using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Threading;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Models;
using HC_APTBS.Services;
using HC_APTBS.ViewModels.Dialogs;
using HC_APTBS.ViewModels.Pages;
using HC_APTBS.Views.Dialogs;

namespace HC_APTBS.ViewModels
{
    /// <summary>Identifies the top-level navigation page shown in the shell.</summary>
    public enum AppPage
    {
        /// <summary>Bench controls, flowmeter charts, encoder angles.</summary>
        Bench = 0,
        /// <summary>Pump manual control, DFI, status displays.</summary>
        Pump = 1,
        /// <summary>Test suite, live progress, results.</summary>
        Tests = 2,
        /// <summary>At-a-glance operator landing page: readings, connections, alarms, quick actions.</summary>
        Dashboard = 3,
        /// <summary>Application configuration: safety limits, PID, motor, report, K-Line, language.</summary>
        Settings = 4,
        /// <summary>Session-only history of completed test runs with detail view and PDF export.</summary>
        Results = 5
    }

    /// <summary>
    /// Root ViewModel for the application's main window.
    ///
    /// <para>Responsibilities:</para>
    /// <list type="bullet">
    ///   <item>CAN connection lifecycle.</item>
    ///   <item>Bench status display (RPM, temperatures, flow measurements).</item>
    ///   <item>Test start/stop and progress reporting.</item>
    ///   <item>Relay toggle commands.</item>
    ///   <item>Report generation trigger.</item>
    /// </list>
    ///
    /// <para>Pump selection and K-Line ECU identification are delegated to
    /// <see cref="PumpIdentification"/>.</para>
    /// </summary>
    public sealed partial class MainViewModel : ObservableObject
    {
        // ── Services ──────────────────────────────────────────────────────────────

        private readonly ICanService _can;
        private readonly IKwpService _kwp;
        private readonly IBenchService _bench;
        private readonly IConfigurationService _config;
        private readonly IPdfService _pdf;
        private readonly IUnlockService _unlock;
        private readonly ILocalizationService _loc;
        private readonly IAppLogger _log;
        private const string LogId = "MainViewModel";

        // ── CancellationToken for test runs ───────────────────────────────────────

        private CancellationTokenSource? _testCts;

        // ── Test elapsed timer ────────────────────────────────────────────────────

        /// <summary>Ticks every second while a test is running to update <see cref="TestElapsed"/>.</summary>
        private DispatcherTimer? _testTimer;

        /// <summary>UTC start time of the current test; used by the timer to compute elapsed duration.</summary>
        private DateTime _testStartedUtc;

        // ── Unlock tracking ──────────────────────────────────────────────────────

        /// <summary>CTS for the currently running immobilizer unlock, if any.</summary>
        private CancellationTokenSource? _unlockCts;

        /// <summary>ViewModel for the non-modal unlock progress window.</summary>
        private UnlockProgressViewModel? _unlockVm;

        /// <summary>
        /// Publicly observable accessor for the currently running (or last completed)
        /// immobilizer unlock VM. Used by the Pump page's inline unlock panel to
        /// display the same state that the floating dialog shows. Null while no
        /// unlock has been started for the current pump.
        /// </summary>
        public UnlockProgressViewModel? CurrentUnlockVm
        {
            get => _unlockVm;
            private set
            {
                if (!ReferenceEquals(_unlockVm, value))
                {
                    _unlockVm = value;
                    OnPropertyChanged();
                }
            }
        }

        /// <summary>Remembers the last authenticated username to pre-fill the next auth dialog.</summary>
        private string _lastAuthenticatedUser = string.Empty;

        /// <summary>Tracks whether the last selected pump required 27 V, for transition-based voltage warnings.</summary>
        private bool _lastPumpWas27V;

        // ── Child ViewModels ──────────────────────────────────────────────────────

        /// <summary>ViewModel for pump selection and K-Line ECU identification.</summary>
        public PumpIdentificationViewModel PumpIdentification { get; }

        /// <summary>ViewModel for the DFI manage user control.</summary>
        public DfiManageViewModel DfiViewModel { get; }

        /// <summary>ViewModel for the test panel showing all test sections and phase cards.</summary>
        public TestPanelViewModel TestPanel { get; }

        /// <summary>ViewModel for the measurement results table.</summary>
        public ResultDisplayViewModel ResultDisplay { get; }

        /// <summary>ViewModel for the manual pump control sliders (FBKW, ME, PreIn).</summary>
        public PumpControlViewModel PumpControl { get; private set; } = null!;

        /// <summary>ViewModel for manual bench controls (direction, RPM, oil pump, counter).</summary>
        public BenchControlViewModel BenchControl { get; }

