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

namespace LehrerApp.Desktop.ViewModels.Groups;

// ── Gruppenliste ──────────────────────────────────────────────────────────────

public partial class GroupListViewModel : ObservableObject
{
    private readonly IGroupRepository _groups;
    private readonly SchoolYearService _sy;

    public Action<Guid>? OnNavigateToDetail { get; set; }
    public Action? OnAddGroup { get; set; }

    [ObservableProperty] private string _selectedSchoolYear = "";
    [ObservableProperty] private string _searchText = "";
    [ObservableProperty] private GroupListItem? _selectedGroup;

    public ObservableCollection<string> SchoolYears { get; } = [];
    public ObservableCollection<GroupListItem> Groups { get; } = [];

    public GroupListViewModel(IGroupRepository groups, SchoolYearService sy)
    {
        _groups = groups; _sy = sy;
        foreach (var y in sy.RecentSchoolYears()) SchoolYears.Add(y);
        SelectedSchoolYear = sy.CurrentSchoolYear();
    }

    partial void OnSelectedSchoolYearChanged(string value) => LoadGroups();
    partial void OnSearchTextChanged(string value)          => LoadGroups();
    partial void OnSelectedGroupChanged(GroupListItem? value)
    {
        if (value is not null) OnNavigateToDetail?.Invoke(value.Id);
    }

    public void LoadGroups()
    {
        Groups.Clear();
        var all = _groups.GetBySchoolYear(SelectedSchoolYear);
        var filtered = string.IsNullOrWhiteSpace(SearchText) ? all
            : all.Where(g => g.Name.Contains(SearchText, StringComparison.OrdinalIgnoreCase)
                          || (g.Subject?.Contains(SearchText, StringComparison.OrdinalIgnoreCase) ?? false));
        foreach (var g in filtered.OrderBy(g => g.Name))
            Groups.Add(new GroupListItem(g));
    }

    [RelayCommand] private void AddGroup() => OnAddGroup?.Invoke();
    [RelayCommand] private void Refresh()   => LoadGroups();
}

public class GroupListItem
{
    public Guid Id { get; }
    public string Name { get; }
    public string Subject { get; }
    public string DisplayName { get; }
    public string TypeLabel { get; }
    public string GradingLabel { get; }

    public GroupListItem(LearningGroup g)
    {
        Id           = g.Id;
        Name         = g.Name;
        Subject      = g.Subject ?? "";
        TypeLabel    = g.Type == GroupType.Class ? "Klasse" : "Kurs";
        GradingLabel = g.GradingSystem == GradingSystem.Grades1To6 ? "1–6" : "0–15";
        DisplayName  = string.IsNullOrEmpty(Subject) ? Name : $"{Name} · {Subject}";
    }
}

// ── Gruppendetail ─────────────────────────────────────────────────────────────

public partial class GroupDetailViewModel : ObservableObject
{
    private readonly IGroupRepository _groups;
    private readonly IStudentRepository _students;
    private readonly IExamRepository _exams;
    private readonly IGradeRepository _grades;

    [ObservableProperty] private LearningGroup? _group;
    [ObservableProperty] private string _groupTitle = "";
    [ObservableProperty] private string _groupSubtitle = "";
    [ObservableProperty] private int _studentCount;

    public ObservableCollection<StudentSummary> Students { get; } = [];
    public ObservableCollection<ExamSummary> Exams { get; } = [];

    public GroupDetailViewModel(IGroupRepository groups, IStudentRepository students,
        IExamRepository exams, IGradeRepository grades)
    {
        _groups = groups; _students = students; _exams = exams; _grades = grades;
    }

    public void LoadGroup(Guid id)
    {
        Group = _groups.GetById(id);
        if (Group is null) return;
        GroupTitle    = Group.Name;
        GroupSubtitle = $"{Group.SchoolYear} · " +
                        $"{(Group.Type == GroupType.Class ? "Klasse" : "Kurs")} · " +
                        $"Stufe {Group.GradeLevel} · Noten {(Group.GradingSystem == GradingSystem.Grades1To6 ? "1–6" : "0–15")}";

        Students.Clear();
        var enrolled = _students.GetByGroup(Group.Id, Group.SchoolYear);
        StudentCount = enrolled.Count;
        foreach (var s in enrolled) Students.Add(new StudentSummary(s));

        Exams.Clear();
        foreach (var e in _exams.GetByGroup(Group.Id)) Exams.Add(new ExamSummary(e));
    }

    [RelayCommand] private void AddStudent() { /* TODO */ }
    [RelayCommand] private void AddExam()    { /* TODO */ }
    [RelayCommand] private void Refresh()    { if (Group is not null) LoadGroup(Group.Id); }
}

public class StudentSummary
{
    public Guid Id { get; }
    public string FullName { get; }
    public StudentSummary(Core.Models.Student s) { Id = s.Id; FullName = s.FullName; }
}

public class ExamSummary
{
    public Guid Id { get; }
    public string Title { get; }
    public string Date { get; }
    public string StatusLabel { get; }
    public ExamSummary(Core.Models.Exam e)
    {
        Id = e.Id; Title = e.Title; Date = e.Date.ToString("dd.MM.yyyy");
        StatusLabel = e.Status switch
        {
            ExamStatus.Planned   => "Geplant",
            ExamStatus.Conducted => "Durchgeführt",
            ExamStatus.Graded    => "Korrigiert",
            ExamStatus.Returned  => "Zurückgegeben",
            _ => "",
        };
    }
}

// ── Dialog: Neue Lerngruppe anlegen ──────────────────────────────────────────

public partial class AddGroupDialogViewModel : ObservableObject
{
    private readonly IGroupRepository _groups;
    private readonly SchoolYearService _sy;

    [ObservableProperty] private string _name = "";
    [ObservableProperty] private string _subject = "";
    [ObservableProperty] private int _gradeLevel = 10;
    [ObservableProperty] private GradingSystem _gradingSystem = GradingSystem.Grades1To6;
    [ObservableProperty] private string _selectedSchoolYear = "";
    [ObservableProperty] private string _validationMessage = "";

    public List<string> SchoolYears { get; }
    public LearningGroup? Result { get; private set; }

    public AddGroupDialogViewModel(IGroupRepository groups, SchoolYearService sy)
    {
        _groups = groups; _sy = sy;
        SchoolYears        = sy.RecentSchoolYears(3);
        SelectedSchoolYear = sy.CurrentSchoolYear();
        // Notensystem automatisch nach Klassenstufe
        PropertyChanged += (_, e) =>
        {
            if (e.PropertyName == nameof(GradeLevel))
                GradingSystem = GradeLevel >= 11 ? GradingSystem.Points0To15
                                                 : GradingSystem.Grades1To6;
        };
    }

    [RelayCommand]
    private void Save()
    {
        if (string.IsNullOrWhiteSpace(Name)) { ValidationMessage = "Name erforderlich."; return; }
        if (GradeLevel is < 1 or > 13)       { ValidationMessage = "Klassenstufe 1–13."; return; }
        Result = new LearningGroup
        {
            Name          = Name.Trim(),
            Subject       = string.IsNullOrWhiteSpace(Subject) ? null : Subject.Trim(),
            Type          = GroupType.Course,
            GradeLevel    = GradeLevel,
            GradingSystem = GradingSystem,
            SchoolYear    = SelectedSchoolYear,
        };
        _groups.Save(Result);
    }
}