using Xamarin.Forms;
using TINK.View;
using TINK.Model.Station;
using System;
using System.Linq;
using TINK.Model.Bike;
using TINK.Repository.Exception;
using TINK.Model;
using Serilog;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.ComponentModel;
using Xamarin.Forms.GoogleMaps;
using System.Collections.ObjectModel;
#if USEFLYOUT
using TINK.View.MasterDetail;
#endif
using TINK.Services.Permissions;
using Xamarin.Essentials;
using System.Threading;
using TINK.MultilingualResources;
using TINK.ViewModel.Info;
using TINK.Repository;
using TINK.Model.Services.Geolocation;

namespace TINK.ViewModel.Contact
{
    public class SelectStationPageViewModel : INotifyPropertyChanged
    {
        /// <summary> Holds the count of custom icons availalbe.</summary>
        private const int CUSTOM_ICONS_COUNT = 30;

        /// <summary> Reference on view service to show modal notifications and to perform navigation. </summary>
        private IViewService ViewService { get; }

        /// <summary>
        /// Holds the exception which occurred getting bikes occupied information.
        /// </summary>
        private Exception m_oException;


        /// <summary>
        /// Service to query/ manage permissions (location) of the app.
        /// </summary>
        private ILocationPermission PermissionsService { get; }

        /// <summary>
        /// Service to manage bluetooth stack.
        /// </summary>
        private Plugin.BLE.Abstractions.Contracts.IBluetoothLE BluetoothService { get; set; }


        /// <summary> Notifies view about changes. </summary>
        public event PropertyChangedEventHandler PropertyChanged;


        /// <summary> Reference on the tink app instance. </summary>
        private ITinkApp TinkApp { get; }

        /// <summary>Delegate to perform navigation.</summary>
        private INavigation m_oNavigation;

#if USEFLYOUT
        /// <summary>Delegate to perform navigation.</summary>
        private INavigationMasterDetail m_oNavigationMasterDetail;
#endif
        private ObservableCollection<Pin> pins;

        public ObservableCollection<Pin> Pins
        {
            get
            {
                if (pins == null)
                    pins = new ObservableCollection<Pin>(); // If view model is not binding context pins collection must be set programmatically.

                return pins;
            }

            set => pins = value;
        }

        /// <summary>Delegate to move map to region.</summary>
        private Action<MapSpan> m_oMoveToRegionDelegate;

        /// <summary> False if user tabed on station marker to show bikes at a given station.</summary>
        private bool isMapPageEnabled = false;

        Model.Services.Geolocation.IGeolocation GeolocationService { get; }

        /// <summary> False if user tabed on station marker to show bikes at a given station.</summary>
        public bool IsMapPageEnabled
        {
            get => isMapPageEnabled;
            private set
            {
                if (isMapPageEnabled == value)
                    return;

                isMapPageEnabled = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsMapPageEnabled)));
            }
        }

        /// <summary> Prevents an invalid instane to be created. </summary>
        /// <param name="tinkApp"> Reference to tink app model.</param>
        /// <param name="moveToRegionDelegate">Delegate to center map and set zoom level.</param>
        /// <param name="viewService">View service to notify user.</param>
        /// <param name="navigation">Interface to navigate.</param>
        public SelectStationPageViewModel(
            ITinkApp tinkApp,
            ILocationPermission permissionsService,
            Plugin.BLE.Abstractions.Contracts.IBluetoothLE bluetoothService,
            IGeolocation geolocationService,
            Action<MapSpan> moveToRegionDelegate,
            IViewService viewService,
            INavigation navigation)
        {
            TinkApp = tinkApp
                ?? throw new ArgumentException("Can not instantiate map page view model- object. No tink app object available.");

            PermissionsService = permissionsService ??
                throw new ArgumentException($"Can not instantiate {nameof(SelectStationPageViewModel)}. Permissions service object must never be null.");

            BluetoothService = bluetoothService ??
                throw new ArgumentException($"Can not instantiate {nameof(SelectStationPageViewModel)}. Bluetooth service object must never be null.");

            GeolocationService = geolocationService ??
                throw new ArgumentException($"Can not instantiate {nameof(SelectStationPageViewModel)}. Geolocation service object must never be null.");

            m_oMoveToRegionDelegate = moveToRegionDelegate
                ?? throw new ArgumentException("Can not instantiate map page view model- object. No move delegate available.");

