using System;
using System.Text.RegularExpressions;
using System.Threading;
using System.Windows;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Services;

namespace HC_APTBS.ViewModels.Dialogs
{
    /// <summary>
    /// ViewModel for the Ford VP44 immobilizer unlock progress dialog.
    /// Tracks Phase 1 (CAN flood ~600 s), Phase 2 (handshake ~4 s), and verification.
    /// Equivalent to the old <c>WUnlocker</c> window.
    /// </summary>
    public sealed partial class UnlockProgressViewModel : ObservableObject, IDisposable
    {
        private readonly IUnlockService _unlockService;
        private readonly ILocalizationService _loc;
        private readonly CancellationTokenSource _cts;

        /// <summary>Regex to extract percentage and elapsed time from Phase 1 status messages.</summary>
        private static readonly Regex ProgressRegex =
            new(@"Unlocking\.\.\. (\d+)% \((\d{2}:\d{2})\)", RegexOptions.Compiled);

        /// <summary>Creates the ViewModel and subscribes to unlock service events.</summary>
        /// <param name="unlockService">The unlock service to monitor.</param>
        /// <param name="unlockType">Pump unlock type (1 or 2).</param>
        /// <param name="cts">Cancellation token source to cancel the unlock.</param>
        public UnlockProgressViewModel(IUnlockService unlockService, int unlockType, CancellationTokenSource cts, ILocalizationService loc)
        {
            _unlockService = unlockService;
            _loc = loc;
            _cts = cts;
            _unlockTypeLabel = string.Format(_loc.GetString("Dialog.Unlock.TypeLabel"), unlockType);
            _phaseText = _loc.GetString("Dialog.Unlock.Phase1");
            _elapsedTime = "00:00";
            _isCancellable = true;

            _unlockService.StatusChanged    += OnStatusChanged;
            _unlockService.UnlockCompleted  += OnUnlockCompleted;
            _unlockService.PumpRelocked     += OnPumpRelocked;
            // PumpUnlocked fires as soon as the CAN TestUnlock parameter flips —
            // regardless of which code path caused the unlock (fast unlock, Phase 1
            // flood finishing, external manual unlock). This lets the dialog flip
            // to its success state the instant the hardware confirms unlock, rather
            // than waiting for UnlockService.UnlockAsync to reach its final
            // verification step.
            _unlockService.PumpUnlocked += OnPumpUnlocked;
        }

        // ── Observable properties ────────────────────────────────────────────────

        /// <summary>Progress percentage (0–100).</summary>
        [ObservableProperty] private int _progress;

        /// <summary>Elapsed time formatted as MM:SS.</summary>
        [ObservableProperty] private string _elapsedTime;

        /// <summary>Current phase description.</summary>
        [ObservableProperty] private string _phaseText;

        /// <summary>Result text shown after completion.</summary>
        [ObservableProperty] private string _resultText = string.Empty;

        /// <summary>Label for unlock type (e.g. "Type 1").</summary>
        [ObservableProperty] private string _unlockTypeLabel;

        /// <summary>True when the unlock sequence has finished (success, failure, or cancelled).</summary>
        [NotifyCanExecuteChangedFor(nameof(CloseCommand))]
        [ObservableProperty] private bool _isComplete;

        /// <summary>True while cancellation is allowed (Phase 1 only).</summary>
        [NotifyCanExecuteChangedFor(nameof(CancelCommand))]
        [ObservableProperty] private bool _isCancellable;

        /// <summary>Tri-state result: null = in progress, true = success, false = failure.</summary>
        [ObservableProperty] private bool? _isSuccess;

        /// <summary>True when the pump is currently LOCKED and the operator can retry the unlock.</summary>
        [NotifyCanExecuteChangedFor(nameof(RetryCommand))]
        [ObservableProperty] private bool _canRetry;

        // ── Commands ─────────────────────────────────────────────────────────────

        /// <summary>Cancels the unlock sequence (only available during Phase 1).</summary>
        [RelayCommand(CanExecute = nameof(IsCancellable))]
        private void Cancel()
        {
            _cts.Cancel();
            IsCancellable = false;
            IsComplete = true;
            IsSuccess = false;
            ResultText = _loc.GetString("Dialog.Unlock.Cancelled");
        }

