using System.Collections.ObjectModel;
using System.IO;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using foodmarket.Pos.Core.Auth;
using foodmarket.Pos.Core.Logic;
using foodmarket.Pos.Core.Models;
using foodmarket.Pos.Core.Sync;
using foodmarket.Pos.Services;

namespace foodmarket.Pos.ViewModels;

public abstract partial class ViewModelBase : ObservableObject { }

/// <summary>Оболочка: статус-бар (касса/смена/сеть/очередь), текущая страница,
/// модальная оплата, горячие клавиши и фоновая синхронизация. Логин-гейт:
/// без валидной сессии показывается экран входа.</summary>
public partial class MainWindowViewModel : ViewModelBase
{
    private readonly AppServices? _svc;
    private SaleViewModel? _sale;
    private System.Timers.Timer? _syncTimer;

    [ObservableProperty] private object? _currentPage;
    [ObservableProperty] private string _cashierName = "—";
    [ObservableProperty] private string _shiftNumber = "смена не открыта";
    [ObservableProperty] private bool _isOnline = true;
    [ObservableProperty] private int _queueCount;
    [ObservableProperty] private PaymentViewModel? _payment;
    [ObservableProperty] private bool _isPaymentOpen;
    [ObservableProperty] private string? _updateMessage;

    public string NetBadge => IsOnline ? "● на связи" : "○ нет связи";
    public string QueueBadge => QueueCount > 0 ? $"{QueueCount} чек(ов) в очереди" : "очередь пуста";
    partial void OnIsOnlineChanged(bool value) { OnPropertyChanged(nameof(NetBadge)); }
    partial void OnQueueCountChanged(int value) { OnPropertyChanged(nameof(QueueBadge)); }

    /// <summary>Конструктор для дизайнера/скриншотов (демо-данные).</summary>
    public MainWindowViewModel() { CurrentPage = SaleViewModel.Sample(); CashierName = "Пётр Кассиров"; ShiftNumber = "С-2026-000001"; }

    public MainWindowViewModel(AppServices svc) { _svc = svc; if (svc.Session is not null) StartSession(); else ShowLogin(); }

    private void ShowLogin()
    {
        CashierName = "—"; ShiftNumber = "вход…";
        CurrentPage = new LoginViewModel(_svc!) { OnLoggedIn = StartSession };
    }

    private void StartSession()
    {
        CashierName = _svc!.Session?.CashierName ?? "кассир";
        QueueCount = _svc.Store.PendingCount();
        _sale = new SaleViewModel(_svc) { PaymentRequested = OpenPayment, SaleCommitted = _ => RefreshStatus() };
        CurrentPage = _sale;
        StartSyncLoop();
        _ = CheckForUpdateAsync();
    }

    private async Task CheckForUpdateAsync()
    {
        if (_svc?.Api is null) return;
        try
        {
            var info = await _svc.Api.VersionAsync();
            var local = LocalVersion();
            if (UpdateCheck.IsNewer(local, info.Version))
            {
                var url = OperatingSystem.IsWindows() ? info.WindowsUrl : info.LinuxUrl;
                UpdateMessage = $"Доступно обновление {info.Version}" + (string.IsNullOrEmpty(url) ? "" : $" — {url}");
            }
        }
        catch { /* проверка версии не критична */ }
    }

    private static string LocalVersion()
    {
        try
        {
            var f = Path.Combine(AppContext.BaseDirectory, "VERSION.txt");
            if (File.Exists(f)) return File.ReadAllText(f).Trim();
        }
        catch { }
        return System.Reflection.Assembly.GetEntryAssembly()?.GetName().Version?.ToString() ?? "0.0.0";
    }

    private void RefreshStatus() { if (_svc is not null) QueueCount = _svc.Store.PendingCount(); }

    [RelayCommand] private void ShowSale() { CurrentPage = _sale ??= (_svc is null ? SaleViewModel.Sample() : new SaleViewModel(_svc) { PaymentRequested = OpenPayment, SaleCommitted = _ => RefreshStatus() }); }
    [RelayCommand] private void ShowShift() => CurrentPage = _svc is null ? ShiftViewModel.Sample() : new ShiftViewModel(_svc) { OnShiftChanged = s => { ShiftNumber = s ?? "смена не открыта"; } };
    [RelayCommand] private void ShowReturn() => CurrentPage = _svc is null ? ReturnViewModel.Sample() : new ReturnViewModel(_svc);

    private void OpenPayment(PaymentViewModel pvm)
    {
        pvm.OnCancel = ClosePayment;
        var confirm = pvm.OnConfirm;
        pvm.OnConfirm = async (cash, card, change) => { if (confirm is not null) await confirm(cash, card, change); ClosePayment(); };
        Payment = pvm; IsPaymentOpen = true;
    }
    private void ClosePayment() { IsPaymentOpen = false; Payment = null; }

