sharee.bike-App/TINKLib/ViewModel/Map/MapPageViewModel.cs

using Xamarin.Forms;
using TINK.View;
using TINK.Model.Stations;
using System;
using System.Linq;
using TINK.Model.Bikes;
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.Settings;
using TINK.Model.Connector;
using TINK.Model.Services.CopriApi;
using TINK.Services.Permissions;
using Xamarin.Essentials;
using System.Threading;
using TINK.MultilingualResources;
using TINK.Repository;
using TINK.Services.Geolocation;
using TINK.Model.State;
using TINK.Model.Bikes.BikeInfoNS.BC;
using TINK.Model.Stations.StationNS;

#if !TRYNOTBACKSTYLE
#endif

namespace TINK.ViewModel.Map
{
	public class MapPageViewModel : INotifyPropertyChanged
	{
		/// <summary> True if message was already shown to user. </summary>
		private static bool WasMerchantMessageAlreadyShown { get; set; } = false;


		/// <summary> Holds the count of custom icons centered.</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> Object to manage update of view model objects from Copri.</summary>
		private IPollingUpdateTaskManager m_oViewUpdateManager;

		/// <summary>Holds whether to poll or not and the period length is polling is on.</summary>
		private PollingParameters Polling { get; set; }

		/// <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;

		IGeolocationService 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 MapPageViewModel(
			ITinkApp tinkApp,
			ILocationPermission permissionsService,
			Plugin.BLE.Abstractions.Contracts.IBluetoothLE bluetoothService,
			IGeolocationService 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(MapPageViewModel)}. Permissions service object must never be null.");

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

			GeolocationService = geolocationService ??
				throw new ArgumentException($"Can not instantiate {nameof(MapPageViewModel)}. 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.");

			m_oViewUpdateManager = new IdlePollingUpdateTaskManager();

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

			Polling = PollingParameters.NoPolling;

			tinkKonradToggleViewModel = new EmptyToggleViewModel();

			IsConnected = TinkApp.GetIsConnected();
		}

		/// <summary>Sets the stations filter to to apply (Konrad or TINK). </summary>
		public IGroupFilterMapPage ActiveFilterMap
		{
			get => tinkKonradToggleViewModel.FilterDictionary ?? new GroupFilterMapPage();
			set
			{
				tinkKonradToggleViewModel = new TinkKonradToggleViewModel(value);

				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(TinkColor)));
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(KonradColor)));
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(NoTinkColor)));
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(NoKonradColor)));
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsToggleVisible)));
			}
		}

#if USEFLYOUT
        /// <summary> Delegate to perform navigation.</summary>
        public INavigationMasterDetail NavigationMasterDetail
        {
            set { m_oNavigationMasterDetail = value; }
        }
#endif
		/// <summary>
		/// Counts the number of reserved or occupied bikes -> visualized in MyBikes-Icon
		/// </summary>
		public void GetMyBikesCount(BikeCollection bikesAll)
		{
			int MyBikesCount = 0;
			Log.ForContext<MapPageViewModel>().Debug($"Number of reserved or rented bikes is extracted.");
			if (bikesAll != null)
			{
				foreach (var bike in bikesAll)
				{
					if (bike.State.Value.IsOccupied())
					{
						MyBikesCount = MyBikesCount + 1;
						continue;
					}

				}
			}
			MyBikesCountText = MyBikesCount > 0 ? string.Format(MyBikesCount.ToString()) : string.Empty;
		}

		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>
		public void InitializePins(StationDictionary stations)
		{
			// Add pins to stations.
			Log.ForContext<MapPageViewModel>().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 already occurred in past.
					Log.ForContext<MapPageViewModel>().Error("Position object of station {@l_oStation} is null.", station);
					continue;
				}

				var pin = 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(pin);
			}
		}

		/// <summary> Update all stations from TINK. </summary>
		/// <param name="stationsColorList">List of colors to apply.</param>
		private void UpdatePinsColor(IList<Color> stationsColorList)
		{
			Log.ForContext<MapPageViewModel>().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 = GetResourceNameColorPart(stationsColorList[pinIndex]);
				var name = $"{indexPartPrefix.ToString().PadLeft(2, '0')}_{colorPartPrefix}{(DeviceInfo.Platform == DevicePlatform.Android ? ".png" : string.Empty)}";
				try
				{
					Pins[pinIndex].Icon = BitmapDescriptorFactory.FromBundle(name);
				}
				catch (Exception excption)
				{
					Log.ForContext<MapPageViewModel>().Error("Station icon {name} can not be loaded. {@excption}.", name, excption);
					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<MapPageViewModel>().Error($"Unexpected count of pins detected. Expected {stationsColorList.Count} but is {pinsCount}.");
				Pins[pinIndex].IsVisible = false;
			}

