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 _schoolYearService;

    [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 schoolYearService)
    {
        _groups = groups;
        _schoolYearService = schoolYearService;

        foreach (var y in schoolYearService.RecentSchoolYears())
            SchoolYears.Add(y);

        SelectedSchoolYear = schoolYearService.CurrentSchoolYear();
        LoadGroups();
    }

    partial void OnSelectedSchoolYearChanged(string value) => LoadGroups();
    partial void OnSearchTextChanged(string value) => LoadGroups();

    private 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)
            Groups.Add(new GroupListItem(g));
    }

    [RelayCommand]
    private void AddGroup()
    {
        // TODO: Dialog öffnen
    }

    [RelayCommand]
    private void Refresh() => LoadGroups();
}

public class GroupListItem
{
    public Guid Id { get; }
    public string Name { get; }
    public string Subject { get; }
    public string SchoolYear { get; }
    public int GradeLevel { get; }
    public string TypeLabel { get; }
    public string GradingLabel { get; }

    public GroupListItem(LearningGroup g)
    {
        Id = g.Id;
        Name = g.Name;
        Subject = g.Subject ?? "";
        SchoolYear = g.SchoolYear;
        GradeLevel = g.GradeLevel;
        TypeLabel = g.Type == GroupType.Class ? "Klasse" : "Kurs";
        GradingLabel = g.GradingSystem == GradingSystem.Grades1To6
            ? "Noten 1–6"
            : "Punkte 0–15";
    }
}

// ── Gruppendetail (Tab-Navigation) ────────────────────────────────────────────

public partial class GroupDetailViewModel : ObservableObject
{
    private readonly IGroupRepository _groups;
    private readonly IStudentRepository _students;
    private readonly IEnrollmentRepository _enrollments;
    private readonly IExamRepository _exams;
    private readonly SchoolYearService _schoolYearService;

    [ObservableProperty] private LearningGroup? _group;
    [ObservableProperty] private string _groupTitle = "";
    [ObservableProperty] private int _studentCount;
    [ObservableProperty] private GroupTab _activeTab = GroupTab.Overview;

    // Sub-ViewModels für Tabs – lazy geladen
    public ObservableCollection<StudentSummary> Students { get; } = [];
    public ObservableCollection<ExamSummary> Exams { get; } = [];

    public GroupDetailViewModel(
        IGroupRepository groups,
        IStudentRepository students,
        IEnrollmentRepository enrollments,
        IExamRepository exams,
        SchoolYearService schoolYearService)
    {
        _groups = groups;
        _students = students;
        _enrollments = enrollments;
        _exams = exams;
        _schoolYearService = schoolYearService;
    }

    public void LoadGroup(Guid groupId)
    {
        Group = _groups.GetById(groupId);
        if (Group is null) return;

        GroupTitle = $"{Group.Name} · {Group.SchoolYear}";
        LoadStudents();
        LoadExams();
    }

    [RelayCommand]
    private void SwitchTab(GroupTab tab)
    {
        ActiveTab = tab;
    }

    private void LoadStudents()
    {
        if (Group is null) return;
        Students.Clear();

        var enrolled = _students.GetByGroup(Group.Id, Group.SchoolYear);
        StudentCount = enrolled.Count;

        foreach (var s in enrolled)
            Students.Add(new StudentSummary(s));
    }

    private void LoadExams()
    {
        if (Group is null) return;
        Exams.Clear();

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

    [RelayCommand]
    private void AddStudent()
    {
        // TODO: Schüler-Auswahl-Dialog
    }

    [RelayCommand]
    private void AddExam()
    {
        // TODO: Klausur-Erstellen-Dialog
    }
}

public enum GroupTab { Overview, Students, Exams, Grades, Planner, Documentation }

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 Status { get; }

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