    /// <summary>Горячие клавиши (работа без мыши). Вызывается из code-behind окна.</summary>
    public void HandleHotkey(string key)
    {
        switch (key)
        {
            case "F2": if (_sale is not null) _sale.Message = "Введите название или штрихкод"; break;
            case "F7": case "F10": ShowShiftCommand.Execute(null); break;
            case "F9": ShowReturnCommand.Execute(null); break;
            case "F12": if (IsPaymentOpen) Payment?.ConfirmCommand.Execute(null); else _sale?.PayCommand.Execute(null); break;
            case "Delete": _sale?.RemoveSelectedCommand.Execute(null); break;
            case "Escape": if (IsPaymentOpen) ClosePayment(); else _sale?.ClearCommand.Execute(null); break;
        }
    }

    private void StartSyncLoop()
    {
        if (_svc?.Sync is null) return;
        _syncTimer = new System.Timers.Timer(15_000) { AutoReset = true };
        _syncTimer.Elapsed += async (_, _) => await SyncTickAsync();
        _syncTimer.Start();
        _ = SyncTickAsync();
    }

    private async Task SyncTickAsync()
    {
        if (_svc?.Sync is null) return;
        try
        {
            await _svc.Sync.PushSalesAsync();
            await _svc.Sync.PullCatalogAsync();
            IsOnline = true;
        }
        catch { IsOnline = false; }
        finally { QueueCount = _svc.Store.PendingCount(); }
    }
}

/// <summary>Экран входа: адрес сервера, логин, PIN. Регистрирует кассу на точке
/// продаж (берёт точку из привязки кассира). Хранит refresh-токен защищённо.</summary>
public partial class RetailPointOption : ObservableObject
{
    public required Guid Id { get; init; }
    public required string Name { get; init; }
    public override string ToString() => Name;
}

public partial class LoginViewModel : ViewModelBase
{
    private const string DevicePointKey = "device.retailPointId";
    private const string DeviceUrlKey = "device.serverUrl";
    private readonly AppServices? _svc;
    private PosSession? _pending;          // сессия, ожидающая выбора точки
    private bool _canManagePoints;
    private Guid? _devicePoint;

    [ObservableProperty] private string _serverUrl = "https://test.admin.food-market.kz";
    [ObservableProperty] private string _username = "";
    [ObservableProperty] private string _pin = "";
    [ObservableProperty] private string? _error;
    [ObservableProperty] private bool _busy;

    // Шаг выбора точки продаж (регистрация устройства администратором).
    [ObservableProperty] private bool _requirePointSelection;
    [ObservableProperty] private RetailPointOption? _selectedPoint;
    public ObservableCollection<RetailPointOption> Points { get; } = new();

    // Быстрый вход по PIN (на зарегистрированном устройстве).
    [ObservableProperty] private bool _pinMode;
    [ObservableProperty] private bool _deviceRegistered;
    [ObservableProperty] private string _pinEntry = "";
    public string PinMasked => new string('●', PinEntry.Length);
    partial void OnPinEntryChanged(string value) => OnPropertyChanged(nameof(PinMasked));

    public Action? OnLoggedIn;

    public LoginViewModel() { }
    public LoginViewModel(AppServices svc)
    {
        _svc = svc;
        _devicePoint = Guid.TryParse(svc.Store.GetKv(DevicePointKey), out var dp) ? dp : null;
        var savedUrl = svc.Store.GetKv(DeviceUrlKey);
        if (!string.IsNullOrEmpty(savedUrl)) ServerUrl = savedUrl;
        DeviceRegistered = _devicePoint is not null;
        PinMode = DeviceRegistered && !string.IsNullOrEmpty(savedUrl);
    }

    [RelayCommand]
    private async Task LoginAsync()
    {
        if (_svc is null) { OnLoggedIn?.Invoke(); return; }
        Error = null; Busy = true; RequirePointSelection = false;
        try
        {
            var t = await _svc.Auth.LoginAsync(ServerUrl.Trim(), Username.Trim(), Pin);
            var session = new PosSession { ServerUrl = ServerUrl.Trim(), AccessToken = t.AccessToken, RefreshToken = t.RefreshToken };
            _svc.ConfigureApi(session);

            Guid[] assigned = Array.Empty<Guid>();
            try
            {
                var me = await _svc.Api!.MeAsync();
                session.CashierName = me.name ?? Username.Trim();
                session.Roles = me.roles;
                if (Guid.TryParse(me.sub, out var uid)) session.CashierUserId = uid;
                assigned = me.retailPointIds ?? Array.Empty<Guid>();
                _canManagePoints = me.roles.Contains("Admin") || me.roles.Contains("SuperAdmin")
                                   || (me.permissions?.TryGetValue("RetailPointsManage", out var m) == true && m);
            }
            catch { session.CashierName = Username.Trim(); }