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

		/// <summary>
		/// label for number of reserved/rented bikes;
		/// </summary>
		private string _myBikesCountText = string.Empty;
		public string MyBikesCountText
		{
			get { return _myBikesCountText; }
			set
			{
				_myBikesCountText = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MyBikesCountText)));
			}
		}

		/// <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 GetResourceNameColorPart(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>
		public async Task OnAppearing()
		{
			try
			{
				//Request Location Permission on iOS
				if (DeviceInfo.Platform == DevicePlatform.iOS)
				{
					var status = await PermissionsService.RequestAsync();
				}

				IsProcessWithRunningProcessView = true;
				IsNavBarVisible = false;

				// Get and expose status of location permission
				GetLocationPermissionStatus();

				// Process map page.
				Polling = TinkApp.Polling;

				Log.ForContext<MapPageViewModel>().Information(
					$"{(Polling != null && Polling.IsActivated ? $"Map page is appearing. Update period is {Polling.Periode.TotalSeconds} sec." : "Map page is appearing. Polling is off.")}" +
					$"Current UI language is {Thread.CurrentThread.CurrentUICulture.Name}.");

				// Update map page filter
				ActiveFilterMap = TinkApp.GroupFilterMapPage;

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

				TinkApp.Stations = resultStationsAndBikes.Response.StationsAll;
				TinkApp.ResourceUrls = resultStationsAndBikes.GeneralData.ResourceUrls;

				// Check if there is a message from COPRI ("merchant_message") to be shown to user. 
				if (!string.IsNullOrEmpty(resultStationsAndBikes?.GeneralData?.MerchantMessage)
					&& !WasMerchantMessageAlreadyShown)
				{
					// Context switch should not be required because code is called from GUI thread
					// but a xf-issue requires call (see issue #594).
					TinkApp.PostAction(async (x) =>
					{
						// Show COPRI message once. 
						await ViewService.DisplayAlert(
							AppResources.MessageInformationTitle,
							resultStationsAndBikes.GeneralData.MerchantMessage,
							AppResources.MessageAnswerOk);
					}, null);

					WasMerchantMessageAlreadyShown = true;
				}

				await SetStationsOnMap(resultStationsAndBikes.Response.StationsAll);
				await HandleAuthCookieNotDefinedException(resultStationsAndBikes.Exception);

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

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

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

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

				// Load MyBikes Count -> MyBikes Icon/Button
				GetMyBikesCount(resultStationsAndBikes.Response.BikesOccupied);

				// Move and scale before getting stations and bikes which takes some time.
				ActionText = AppResources.ActivityTextCenterMap;

				// Get map display area
				Model.Map.IMapSpan mapSpan = null;
				if (TinkApp.CenterMapToCurrentLocation)
				{
					var status = await PermissionsService.CheckStatusAsync();
					if (status == Status.Granted)
					{
						// Get from smart device
						mapSpan = await GetFromLocationService(status);
					}
				}

				if (mapSpan == null)
				{
					// Use map display are from COPRI 
					mapSpan = resultStationsAndBikes.GeneralData.InitialMapSpan;
				}

				if (mapSpan.IsValid)
				{
					TinkApp.UserMapSpan = MapSpan.FromCenterAndRadius(
						new Xamarin.Forms.GoogleMaps.Position(mapSpan.Center.Latitude, mapSpan.Center.Longitude),
						new Distance(mapSpan.Radius * 1000));
					TinkApp.Save();

					MoveAndScale(m_oMoveToRegionDelegate, TinkApp.ActiveMapSpan);
				}

				m_oViewUpdateManager = CreateUpdateTask();

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

				try
				{
					// Update bikes at station or my bikes depending on context.
					await m_oViewUpdateManager.StartAsync(Polling);
				}
				catch (Exception)
				{
					// Excpetions are handled insde update task;
				}

