sharee.bike-App/SharedBusinessLogic/ViewModel/Help/HelpPageViewModel.cs

using System;
using System.ComponentModel;
using System.Threading.Tasks;
using Serilog;
using ShareeBike.Model;
using ShareeBike.Model.Connector;
using ShareeBike.Model.Services.CopriApi;
using Xamarin.Forms;

namespace ShareeBike.ViewModel.Help
{
	public class HelpPageViewModel : INotifyPropertyChanged
	{
		public event PropertyChangedEventHandler PropertyChanged;

		/// <summary>
		/// Holds the current ui two letter ISO language name.
		/// </summary>
		private string UiIsoLanguageName { get; }

		/// <summary> Holds value whether site caching is on or off.</summary>
		bool IsSiteCachingOn { get; }

		/// <summary>
		/// Relative path to fees resources of empty if value was not yet querried from backend.
		/// </summary>
		private string TariffsResourcePath { get; set; }

		/// <summary>
		/// Relative path to bike info resources of empty if value was not yet querried from backend.
		/// </summary>
		private string ManualResourcePath { get; set; }

		private bool _IsIdle = false;

		/// <summary>
		/// Is true if no action is pending, false otherwise.
		/// </summary>
		public bool IsIdle
		{
			get => _IsIdle;
			private set
			{
				if (_IsIdle == value)
				{
					// Nothing to do.
					return;
				}

				_IsIdle = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsIdle)));
				return;
			}
		}

		/// <summary>
		/// Object to query resources urls object from backend if required.
		/// This object is used to update resources path values <see cref="TariffsResourcePath"/>, and <see cref="ManualResourcePath"/> from.
		/// </summary>
		private Func<IQuery> QueryProvider { get; }

		/// <summary>
		/// Action to update shared resources urls object exposed by main model. 
		/// </summary>
		private Action<IResourceUrls> UpdateUrlsAction { get; }

		/// <summary> Constructs view model.</summary>
		/// <param name="isSiteCachingOn">Set of user permissions</param>
		/// <param name="resourceProvider">Delegate to get embedded html resource. Used as fallback if download from web page does not work and cache is empty.</param>
		/// <param name="query">Object to query resources path values if required.</param>
		public HelpPageViewModel(
			string hostName,
			string tariffsResourcePath,
			string manualResourcePath,
			bool isSiteCachingOn,
			string uiIsoLangugageName,
			Func<IQuery> queryProvider,
			Action<IResourceUrls> updateUrlsAction)
		{
			HostName = hostName;
			TariffsResourcePath = tariffsResourcePath;
			ManualResourcePath = manualResourcePath;
			IsSiteCachingOn = isSiteCachingOn;
			QueryProvider = queryProvider;
			UpdateUrlsAction = updateUrlsAction;
			UiIsoLanguageName = uiIsoLangugageName;
		}

		/// <summary> Holds the name of the host.</summary>
		private string HostName { get; }

		// Get resource urls object from backend.
		public async Task<IResourceUrls> GetUrls()
		{
			Result<StationsAndBikesContainer> stations;
			try
			{
				stations = await QueryProvider().GetBikesAndStationsAsync();
			}
			catch (Exception ex)
			{
				Log.ForContext<HelpPageViewModel>().Error($"Getting resource urls from COPRI failed. {ex.Message}");
				return new ResourceUrls();
			}

			return stations?.GeneralData?.ResourceUrls ?? new ResourceUrls();
		}

		/// <summary> Called when page is shown. </summary>
		public async void OnAppearing()
		{
			// Set state to busy.
			IsIdle = false;

			if (string.IsNullOrEmpty(TariffsResourcePath))
			{
				var urls = await GetUrls();
				TariffsResourcePath = urls.TariffsResourcePath;
				ManualResourcePath = urls.ManualResourcePath;
				UpdateUrlsAction(urls); // Update main model to prevent duplicate queries.
			}

			//set font size for html content (necessary for iOS)
			string headerString = "<header><meta name='viewport' content='width=device-width, intial-scale=2.0, maximum-scale=5.0, minimum-scale=1.0, user-scalable=no'></header>";

			ManualHtml = new HtmlWebViewSource
			{
				Html = !string.IsNullOrEmpty(ManualResourcePath)
					? headerString + await ViewModelHelper.GetSource($"https://{HostName}/{ManualResourcePath}" /*"site/bike_info_....html"*/, IsSiteCachingOn)
					: headerString + await Task.FromResult(ViewModelHelper.FromBody("No manual resource available. Resource path is null or empty."))
			};

			TariffsHtml = new HtmlWebViewSource
			{
				Html = !string.IsNullOrEmpty(TariffsResourcePath)
					? headerString + await ViewModelHelper.GetSource($"https://{HostName}/{TariffsResourcePath}" /*"site/tarif_info_....html"*/, IsSiteCachingOn)
					: headerString + await Task.FromResult(ViewModelHelper.FromBody("No tariffs resource available. Resource path is null or empty."))
			};

			FaqHtml = new HtmlWebViewSource
			{
				Html = UiIsoLanguageName == "de"
					? await ViewModelHelper.GetSource($"https://sharee.bike/faqHtml/fahrrad-nutzung/", IsSiteCachingOn)
					: await ViewModelHelper.GetSource($"https://sharee.bike/faqHtml/bike-usage/", IsSiteCachingOn)
			};

			// Set state to idle.
			IsIdle = true;
		}

		private HtmlWebViewSource manualHtml;

		private HtmlWebViewSource tariffsHtml;

		private HtmlWebViewSource faqHtml;

		public HtmlWebViewSource ManualHtml
		{
			get => manualHtml;
			set
			{
				manualHtml = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(ManualHtml)));
			}
		}

		public HtmlWebViewSource TariffsHtml
		{
			get => tariffsHtml;
			set
			{
				tariffsHtml = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(TariffsHtml)));
			}
		}

		public HtmlWebViewSource FaqHtml
		{
			get => faqHtml;
			set
			{
				faqHtml = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(FaqHtml)));
			}
		}
	}
}