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

namespace LehrerApp.Desktop.ViewModels.Settings;

// ── Haupt-ViewModel ───────────────────────────────────────────────────────────

public partial class SettingsViewModel : ObservableObject
{
    private readonly ISubjectRepository          _subjects;
    private readonly ICompetencyDomainRepository _domainRepo;
    private readonly IGradingKeyTemplateRepository _gradingKeyTemplates;
    private readonly GradingService _grading;

    // ── Fächer ────────────────────────────────────────────────────────────────

    [ObservableProperty] private string _newName          = "";
    [ObservableProperty] private string _newShort         = "";
    [ObservableProperty] private string _validationMessage = "";

    public ObservableCollection<SubjectListItem> Subjects { get; } = [];

    // ── Kompetenzkatalog ──────────────────────────────────────────────────────

    [ObservableProperty] private SubjectListItem? _catalogSubject;
    [ObservableProperty] private int              _catalogGradeLevel = 10;
    [ObservableProperty] private string           _newDomainName     = "";
    [ObservableProperty] private string           _newDomainCode     = "";
    [ObservableProperty] private string           _catalogValidation = "";

    public ObservableCollection<DomainEditItem> Domains { get; } = [];

    // ── Notenschlüssel-Vorlagen (1.3.2) ──────────────────────────────────────

    [ObservableProperty] private string _newTemplateName = "";
    [ObservableProperty] private string _newTemplateGradingSystemName = "Noten 1–6";
    [ObservableProperty] private string _templateValidationMessage = "";

    public List<string> GradingSystemOptions { get; } = ["Noten 1–6", "Punkte 0–15"];
    public ObservableCollection<GradingKeyTemplateEditItem> GradingKeyTemplateList { get; } = [];

    // ── Konstruktor ───────────────────────────────────────────────────────────

    public SettingsViewModel(ISubjectRepository subjects, ICompetencyDomainRepository domainRepo,
        IGradingKeyTemplateRepository gradingKeyTemplates, GradingService grading)
    {
        _subjects   = subjects;
        _domainRepo = domainRepo;
        _gradingKeyTemplates = gradingKeyTemplates;
        _grading    = grading;
        LoadSubjects();
        LoadGradingKeyTemplates();
    }

    // ── Notenschlüssel-Vorlagen: Laden / Hinzufügen / Löschen ────────────────

    private void LoadGradingKeyTemplates()
    {
        GradingKeyTemplateList.Clear();
        foreach (var t in _gradingKeyTemplates.GetAll())
            GradingKeyTemplateList.Add(new GradingKeyTemplateEditItem(t, _gradingKeyTemplates, _grading));
    }

    [RelayCommand]
    private void AddGradingKeyTemplate()
    {
        if (string.IsNullOrWhiteSpace(NewTemplateName)) { TemplateValidationMessage = "Vorlagenname erforderlich."; return; }

        var system = NewTemplateGradingSystemName == "Punkte 0–15"
            ? GradingSystem.Points0To15 : GradingSystem.Grades1To6;
        var defaults = system == GradingSystem.Grades1To6
            ? GradingService.DefaultKey1To6() : GradingService.DefaultKey0To15();

        var template = new GradingKeyTemplate
        {
            Name = NewTemplateName.Trim(),
            GradingSystem = system,
            Entries = defaults.Select(e => new GradingKeyEntry { Grade = e.Grade, MinPercent = e.MinPercent }).ToList(),
        };
        _gradingKeyTemplates.Save(template);
        GradingKeyTemplateList.Add(new GradingKeyTemplateEditItem(template, _gradingKeyTemplates, _grading));
        NewTemplateName = "";
        TemplateValidationMessage = "";
    }

    [RelayCommand]
    private void DeleteGradingKeyTemplate(GradingKeyTemplateEditItem? item)
    {
        if (item is null) return;
        _gradingKeyTemplates.Delete(item.Id);
        GradingKeyTemplateList.Remove(item);
    }