            ViewService = viewService
                ?? throw new ArgumentException("Can not instantiate map page view model- object. No view available.");

            m_oNavigation = navigation
                ?? throw new ArgumentException("Can not instantiate map page view model- object. No navigation service available.");

#if USEFLYOUT
            m_oNavigationMasterDetail = new EmptyNavigationMasterDetail();
#endif

            IsConnected = TinkApp.GetIsConnected();
        }

#if USEFLYOUT
        /// <summary> Delegate to perform navigation.</summary>
        public INavigationMasterDetail NavigationMasterDetail
        {
            set { m_oNavigationMasterDetail = value; }
        }
#endif

        public Command<PinClickedEventArgs> PinClickedCommand => new Command<PinClickedEventArgs>(
            args =>
            {
                OnStationClicked(args.Pin.Tag.ToString());
                args.Handled = true; // Prevents map to be centered to selected pin.
            });

        /// <summary>
        /// One time setup: Sets pins into map and connects to events.
        /// </summary>
        private void InitializePins(StationDictionary stations)
        {
            // Add pins to stations.
            Log.ForContext<SelectStationPageViewModel>().Debug($"Request to draw {stations.Count} pins.");
            foreach (var station in stations)
            {
                if (station.Position == null)
                {
                    // There should be no reason for a position object to be null but this alreay occurred in past.
                    Log.ForContext<SelectStationPageViewModel>().Error("Postion object of station {@l_oStation} is null.", station);
                    continue;
                }

                var l_oPin = new Pin
                {

                    Position = new Xamarin.Forms.GoogleMaps.Position(station.Position.Latitude, station.Position.Longitude),
                    Label = long.TryParse(station.Id, out long stationId) && stationId > CUSTOM_ICONS_COUNT
                        ? station.GetStationName()
                        : string.Empty, // Stations with custom icons have already a id marker. No need for a label.

                    Tag = station.Id,
                    IsVisible = false, // Set to false to prevent showing default icons (flickering).
                };

                Pins.Add(l_oPin);
            }
        }

        /// <summary> Update all stations from TINK. </summary>
        /// <param name="stationsColorList">List of colors to apply.</param>
        private void UpdatePinsColor(IList<Color> stationsColorList)
        {
            Log.ForContext<SelectStationPageViewModel>().Debug($"Starting update of stations pins color for {stationsColorList.Count} stations...");

            // Update colors of pins.
            for (int pinIndex = 0; pinIndex < stationsColorList.Count; pinIndex++)
            {

                var indexPartPrefix = int.TryParse(Pins[pinIndex].Tag.ToString(), out int stationId)
                    && stationId <= CUSTOM_ICONS_COUNT
                    ? $"{stationId}" // there is a station marker with index letter for given station id
                    : "Open"; // there is no station marker. Use open marker.

                var colorPartPrefix = GetRessourceNameColorPart(stationsColorList[pinIndex]);

                var l_iName = $"{indexPartPrefix.ToString().PadLeft(2, '0')}_{colorPartPrefix}{(DeviceInfo.Platform == DevicePlatform.Android ? ".png" : string.Empty)}";
                try
                {
                    Pins[pinIndex].Icon = BitmapDescriptorFactory.FromBundle(l_iName);
                }
                catch (Exception l_oException)
                {
                    Log.ForContext<SelectStationPageViewModel>().Error("Station icon {l_strName} can not be loaded. {@l_oException}.", l_oException);
                    Pins[pinIndex].Label = stationId.ToString();
                    Pins[pinIndex].Icon = BitmapDescriptorFactory.DefaultMarker(stationsColorList[pinIndex]);
                }

                Pins[pinIndex].IsVisible = true;
            }

            var pinsCount = Pins.Count;
            for (int pinIndex = stationsColorList.Count; pinIndex < pinsCount; pinIndex++)
            {
                Log.ForContext<SelectStationPageViewModel>().Error($"Unexpected count of pins detected. Expected {stationsColorList.Count} but is {pinsCount}.");
                Pins[pinIndex].IsVisible = false;
            }

            Log.ForContext<SelectStationPageViewModel>().Debug("Update of stations pins color done.");
        }