            // Точка продаж, на которой зарегистрировано это устройство.
            Guid? devicePoint = Guid.TryParse(_svc.Store.GetKv(DevicePointKey), out var dp) ? dp : null;
            var decision = DeviceRegistration.Evaluate(devicePoint, _canManagePoints, assigned);

            switch (decision)
            {
                case DeviceRegistration.Decision.Proceed:
                    session.RetailPointId = devicePoint;
                    _svc.Store.SetKv(DeviceUrlKey, ServerUrl.Trim()); // для быстрого входа по PIN
                    _svc.Tokens.Save(session); _svc.Session = session;
                    OnLoggedIn?.Invoke();
                    break;

                case DeviceRegistration.Decision.NeedSelection:
                    _pending = session;
                    await LoadActivePointsAsync();
                    RequirePointSelection = true;
                    Error = null;
                    break;

                case DeviceRegistration.Decision.NotRegistered:
                    Error = "Устройство не зарегистрировано на точке продаж. Обратитесь к администратору для регистрации кассы.";
                    break;

                case DeviceRegistration.Decision.NotAssigned:
                    var name = await PointNameAsync(devicePoint!.Value);
                    Error = $"Вы не привязаны к кассе{(name is null ? "" : " «" + name + "»")}. Обратитесь к администратору.";
                    break;
            }
        }
        catch (AuthException ex) { Error = ex.Message; }
        catch (Exception ex) { Error = "Нет связи с сервером: " + ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand]
    private void ConfirmPoint()
    {
        if (_pending is null || SelectedPoint is null) { Error = "Выберите точку продаж"; return; }
        _svc!.Store.SetKv(DevicePointKey, SelectedPoint.Id.ToString());
        _svc.Store.SetKv(DeviceUrlKey, ServerUrl.Trim());
        _pending.RetailPointId = SelectedPoint.Id;
        _svc.Tokens.Save(_pending); _svc.Session = _pending;
        RequirePointSelection = false;
        OnLoggedIn?.Invoke();
    }

    // ── Быстрый вход по PIN ───────────────────────────────────────────────
    [RelayCommand] private void PinDigit(string d) { if (PinEntry.Length < 6) PinEntry += d; }
    [RelayCommand] private void PinBack() { if (PinEntry.Length > 0) PinEntry = PinEntry[..^1]; }
    [RelayCommand] private void UsePassword() { PinMode = false; Error = null; }
    [RelayCommand] private void UsePin() { if (DeviceRegistered) { PinMode = true; Error = null; } }

    [RelayCommand]
    private async Task PinLogin()
    {
        if (_svc is null || _devicePoint is null) { PinMode = false; return; }
        if (PinEntry.Length < 4) { Error = "Введите PIN (4–6 цифр)"; return; }
        Error = null; Busy = true;
        try
        {
            var t = await _svc.Auth.PinLoginAsync(ServerUrl.Trim(), _devicePoint.Value, PinEntry);
            var session = new PosSession { ServerUrl = ServerUrl.Trim(), AccessToken = t.AccessToken, RefreshToken = t.RefreshToken, RetailPointId = _devicePoint };
            _svc.ConfigureApi(session);
            try
            {
                var me = await _svc.Api!.MeAsync();
                session.CashierName = me.name ?? "кассир";
                session.Roles = me.roles;
                if (Guid.TryParse(me.sub, out var uid)) session.CashierUserId = uid;
            }
            catch { session.CashierName = "кассир"; }
            _svc.Tokens.Save(session); _svc.Session = session;
            OnLoggedIn?.Invoke();
        }
        catch (AuthException ex) { Error = ex.Message; PinEntry = ""; }
        catch (Exception ex) { Error = "Нет связи с сервером: " + ex.Message; PinEntry = ""; }
        finally { Busy = false; }
    }

    /// <summary>Сбросить регистрацию устройства (сменить точку). Новую точку
    /// сможет выбрать только администратор (кассир после сброса получит
    /// «устройство не зарегистрировано»).</summary>
    [RelayCommand]
    private void ResetDevice()
    {
        _svc?.Store.SetKv(DevicePointKey, "");
        Error = "Точка продаж сброшена. Войдите под администратором, чтобы выбрать новую.";
        RequirePointSelection = false;
    }

    private async Task LoadActivePointsAsync()
    {
        Points.Clear();
        var points = await _svc!.Api!.RetailPointsAsync();
        foreach (var p in points.items.Where(x => x.isActive))
            Points.Add(new RetailPointOption { Id = p.id, Name = p.name });
        SelectedPoint = Points.FirstOrDefault();
    }

    private async Task<string?> PointNameAsync(Guid id)
    {
        try { var points = await _svc!.Api!.RetailPointsAsync(); return points.items.FirstOrDefault(p => p.id == id)?.name; }
        catch { return null; }
    }

    public static LoginViewModel Sample() => new() { Username = "cashier@food-market.kz" };
    public static LoginViewModel SamplePin() => new() { PinMode = true, DeviceRegistered = true, PinEntry = "1234" };
}