        /// <summary>ViewModel for the two flowmeter real-time charts (Q-Delivery, Q-Over).</summary>
        public FlowmeterChartViewModel FlowmeterChart { get; } = new();

        /// <summary>ViewModel for the encoder angle monitoring display (PSG, INJ, Manual, Lock Angle).</summary>
        public AngleDisplayViewModel AngleDisplay { get; }

        /// <summary>ViewModel for the first pump status display (Status word).</summary>
        public StatusDisplayViewModel StatusDisplay1 { get; } = new();

        /// <summary>ViewModel for the second pump status display (Empf3 word).</summary>
        public StatusDisplayViewModel StatusDisplay2 { get; } = new();

        /// <summary>ViewModel for the Dashboard's active-alarm list.</summary>
        public DashboardAlarmsViewModel DashboardAlarms { get; }

        /// <summary>Diagnostic Trouble Code list for the Pump page §3.b sub-section.</summary>
        public DtcListViewModel DtcList { get; }

        // ── Page ViewModels (thin façades over the child VMs above) ───────────────

        /// <summary>Dashboard navigation page VM.</summary>
        public DashboardPageViewModel DashboardPage { get; private set; } = null!;

        /// <summary>Bench navigation page VM.</summary>
        public BenchPageViewModel BenchPage { get; private set; } = null!;

        /// <summary>Pump navigation page VM.</summary>
        public PumpPageViewModel PumpPage { get; private set; } = null!;

        /// <summary>Tests navigation page VM.</summary>
        public TestsPageViewModel TestsPage { get; private set; } = null!;

        /// <summary>Settings navigation page VM.</summary>
        public SettingsPageViewModel SettingsPage { get; private set; } = null!;

        /// <summary>Results navigation page VM (session-only test-run history).</summary>
        public ResultsPageViewModel ResultsPage { get; private set; } = null!;

        // ── Navigation state ──────────────────────────────────────────────────────

        /// <summary>Currently selected top-level navigation page.</summary>
        [ObservableProperty] private AppPage _selectedPage = AppPage.Dashboard;

        // ── Constructor ───────────────────────────────────────────────────────────

        /// <summary>
        /// Constructs the MainViewModel and wires all service events to UI-bound properties.
        /// Call <see cref="InitialiseAsync"/> after construction.
        /// </summary>
        public MainViewModel(
            ICanService canService,
            IKwpService kwpService,
            IBenchService benchService,
            IConfigurationService configService,
            IPdfService pdfService,
            IUnlockService unlockService,
            ILocalizationService localizationService,
            IAppLogger logger)
        {
            _can    = canService;
            _kwp    = kwpService;
            _bench  = benchService;
            _config = configService;
            _pdf    = pdfService;
            _unlock = unlockService;
            _loc    = localizationService;
            _log    = logger;

            _loc.LanguageChanged += RefreshLocalisedStrings;

            TestPanel      = new TestPanelViewModel(localizationService);
            ResultDisplay  = new ResultDisplayViewModel(localizationService);
            PumpIdentification = new PumpIdentificationViewModel(kwpService, configService, localizationService, logger);
            DfiViewModel       = new DfiManageViewModel(kwpService, configService, localizationService);
            PumpControl        = new PumpControlViewModel(benchService);
            BenchControl       = new BenchControlViewModel(benchService, configService);
            AngleDisplay       = new AngleDisplayViewModel(configService);
            DashboardAlarms    = new DashboardAlarmsViewModel(configService.Settings.Alarms);
            DtcList            = new DtcListViewModel(kwpService, localizationService, logger);
            // Page ViewModels are thin façades over the child VMs above; they hold a
            // reference back to this coordinator so page XAML can bind MainViewModel-owned
            // values via {Binding Root.X}.
            DashboardPage = new DashboardPageViewModel(this, canService, kwpService);
            BenchPage     = new BenchPageViewModel(this, benchService, configService);
            PumpPage      = new PumpPageViewModel(this, DtcList);
            TestsPage     = new TestsPageViewModel(this, configService, localizationService);
            SettingsPage  = new SettingsPageViewModel(configService, localizationService);
            SettingsPage.SettingsSaved += OnSettingsSaved;
            ResultsPage   = new ResultsPageViewModel(this, pdfService, configService, localizationService, logger);

            // React to pump changes from the identification child VM.
            PumpIdentification.PumpChanged += OnPumpChanged;

            // Sync sliders when test execution sets pump control values.
            _bench.PumpControlValueSet += (name, value) => App.Current.Dispatcher.Invoke(
                () => PumpControl.SetValueFromTest(name, value));

            // CAN status → status bar
            _can.StatusChanged += (msg, ok) =>
                App.Current.Dispatcher.Invoke(() =>
                {
                    CanStatusText = msg;
                    IsCanConnected = ok;
                });