    // ── Fächer: Laden / Hinzufügen / Löschen ─────────────────────────────────

    public void LoadSubjects()
    {
        Subjects.Clear();
        foreach (var s in _subjects.GetAll())
            Subjects.Add(new SubjectListItem(s));
    }

    [RelayCommand]
    private void AddSubject()
    {
        if (string.IsNullOrWhiteSpace(NewName)) { ValidationMessage = "Name erforderlich."; return; }
        _subjects.Save(new Subject { Name = NewName.Trim(), ShortName = NewShort.Trim() });
        NewName = ""; NewShort = ""; ValidationMessage = "";
        LoadSubjects();
    }

    [RelayCommand]
    private void DeleteSubject(SubjectListItem? item)
    {
        if (item is null) return;
        _subjects.Delete(item.Id);
        if (CatalogSubject?.Id == item.Id) CatalogSubject = null;
        LoadSubjects();
    }

    // ── Katalog: Laden ────────────────────────────────────────────────────────

    partial void OnCatalogSubjectChanged(SubjectListItem? value)  => LoadCatalog();
    partial void OnCatalogGradeLevelChanged(int value)            => LoadCatalog();

    private void LoadCatalog()
    {
        Domains.Clear();
        CatalogValidation = "";
        if (CatalogSubject is null) return;
        foreach (var d in _domainRepo.GetBySubjectAndGrade(CatalogSubject.Id, CatalogGradeLevel))
            Domains.Add(new DomainEditItem(d, _domainRepo));
    }

    // ── Katalog: Bereich hinzufügen / löschen ────────────────────────────────

    [RelayCommand]
    private void AddDomain()
    {
        if (CatalogSubject is null) { CatalogValidation = "Bitte zuerst ein Fach auswählen."; return; }
        if (string.IsNullOrWhiteSpace(NewDomainName)) { CatalogValidation = "Bereichsname erforderlich."; return; }

        var domain = new CompetencyDomain
        {
            SubjectId  = CatalogSubject.Id,
            GradeLevel = CatalogGradeLevel,
            Name       = NewDomainName.Trim(),
            Code       = NewDomainCode.Trim(),
            SortOrder  = Domains.Count,
        };
        _domainRepo.Save(domain);
        Domains.Add(new DomainEditItem(domain, _domainRepo));
        NewDomainName = ""; NewDomainCode = ""; CatalogValidation = "";
    }

    [RelayCommand]
    private void DeleteDomain(DomainEditItem? item)
    {
        if (item is null) return;
        _domainRepo.Delete(item.Id);
        Domains.Remove(item);
    }

    // ── JSON Import / Export ──────────────────────────────────────────────────

    public void ImportCatalog(string json)
    {
        if (CatalogSubject is null) { CatalogValidation = "Bitte zuerst ein Fach auswählen."; return; }
        try
        {
            var opts = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };
            var dto  = JsonSerializer.Deserialize<CatalogDto>(json, opts);
            if (dto?.Domains is null) { CatalogValidation = "Ungültiges JSON-Format."; return; }

            _domainRepo.DeleteBySubjectAndGrade(CatalogSubject.Id, CatalogGradeLevel);

            for (int i = 0; i < dto.Domains.Count; i++)
            {
                var d = dto.Domains[i];
                var domain = new CompetencyDomain
                {
                    SubjectId  = CatalogSubject.Id,
                    GradeLevel = CatalogGradeLevel,
                    Name       = d.Name ?? "",
                    Code       = d.Code ?? "",
                    SortOrder  = i,
                    Items      = (d.Competencies ?? [])
                                 .Select((c, j) => new CompetencyItem
                                 {
                                     Code        = c.Code ?? "",
                                     Description = c.Description ?? "",
                                     SortOrder   = j,
                                 }).ToList(),
                };
                _domainRepo.Save(domain);
            }
            CatalogValidation = "";
            LoadCatalog();
        }
        catch
        {
            CatalogValidation = "Import fehlgeschlagen – bitte JSON-Format prüfen.";
        }
    }