public partial class SaleLineVm : ObservableObject
{
    internal CartLine? Model;
    public required Guid ProductId { get; init; }
    [ObservableProperty] private string _name = "";
    [ObservableProperty] private string _unit = "шт";
    [ObservableProperty] private decimal _price;
    [ObservableProperty] private decimal _quantity = 1m;
    [ObservableProperty] private decimal _discount;
    public decimal Gross => decimal.Round(Price * Quantity, 2);
    public decimal LineTotal => Math.Max(0m, Gross - Discount);
    /// <summary>Количество с единицей измерения: «3 шт», «1,235 кг».</summary>
    public string QtyText
    {
        get
        {
            var n = Quantity == decimal.Truncate(Quantity) && Unit == "шт"
                ? Quantity.ToString("0")
                : Quantity.ToString("0.###");
            return $"{n} {Unit}";
        }
    }
    public bool HasDiscount => Discount > 0m;
    /// <summary>Пояснение скидки в строке, чтобы цена×кол-во ≠ сумма не выглядело
    /// ошибкой: «1 560 → 1 500 ₸, скидка 60».</summary>
    public string DiscountText => $"{Gross:N0} → {LineTotal:N0} ₸, скидка {Discount:N0}";
    partial void OnQuantityChanged(decimal value)
    { OnPropertyChanged(nameof(LineTotal)); OnPropertyChanged(nameof(QtyText)); OnPropertyChanged(nameof(Gross)); OnPropertyChanged(nameof(DiscountText)); }
    partial void OnDiscountChanged(decimal value)
    { OnPropertyChanged(nameof(LineTotal)); OnPropertyChanged(nameof(HasDiscount)); OnPropertyChanged(nameof(DiscountText)); }
    partial void OnPriceChanged(decimal value)
    { OnPropertyChanged(nameof(Gross)); OnPropertyChanged(nameof(LineTotal)); OnPropertyChanged(nameof(DiscountText)); }
}

/// <summary>Экран продажи — сердце кассы. Пробитие по сканеру/поиску, корзина,
/// итоги, скидка, оплата. Горячие клавиши назначены в оболочке/View.</summary>
public partial class SaleViewModel : ViewModelBase
{
    private readonly AppServices? _svc;
    private readonly Cart _cart = new();
    private readonly Stack<CartSnapshot> _parked = new();
    public ObservableCollection<SaleLineVm> Lines { get; } = new();

    [ObservableProperty] private string _scanInput = "";
    [ObservableProperty] private string _shiftNumber = "С-2026-000001";
    [ObservableProperty] private string _message = "Отсканируйте товар или введите штрихкод";
    [ObservableProperty] private decimal _subtotal;
    [ObservableProperty] private decimal _discount;
    [ObservableProperty] private decimal _total;
    [ObservableProperty] private int _itemCount;
    [ObservableProperty] private SaleLineVm? _selectedLine;

    /// <summary>Поднять модальную оплату (обрабатывает оболочка).</summary>
    public Action<PaymentViewModel>? PaymentRequested;
    /// <summary>Чек проведён — оболочка обновляет индикатор очереди.</summary>
    public Action<CheckoutService.CommitResult>? SaleCommitted;

    public SaleViewModel() { }
    public SaleViewModel(AppServices svc) { _svc = svc; }

    private void Recalc()
    {
        var t = _cart.Totals();
        Subtotal = t.Subtotal; Discount = t.LineDiscounts + t.CartDiscount; Total = t.Total; ItemCount = t.LineCount;
    }

    public void AddProduct(PosProduct p, decimal qty, decimal? priceOverride = null)
    {
        var line = _cart.AddProduct(p, qty, priceOverride);
        var vm = Lines.FirstOrDefault(l => ReferenceEquals(l.Model, line));
        if (vm is not null) { vm.Quantity = line.Quantity; }
        else
        {
            vm = new SaleLineVm { ProductId = line.ProductId, Name = line.Name, Unit = line.UnitCode, Price = line.UnitPrice, Quantity = line.Quantity, Model = line };
            Lines.Insert(0, vm);
        }
        SelectedLine = vm;
        Recalc();
        Message = $"{p.Name} · {(p.IsWeighed ? qty.ToString("0.###") + " " + p.UnitCode : "×" + line.Quantity.ToString("0"))}";
    }

    [RelayCommand]
    private void Scan()
    {
        var raw = ScanInput.Trim();
        ScanInput = "";
        if (raw.Length == 0) return;
        var parsed = BarcodeParser.Parse(raw);
        var p = _svc?.Store.FindByBarcode(parsed.Lookup);
        if (p is null) { Message = $"Штрихкод {parsed.Lookup} не найден"; return; }
        var qty = parsed.IsWeighted && parsed.EmbeddedWeight is { } w ? w : 1m;
        var price = parsed.IsWeighted && parsed.EmbeddedPrice is { } pr ? pr / Math.Max(0.001m, qty) : (decimal?)null;
        AddProduct(p, qty, price);
    }

