using System;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using StreamPlayer.Desktop.Models;
using StreamPlayer.Desktop.Services;

namespace StreamPlayer.Desktop.ViewModels;

public partial class MainWindowViewModel : ViewModelBase
{
    private readonly EventService _eventService = new();
    private readonly UpdateService _updateService = new();
    private readonly DeviceRegistryService _deviceRegistryService = new();
    private readonly WindowsDnsService _dnsService = new();
    private readonly ReadOnlyCollection<ChannelSection> _sections;
    private readonly AsyncRelayCommand _refreshEventsCommand;
    private readonly RelayCommand<StreamChannel> _openChannelCommand;
    private readonly RelayCommand<LiveEvent> _openEventCommand;

    private bool _isInitialized;
    private CancellationTokenSource? _eventsCts;

    public ObservableCollection<StreamChannel> VisibleChannels { get; } = new();
    public ObservableCollection<LiveEvent> VisibleEvents { get; } = new();

    [ObservableProperty]
    private ChannelSection? selectedSection;

    [ObservableProperty]
    private bool isLoading;

    [ObservableProperty]
    private bool isShowingEvents;

    [ObservableProperty]
    private bool isRefreshingEvents;

    [ObservableProperty]
    private bool isDeviceCheckInProgress = true;

    [ObservableProperty]
    private bool isDeviceAllowed;

    [ObservableProperty]
    private string statusMessage = string.Empty;

    [ObservableProperty]
    private string deviceStatusMessage = "Verificando dispositivo…";

    public ReadOnlyCollection<ChannelSection> Sections => _sections;

    public string RefreshButtonLabel => IsRefreshingEvents
        ? "Actualizando..."
        : "Actualizar eventos";

    public bool IsInteractionLocked => IsDeviceCheckInProgress || !IsDeviceAllowed;

    public IAsyncRelayCommand RefreshEventsCommand => _refreshEventsCommand;
    public IRelayCommand<StreamChannel> OpenChannelCommand => _openChannelCommand;
    public IRelayCommand<LiveEvent> OpenEventCommand => _openEventCommand;

    public event EventHandler<StreamChannel>? ChannelRequested;
    public event EventHandler<string>? ErrorRaised;
    public event EventHandler<UpdateInfo>? UpdateAvailable;
    public event EventHandler<DeviceStatus>? DeviceStatusEvaluated;

    public MainWindowViewModel()
    {
        var sections = SectionBuilder.BuildSections().ToList();
        _sections = new ReadOnlyCollection<ChannelSection>(sections);
        _refreshEventsCommand = new AsyncRelayCommand(
            () => LoadEventsAsync(forceRefresh: true, CancellationToken.None),
            () => IsShowingEvents && !IsRefreshingEvents && CanInteract());

        _openChannelCommand = new RelayCommand<StreamChannel>(
            channel =>
            {
                if (channel != null)
                {
                    ChannelRequested?.Invoke(this, channel);
                }
            },
            _ => CanInteract());

        _openEventCommand = new RelayCommand<LiveEvent>(
            evt =>
            {
                if (evt == null || string.IsNullOrWhiteSpace(evt.PageUrl))
                {
                    return;
                }
                ChannelRequested?.Invoke(this, new StreamChannel(evt.Title, evt.PageUrl));
            },
            _ => CanInteract());

        SelectedSection = _sections.FirstOrDefault();
    }

    public async Task InitializeAsync(CancellationToken cancellationToken)
    {
        if (_isInitialized)
        {
            return;
        }

        var dnsResult = await _dnsService.EnsureGoogleDnsAsync(cancellationToken);
        if (!dnsResult.Success)
        {
            ErrorRaised?.Invoke(this, dnsResult.Message);
        }
        else if (!string.IsNullOrWhiteSpace(dnsResult.Message))
        {
            StatusMessage = dnsResult.Message;
        }

        DnsHelper.WarmUp();
        _isInitialized = true;
        if (SelectedSection != null)
        {
            await LoadSectionAsync(SelectedSection, cancellationToken);
        }
    }

    public async Task CheckForUpdatesAsync(CancellationToken cancellationToken)
    {
        try
        {
            var info = await _updateService.CheckForUpdatesAsync(cancellationToken);
            if (info != null && info.IsUpdateAvailable(AppVersion.VersionCode))
            {
                UpdateAvailable?.Invoke(this, info);
            }
        }
        catch (Exception ex)
        {
            ErrorRaised?.Invoke(this, $"No se pudo verificar actualizaciones: {ex.Message}");
        }
    }