            // Bench/pump liveness → connection indicators
            _can.BenchLivenessChanged += alive =>
                App.Current.Dispatcher.Invoke(() => IsBenchConnected = alive);
            _can.PumpLivenessChanged += alive =>
                App.Current.Dispatcher.Invoke(() => IsPumpConnected = alive);

            // K-Line session state → indicator
            _kwp.KLineStateChanged += state =>
                App.Current.Dispatcher.Invoke(() => KLineState = state);

            // Bench service events
            _bench.TestStarted    += OnTestStarted;
            _bench.TestFinished   += OnTestFinished;
            _bench.PhaseChanged   += phase => App.Current.Dispatcher.Invoke(() =>
            {
                CurrentPhaseName = phase;
                TestPanel.SetActivePhase(phase);
                // Clear real-time plot traces at each new phase boundary.
                FlowmeterChart.Delivery.Clear();
                FlowmeterChart.Over.Clear();
            });
            _bench.PhaseTimerTick += (section, remaining, total) => App.Current.Dispatcher.Invoke(
                () => TestPanel.ApplyPhaseTimerTick(section, remaining, total));
            _bench.VerboseMessage += msg => App.Current.Dispatcher.Invoke(() =>
            {
                VerboseStatus = msg;
                TestPanel.StatusText = msg;
            });
            _bench.PsgSyncError += () => App.Current.Dispatcher.Invoke(
                () => ShowPsgSyncError());
            _bench.PhaseCompleted += (phase, passed) => App.Current.Dispatcher.Invoke(
                () => TestPanel.SetPhaseResult(phase, passed));
            _bench.ToleranceUpdated += (paramName, value, tolerance) => App.Current.Dispatcher.Invoke(
                () =>
                {
                    TestPanel.UpdateLiveIndicator(paramName, value);
                    FlowmeterChart.SetTolerance(paramName, value, tolerance);
                });

            _bench.MeasurementSampled += (name, value) => App.Current.Dispatcher.Invoke(() =>
            {
                if (name == BenchParameterNames.QDelivery)
                    FlowmeterChart.Delivery.AddValue(value);
                else if (name == BenchParameterNames.QOver)
                    FlowmeterChart.Over.AddValue(value);
            });
            _bench.EmergencyStopTriggered += reason => App.Current.Dispatcher.Invoke(() =>
            {
                VerboseStatus = string.Format(_loc.GetString("Error.EmergencyStop"), reason);
            });
            _bench.StatusReactionTriggered += (bit, reaction, desc) => App.Current.Dispatcher.Invoke(() =>
            {
                VerboseStatus = $"[STATUS] bit {bit} reaction={reaction}: {desc}";
            });

            // Angle display: lock angle and PSG zero from test phases
            _bench.LockAngleFaseReady += () => App.Current.Dispatcher.Invoke(() =>
            {
                if (CurrentPump != null)
                    CurrentPump.LockAngleResult = AngleDisplay.SetLockAngle(CurrentPump.LockAngle);
            });
            _bench.PsgModeFaseReady += () => App.Current.Dispatcher.Invoke(
                () => AngleDisplay.SetPsgZeroFromTest());

            // Unlock service status → verbose display
            _unlock.StatusChanged += msg => App.Current.Dispatcher.Invoke(
                () => VerboseStatus = msg);

            // KWP pump power-cycle callbacks
            kwpService.PumpDisconnectRequested += OnKwpDisconnectPump;
            kwpService.PumpReconnectRequested  += OnKwpReconnectPump;
        }

        // ── Pump change handling ──────────────────────────────────────────────────

        /// <summary>Convenience accessor for the currently loaded pump definition.</summary>
        public PumpDefinition? CurrentPump => PumpIdentification.CurrentPump;

        private void OnPumpChanged(PumpDefinition? pump)
        {
            if (pump == null) return;

            // Stop any senders from the previous pump.
            _bench.StopMemoryRequestSender();
            _bench.StopPumpSender();

            // Register the pump with BenchService so ReadParameter/SetParameter resolve pump params.
            _bench.SetActivePump(pump);

            // Load all test sections into the test panel.
            TestPanel.LoadAllTests(pump);

            // Register the pump's CAN parameters with the bus adapter.
            _can.AddParameters(pump.ParametersById);
            _can.RegisterPumpMessageIds(GetReceiveMessageIds(pump.ParametersById));

            // Configure pump control sliders.
            PumpControl.IsPreInVisible = pump.HasPreInjection;
            PumpControl.IsEnabled = true;
            PumpControl.Reset();

