy(u => u.Title, StringComparer.CurrentCultureIgnoreCase))
            Units.Add(new TimetableUnitOption(unit));
        SelectedUnit = Units.FirstOrDefault();
    }

    [RelayCommand]
    private void Save()
    {
        Error = "";
        if (!string.IsNullOrWhiteSpace(NewUnitTitle))
        {
            Result = new Unit
            {
                GroupId = _groupId,
                Title = NewUnitTitle.Trim(),
                StartDate = _date,
                Status = UnitStatus.Active,
            };
            // Erst speichern, wenn auch der anschließende Stunden-Dialog bestätigt wurde. So
            // hinterlässt ein Abbruch keine leere Einheit.
            ResultIsNew = true;
            return;
        }

        if (SelectedUnit is null)
        {
            Error = "Bitte eine Einheit auswählen oder eine neue benennen.";
            return;
        }
        Result = SelectedUnit.Model;
        ResultIsNew = false;
    }
}

public sealed record TimetableLessonRequest(Guid GroupId, DateOnly Date, int PeriodNumber);
public sealed record TimetableLessonMoveRequest(Lesson Lesson, int SelectedPeriod);