				Exception = resultStationsAndBikes.Exception;
				ActionText = string.Empty;
				IsProcessWithRunningProcessView = false;
				IsNavBarVisible = true;
				IsMapPageEnabled = true;
			}
			catch (Exception l_oException)
			{
				Log.ForContext<MapPageViewModel>().Error($"An error occurred showing bike stations page.\r\n{l_oException.Message}");

				IsProcessWithRunningProcessView = false;
				IsNavBarVisible = true;

				await ViewService.DisplayAlert(
					AppResources.ErrorPageNotLoadedTitle,
					$"{AppResources.ErrorPageNotLoaded}\r\n{l_oException.Message}",
					AppResources.MessageAnswerOk);

				IsMapPageEnabled = true;
			}
		}

		/// <summary>
		/// IsLocationPermissionGranted = true, if Location Permissions granted.
		/// </summary>
		private async void GetLocationPermissionStatus()
		{
			Log.ForContext<MapPageViewModel>().Verbose("Check Location permissions.");
			var status = await PermissionsService.CheckStatusAsync();
			IsLocationPermissionGranted = status == Status.Granted ? true : false;
			Log.ForContext<MapPageViewModel>().Verbose("Location permissions: {0}.", status);
		}

		private bool isLocationPermissionGranted = false;
		/// <summary>
		/// Exposes IsLocationPermissionGranted.
		/// </summary>
		public bool IsLocationPermissionGranted
		{
			get => isLocationPermissionGranted;
			set
			{
				if (value == isLocationPermissionGranted)
					return;

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

		/// <summary>
		/// Invoked when the auth cookie is not defined.
		/// </summary>
		private async Task HandleAuthCookieNotDefinedException(Exception exception)
		{
			if (exception?.GetType() == typeof(AuthcookieNotDefinedException))
			{
				Log.ForContext<MapPageViewModel>().Error("Map page is shown (probable for the first time after startup of app) and COPRI auth cookie is not defined. {@l_oException}", exception);

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

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

		/// <summary>
		/// Sets the available stations on the map.
		/// </summary>
		private async Task SetStationsOnMap(StationDictionary stations)
		{
			if (Pins.Count > 0 && Pins.Count != stations.Count)
			{
				// Either
				// - user logged in/ logged out which might lead to more/ less stations being available
				// - new stations were added/ existing ones remove
				Pins.Clear();
			}

			// Check if there are already any pins to the map
			// i.e detects first call of member OnAppearing after construction
			if (Pins.Count <= 0)
			{
				Log.ForContext<MapPageViewModel>().Debug($"{(ActiveFilterMap.GetGroup().Any() ? $"Active map filter is {string.Join(",", ActiveFilterMap.GetGroup())}." : "Map filter is off.")}");

				// Map was not yet initialized.
				// Get stations from Copri
				Log.ForContext<MapPageViewModel>().Verbose("No pins detected on page.");
				if (stations.CopriVersion < CopriCallsStatic.UnsupportedVersionLower)
				{
					await ViewService.DisplayAlert(
						AppResources.MessageWaring,
						string.Format(AppResources.MessageCopriVersionIsOutdated, TinkApp.Flavor.GetDisplayName()),
						AppResources.MessageAnswerOk);

					Log.ForContext<MapPageViewModel>().Error($"Outdated version of app detected. Version expected is {stations.CopriVersion}.");
				}

				if (stations.CopriVersion >= CopriCallsStatic.UnsupportedVersionUpper)
				{
					await ViewService.DisplayAlert(
						AppResources.MessageWaring,
						string.Format(AppResources.MessageAppVersionIsOutdated, TinkApp.Flavor.GetDisplayName()),
						AppResources.MessageAnswerOk);

					Log.ForContext<MapPageViewModel>().Error($"Outdated version of app detected. Version expected is {stations.CopriVersion}.");
				}

				// Set pins to their positions on map.
				InitializePins(stations);

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

		/// <summary>
		/// Moves the map to the current position of the user.
		/// If location permission hasn't been granted, the position is not adjusted.
		/// </summary>
		private async Task<Model.Map.IMapSpan> GetFromLocationService(Status status)
		{
			IGeolocation currentLocation = null;
			try
			{
				currentLocation = await GeolocationService.GetAsync();
			}
			catch (Exception ex)
			{
				Log.ForContext<MapPageViewModel>().Error("Getting location failed. {Exception}", ex);
			}
			if (currentLocation == null)
				return null;

			return Model.Map.MapSpanFactory.Create(
				PositionFactory.Create(currentLocation.Latitude, currentLocation.Longitude),
				TinkApp.ActiveMapSpan.Radius.Kilometers);
		}