            // Initialise status displays with zero values.
            StatusDisplay1.Reset();
            StatusDisplay2.Reset();
            if (pump.ParametersByName.TryGetValue(PumpParameterNames.Status, out var statusParam))
            {
                var def = _config.LoadPumpStatus(statusParam.Type);
                if (def != null) StatusDisplay1.UpdateStatusWord(def, 0);
            }
            if (pump.ParametersByName.TryGetValue(PumpParameterNames.Empf3, out var empf3Param))
            {
                var def = _config.LoadPumpStatus(empf3Param.Type);
                if (def != null) StatusDisplay2.UpdateStatusWord(def, 0);
            }

            // Start periodic senders for the new pump.
            _bench.StartMemoryRequestSender();
            _bench.StartPumpSender();

            // Notify commands that depend on pump availability.
            StartTestCommand.NotifyCanExecuteChanged();
            GenerateReportCommand.NotifyCanExecuteChanged();

            // Show voltage warning on 27V ↔ 13.5V transitions (WAlert27v equivalent).
            CheckVoltageWarning(pump);

            // Start immobilizer unlock if this pump requires it (Ford VP44).
            StartUnlockIfRequired(pump);
        }

        // ── Immobilizer unlock ────────────────────────────────────────────────────

        /// <summary>
        /// Starts the immobilizer unlock sequence in a non-modal window if the pump
        /// requires it (UnlockType != 0). Cancels any previously running unlock first.
        /// </summary>
        private void StartUnlockIfRequired(PumpDefinition pump)
        {
            // Cancel and close any previous unlock window.
            CloseUnlockDialog();

            if (pump.UnlockType == 0) return;

            _unlockCts = new CancellationTokenSource();
            CurrentUnlockVm = new UnlockProgressViewModel(_unlock, pump.UnlockType, _unlockCts, _loc);
            CurrentUnlockVm.RequestClose += CloseUnlockDialog;

            // Start unlock in background — ViewModel tracks via event subscriptions.
            var unlockTask = _unlock.UnlockAsync(pump, _unlockCts.Token);
            _ = unlockTask.ContinueWith(_ => { }, TaskContinuationOptions.OnlyOnFaulted);
        }

        /// <summary>
        /// Cancels any running unlock, stops persistent CAN senders, closes the
        /// window, and disposes resources. Safe to call when no unlock is active.
        /// </summary>
        private void CloseUnlockDialog()
        {
            // Stop the persistent CAN unlock senders (prevents re-lock until
            // this point — only called when the pump is deselected).
            _unlock.StopSenders();

            if (_unlockCts != null)
            {
                _unlockCts.Cancel();
                _unlockCts.Dispose();
                _unlockCts = null;
            }

            if (_unlockVm != null)
            {
                _unlockVm.RequestClose -= CloseUnlockDialog;
                _unlockVm.Dispose();
                CurrentUnlockVm = null;
            }
        }

        // ── CAN connection ────────────────────────────────────────────────────────

        /// <summary>CAN bus status display text.</summary>
        [ObservableProperty] private string _canStatusText = string.Empty;

        /// <summary>True when the CAN bus adapter is connected.</summary>
        [ObservableProperty] private bool   _isCanConnected;

        /// <summary>Connects to the CAN bus adapter.</summary>
        [RelayCommand]
        private void ConnectCan()
        {
            _can.SetParameters(_config.Bench.ParametersById);
            _can.RegisterBenchMessageIds(GetReceiveMessageIds(_config.Bench.ParametersById));
            bool ok = _can.Connect();
            CanStatusText = ok ? _loc.GetString("Status.Connected") : _loc.GetString("Status.ConnectionFailed");
            IsCanConnected = ok;

            if (ok)
            {
                // ElectronicMsg keepalive (0x51) and relay bitmask (0x15) must
                // begin transmitting as soon as the CAN bus is up.
                _bench.StartElectronicMsgSender();
                _bench.StartRelaySender();
            }
        }

        /// <summary>Disconnects from the CAN bus adapter.</summary>
        [RelayCommand]
        private void DisconnectCan()
        {
            _bench.StopElectronicMsgSender();
            _bench.StopRelaySender();
            _bench.StopMemoryRequestSender();
            _bench.StopPumpSender();
            _can.Disconnect();
            IsCanConnected = false;
            CanStatusText  = _loc.GetString("Status.Disconnected");
        }

        // ── Live bench readings ───────────────────────────────────────────────────

        /// <summary>Bench motor speed (RPM), updated by the refresh timer.</summary>
        [ObservableProperty] private double _benchRpm;

        /// <summary>Oil inlet temperature T-in (°C).</summary>
        [ObservableProperty] private double _tempIn;

        /// <summary>Oil outlet temperature T-out (°C).</summary>
        [ObservableProperty] private double _tempOut;

        /// <summary>Auxiliary temperature T4 (°C).</summary>
        [ObservableProperty] private double _temp4;