    [RelayCommand]
    private void RemoveSelected()
    {
        if (SelectedLine is null) return;
        if (SelectedLine.Model is { } m) _cart.Remove(m);
        Lines.Remove(SelectedLine);
        SelectedLine = Lines.FirstOrDefault();
        Recalc();
        Message = "Позиция удалена";
    }

    public void SetLineQuantity(SaleLineVm line, decimal qty)
    {
        if (line.Model is null) return;
        _cart.SetQuantity(line.Model, qty);
        if (qty <= 0) { Lines.Remove(line); }
        else line.Quantity = line.Model.Quantity;
        Recalc();
    }

    public void SetCartDiscount(decimal amount) { _cart.SetCartDiscount(amount); Recalc(); Message = $"Скидка на чек: {amount:N0} ₸"; }

    [RelayCommand]
    private void Pay()
    {
        if (_cart.IsEmpty) { Message = "Чек пуст — нечего оплачивать"; return; }
        if (_svc is not null && !_svc.Checkout.HasOpenShift) { Message = "Смена не открыта — F10, откройте смену"; return; }
        var pvm = new PaymentViewModel { Total = Total };
        pvm.OnConfirm = (cash, card, change) => CommitPaymentAsync(cash, card, change);
        if (PaymentRequested is not null) PaymentRequested(pvm);
        else _ = CommitPaymentAsync(Total, 0m, 0m); // без оболочки (тест/демо) — оплата наличными «под расчёт»
    }

    /// <summary>Провести оплату: офлайн-устойчивая запись чека + печать + попытка
    /// отправки. Очищает корзину.</summary>
    public async Task CommitPaymentAsync(decimal cash, decimal card, decimal change)
    {
        if (_cart.IsEmpty) return;
        if (_svc is null)
        {
            _cart.Clear(); Lines.Clear(); Recalc(); Message = "Оплата проведена (демо)"; return;
        }
        var res = await _svc.Checkout.CommitAsync(_cart, cash, card, change);
        _cart.Clear(); Lines.Clear(); SelectedLine = null; Recalc();
        Message = res.PushedNow ? "Чек проведён и отправлен на сервер" : $"Чек проведён (в очереди: {res.PendingAfter})";
        if (!res.Printed && res.PrintError is not null) Message += " · печать не удалась";
        SaleCommitted?.Invoke(res);
    }

    [RelayCommand] private void Clear() { _cart.Clear(); Lines.Clear(); SelectedLine = null; Recalc(); Message = "Чек очищен"; }

    public int ParkedCount => _parked.Count;

    /// <summary>Отложить текущий чек и начать новый (обслужить другого покупателя).</summary>
    [RelayCommand]
    private void Park()
    {
        if (_cart.IsEmpty) { Message = "Нечего откладывать"; return; }
        _parked.Push(_cart.Snapshot());
        _cart.Clear(); Lines.Clear(); SelectedLine = null; Recalc();
        OnPropertyChanged(nameof(ParkedCount));
        Message = $"Чек отложен (отложенных: {_parked.Count})";
    }

    /// <summary>Вернуть последний отложенный чек (поверх пустого).</summary>
    [RelayCommand]
    private void Resume()
    {
        if (_parked.Count == 0) { Message = "Нет отложенных чеков"; return; }
        if (!_cart.IsEmpty) { Message = "Сначала завершите или отложите текущий чек"; return; }
        _cart.Restore(_parked.Pop());
        RebuildLines();
        OnPropertyChanged(nameof(ParkedCount));
        Message = "Отложенный чек возвращён";
    }

    private void RebuildLines()
    {
        Lines.Clear();
        foreach (var l in _cart.Lines)
            Lines.Insert(0, new SaleLineVm { ProductId = l.ProductId, Name = l.Name, Unit = l.UnitCode, Price = l.UnitPrice, Quantity = l.Quantity, Discount = l.Discount, Model = l });
        SelectedLine = Lines.FirstOrDefault();
        Recalc();
    }

    /// <summary>Пример заполненного чека для скриншотов/демо.</summary>
    public static SaleViewModel Sample()
    {
        var vm = new SaleViewModel();
        vm.Lines.Add(new SaleLineVm { ProductId = Guid.NewGuid(), Name = "Хлеб «Семейный» нарезной", Unit = "шт", Price = 280m, Quantity = 2 });
        vm.Lines.Add(new SaleLineVm { ProductId = Guid.NewGuid(), Name = "Молоко 2.5% 1л", Unit = "шт", Price = 450m, Quantity = 1 });
        vm.Lines.Add(new SaleLineVm { ProductId = Guid.NewGuid(), Name = "Яблоки «Апорт» (вес)", Unit = "кг", Price = 690m, Quantity = 1.235m });
        vm.Lines.Add(new SaleLineVm { ProductId = Guid.NewGuid(), Name = "Сахар-песок 1кг", Unit = "шт", Price = 520m, Quantity = 3, Discount = 60m });
        vm.Subtotal = vm.Lines.Sum(l => l.Price * l.Quantity);
        vm.Discount = 60m;
        vm.Total = decimal.Round(vm.Subtotal - vm.Discount, 2);
        vm.ItemCount = vm.Lines.Count;
        vm.Message = "Чек готов к оплате — F12 Оплата";
        return vm;
    }
}

