using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Core.Services;
using LehrerApp.Data;
using LehrerApp.Desktop.Services;
using LehrerApp.Desktop.ViewModels.Planning;
using LehrerApp.Sync;
using LehrerApp.Sync.Crypto;
using System.Collections.ObjectModel;
using System.Globalization;
using System.Security.Cryptography;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace LehrerApp.Desktop.ViewModels.Settings;

public partial class SettingsViewModel
{
    // ── Datenschutz: Löschfristen (5.4.2) ────────────────────────────────────

    [ObservableProperty] private int _retentionYears = 3;
    [ObservableProperty] private string _retentionStatus = "";

    public ObservableCollection<ExpiredDocumentItem> ExpiredDocuments { get; } = [];

    /// Vom Code-Behind gesetzt: zeigt einen Bestätigungsdialog vor dem endgültigen Löschen.
    public Func<ExpiredDocumentItem, Task<bool>>? OnConfirmHardDelete { get; set; }

    // ── Datenschutz: Löschfristen ─────────────────────────────────────────────

    private void LoadExpiredDocuments()
    {
        ExpiredDocuments.Clear();
        var cutoff = _privacy.RetentionCutoff();
        foreach (var d in _documentation.GetAll().Where(d => d.CreatedAt < cutoff))
        {
            var student = _students.GetById(d.StudentId);
            ExpiredDocuments.Add(new ExpiredDocumentItem(d, student?.FullName ?? "?"));
        }
    }

    [RelayCommand]
    private void SaveRetentionYears()
    {
        _privacy.SetRetentionYears(RetentionYears);
        LoadExpiredDocuments();
        RetentionStatus = "Gespeichert.";
    }

    [RelayCommand]
    private async Task HardDeleteDocument(ExpiredDocumentItem? item)
    {
        if (item is null) return;
        if (OnConfirmHardDelete is not null && !await OnConfirmHardDelete(item)) return;
        _documentation.HardDelete(item.Id);
        ExpiredDocuments.Remove(item);
    }
}

public class ExpiredDocumentItem(Documentation d, string studentName)
{
    public Guid Id { get; } = d.Id;
    public string StudentName { get; } = studentName;
    public string Title { get; } = d.Title;
    public string CreatedAtDisplay { get; } = d.CreatedAt.ToLocalTime().ToString("dd.MM.yyyy");
}