        /// <summary>Oil tank temperature (°C).</summary>
        [ObservableProperty] private double _benchTemp;

        /// <summary>Fuel delivery measurement Q-delivery (cc/stroke).</summary>
        [ObservableProperty] private double _qDelivery;

        /// <summary>Fuel overflow/pilot measurement Q-over (cc/stroke).</summary>
        [ObservableProperty] private double _qOver;

        /// <summary>Bench oil pressure P1 (bar), sensor-calibrated.</summary>
        [ObservableProperty] private double _pressure;

        /// <summary>Analogue sensor 2 pressure P2 (bar), sensor-calibrated.</summary>
        [ObservableProperty] private double _pressure2;

        /// <summary>PSG encoder position value.</summary>
        [ObservableProperty] private double _psgEncoderValue;

        /// <summary>
        /// True when the Oil Pump relay is currently energised. Mirrored on each refresh
        /// tick from <c>_config.Bench.Relays[RelayNames.OilPump]</c> so the Tests page
        /// preconditions checklist can bind to it without walking the relay dictionary.
        /// </summary>
        [ObservableProperty] private bool _isOilPumpOn;

        // ── Pump live readings (from pump CAN parameters) ──────────────────────────

        /// <summary>Pump RPM reported by the ECU over CAN.</summary>
        [ObservableProperty] private double _pumpRpm;

        /// <summary>Pump internal temperature reported by the ECU over CAN.</summary>
        [ObservableProperty] private double _pumpTemp;

        /// <summary>Pump ME (metering) value from CAN.</summary>
        [ObservableProperty] private double _pumpMe;

        /// <summary>Pump FBkW (feedback) value from CAN.</summary>
        [ObservableProperty] private double _pumpFbkw;

        /// <summary>Pump T-ein (inlet timing) value from CAN, in microseconds.</summary>
        [ObservableProperty] private double _pumpTein;

        // ── Bench/pump connection status ──────────────────────────────────────────

        /// <summary>True when the bench controller is connected.</summary>
        [ObservableProperty] private bool _isBenchConnected;

        /// <summary>True when the pump ECU is responding on CAN.</summary>
        [ObservableProperty] private bool _isPumpConnected;

        /// <summary>True when oil circulation has been detected.</summary>
        [ObservableProperty] private bool _isOilCirculating;

        /// <summary>Current K-Line session state (Disconnected / Connected / Failed).</summary>
        [ObservableProperty] private KLineConnectionState _kLineState = KLineConnectionState.Disconnected;

        // ── Test status ───────────────────────────────────────────────────────────

        /// <summary>True while a test sequence is running.</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(StartTestCommand))]
        [NotifyCanExecuteChangedFor(nameof(StopTestCommand))]
        private bool _isTestRunning;

        /// <summary>True if the last test passed.</summary>
        [ObservableProperty] private bool   _lastTestSuccess;

        /// <summary>Name of the currently executing test phase.</summary>
        [ObservableProperty] private string _currentPhaseName = string.Empty;

        /// <summary>Verbose status message from bench/test operations.</summary>
        [ObservableProperty] private string _verboseStatus    = string.Empty;

        // ── Test saved state ──────────────────────────────────────────────────────

        /// <summary>True when the current test results have been saved to a report.</summary>
        [ObservableProperty] private bool _isTestSaved = true;

        /// <summary>Elapsed time since the current test started. Updated every second; retains last value when idle.</summary>
        [ObservableProperty] private TimeSpan _testElapsed;

        // ── Commands: test ────────────────────────────────────────────────────────

        /// <summary>Starts the test sequence for the current pump.</summary>
        [RelayCommand(CanExecute = nameof(CanStartTest))]
        private async Task StartTestAsync()
        {
            if (CurrentPump == null) return;

            // Block test start if an unlock is still in progress.
            if (_unlockVm != null && !_unlockVm.IsComplete)
            {
                VerboseStatus = _loc.GetString("Status.UnlockInProgress");
                return;
            }

            // Block test start if the unlock failed or was cancelled.
            if (CurrentPump.UnlockType != 0 && _unlockVm?.IsSuccess != true)
            {
                VerboseStatus = _loc.GetString("Status.UnlockRequired");
                return;
            }

            _testCts        = new CancellationTokenSource();
            IsTestRunning   = true;
            IsTestSaved     = false;

            await _bench.RunTestsAsync(CurrentPump, _testCts.Token);
        }

        private bool CanStartTest()
            => CurrentPump != null && !IsTestRunning && IsCanConnected;

        /// <summary>Requests a controlled stop of the running test.</summary>
        [RelayCommand(CanExecute = nameof(CanStopTest))]
        private void StopTest()
        {
            _bench.StopTests();
            _testCts?.Cancel();
        }

        private bool CanStopTest() => IsTestRunning;