    public string ExportCatalog()
    {
        var dto = new CatalogDto
        {
            Subject    = CatalogSubject?.Name ?? "",
            GradeLevel = CatalogGradeLevel,
            Domains    = Domains.Select(d => new DomainDto
            {
                Name         = d.Name,
                Code         = d.Code,
                Competencies = d.Items.Select(i => new CompetencyDto
                {
                    Code        = i.Code,
                    Description = i.Description,
                }).ToList(),
            }).ToList(),
        };
        return JsonSerializer.Serialize(dto, new JsonSerializerOptions { WriteIndented = true });
    }
}

// ── DomainEditItem ────────────────────────────────────────────────────────────

public partial class DomainEditItem : ObservableObject
{
    private readonly CompetencyDomain            _domain;
    private readonly ICompetencyDomainRepository _repo;

    public Guid   Id          { get; }
    public string Name        { get; }
    public string Code        { get; }
    public string DisplayName { get; }

    [ObservableProperty] private string _newItemCode = "";
    [ObservableProperty] private string _newItemDesc = "";

    public ObservableCollection<CompetencyItemVm> Items { get; } = [];

    public DomainEditItem(CompetencyDomain domain, ICompetencyDomainRepository repo)
    {
        _domain     = domain;
        _repo       = repo;
        Id          = domain.Id;
        Name        = domain.Name;
        Code        = domain.Code;
        DisplayName = string.IsNullOrEmpty(domain.Code)
            ? domain.Name
            : $"{domain.Name}  ({domain.Code})";

        foreach (var item in domain.Items.OrderBy(i => i.SortOrder))
            Items.Add(new CompetencyItemVm(item, DeleteItem));
    }

    [RelayCommand]
    private void AddItem()
    {
        if (string.IsNullOrWhiteSpace(NewItemDesc)) return;
        var item = new CompetencyItem
        {
            Code        = NewItemCode.Trim(),
            Description = NewItemDesc.Trim(),
            SortOrder   = _domain.Items.Count,
        };
        _domain.Items.Add(item);
        _repo.Save(_domain);
        Items.Add(new CompetencyItemVm(item, DeleteItem));
        NewItemCode = ""; NewItemDesc = "";
    }

    private void DeleteItem(CompetencyItemVm vm)
    {
        _domain.Items.RemoveAll(i => i.Id == vm.ItemId);
        _repo.Save(_domain);
        Items.Remove(vm);
    }
}

// ── CompetencyItemVm ──────────────────────────────────────────────────────────

public class CompetencyItemVm
{
    public Guid   ItemId  { get; }
    public string Code    { get; }
    public string Description { get; }
    public string Display { get; }
    public IRelayCommand DeleteCommand { get; }

    public CompetencyItemVm(CompetencyItem item, Action<CompetencyItemVm> onDelete)
    {
        ItemId      = item.Id;
        Code        = item.Code;
        Description = item.Description;
        Display     = string.IsNullOrEmpty(item.Code)
            ? item.Description
            : $"[{item.Code}]  {item.Description}";
        DeleteCommand = new RelayCommand(() => onDelete(this));
    }
}

// ── GradingKeyTemplateEditItem (1.3.2) ─────────────────────────────────────────

public partial class GradingKeyTemplateEditItem : ObservableObject
{
    private readonly GradingKeyTemplate _template;
    private readonly IGradingKeyTemplateRepository _repo;
    private readonly GradingService _grading;

    public Guid   Id                 { get; }
    public string Name               { get; }
    public string GradingSystemLabel { get; }