    public async Task VerifyDeviceAsync(CancellationToken cancellationToken)
    {
        IsDeviceCheckInProgress = true;
        DeviceStatusMessage = "Verificando dispositivo…";
        try
        {
            var status = await _deviceRegistryService.SyncAsync(cancellationToken);
            IsDeviceAllowed = !status.IsBlocked;
            DeviceStatusMessage = status.IsBlocked ? "Dispositivo bloqueado" : string.Empty;
            DeviceStatusEvaluated?.Invoke(this, status);
        }
        catch (Exception ex)
        {
            ErrorRaised?.Invoke(this, $"Error sincronizando dispositivo: {ex.Message}");
            IsDeviceAllowed = true;
            DeviceStatusMessage = string.Empty;
        }
        finally
        {
            IsDeviceCheckInProgress = false;
        }
    }

    partial void OnSelectedSectionChanged(ChannelSection? value)
    {
        IsShowingEvents = value?.IsEvents == true;
        _refreshEventsCommand.NotifyCanExecuteChanged();
        if (!_isInitialized || value == null)
        {
            return;
        }
        _ = LoadSectionSafeAsync(value);
    }

    private async Task LoadSectionAsync(ChannelSection section, CancellationToken cancellationToken)
    {
        if (section.IsEvents)
        {
            await LoadEventsAsync(false, cancellationToken);
            return;
        }

        CancelPendingEvents();
        SetLoading(false);
        VisibleEvents.Clear();
        VisibleChannels.Clear();
        foreach (var channel in section.Channels)
        {
            VisibleChannels.Add(channel);
        }
        StatusMessage = VisibleChannels.Count == 0
            ? "No hay canales en esta sección."
            : string.Empty;
    }

    private async Task LoadEventsAsync(bool forceRefresh, CancellationToken cancellationToken)
    {
        if (SelectedSection?.IsEvents != true)
        {
            return;
        }
        CancelPendingEvents();
        _eventsCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        var token = _eventsCts.Token;
        try
        {
            SetLoading(true);
            IsRefreshingEvents = true;
            StatusMessage = string.Empty;
            var events = await _eventService.GetEventsAsync(forceRefresh, token);
            if (token.IsCancellationRequested)
            {
                return;
            }
            VisibleChannels.Clear();
            VisibleEvents.Clear();
            foreach (var evt in events.OrderBy(e => e.StartTimestamp <= 0 ? long.MaxValue : e.StartTimestamp))
            {
                VisibleEvents.Add(evt);
            }
            if (VisibleEvents.Count == 0)
            {
                StatusMessage = "No hay eventos próximos.";
            }
        }
        catch (OperationCanceledException)
        {
            // Ignore cancellation.
        }
        catch (Exception ex)
        {
            StatusMessage = "No se pudieron cargar los eventos.";
            ErrorRaised?.Invoke(this, $"No se pudieron cargar los eventos: {ex.Message}");
        }
        finally
        {
            if (!cancellationToken.IsCancellationRequested)
            {
                SetLoading(false);
            }
            IsRefreshingEvents = false;
            _refreshEventsCommand.NotifyCanExecuteChanged();
        }
    }

    private async Task LoadSectionSafeAsync(ChannelSection section)
    {
        try
        {
            await LoadSectionAsync(section, CancellationToken.None);
        }
        catch (Exception ex)
        {
            ErrorRaised?.Invoke(this, $"Error al actualizar la sección: {ex.Message}");
        }
    }

    private void SetLoading(bool value)
    {
        IsLoading = value;
    }

    private void CancelPendingEvents()
    {
        if (_eventsCts != null)
        {
            _eventsCts.Cancel();
            _eventsCts.Dispose();
            _eventsCts = null;
        }
    }

    private bool CanInteract() => !IsInteractionLocked;

    private void NotifyInteractionChanged()
    {
        _openChannelCommand.NotifyCanExecuteChanged();
        _openEventCommand.NotifyCanExecuteChanged();
        _refreshEventsCommand.NotifyCanExecuteChanged();
        OnPropertyChanged(nameof(IsInteractionLocked));
    }

    partial void OnIsDeviceCheckInProgressChanged(bool value)
    {
        NotifyInteractionChanged();
    }

    partial void OnIsDeviceAllowedChanged(bool value)
    {
        NotifyInteractionChanged();
    }

    partial void OnIsRefreshingEventsChanged(bool value)
    {
        _refreshEventsCommand.NotifyCanExecuteChanged();
        OnPropertyChanged(nameof(RefreshButtonLabel));
    }
}