        /// <summary> Gets the color related part of the ressrouce name.</summary>
        /// <param name="color">Color to get name for.</param>
        /// <returns>Resource name.</returns>
        private static string GetRessourceNameColorPart(Color color)
        {
            if (color == Color.Blue)
            {
                return "Blue";
            }

            if (color == Color.Green)
            {
                return "Green";
            }

            if (color == Color.LightBlue)
            {
                return "LightBlue";
            }

            if (color == Color.Red)
            {
                return "Red";
            }

            return color.ToString();
        }

        /// <summary>
        /// Invoked when page is shown. 
        /// Starts update process.
        /// </summary>
        /// <param name="p_oFilterDictionaryMapPage">Holds map page filter settings.</param>
        /// <param name="p_oPolling">Holds polling management object.</param>
        /// <param name="p_bIsShowWhatsNewRequired">If true whats new page will be shown.</param>
        public async Task OnAppearing()
        {
            try
            {
                IsRunning = true;
                // Process map page.

                Log.ForContext<SelectStationPageViewModel>().Information(
                    $"Current UI language is {Thread.CurrentThread.CurrentUICulture.Name}.");

                if (Pins.Count <= 0)
                {
                    ActionText = AppResources.ActivityTextRequestingLocationPermissions;

                    // Check location permission
                    var status = await PermissionsService.CheckStatusAsync();
                    if (TinkApp.CenterMapToCurrentLocation
                        && !GeolocationService.IsSimulation
                        && status != Status.Granted)
                    {
                        var permissionResult = await PermissionsService.RequestAsync();

                        if (permissionResult != Status.Granted)
                        {
                            var dialogResult = await ViewService.DisplayAlert(
                                AppResources.MessageTitleHint,
                                AppResources.MessageCenterMapLocationPermissionOpenDialog,
                                AppResources.MessageAnswerYes,
                                AppResources.MessageAnswerNo);

                            if (dialogResult)
                            {
                                // User decided to give access to locations permissions.
                                PermissionsService.OpenAppSettings();
                                ActionText = "";
                                IsRunning = false;
                                IsMapPageEnabled = true;
                                return;
                            }
                        }
                    }

                    // Move and scale before getting stations and bikes which takes some time.
                    ActionText = AppResources.ActivityTextCenterMap;
                    Location currentLocation = null;
                    try
                    {
                        currentLocation = TinkApp.CenterMapToCurrentLocation
                            ? await GeolocationService.GetAsync()
                            : null;
                    }
                    catch (Exception ex)
                    {
                        Log.ForContext<SelectStationPageViewModel>().Error("Getting location failed. {Exception}", ex);
                    }

                    MoveAndScale(m_oMoveToRegionDelegate, TinkApp.Uris.ActiveUri, currentLocation);
                }

                ActionText = AppResources.ActivityTextMapLoadingStationsAndBikes;
                IsConnected = TinkApp.GetIsConnected();
                var resultStationsAndBikes = await TinkApp.GetConnector(IsConnected).Query.GetBikesAndStationsAsync();

                TinkApp.Stations = resultStationsAndBikes.Response.StationsAll;

                if (Pins.Count > 0 && Pins.Count != resultStationsAndBikes.Response.StationsAll.Count)
                {
                    // Either
                    // - user logged in/ logged out which might lead to more/ less stations beeing available
                    // - new stations were added/ existing ones remove
                    Pins.Clear();
                }

                // Check if there are alreay any pins to the map 
                // i.e detecte first call of member OnAppearing after construction
                if (Pins.Count <= 0)
                {
                    // Map was not yet initialized.
                    // Get stations from Copri
                    Log.ForContext<SelectStationPageViewModel>().Verbose("No pins detected on page.");
                    if (resultStationsAndBikes.Response.StationsAll.CopriVersion < CopriCallsStatic.UnsupportedVersionLower)
                    {
                        await ViewService.DisplayAlert(
                            AppResources.MessageWaring,
                            string.Format(AppResources.MessageCopriVersionIsOutdated, ContactPageViewModel.GetAppName(TinkApp.Uris.ActiveUri)),
                            AppResources.MessageAnswerOk);