public partial class PaymentViewModel : ViewModelBase
{
    [ObservableProperty] private decimal _total;
    [ObservableProperty] private decimal _paidCash;
    [ObservableProperty] private decimal _paidCard;
    [ObservableProperty] private string _method = "Наличные";
    public decimal Change => PaymentMath.Compute(Total, PaidCash, PaidCard).Change;
    public decimal Shortfall => PaymentMath.Compute(Total, PaidCash, PaidCard).Shortfall;
    public bool Sufficient => PaymentMath.Compute(Total, PaidCash, PaidCard).Sufficient;
    partial void OnPaidCashChanged(decimal value) => RaisePay();
    partial void OnPaidCardChanged(decimal value) => RaisePay();
    partial void OnTotalChanged(decimal value) => RaisePay();
    private void RaisePay() { OnPropertyChanged(nameof(Change)); OnPropertyChanged(nameof(Shortfall)); OnPropertyChanged(nameof(Sufficient)); }

    /// <summary>Вызывается при подтверждении оплаты (cash, card, change).</summary>
    public Func<decimal, decimal, decimal, Task>? OnConfirm;
    public Action? OnCancel;

    [RelayCommand] private void ExactCash() { PaidCash = Total; PaidCard = 0m; Method = "Наличные"; }

    [RelayCommand]
    private async Task Confirm()
    {
        if (!Sufficient) return;
        if (OnConfirm is not null) await OnConfirm(PaidCash, PaidCard, Change);
    }

    [RelayCommand] private void Cancel() => OnCancel?.Invoke();

    public static PaymentViewModel SampleCash() => new() { Total = 3365m, PaidCash = 5000m, Method = "Наличные" };
    public static PaymentViewModel SampleMixed() => new() { Total = 3365m, PaidCash = 1365m, PaidCard = 2000m, Method = "Смешанная" };
}

/// <summary>Смена: открыть (размен) / закрыть (факт → должно/факт/разница),
/// внесение/выплата, X/Z-отчёты. Живые вызовы идут на серверный модуль «Деньги».</summary>
public partial class ShiftViewModel : ViewModelBase
{
    private readonly AppServices? _svc;

    [ObservableProperty] private bool _isOpen = true;
    [ObservableProperty] private string _number = "С-2026-000001";
    [ObservableProperty] private decimal _openingFloat = 5000m;
    [ObservableProperty] private decimal _salesCash = 3775m;
    [ObservableProperty] private decimal _salesCard = 2325m;
    [ObservableProperty] private decimal _returnsCash = 1500m;
    [ObservableProperty] private decimal _drawerIn = 10000m;
    [ObservableProperty] private decimal _drawerOut = 3000m;
    [ObservableProperty] private decimal _actualCash = 14775m;
    [ObservableProperty] private string? _message;
    [ObservableProperty] private bool _busy;

    public decimal ExpectedCash => ShiftMath.ExpectedCash(OpeningFloat, SalesCash, ReturnsCash, DrawerIn, DrawerOut);
    public decimal Difference => ShiftMath.CashDifference(ActualCash, ExpectedCash);
    partial void OnOpeningFloatChanged(decimal v) => RaiseCalc();
    partial void OnActualCashChanged(decimal v) => RaiseCalc();
    private void RaiseCalc() { OnPropertyChanged(nameof(ExpectedCash)); OnPropertyChanged(nameof(Difference)); }

    /// <summary>Сообщить оболочке новый номер смены (или null — закрыта).</summary>
    public Action<string?>? OnShiftChanged;

    public ShiftViewModel() { }
    public ShiftViewModel(AppServices svc)
    {
        _svc = svc; IsOpen = svc.Checkout.HasOpenShift;
        if (svc.Checkout.CurrentShift is { } s) { Number = s.Number; OpeningFloat = s.OpeningFloat; }
        _ = RefreshAsync();
    }

    private async Task RefreshAsync()
    {
        if (_svc?.Api is null || _svc.Session?.RetailPointId is not Guid rp) return;
        try
        {
            var cur = await _svc.Api.CurrentShiftAsync(rp);
            if (cur.Content is { open: true, shift: { } sh })
            {
                IsOpen = true; Number = sh.number; OpeningFloat = sh.openingFloat;
                _svc.Checkout.CurrentShift = new PosShift { Id = sh.id, Number = sh.number, RetailPointId = sh.retailPointId, CashAccountId = sh.cashAccountId, AcquiringAccountId = sh.acquiringAccountId, OpeningFloat = sh.openingFloat };
                OnShiftChanged?.Invoke(sh.number);
            }
            else { IsOpen = false; OnShiftChanged?.Invoke(null); }
        }
        catch (Exception ex) { Message = "Нет связи со сменой: " + ex.Message; }
    }