		/// <summary>
		/// Requests the location permission from the user.
		/// If the user declines, a dialog prompot is shown, telling the user to toggle the permission in the device settings.
		/// </summary>
		/// <returns>The permission status.</returns>
		private async Task<Status> RequestLocationPermission()
		{
			// Check location permission
			var status = await PermissionsService.CheckStatusAsync();
			if (!GeolocationService.IsSimulation
				// && DeviceInfo.Platform == DevicePlatform.Android
				&& status != Status.Granted)
			{
				var dialogResult = await ViewService.DisplayAlert(
					AppResources.MessageHintTitle,
					AppResources.ErrorMapCenterNoLocationPermissionOpenDialog,
					AppResources.MessageAnswerYes,
					AppResources.MessageAnswerNo);

				if (dialogResult)
				{
					// User decided to give access to locations permissions.
					PermissionsService.OpenAppSettings();
					ActionText = string.Empty;
					IsProcessWithRunningProcessView = false;
					IsNavBarVisible = true;
					IsMapPageEnabled = true;
				}
			}
			return status;
		}

		/// <summary> Moves map and scales visible region depending on active filter. </summary>
		public static void MoveAndScale(
			Action<MapSpan> moveToRegionDelegate,
			MapSpan currentMapSpan = null)
		{
			if (currentMapSpan != null)
			{
				// Move to current location.
				moveToRegionDelegate(currentMapSpan);
				return;
			}
		}

		/// <summary> Creates a update task object. </summary>
		/// <param name="p_oSynchronizationContext">Object to use for synchronization.</param>
		private PollingUpdateTaskManager CreateUpdateTask()
		{
			// Start task which periodically updates pins.
			return new PollingUpdateTaskManager(
				() =>
				{
					try
					{
						Log.ForContext<MapPageViewModel>().Verbose("Entering update cycle.");
						Result<StationsAndBikesContainer> resultStationsAndBikes;

						TinkApp.PostAction(
							unused =>
							{
								ActionText = AppResources.ActivityTextUpdating;
								IsConnected = TinkApp.GetIsConnected();
							},
							null);

						resultStationsAndBikes = TinkApp.GetConnector(IsConnected).Query.GetBikesAndStationsAsync().Result;

						var exception = resultStationsAndBikes.Exception;
						if (exception != null)
						{
							Log.ForContext<MapPageViewModel>().Error("Getting bikes and stations in polling context failed with exception {Exception}.", exception);
						}

						// Get and expose status of location permission
						GetLocationPermissionStatus();

						// Load MyBikes Count -> MyBikes Icon/Button
						GetMyBikesCount(resultStationsAndBikes.Response.BikesOccupied);

						// Check if there are already any pins to the map. 
						// If no initialize pins.
						if (Pins.Count <= 0)
						{
							// Set pins to their positions on map.
							TinkApp.PostAction(
								unused => { InitializePins(resultStationsAndBikes.Response.StationsAll); },
								null);
						}

						// Set/ update pins colors.
						var l_oColors = GetStationColors(
							Pins.Select(x => x.Tag.ToString()).ToList(),
							resultStationsAndBikes.Response.StationsAll,
							resultStationsAndBikes.Response.BikesOccupied);

						// Update pins color form count of bikes located at station.
						TinkApp.PostAction(
							unused =>
							{
								UpdatePinsColor(l_oColors);
								ActionText = string.Empty;
								Exception = resultStationsAndBikes.Exception;
							},
							null);

						Log.ForContext<MapPageViewModel>().Verbose("Leaving update cycle.");
					}
					catch (Exception exception)
					{
						Log.ForContext<MapPageViewModel>().Error("Getting stations and bikes from update task failed. {Exception}", exception);
						TinkApp.PostAction(
							unused =>
							{
								Exception = exception;
								ActionText = string.Empty;
							},
							 null);

						Log.ForContext<MapPageViewModel>().Verbose("Leaving update cycle.");

						return;
					}
				});
		}

		/// <summary>
		/// Invoked when pages is closed/ hidden. 
		/// Stops update process.
		/// </summary>
		public async Task OnDisappearing()
		{
			Log.Information("Map page is disappearing...");

			await m_oViewUpdateManager.StopAsync();
		}

		/// <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<MapPageViewModel>().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 Model.Stations.StationNS.Station(selectedStationId, new List<string>(), null); // Station might not be in list StationDictinaly because this list is not updated in background task.