                        Log.ForContext<SelectStationPageViewModel>().Error($"Outdated version of app detected. Version expected is {resultStationsAndBikes.Response.StationsAll.CopriVersion}.");
                    }

                    if (resultStationsAndBikes.Response.StationsAll.CopriVersion >= CopriCallsStatic.UnsupportedVersionUpper)
                    {
                        await ViewService.DisplayAlert(
                            AppResources.MessageWaring,
                            string.Format(AppResources.MessageAppVersionIsOutdated, ContactPageViewModel.GetAppName(TinkApp.Uris.ActiveUri)),
                            AppResources.MessageAnswerOk);

                        Log.ForContext<SelectStationPageViewModel>().Error($"Outdated version of app detected. Version expected is {resultStationsAndBikes.Response.StationsAll.CopriVersion}.");
                    }

                    // Set pins to their positions on map.
                    InitializePins(resultStationsAndBikes.Response.StationsAll);

                    Log.ForContext<SelectStationPageViewModel>().Verbose("Update of pins done.");
                }


                if (resultStationsAndBikes.Exception?.GetType() == typeof(AuthcookieNotDefinedException))
                {
                    Log.ForContext<SelectStationPageViewModel>().Error("Map page is shown (probable for the first time after startup of app) and COPRI auth cookie is not defined. {@l_oException}", resultStationsAndBikes.Exception);

                    // COPRI reports an auth cookie error.
                    await ViewService.DisplayAlert(
                        AppResources.MessageWaring,
                        AppResources.MessageMapPageErrorAuthcookieUndefined,
                        AppResources.MessageAnswerOk);

                    await TinkApp.GetConnector(IsConnected).Command.DoLogout();
                    TinkApp.ActiveUser.Logout();
                }

                // Update pin colors.
                Log.ForContext<SelectStationPageViewModel>().Verbose("Starting update pins color...");

                var colors = GetStationColors(
                     Pins.Select(x => x.Tag.ToString()).ToList(),
                     resultStationsAndBikes.Response.Bikes);

                // Update pins color form count of bikes located at station.
                UpdatePinsColor(colors);


                Log.ForContext<SelectStationPageViewModel>().Verbose("Update pins color done.");

                Exception = resultStationsAndBikes.Exception;
                ActionText = "";
                IsRunning = false;
                IsMapPageEnabled = true;
            }
            catch (Exception l_oException)
            {
                Log.ForContext<SelectStationPageViewModel>().Error($"An error occurred switching view TINK/ Konrad.\r\n{l_oException.Message}");

                IsRunning = false;

                await ViewService.DisplayAlert(
                    "Fehler",
                    $"Beim Anzeigen der Fahrradstandorte- Seite ist ein Fehler aufgetreten.\r\n{l_oException.Message}",
                    "OK");

                IsMapPageEnabled = true;
            }
        }

        /// <summary> Moves map and scales visible region depending on active filter. </summary>
        public static void MoveAndScale(
            Action<MapSpan> moveToRegionDelegate,
            Uri activeUri,
            Location currentLocation = null)
        {
            if (currentLocation != null)
            {
                // Move to current location.
                moveToRegionDelegate(MapSpan.FromCenterAndRadius(
                    new Xamarin.Forms.GoogleMaps.Position(currentLocation.Latitude, currentLocation.Longitude),
                    Distance.FromKilometers(1.0)));
                return;
            }

            // Center map to Freiburg
            moveToRegionDelegate(MapSpan.FromCenterAndRadius(
                new Xamarin.Forms.GoogleMaps.Position(47.995865, 7.815086),
                Distance.FromKilometers(2.9)));
        }

        /// <summary> User clicked on a bike. </summary>
        /// <param name="selectedStationId">Id of station user clicked on.</param>
        public async void OnStationClicked(string selectedStationId)
        {
            try
            {
                Log.ForContext<SelectStationPageViewModel>().Information($"User taped station {selectedStationId}.");

                // Lock action to prevent multiple instances of "BikeAtStation" being opened.
                IsMapPageEnabled = false;

                TinkApp.SelectedStation = TinkApp.Stations.FirstOrDefault(x => x.Id == selectedStationId)
                    ?? new Station(selectedStationId, new List<string>(), null); // Station might not be in list StationDictinaly because this list is not updatd in background task.