    [RelayCommand]
    private async Task OpenShift()
    {
        if (_svc?.Api is null || _svc.Session?.RetailPointId is not Guid rp) { Message = "Нет привязки к точке/серверу"; return; }
        Busy = true; Message = null;
        try
        {
            // Денежный счёт точки (наличная касса) — первый наличный привязанный к складу точки.
            var accounts = await _svc.Api.MoneyAccountsAsync();
            var cash = accounts.items.FirstOrDefault(a => a.kind == 1 && a.isActive) ?? accounts.items.FirstOrDefault(a => a.kind == 1);
            if (cash is null) { Message = "Не найдена наличная касса (создайте счёт в админке)"; return; }
            var res = await _svc.Api.OpenShiftAsync(new OpenShiftBody(rp, cash.id, null, OpeningFloat));
            IsOpen = true; Number = res.number;
            _svc.Checkout.CurrentShift = new PosShift { Id = res.id, Number = res.number, RetailPointId = rp, CashAccountId = cash.id, OpeningFloat = OpeningFloat };
            OnShiftChanged?.Invoke(res.number);
            Message = $"Смена {res.number} открыта";
        }
        catch (Exception ex) { Message = "Открыть смену не удалось: " + ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand]
    private async Task CloseShift()
    {
        if (_svc?.Api is null || _svc.Checkout.CurrentShift is not { } s) { Message = "Смена не открыта"; return; }
        Busy = true; Message = null;
        try
        {
            var res = await _svc.Api.CloseShiftAsync(s.Id, new CloseShiftBody(ActualCash, null));
            IsOpen = false;
            _svc.Checkout.CurrentShift = null;
            OnShiftChanged?.Invoke(null);
            Message = $"Смена закрыта. Должно {res.expectedCash:N0} ₸, факт {ActualCash:N0} ₸, разница {res.difference:N0} ₸";
        }
        catch (Exception ex) { Message = "Закрыть смену не удалось: " + ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand]
    private async Task DepositCash() => await DrawerAsync(1, DrawerIn, "Внесение");
    [RelayCommand]
    private async Task WithdrawCash() => await DrawerAsync(2, DrawerOut, "Выплата/инкассация");

    private async Task DrawerAsync(int direction, decimal amount, string reason)
    {
        if (_svc?.Api is null || _svc.Checkout.CurrentShift is not { } s) { Message = "Смена не открыта"; return; }
        try { await _svc.Api.DrawerAsync(s.Id, new DrawerBody(direction, amount, reason)); Message = $"{reason}: {amount:N0} ₸"; }
        catch (Exception ex) { Message = "Операция с кассой не удалась: " + ex.Message; }
    }

    public static ShiftViewModel Sample() => new();
    public static ShiftViewModel SampleClosed() { var s = new ShiftViewModel { IsOpen = false }; return s; }
}

/// <summary>Строка возврата: сколько продано/уже возвращено и сколько кассир
/// выбирает к возврату (0..ReturnableQty).</summary>
public partial class ReturnLineVm : ObservableObject
{
    public required Guid ProductId { get; init; }
    [ObservableProperty] private string _name = "";
    [ObservableProperty] private string _unit = "шт";
    [ObservableProperty] private decimal _unitPrice;
    [ObservableProperty] private decimal _soldQty;
    [ObservableProperty] private decimal _returnableQty;
    [ObservableProperty] private decimal _qty;
    public decimal LineRefund => decimal.Round(UnitPrice * Qty, 2);
    public string QtyText => Qty == decimal.Truncate(Qty) && Unit == "шт" ? Qty.ToString("0") : Qty.ToString("0.###");
    public string AvailText => $"доступно к возврату: {(ReturnableQty == decimal.Truncate(ReturnableQty) ? ReturnableQty.ToString("0") : ReturnableQty.ToString("0.###"))} {Unit}";
    partial void OnQtyChanged(decimal value) { OnPropertyChanged(nameof(LineRefund)); OnPropertyChanged(nameof(QtyText)); }
}

/// <summary>Возврат по чеку: найти чек (номер/скан QR), отметить позиции и
/// количество (не больше проданного минус уже возвращённого), сумма к выдаче,
/// способ (нал/карта как в исходном чеке).</summary>
public partial class ReturnViewModel : ViewModelBase
{
    private readonly AppServices? _svc;
    [ObservableProperty] private string _receiptNumber = "";
    [ObservableProperty] private string _message = "Отсканируйте QR чека или введите номер";
    [ObservableProperty] private bool _busy;
    [ObservableProperty] private bool _found;
    private Guid? _saleId;
    private int _payment; // способ оплаты исходного чека (0=нал,1=карта,…)

    public ObservableCollection<ReturnLineVm> Lines { get; } = new();
    public decimal RefundTotal => Lines.Sum(l => l.LineRefund);
    public Action<CheckoutService.CommitResult>? ReturnCommitted;

    public ReturnViewModel() { }
    public ReturnViewModel(AppServices svc) { _svc = svc; }