        /// <summary>Closes the dialog (only available after completion).</summary>
        [RelayCommand(CanExecute = nameof(IsComplete))]
        private void Close()
        {
            RequestClose?.Invoke();
        }

        /// <summary>Requests a new unlock attempt (only available when complete and pump is LOCKED).</summary>
        [RelayCommand(CanExecute = nameof(CanRetry))]
        private void Retry()
        {
            CanRetry = false;
            RequestRetry?.Invoke();
        }

        // ── Events ───────────────────────────────────────────────────────────────

        /// <summary>Raised when the dialog should close itself.</summary>
        public event Action? RequestClose;

        /// <summary>Raised when the operator presses Retry — parent should restart the unlock sequence.</summary>
        public event Action? RequestRetry;

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

        private void OnStatusChanged(string msg)
        {
            Application.Current?.Dispatcher?.Invoke(() =>
            {
                var match = ProgressRegex.Match(msg);
                if (match.Success)
                {
                    Progress = int.Parse(match.Groups[1].Value);
                    ElapsedTime = match.Groups[2].Value;
                    return;
                }

                if (msg == "Fast unlock attempt...")
                {
                    PhaseText = _loc.GetString("Dialog.Unlock.FastAttempt");
                }
                else if (msg == "Unlocking...")
                {
                    PhaseText = _loc.GetString("Dialog.Unlock.Phase1");
                }
                else if (msg == "Testing unlock...")
                {
                    PhaseText = _loc.GetString("Dialog.Unlock.Phase2Testing");
                    IsCancellable = false;
                    Progress = 100;
                }
                else if (msg == "Sending...")
                {
                    PhaseText = _loc.GetString("Dialog.Unlock.Phase2Sending");
                }
            });
        }

        private void OnUnlockCompleted(bool success)
        {
            Application.Current?.Dispatcher?.Invoke(() =>
            {
                IsComplete = true;
                IsCancellable = false;
                IsSuccess = success;
                ResultText = success ? _loc.GetString("Dialog.Unlock.Unlocked") : _loc.GetString("Dialog.Unlock.Failed");
                // Enable Retry when the unlock finished but the pump is still LOCKED.
                CanRetry = !_unlockService.IsPumpUnlocked;
            });
        }

        /// <summary>
        /// Observer says the pump is now unlocked. Flip the dialog to the
        /// success state immediately so the operator sees a responsive UI; the
        /// later UnlockCompleted(true) event is idempotent and leaves this state
        /// intact. If UnlockCompleted later arrives with failure=false, that
        /// would overwrite — but that combination (observer unlocks then service
        /// reports failure) is not a real scenario in the current state machine.
        /// </summary>
        private void OnPumpUnlocked()
        {
            Application.Current?.Dispatcher?.Invoke(() =>
            {
                if (IsComplete) return;
                IsComplete = true;
                IsCancellable = false;
                IsSuccess = true;
                CanRetry = false;
                ResultText = _loc.GetString("Dialog.Unlock.Unlocked");
            });
        }

        /// <summary>
        /// Observer says the pump re-locked after a previously successful unlock.
        /// If the snackbar is still visible (not dismissed), light up the Retry button
        /// so the operator has a manual fallback without needing to reselect the pump.
        /// </summary>
        private void OnPumpRelocked()
        {
            Application.Current?.Dispatcher?.Invoke(() =>
            {
                if (IsComplete)
                    CanRetry = true;
            });
        }

        // ── IDisposable ──────────────────────────────────────────────────────────

        /// <summary>Unsubscribes from service events to prevent leaks.</summary>
        public void Dispose()
        {
            _unlockService.StatusChanged   -= OnStatusChanged;
            _unlockService.UnlockCompleted -= OnUnlockCompleted;
            _unlockService.PumpUnlocked    -= OnPumpUnlocked;
            _unlockService.PumpRelocked    -= OnPumpRelocked;
        }
    }
}