    [ObservableProperty] private string _newGrade = "";
    [ObservableProperty] private double _newMinPercent;
    [ObservableProperty] private string _validation = "";
    [ObservableProperty] private string _completenessWarning = "";

    public ObservableCollection<GradingKeyEntryVm> Entries { get; } = [];

    public GradingKeyTemplateEditItem(GradingKeyTemplate template, IGradingKeyTemplateRepository repo,
        GradingService grading)
    {
        _template = template; _repo = repo; _grading = grading;
        Id   = template.Id;
        Name = template.Name;
        GradingSystemLabel = template.GradingSystem == GradingSystem.Grades1To6
            ? "Noten 1–6" : "Punkte 0–15";

        foreach (var e in template.Entries.OrderByDescending(e => e.MinPercent))
            Entries.Add(new GradingKeyEntryVm(e, DeleteEntry));
        RecomputeCompleteness();
    }

    [RelayCommand]
    private void AddEntry()
    {
        if (string.IsNullOrWhiteSpace(NewGrade)) { Validation = "Bezeichnung erforderlich."; return; }
        if (NewMinPercent is < 0 or > 100) { Validation = "Prozentgrenze muss zwischen 0 und 100 liegen."; return; }
        if (_template.Entries.Any(e => Math.Abs(e.MinPercent - NewMinPercent) < 0.0001))
        { Validation = "Diese Prozentgrenze existiert bereits."; return; }

        var entry = new GradingKeyEntry { Grade = NewGrade.Trim(), MinPercent = NewMinPercent };
        _template.Entries.Add(entry);
        _template.Entries = _template.Entries.OrderByDescending(e => e.MinPercent).ToList();
        _repo.Save(_template);

        Entries.Clear();
        foreach (var e in _template.Entries) Entries.Add(new GradingKeyEntryVm(e, DeleteEntry));
        NewGrade = ""; NewMinPercent = 0; Validation = "";
        RecomputeCompleteness();
    }

    private void DeleteEntry(GradingKeyEntryVm vm)
    {
        _template.Entries.RemoveAll(e => e.Grade == vm.Grade && Math.Abs(e.MinPercent - vm.MinPercent) < 0.0001);
        _repo.Save(_template);
        Entries.Remove(vm);
        RecomputeCompleteness();
    }

    private void RecomputeCompleteness() =>
        CompletenessWarning = _grading.ValidateGradingKey(_template.Entries) ?? "";
}

// ── GradingKeyEntryVm ─────────────────────────────────────────────────────────

public class GradingKeyEntryVm
{
    public string Grade      { get; }
    public double MinPercent { get; }
    public string Display    { get; }
    public IRelayCommand DeleteCommand { get; }

    public GradingKeyEntryVm(GradingKeyEntry e, Action<GradingKeyEntryVm> onDelete)
    {
        Grade      = e.Grade;
        MinPercent = e.MinPercent;
        Display    = $"{Grade} — ab {MinPercent.ToString("0.##")} %";
        DeleteCommand = new RelayCommand(() => onDelete(this));
    }
}

// ── Hilfklassen ───────────────────────────────────────────────────────────────

public class SubjectListItem(Subject s)
{
    public Guid   Id        { get; } = s.Id;
    public string Name      { get; } = s.Name;
    public string ShortName { get; } = s.ShortName;
}

// ── JSON DTOs ─────────────────────────────────────────────────────────────────

internal class CatalogDto
{
    [JsonPropertyName("subject")]    public string?          Subject    { get; set; }
    [JsonPropertyName("gradeLevel")] public int              GradeLevel { get; set; }
    [JsonPropertyName("domains")]    public List<DomainDto>? Domains    { get; set; }
}

internal class DomainDto
{
    [JsonPropertyName("name")]          public string?               Name         { get; set; }
    [JsonPropertyName("code")]          public string?               Code         { get; set; }
    [JsonPropertyName("competencies")]  public List<CompetencyDto>?  Competencies { get; set; }
}

internal class CompetencyDto
{
    [JsonPropertyName("code")]        public string? Code        { get; set; }
    [JsonPropertyName("description")] public string? Description { get; set; }
}