    [RelayCommand]
    private async Task Lookup()
    {
        var number = ReceiptNumber.Trim();
        if (number.Length == 0) { Message = "Введите номер чека или отсканируйте QR"; return; }
        if (_svc?.Api is null) { Message = "Нет связи с сервером"; return; }
        Busy = true; Found = false; Lines.Clear();
        try
        {
            var r = await _svc.Api.ReturnLookupAsync(number);
            _saleId = r.SaleId; _payment = r.Payment;
            foreach (var l in r.Lines.Where(x => x.ReturnableQty > 0))
                Lines.Add(new ReturnLineVm
                {
                    ProductId = l.ProductId, Name = l.Name, Unit = l.UnitCode,
                    UnitPrice = l.UnitPrice, SoldQty = l.SoldQty, ReturnableQty = l.ReturnableQty, Qty = 0m,
                });
            OnPropertyChanged(nameof(RefundTotal));
            Found = Lines.Count > 0;
            Message = Found
                ? $"Чек {r.Number} найден — отметьте позиции к возврату"
                : $"Чек {r.Number}: все позиции уже возвращены";
        }
        catch (Refit.ApiException ex) when (ex.StatusCode == System.Net.HttpStatusCode.NotFound)
        { Message = "Чек не найден или не проведён"; }
        catch (Exception ex) { Message = "Ошибка поиска: " + ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand] private void Inc(ReturnLineVm l) { if (l.Qty < l.ReturnableQty) { l.Qty = Math.Min(l.ReturnableQty, l.Qty + 1m); OnPropertyChanged(nameof(RefundTotal)); } }
    [RelayCommand] private void Dec(ReturnLineVm l) { if (l.Qty > 0) { l.Qty = Math.Max(0m, l.Qty - 1m); OnPropertyChanged(nameof(RefundTotal)); } }
    [RelayCommand] private void Full(ReturnLineVm l) { l.Qty = l.ReturnableQty; OnPropertyChanged(nameof(RefundTotal)); }

    [RelayCommand]
    private async Task Submit()
    {
        if (_svc is null || _saleId is null) { Message = "Сначала найдите чек"; return; }
        var chosen = Lines.Where(l => l.Qty > 0m).ToList();
        if (chosen.Count == 0) { Message = "Отметьте хотя бы одну позицию к возврату"; return; }
        Busy = true;
        try
        {
            var lines = chosen.Select(l => new foodmarket.Shared.Pos.V1.PosSaleLineDto
            { ProductId = l.ProductId, Quantity = l.Qty, UnitPrice = l.UnitPrice, Discount = 0m, VatPercent = 0m }).ToList();
            var display = chosen.Select(l => (l.Name, l.Unit)).ToList();
            var refund = RefundTotal;
            var toCard = _payment == 1; // карта как в исходном чеке, иначе наличные
            var res = await _svc.Checkout.CommitReturnAsync(lines, _saleId.Value,
                refundCash: toCard ? 0m : refund, refundCard: toCard ? refund : 0m, display);
            Message = res.PushedNow
                ? $"Возврат оформлен — к выдаче {refund:N0} ₸"
                : $"Возврат в очереди — к выдаче {refund:N0} ₸ (отправится при связи)";
            Lines.Clear(); Found = false; _saleId = null; ReceiptNumber = "";
            OnPropertyChanged(nameof(RefundTotal));
            ReturnCommitted?.Invoke(res);
        }
        catch (Exception ex) { Message = "Не удалось оформить возврат: " + ex.Message; }
        finally { Busy = false; }
    }

    public static ReturnViewModel Sample()
    {
        var vm = new ReturnViewModel { ReceiptNumber = "ПР-2026-000128", Message = "Чек найден — отметьте позиции к возврату", Found = true };
        vm.Lines.Add(new ReturnLineVm { ProductId = Guid.NewGuid(), Name = "Молоко 2.5% 1л", Unit = "шт", UnitPrice = 450m, SoldQty = 2, ReturnableQty = 2, Qty = 1 });
        vm.Lines.Add(new ReturnLineVm { ProductId = Guid.NewGuid(), Name = "Хлеб «Семейный» нарезной", Unit = "шт", UnitPrice = 280m, SoldQty = 1, ReturnableQty = 1, Qty = 1 });
        vm.Lines.Add(new ReturnLineVm { ProductId = Guid.NewGuid(), Name = "Яблоки «Апорт» (вес)", Unit = "кг", UnitPrice = 690m, SoldQty = 1.235m, ReturnableQty = 1.235m, Qty = 0 });
        return vm;
    }
}