#if TRYNOTBACKSTYLE
                m_oNavigation.ShowPage(
                    typeof(BikesAtStationPage),
                    p_strStationName);
#else
				{
					// Show page.
					await ViewService.PushAsync(ViewTypes.BikesAtStation);

					IsMapPageEnabled = true;
					ActionText = string.Empty;
				}
			}
			catch (Exception exception)
			{
				IsMapPageEnabled = true;
				ActionText = string.Empty;

				Log.ForContext<MapPageViewModel>().Error("Fehler beim Öffnen der Ansicht \"Fahrräder an Station\" aufgetreten. {Exception}", exception);
				await ViewService.DisplayAlert(
					 AppResources.ErrorPageNotLoadedTitle,
					 $"{AppResources.ErrorPageNotLoaded}\r\n {exception.Message}",
					 AppResources.MessageAnswerOk);
			}
#endif
		}

		/// <summary>
		/// Gets the list of station color for all stations.
		/// </summary>
		/// <param name="stationsId">Station id list to get color for.</param>
		/// <param name="stations">Station object dictionary to get count of available bike from for each station.</param>
		/// <param name="bikesReserved">Bike collection to get count of reserved/ rented bikes from for each station.</param>
		/// <returns></returns>
		internal static IList<Color> GetStationColors(
			IEnumerable<string> stationsId,
			IEnumerable<IStation> stations,
			IEnumerable<BikeInfo> bikesReserved)
		{
			if (stationsId == null)
			{
				Log.ForContext<MapPageViewModel>().Debug("No stations available to update color for.");
				return new List<Color>();
			}

			if (stations == null)
			{
				Log.ForContext<MapPageViewModel>().Error("No stations info available to get count of bikes available to determine whether a pin is green or not.");
			}

			if (bikesReserved == null)
			{
				Log.ForContext<MapPageViewModel>().Error("No bikes info available to determine whether a pins is light blue or not.");
			}

			// Get state for each station.
			var colors = new List<Color>();
			foreach (var stationId in stationsId)
			{
				// Get color of given station.
				if (bikesReserved?.Where(x => x.StationId == stationId).Count() > 0)
				{
					// There is at least one requested or booked bike
					colors.Add(Color.LightBlue);
					continue;
				}

				if (stations?.FirstOrDefault(x => x.Id == stationId)?.AvailableBikesCount > 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 isProcessWithRunningProcessView = false;

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

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

		private bool isNavBarVisible = true;

		public bool IsNavBarVisible
		{
			get => isNavBarVisible;
			set
			{
				if (value == isNavBarVisible)
					return;

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

		/// <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 Exception.GetShortErrorInfoText(TinkApp.IsReportLevelVerbose);
				//}

				return ActionText ?? string.Empty;
			}
		}

		/// <summary> Processes request to view my bikes.</summary>
		public System.Windows.Input.ICommand OnMyBikesButtonClicked => new Xamarin.Forms.Command(async () =>
		{
			try
			{
				Log.ForContext<MapPageViewModel>().Information($"User clicked on MyBikesButton.");

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

				// Show page.
				await ViewService.PushAsync(ViewTypes.MyBikesPage);

				IsMapPageEnabled = true;
				ActionText = string.Empty;
			}
			catch (Exception exception)
			{
				IsMapPageEnabled = true;
				ActionText = string.Empty;

				Log.ForContext<MapPageViewModel>().Error("Fehler beim Öffnen der Ansicht \"Meine Räder\" aufgetreten. {Exception}", exception);
				await ViewService.DisplayAlert(
					 AppResources.ErrorPageNotLoadedTitle,
					 $"{AppResources.ErrorPageNotLoaded}\r\n{exception.Message}",
					 AppResources.MessageAnswerOk);
			}
		});

		/// <summary> Command object to bind login button to view model.</summary>
		public System.Windows.Input.ICommand OnToggleTinkToKonrad => new Xamarin.Forms.Command(async () => await ToggleTinkToKonrad());

