sharee.bike-App/LastenradBayern/ShareeBike/View/Map/MapPage.xaml.cs

using System;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace ShareeBike.View.Map
{
	using Serilog;
	using ShareeBike.Model.Bikes.BikeInfoNS.DriveNS.BatteryNS;
	using ShareeBike.ViewModel.Map;

	[XamlCompilation(XamlCompilationOptions.Compile)]
	public partial class MapPage : ContentPage, IViewService
	{
		/// <summary> View model to notify about whether page appears or hides. </summary>
		private MapPageViewModel MapPageViewModel { get; set; }

		/// <summary> Initialization status to ensure initialization logic is not called multiple times. </summary>
		private bool isInitializationStarted = false;

		/// <summary>
		/// Constructs map page instance.
		/// </summary>
		public MapPage()
		{
			InitializeComponent();
		}

		/// <summary>
		/// Displays alert message.
		/// </summary>
		/// <param name="title">Title of message.</param>
		/// <param name="message">Message to display.</param>
		/// <param name="cancel">Type of buttons.</param>
		public new async Task DisplayAlert(string title, string message, string cancel)
			=> await App.Current.MainPage.DisplayAlert(title, message, cancel);

		/// <summary> Displays alert message.</summary>
		/// <param name="title">Title of message.</param>
		/// <param name="message">Message to display.</param>
		/// <param name="details">Detailed error description.</param>
		/// <param name="cancel">Type of buttons.</param>
		public async Task DisplayAdvancedAlert(
			string title,
			string message,
			string details,
			string cancel)
			=> await App.Current.MainPage.DisplayAlert(title, $"{message}\r\nDetails:\r\n{details}", cancel);

		/// <summary> Displays detailed alert message.</summary>
		/// <param name="title">Title of message.</param>
		/// <param name="message">Message to display.</param>
		/// <param name="details">Detailed error description.</param>
		/// <param name="accept">Text of accept button.</param>
		/// <param name="cancel">Text of cancel button.</param>
		/// <returns>True if user pressed accept.</returns>
		public async Task<bool> DisplayAdvancedAlert(string title, string message, string details, string accept, string cancel)
			=> await App.Current.MainPage.DisplayAlert(title, !string.IsNullOrEmpty(details) ? $"{message}\r\nDetails:\r\n{details}" : $"{message}", accept, cancel);

		/// <summary>
		/// Displays alert message.
		/// </summary>
		/// <param name="title">Title of message.</param>
		/// <param name="message">Message to display.</param>
		/// <param name="accept">Text of accept button.</param>
		/// <param name="cancel">Text of button.</param>
		/// <returns>True if user pressed accept.</returns>
		public new async Task<bool> DisplayAlert(string title, string message, string accept, string cancel)
			=> await App.Current.MainPage.DisplayAlert(title, message, accept, cancel);

		/// <summary> Shows a page.</summary>
		/// <param name="route">Route of the page to show.</param>
		public async Task ShowPage(string route) => await Shell.Current.GoToAsync(route);

		/// <summary> Pushes a page onto the modal stack. </summary>
		/// <param name="typeOfPage">Type of page to display.</param>
		public async Task PushModalAsync(ViewTypes typeOfPage)
			=> await Navigation.PushModalAsync((Page)Activator.CreateInstance(typeOfPage.GetViewType()));

		/// <summary> Pops a page from the modal stack. </summary>
		public async Task PopModalAsync()
			=> await Navigation.PopModalAsync();

		/// <summary> Pushes a page onto the stack. </summary>
		/// <param name="typeOfPage">Page to display.</param>
		public async Task PushAsync(ViewTypes typeOfPage)
		{
			var page = Activator.CreateInstance(typeOfPage.GetViewType());
			if (page == null)
			{
				return;
			}

			await Navigation.PushAsync((Page)page);
		}

#if USCSHARP9
        public Task<IViewService.IUserFeedback> DisplayUserFeedbackPopup() => throw new NotSupportedException();
#else
		public async Task<IUserFeedback> DisplayUserFeedbackPopup(IBatteryMutable battery = null) => throw new NotSupportedException();
#endif