        /// <summary>
        /// Operator-initiated emergency stop from the Dashboard.
        /// Zeros the motor, zeros pump parameters, and cancels any running test.
        /// </summary>
        [RelayCommand]
        private void EmergencyStop()
        {
            _bench.RequestEmergencyStop("Operator pressed E-Stop on Dashboard");
            _testCts?.Cancel();
        }

        // ── Commands: relay toggles ───────────────────────────────────────────────

        /// <summary>Toggles the electronic relay (pump solenoid power).</summary>
        [RelayCommand] private void ToggleElectronic()  => ToggleRelay(RelayNames.Electronic);

        /// <summary>Toggles the oil pump relay.</summary>
        [RelayCommand] private void ToggleOilPump()     => ToggleRelay(RelayNames.OilPump);

        /// <summary>Toggles the deposit cooler relay.</summary>
        [RelayCommand] private void ToggleDepositCooler() => ToggleRelay(RelayNames.DepositCooler);

        /// <summary>Toggles the deposit heater relay.</summary>
        [RelayCommand] private void ToggleDepositHeater() => ToggleRelay(RelayNames.DepositHeater);

        private void ToggleRelay(string name)
        {
            if (!_config.Bench.Relays.TryGetValue(name, out var relay)) return;
            _bench.SetRelay(name, !relay.State);
        }

        // ── Commands: report ──────────────────────────────────────────────────────

        /// <summary>Generates and opens the PDF report for the last completed test.</summary>
        [RelayCommand(CanExecute = nameof(CanGenerateReport))]
        private void GenerateReport()
        {
            if (CurrentPump == null) return;

            // Step 1: Authenticate operator.
            var authVm   = new UserCheckViewModel(_config, _loc, _lastAuthenticatedUser);
            var authDlg  = new UserCheckDialog(authVm) { Owner = Application.Current.MainWindow };
            authDlg.ShowDialog();
            if (!authVm.Accepted) return;
            _lastAuthenticatedUser = authVm.AuthenticatedUser;

            // Step 2: Collect report details (client, company, observations).
            var reportVm  = new ReportViewModel(_config) { OperatorName = authVm.AuthenticatedUser };
            var reportDlg = new ReportDialog(reportVm) { Owner = Application.Current.MainWindow };
            reportDlg.ShowDialog();
            if (!reportVm.Accepted) return;

            try
            {
                string desktop = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
                string path    = _pdf.GenerateReport(
                    CurrentPump,
                    reportVm.OperatorName,
                    reportVm.SelectedClientName,
                    desktop,
                    clientInfo: reportVm.ClientInfo,
                    observations: reportVm.Observations);
                _log.Info(LogId, $"Report saved: {path}");
                IsTestSaved = true;

                System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(path)
                    { UseShellExecute = true });
            }
            catch (Exception ex)
            {
                _log.Error(LogId, $"GenerateReport: {ex.Message}");
                MessageBox.Show(string.Format(_loc.GetString("Error.ReportGeneration"), ex.Message),
                    _loc.GetString("Error.ReportTitle"), MessageBoxButton.OK, MessageBoxImage.Error);
            }
        }

        private bool CanGenerateReport()
            => CurrentPump != null && !IsTestRunning && CurrentPump.Tests.Count > 0;

        /// <summary>Refreshes all ViewModel-cached localised strings after a language change.</summary>
        private void RefreshLocalisedStrings()
        {
            CanStatusText = IsCanConnected
                ? _loc.GetString("Status.Connected")
                : _loc.GetString("Status.Disconnected");
        }

        /// <summary>
        /// Reseeds settings-dependent runtime state after the operator saves on the Settings page.
        /// Currently only the bench refresh-timer interval needs re-application.
        /// </summary>
        private void OnSettingsSaved()
        {
            if (_refreshTimer != null)
                _refreshTimer.Interval = TimeSpan.FromMilliseconds(_config.Settings.RefreshBenchInterfaceMs);
        }

        // ── Initialisation ────────────────────────────────────────────────────────

        /// <summary>
        /// Loads pump IDs, wires the refresh timer, and connects to the CAN bus.
        /// Call once from the View after construction.
        /// </summary>
        public async Task InitialiseAsync()
        {
            // Populate the pump selector.
            PumpIdentification.LoadPumpIds();

            // Connect CAN bus.
            _can.SetParameters(_config.Bench.ParametersById);
            _can.RegisterBenchMessageIds(GetReceiveMessageIds(_config.Bench.ParametersById));
            bool canOk = _can.Connect();

            if (canOk)
            {
                _bench.StartElectronicMsgSender();
                _bench.StartRelaySender();
            }