		/// <summary> Command object to bind login button to view model.</summary>
		public System.Windows.Input.ICommand OnToggleKonradToTink => new Xamarin.Forms.Command(async () => await ToggleKonradToTink());

		/// <summary> Manages toggle functionality. </summary>
		private ITinkKonradToggleViewModel tinkKonradToggleViewModel;

		/// <summary> User request to toggle from TINK to Konrad. </summary>
		public async Task ToggleTinkToKonrad()
		{
			if (tinkKonradToggleViewModel.CurrentFilter == FilterHelper.CITYBIKE)
			{
				// Konrad is already activated, nothing to do.
				return;
			}

			Log.ForContext<MapPageViewModel>().Information("User toggles to Konrad.");
			await ActivateFilter(FilterHelper.CARGOBIKE);
		}

		/// <summary> User request to toggle from TINK to Konrad. </summary>
		public async Task ToggleKonradToTink()
		{
			if (tinkKonradToggleViewModel.CurrentFilter == FilterHelper.CARGOBIKE)
			{
				// Konrad is already activated, nothing to do.
				return;
			}

			Log.ForContext<MapPageViewModel>().Information("User toggles to TINK.");

			await ActivateFilter(FilterHelper.CITYBIKE);
		}

		/// <summary> User request to toggle from TINK to Konrad. </summary>
		private async Task ActivateFilter(string selectedFilter)
		{
			try
			{
				IsMapPageEnabled = false;
				IsProcessWithRunningProcessView = true;
				IsNavBarVisible = false;

				Log.ForContext<MapPageViewModel>().Information($"Request to toggle to \"{selectedFilter}\".");

				// Stop polling.
				ActionText = AppResources.ActivityTextOneMomentPlease;
				await m_oViewUpdateManager.StopAsync();

				// Clear error info.
				Exception = null;

				// Toggle view
				tinkKonradToggleViewModel = new TinkKonradToggleViewModel(ActiveFilterMap).DoToggle();

				ActiveFilterMap = tinkKonradToggleViewModel.FilterDictionary;
				TinkApp.GroupFilterMapPage = ActiveFilterMap;
				TinkApp.Save();

				TinkApp.UpdateConnector();

				Pins.Clear();

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

				// Set pins to their positions on map.
				InitializePins(resultStationsAndBikes.Response.StationsAll);
				Log.ForContext<MapPageViewModel>().Verbose("Update of  pins on toggle done...");

				// Update pin colors.
				Log.ForContext<MapPageViewModel>().Verbose("Starting update pins color on toggle...");
				var l_oColors = GetStationColors(
					Pins.Select(x => x.Tag.ToString()).ToList(),
					resultStationsAndBikes.Response.StationsAll,
					resultStationsAndBikes.Response.BikesOccupied);

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

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

				try
				{
					// Update bikes at station or my bikes depending on context.
					await m_oViewUpdateManager.StartAsync(Polling);
				}
				catch (Exception)
				{
					// Excpetions are handled insde update task;
				}

				ActionText = string.Empty;
				IsProcessWithRunningProcessView = false;
				IsNavBarVisible = true;
				IsMapPageEnabled = true;
				Log.ForContext<MapPageViewModel>().Information($"Toggle to \"{selectedFilter}\" done.");
			}
			catch (Exception l_oException)
			{
				Log.ForContext<MapPageViewModel>().Error("An error occurred switching view Cargobike/ Citybike.{}");
				ActionText = string.Empty;
				IsProcessWithRunningProcessView = false;
				IsNavBarVisible = true;

				await ViewService.DisplayAlert(
					AppResources.ErrorPageNotLoadedTitle,
					AppResources.ErrorMapPageSwitchBikeType,
					String.Format(AppResources.ErrorMapPageSwitchBikeType, l_oException.Message),
					AppResources.MessageAnswerOk);

				IsMapPageEnabled = true;
			}
		}

		public Color TinkColor => tinkKonradToggleViewModel.TinkColor;

		public Color KonradColor => tinkKonradToggleViewModel.KonradColor;

		public Color NoTinkColor => tinkKonradToggleViewModel.NoTinkColor;

		public Color NoKonradColor => tinkKonradToggleViewModel.NoKonradColor;

		public bool IsToggleVisible => tinkKonradToggleViewModel.IsToggleVisible;
	}
}