		/// <summary>
		/// Invoked when page is shown. 
		/// Starts update process.
		/// </summary>
		protected async override void OnAppearing()
		{
			// Don't repeat the initialization if it has been completed already.
			if (isInitializationStarted) return;
			isInitializationStarted = true;

			// Pass reference to member Navigation to show bikes at station x dialog.
			try
			{
				Log.ForContext<MapPage>().Verbose("Constructing map page view model.");
				MapPageViewModel = CreateMapPageViewModel();
			}
			catch (Exception exception)
			{
				Log.ForContext<MapPage>().Error("Constructing map page view model failed. {Exception}", exception);
				isInitializationStarted = false;
				return;
			}

			try
			{
				BindingContext = MapPageViewModel;
			}
			catch (Exception exception)
			{
				Log.ForContext<MapPage>().Error("Setting binding/ navigation on map page failed. {Exception}", exception);
				isInitializationStarted = false;
				return;
			}

			try
			{
				base.OnAppearing();
			}
			catch (Exception exception)
			{
				// Continue because styling is not essential.
				Log.ForContext<MapPage>().Error("Invoking OnAppearing of base failed. {Exception}", exception);
			}

			try
			{
				// Premove and scale maps to avoid initial display of map in Rome.
				PremoveAndScaleMap();
			}
			catch (Exception exception)
			{
				// Continue because a map not beeing moved/ scaled is no reason for aborting startup.
				Log.ForContext<MapPage>().Error("Moving and scaling map failed. {Exception}", exception);
			}

			try
			{
				Log.ForContext<MapPage>().Verbose("Invoking OnAppearing on map page view model.");
				await MapPageViewModel.OnAppearing();
			}
			catch (Exception exception)
			{
				Log.ForContext<MapPage>().Error("Invoking OnAppearing on map page view model failed. {Exception}", exception);
				isInitializationStarted = false;
				return;
			}

			try
			{
				Log.ForContext<MapPage>().Verbose("Setting map settings.");

				//show current user position (blue dot) and enable button for centering map manually.
				MyMap.UiSettings.MyLocationButtonEnabled = MapPageViewModel.IsLocationPermissionGranted;
				MyMap.IsShowingUser = MapPageViewModel.IsLocationPermissionGranted;

				//disable +/- buttons
				MyMap.UiSettings.ZoomControlsEnabled = false;
			}
			catch (Exception exception)
			{
				Log.ForContext<MapPage>().Verbose("Setting map settings failed. {Exception}", exception);
			}
			isInitializationStarted = false;
		}

		/// <summary>
		/// Premoves the Map to a certain location.
		/// </summary>
		private void PremoveAndScaleMap()
		{
			Log.ForContext<MapPage>().Verbose("Moving and scaling map.");
			MapPageViewModel.MoveAndScale(
				(mapSpan) => MyMap.MoveToRegion(mapSpan),
				App.ModelRoot.ActiveMapSpan);
		}

		/// <summary>
		/// Creates the Map Page's view model.
		/// </summary>
		private MapPageViewModel CreateMapPageViewModel()
		{
			Log.ForContext<MapPage>().Verbose("Constructing map page view model.");
			return new MapPageViewModel(
				App.ModelRoot,
				App.PermissionsService,
				App.BluetoothService,
				App.LocationServicesContainer.Active,
				(mapspan) => MyMap.MoveToRegion(mapspan),
				this,
				Navigation);
		}

		/// <summary>
		/// Invoked when pages is closed/ hidden. 
		/// Stops update process.
		/// </summary>
		protected async override void OnDisappearing()
		{
			if (MapPageViewModel != null)
			{
				// View model might be null.
				await MapPageViewModel?.OnDisappearing();
			}

			base.OnDisappearing();
		}
	}
}