#if TRYNOTBACKSTYLE
                m_oNavigation.ShowPage(
                    typeof(BikesAtStationPage),
                    p_strStationName);
#else
                // Show page.
                ViewService.ShowPage(ViewTypes.ContactPage, AppResources.MarkingContactPageTitle);

                IsMapPageEnabled = true;
                ActionText = "";
            }
            catch (Exception exception)
            {
                IsMapPageEnabled = true;
                ActionText = "";

                Log.ForContext<SelectStationPageViewModel>().Error("Fehler beim Öffnen der Ansicht \"Fahrräder an Station\" aufgetreten. {Exception}", exception);
                await ViewService.DisplayAlert(
                     "Fehler",
                     $"Fehler beim Öffnen der Ansicht \"Fahrräder an Station\" aufgetreten. {exception.Message}",
                     "OK");
            }
#endif
        }

        /// <summary>
        /// Gets the list of station color for all stations.
        /// </summary>
        /// <param name="stationsId">Station id list to get color for.</param>
        /// <returns></returns>
        private static IList<Color> GetStationColors(
            IEnumerable<string> stationsId,
            BikeCollection bikesAll)
        {
            if (stationsId == null)
            {
                Log.ForContext<SelectStationPageViewModel>().Debug("No stations available to update color for.");
                return new List<Color>();
            }

            if (bikesAll == null)
            {
                // If object is null an error occurred querrying bikes availalbe or bikes occpied which results in an unknown state.
                Log.ForContext<SelectStationPageViewModel>().Error("No bikes available to determine pins color.");
                return new List<Color>(stationsId.Select(x => Color.Blue));
            }

            // Get state for each station.
            var colors = new List<Color>();
            foreach (var stationId in stationsId)
            {
                // Get color of given station.
                var bikesAtStation = bikesAll.Where(x => x.CurrentStation == stationId).ToList();
                if (bikesAtStation.FirstOrDefault(x => x.State.Value != Model.State.InUseStateEnum.Disposable) != null)
                {
                    // There is at least one requested or booked bike
                    colors.Add(Color.LightBlue);
                    continue;
                }

                if (bikesAtStation.ToList().Count > 0)
                {
                    // There is at least one bike available
                    colors.Add(Color.Green);
                    continue;
                }

                colors.Add(Color.Red);
            }

            return colors;
        }

        /// <summary>
        /// Exception which occurred getting bike information.
        /// </summary>
        public Exception Exception
        {
            get
            {
                return m_oException;
            }

            private set
            {
                var statusInfoText = StatusInfoText;
                m_oException = value;
                if (statusInfoText == StatusInfoText)
                {
                    // Nothing to do because value did not change.
                    return;
                }

                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(StatusInfoText)));
            }
        }

        /// <summary> Holds info about current action. </summary>
        private string actionText;

        /// <summary> Holds info about current action. </summary>
        private string ActionText
        {
            get => actionText;
            set
            {
                var statusInfoText = StatusInfoText;
                actionText = value;
                if (statusInfoText == StatusInfoText)
                {
                    // Nothing to do because value did not change.
                    return;
                }

                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(StatusInfoText)));
            }
        }

        /// <summary> Used to block more than on copri requests at a given time.</summary>
        private bool isRunning = false;

        /// <summary>
        /// True if any action can be performed (request and cancel request)
        /// </summary>
        public bool IsRunning
        {
            get => isRunning;
            set
            {
                if (value == isRunning)
                    return;

                Log.ForContext<SelectStationPageViewModel>().Debug($"Switch value of {nameof(isRunning)} to {value}.");
                isRunning = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsRunning)));
            }
        }


        /// <summary> Holds information whether app is connected to web or not. </summary>
        private bool? isConnected = null;

        /// <summary>Exposes the is connected state. </summary>
        private bool IsConnected
        {
            get => isConnected ?? false;
            set
            {
                var statusInfoText = StatusInfoText;
                isConnected = value;
                if (statusInfoText == StatusInfoText)
                {
                    // Nothing to do.
                    return;
                }

                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(StatusInfoText)));
            }
        }

        /// <summary> Holds the status information text. </summary>
        public string StatusInfoText
        {
            get
            {
                if (Exception != null)
                {
                    // An error occurred getting data from copri.
                    return TinkApp.IsReportLevelVerbose
                        ? Exception.GetShortErrorInfoText()
                        : AppResources.ActivityTextException;
                }

                if (!IsConnected)
                {
                    return AppResources.ActivityTextConnectionStateOffline;
                }

                return ActionText ?? string.Empty;
            }
        }
    }
}