            // Start the UI refresh timer.
            StartRefreshTimer();

            _log.Info(LogId, "MainViewModel initialised.");
            await Task.CompletedTask;
        }

        // ── Refresh timer ─────────────────────────────────────────────────────────

        private System.Windows.Threading.DispatcherTimer? _refreshTimer;

        private void StartRefreshTimer()
        {
            _refreshTimer = new System.Windows.Threading.DispatcherTimer
            {
                Interval = TimeSpan.FromMilliseconds(_config.Settings.RefreshBenchInterfaceMs)
            };
            _refreshTimer.Tick += OnRefreshTick;
            _refreshTimer.Start();
        }

        private void OnRefreshTick(object? sender, EventArgs e)
        {
            // Read all bench parameters that have been updated by the CAN receive thread.
            BenchRpm        = _bench.ReadBenchParameter(BenchParameterNames.BenchRpm);
            TempIn          = _bench.ReadBenchParameter(BenchParameterNames.TempIn);
            TempOut         = _bench.ReadBenchParameter(BenchParameterNames.TempOut);
            Temp4           = _bench.ReadBenchParameter(BenchParameterNames.Temp4);
            BenchTemp       = _bench.ReadBenchParameter(BenchParameterNames.Temp);
            QDelivery       = _bench.ReadBenchParameter(BenchParameterNames.QDelivery);
            QOver           = _bench.ReadBenchParameter(BenchParameterNames.QOver);
            PsgEncoderValue = _bench.ReadBenchParameter(BenchParameterNames.PsgEncoderValue);

            // Apply analogue sensor calibration for pressure channels.
            double rawP1 = _bench.ReadBenchParameter(BenchParameterNames.Pressure);
            Pressure  = _config.Settings.Sensors.TryGetValue(1, out var s1) ? s1.GetValueFromRaw(rawP1) : rawP1;
            double rawP2 = _bench.ReadBenchParameter(BenchParameterNames.AnalogSensor2);
            Pressure2 = _config.Settings.Sensors.TryGetValue(2, out var s2) ? s2.GetValueFromRaw(rawP2) : rawP2;

            // Feed the angle display with all three encoder channels + status.
            AngleDisplay.Update(
                PsgEncoderValue,
                _bench.ReadBenchParameter(BenchParameterNames.PsgEncoderWorking) == 1,
                _bench.ReadBenchParameter(BenchParameterNames.InjEncoderValue),
                _bench.ReadBenchParameter(BenchParameterNames.InjEncoderWorking) == 1,
                _bench.ReadBenchParameter(BenchParameterNames.ManualEncoderValue),
                BenchRpm,
                BenchControl.IsDirectionRight);

            // Feed flowmeter charts and refresh bench controls.
            FlowmeterChart.AddSamples(QDelivery, QOver);
            BenchControl.RefreshFromTick();

            // Mirror the oil pump relay state for the Tests page preconditions checklist.
            IsOilPumpOn = _config.Bench.Relays.TryGetValue(RelayNames.OilPump, out var oilRelay) && oilRelay.State;

            // Feed page-scoped Bench VMs (pressure trace + interlock banner).
            BenchPage.RefreshFromTick();

            // Refresh Dashboard's active-alarm list from the bench alarm bitmask.
            DashboardAlarms.Update((int)_bench.ReadBenchParameter(BenchParameterNames.Alarms));

            if (CurrentPump != null)
            {
                PumpRpm  = _bench.ReadPumpParameter(PumpParameterNames.Rpm);
                PumpTemp = _bench.ReadPumpParameter(PumpParameterNames.Temp);
                PumpMe   = _bench.ReadPumpParameter(PumpParameterNames.Me);
                PumpFbkw = _bench.ReadPumpParameter(PumpParameterNames.Fbkw);
                PumpTein = _bench.ReadPumpParameter(PumpParameterNames.Tein);

                // Update status display 1 (Status word) when the CAN receiver flags an update.
                if (CurrentPump.ParametersByName.TryGetValue(PumpParameterNames.Status, out var statusParam)
                    && statusParam.NeedsUpdate)
                {
                    var def = _config.LoadPumpStatus(statusParam.Type);
                    if (def != null) StatusDisplay1.UpdateStatusWord(def, (int)statusParam.Value);
                    statusParam.NeedsUpdate = false;
                }

                // Update status display 2 (Empf3 word).
                if (CurrentPump.ParametersByName.TryGetValue(PumpParameterNames.Empf3, out var empf3Param)
                    && empf3Param.NeedsUpdate)
                {
                    var def = _config.LoadPumpStatus(empf3Param.Type);
                    if (def != null) StatusDisplay2.UpdateStatusWord(def, (int)empf3Param.Value);
                    empf3Param.NeedsUpdate = false;
                }
            }
        }

