sharee.bike-App/TINKLib/ViewModel/FeesAndBikes/FeesAndBikesPageViewModel.cs

using System;
using System.ComponentModel;
using System.Threading.Tasks;
using Serilog;
using TINK.Model;
using TINK.Model.Bikes;
using TINK.Model.Connector;
using TINK.Model.Services.CopriApi;
using TINK.ViewModel.Info;
using Xamarin.Forms;

namespace TINK.ViewModel.Contact
{
	public class FeesAndBikesPageViewModel : INotifyPropertyChanged
	{
		public event PropertyChangedEventHandler PropertyChanged;


		/// <summary> Holds value wether 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 FeesResourcePath { get; set; }

		/// <summary>
		/// Relative path to bike info resources of empty if value was not yet querried from backend.
		/// </summary>
		private string BikesResourcePath { 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 querry resources urls object from backend if required.
		/// This object is used to update resources path values <see cref="FeesResourcePath"/>, and <see cref="BikesResourcePath"/> 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 an an embedded html ressource. Used as fallback if download from web page does not work and cache is empty.</param>
		/// <param name="query">Object to querry resources path values if required.</param>
		public FeesAndBikesPageViewModel(
			string hostName,
			string feesResourcePath,
			string bikesResourcePath,
			bool isSiteCachingOn,
			Func<IQuery> queryProvider,
			Action<IResourceUrls> updateUrlsAction)
		{
			HostName = hostName;
			FeesResourcePath = feesResourcePath;
			BikesResourcePath = bikesResourcePath;
			IsSiteCachingOn = isSiteCachingOn;
			QueryProvider = queryProvider;
			UpdateUrlsAction = updateUrlsAction;
		}

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

		/// <summary> Called when page is shown. </summary>
		public async void OnAppearing()
		{
			// Get resource urls object from backend.
			async Task<IResourceUrls> GetUrls()
			{
				Result<BikeCollection> bikes;
				try
				{
					bikes = await QueryProvider().GetBikesAsync();
				}
				catch (Exception ex)
				{
					Log.ForContext<FeesAndBikesPageViewModel>().Error($"Getting resource urls from COPRI failed. {ex.Message}");
					return new ResourceUrls();
				}

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

			// Set state to busy.
			IsIdle = false;

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

			RentBikeText = new HtmlWebViewSource
			{
				Html = !string.IsNullOrEmpty(FeesResourcePath)
					? await ViewModelHelper.GetSource($"https://{HostName}/{FeesResourcePath}", IsSiteCachingOn)
					: await Task.FromResult(ViewModelHelper.FromBody("No fees resource available. Resource path is null or empty."))
			};

			TypesOfBikesText = new HtmlWebViewSource
			{
				Html = !string.IsNullOrEmpty(BikesResourcePath)
					? await ViewModelHelper.GetSource($"https://{HostName}/{BikesResourcePath}" /*"site/bike_info.html"*/, IsSiteCachingOn)
					: await Task.FromResult(ViewModelHelper.FromBody("No bikes instruction resource available. Resource path is null or empty."))
			};

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

		private HtmlWebViewSource rentBikeText;

		private HtmlWebViewSource typesOfBikesText;

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

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