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

namespace LehrerApp.Desktop.ViewModels.Groups;

/// <summary>
/// Gruppen-Tab "Dokumentation" (bisher Platzhalter): zeigt die Dokumentationseinträge aller
/// aktuellen/ehemaligen Schüler dieser Gruppe an einem Ort, statt sie einzeln im Schüler-Tab
/// aufsuchen zu müssen. Nutzer-Feedback: die Liste soll standardmäßig auch Einträge aus anderen
/// Lerngruppen desselben Schülers mit anzeigen (optisch abgesetzt statt ausgeblendet), damit
/// Muster aus anderen Fächern/Kursen nicht verborgen bleiben — ein Schalter blendet sie bei
/// Bedarf ganz aus.
/// </summary>
public partial class GroupDocumentationTabViewModel : ObservableObject
{
    private readonly IDocumentationRepository _docs;
    private readonly IStudentRepository _students;
    private readonly IGroupRepository _groups;

    private Guid _groupId;
    private List<StudentOption> _groupStudents = [];

    public static readonly StudentOption AllStudentsOption = new(Guid.Empty, "Alle Schüler");
    public static readonly StudentOption WholeGroupOption = new(Guid.Empty, "Gesamte Lerngruppe");

    public ObservableCollection<DocumentationItem> Entries { get; } = [];
    public ObservableCollection<StudentOption> StudentFilterOptions { get; } = [AllStudentsOption];

    [ObservableProperty] private StudentOption _selectedStudentFilter = AllStudentsOption;
    [ObservableProperty] private bool _onlyThisGroup;
    [ObservableProperty] private int _draftCount;

    public Func<Guid, List<StudentOption>, Documentation?, Task<Documentation?>>? OnEditDocumentation { get; set; }
    public Func<DocumentationItem, Task<bool>>? OnConfirmDeleteDocumentation { get; set; }
    public Func<Documentation, string, Task<Documentation?>>? OnConductParentCall { get; set; }

    public GroupDocumentationTabViewModel(IDocumentationRepository docs, IStudentRepository students,
        IGroupRepository groups)
    {
        _docs = docs; _students = students; _groups = groups;
    }

    partial void OnSelectedStudentFilterChanged(StudentOption value) => Load();
    partial void OnOnlyThisGroupChanged(bool value) => Load();

    public void Initialize(Guid groupId)
    {
        _groupId = groupId;
        _groupStudents = _students.GetByGroup(groupId)
            .Select(s => new StudentOption(s.Id, s.FullName)).ToList();

        StudentFilterOptions.Clear();
        StudentFilterOptions.Add(AllStudentsOption);
        foreach (var s in _groupStudents) StudentFilterOptions.Add(s);
        SelectedStudentFilter = AllStudentsOption;
        Load();
    }

    private void Load()
    {
        Entries.Clear();
        var studentNameById = _groupStudents.ToDictionary(s => s.Id, s => s.Name);
        var groupNameCache = new Dictionary<Guid, string>();
        string GroupLabel(Guid id)
        {
            if (groupNameCache.TryGetValue(id, out var cached)) return cached;
            var label = _groups.GetById(id)?.Name ?? "";
            groupNameCache[id] = label;
            return label;
        }

        var relevantStudentIds = SelectedStudentFilter.Id == Guid.Empty
            ? _groupStudents.Select(s => s.Id)
            : [SelectedStudentFilter.Id];

        var all = relevantStudentIds
            .SelectMany(id => _docs.GetByStudent(id))
            .Concat(SelectedStudentFilter.Id == Guid.Empty
                ? _docs.GetAll().Where(d => d.StudentId == Guid.Empty && d.GroupId == _groupId)
                : [])
            .DistinctBy(d => d.Id)
            .Where(d => !OnlyThisGroup || d.GroupId == _groupId)
            .OrderByDescending(d => d.IsDraft)
            .ThenByDescending(d => d.Date)
            .ToList();
        DraftCount = all.Count(d => d.IsDraft && (d.GroupId is null || d.GroupId == _groupId));

        foreach (var d in all)
        {
            var isOwnGroup = d.GroupId is null || d.GroupId == _groupId;
            var otherGroupLabel = isOwnGroup ? "" : GroupLabel(d.GroupId!.Value);
            var studentName = d.StudentId == Guid.Empty
                ? WholeGroupOption.Name
                : studentNameById.GetValueOrDefault(d.StudentId, "");
            Entries.Add(new DocumentationItem(d, studentName,
                isOwnGroup, otherGroupLabel));
        }
    }

    public void Refresh() => Load();

    [RelayCommand]
    private async Task AddDocumentation()
    {
        if (OnEditDocumentation is null) return;
        var result = await OnEditDocumentation(_groupId, _groupStudents, null);
        if (result is null) return;
        _docs.Save(result);
        Load();
    }

    [RelayCommand]
    private async Task EditDocumentation(DocumentationItem? item)
    {
        if (item is null || OnEditDocumentation is null) return;
        var result = await OnEditDocumentation(_groupId, _groupStudents, item.Model);
        if (result is null) return;
        _docs.Save(result);
        Load();
    }

    [RelayCommand]
    private async Task DeleteDocumentation(DocumentationItem? item)
    {
        if (item is null) return;
        if (OnConfirmDeleteDocumentation is not null && !await OnConfirmDeleteDocumentation(item)) return;
        _docs.Delete(item.Model.Id);
        Load();
    }

    [RelayCommand]
    private async Task ConductParentCall(DocumentationItem? item)
    {
        if (item is null || OnConductParentCall is null) return;
        var result = await OnConductParentCall(item.Model, item.StudentName);
        if (result is null) return;
        _docs.Save(result);
        Load();
    }
}