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

namespace LehrerApp.Desktop.ViewModels.Groups;

/// <summary>Erzeugt aus einer in TemplateDesigner gebauten Arbeitsblatt-.lavorlage-Vorlage ein
/// personalisiertes PDF je aktivem Mitglied der aktuell geöffneten Lerngruppe. Nutzt bewusst
/// dieselbe Platzhalter-/Rendering-Infrastruktur wie der Elternbrief-Dialog
/// (<see cref="LetterPlaceholderBuilder"/>, <see cref="ITemplateRenderer"/>), aber eine getrennte
/// <see cref="WorksheetTemplateStore"/>-Vorlagenbibliothek.</summary>
public partial class PersonalizeWorksheetDialogViewModel : ObservableObject
{
    private readonly LearningGroup _group;
    private readonly WorksheetTemplateStore _templates;
    private readonly ITemplateRenderer _renderer;

    [ObservableProperty] private LetterTemplateChoice? _selectedTemplate;
    [ObservableProperty] private string _statusMessage = "";

    public string GroupName => $"{_group.Name} · {_group.SchoolYear}";
    public ObservableCollection<LetterTemplateChoice> Templates { get; } = [];
    public ObservableCollection<WorksheetStudentChoice> Students { get; } = [];
    public ObservableCollection<WorksheetGenerationResult> Results { get; } = [];
    public bool HasNoTemplates => Templates.Count == 0;
    public bool HasResults => Results.Count > 0;

    public PersonalizeWorksheetDialogViewModel(LearningGroup group, IReadOnlyList<Guid> studentIds,
        IStudentRepository students, WorksheetTemplateStore templates, ITemplateRenderer renderer)
    {
        _group = group; _templates = templates; _renderer = renderer;
        foreach (var template in templates.Store.GetTemplates()) Templates.Add(new(template));
        SelectedTemplate = Templates.FirstOrDefault();
        foreach (var id in studentIds)
            if (students.GetById(id) is { } student) Students.Add(new(student));
    }

    public void Generate(string outputFolder)
    {
        Results.Clear();
        if (SelectedTemplate is null) return;
        LoadedTemplate loaded;
        try { loaded = _templates.Store.Load(SelectedTemplate.Model); }
        catch (Exception ex) when (ex is IOException or InvalidDataException or TemplateValidationException)
        { StatusMessage = $"Vorlage ist ungültig: {ex.Message}"; return; }

        Directory.CreateDirectory(outputFolder);
        foreach (var choice in Students.Where(x => x.IsIncluded))
        {
            var student = choice.Model;
            try
            {
                var values = LetterPlaceholderBuilder.BuildStandardValues(student, contact: null, _group,
                    DateOnly.FromDateTime(DateTime.Now), "", "");
                var pdf = _renderer.RenderToPdf(loaded, new LetterDataProvider(values));
                var fileName = SanitizeFileName($"{SelectedTemplate.Name}_{student.LastName}_{student.FirstName}.pdf");
                File.WriteAllBytes(Path.Combine(outputFolder, fileName), pdf);
                Results.Add(new(student.FullName, true, ""));
            }
            catch (Exception ex) when (ex is IOException or InvalidDataException or UnauthorizedAccessException or TemplateValidationException)
            { Results.Add(new(student.FullName, false, ex.Message)); }
        }
        OnPropertyChanged(nameof(HasResults));
        StatusMessage = $"{Results.Count(x => x.Success)} von {Results.Count} Arbeitsblättern erzeugt.";
    }

    private static string SanitizeFileName(string value)
    { foreach (var character in Path.GetInvalidFileNameChars()) value = value.Replace(character, '_'); return value; }
}

public partial class WorksheetStudentChoice(Student model) : ObservableObject
{
    public Student Model { get; } = model;
    public string FullName => Model.FullName;
    [ObservableProperty] private bool _isIncluded = true;
}

public sealed record WorksheetGenerationResult(string StudentName, bool Success, string ErrorMessage)
{
    public string Icon => Success ? "✓" : "⚠";
    public string Color => Success ? "SeaGreen" : "#D97706";
}