        // ── Service event handlers ────────────────────────────────────────────────

        private void OnTestStarted()
            => App.Current.Dispatcher.Invoke(() =>
            {
                IsTestRunning = true;
                VerboseStatus = _loc.GetString("Test.Started");

                _testStartedUtc = DateTime.UtcNow;
                TestElapsed     = TimeSpan.Zero;
                _testTimer      = new DispatcherTimer(
                    TimeSpan.FromSeconds(1),
                    DispatcherPriority.Normal,
                    (_, _) => TestElapsed = DateTime.UtcNow - _testStartedUtc,
                    App.Current.Dispatcher);
                TestPanel.IsRunning = true;
                TestPanel.ResetResults();
                ResultDisplay.Clear();
                PumpControl.Reset();
                _bench.StartPumpSender();
                _log.Info(LogId, "Test sequence started.");
            });

        private void OnTestFinished(bool interrupted, bool success)
            => App.Current.Dispatcher.Invoke(() =>
            {
                _testTimer?.Stop();
                _testTimer = null;

                IsTestRunning   = false;
                LastTestSuccess = !interrupted && success;
                VerboseStatus   = interrupted ? _loc.GetString("Test.Stopped") : (success ? _loc.GetString("Common.Pass") : _loc.GetString("Common.Fail"));
                TestPanel.IsRunning = false;
                TestPanel.ClearPhaseTimer();
                _bench.StopPumpSender();
                StartTestCommand.NotifyCanExecuteChanged();
                StopTestCommand.NotifyCanExecuteChanged();
                GenerateReportCommand.NotifyCanExecuteChanged();

                // Populate results table from all completed tests.
                if (!interrupted && CurrentPump != null)
                    ResultDisplay.LoadAllResults(CurrentPump.Tests);

                // Capture a session-only history entry (Results page §5) — covers normal
                // and interrupted completions. Snapshot is deep-cloned so later runs
                // cannot mutate this entry's data.
                if (CurrentPump != null)
                    ResultsPage.CaptureRun(CurrentPump, interrupted, success);

                _log.Info(LogId,
                    $"Test finished — interrupted={interrupted}, success={success}");
            });

        private void OnKwpDisconnectPump()
            => App.Current.Dispatcher.Invoke(() =>
            {
                _bench.SetRelay(RelayNames.Electronic, false);
            });

        private void OnKwpReconnectPump()
            => App.Current.Dispatcher.Invoke(() =>
            {
                _bench.SetRelay(RelayNames.Electronic, true);
            });

        private void ShowPsgSyncError()
            => MessageBox.Show(
                _loc.GetString("Error.PsgSync"),
                _loc.GetString("Error.PsgTitle"), MessageBoxButton.OK, MessageBoxImage.Warning);

        // ── Voltage warning ────────────────────────────────────────────────────────

        /// <summary>
        /// Shows a voltage warning dialog when the pump supply voltage requirement
        /// changes between 27 V and 13.5 V (or vice versa). Only triggers on
        /// state transitions, matching the old <c>WAlert27v</c> behaviour.
        /// </summary>
        private void CheckVoltageWarning(PumpDefinition pump)
        {
            bool is27V = !string.IsNullOrEmpty(pump.Tension)
                      && pump.Tension.Contains("27");

            if (is27V && !_lastPumpWas27V)
            {
                var vm  = new Dialogs.VoltageWarningViewModel("27 V");
                var dlg = new Views.Dialogs.VoltageWarningDialog(vm)
                    { Owner = Application.Current.MainWindow };
                dlg.ShowDialog();
                _lastPumpWas27V = true;
            }
            else if (!is27V && _lastPumpWas27V)
            {
                var vm  = new Dialogs.VoltageWarningViewModel("13.5 V");
                var dlg = new Views.Dialogs.VoltageWarningDialog(vm)
                    { Owner = Application.Current.MainWindow };
                dlg.ShowDialog();
                _lastPumpWas27V = false;
            }
        }

        // ── Helpers ───────────────────────────────────────────────────────────────

        /// <summary>
        /// Returns only the message IDs that contain at least one receive parameter.
        /// Transmit-only IDs (RPM command, ElectronicMsg, etc.) are excluded because
        /// they are frames we send, not frames the remote device sends to us.
        /// </summary>
        private static HashSet<uint> GetReceiveMessageIds(
            Dictionary<uint, List<CanBusParameter>> parametersById)
        {
            var ids = new HashSet<uint>();
            foreach (var kv in parametersById)
            {
                if (kv.Value.Any(p => p.IsReceive))
                    ids.Add(kv.Key);
            }
            return ids;
        }
    }
}