using System;
using System.ComponentModel;
using System.Threading.Tasks;
using System.Windows.Input;
using TINK.View;
using TINK.ViewModel.Info;
using Xamarin.Forms;

namespace TINK.ViewModel.WhatsNew.Agb
{
	public class AgbViewModel : INotifyPropertyChanged
	{
		/// <summary> Fired whenever a property changed.</summary>
		public event PropertyChangedEventHandler PropertyChanged;

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

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

		/// <summary> Constructs AGB view model</summary>
		/// <param name="isSiteCachingOn">Holds value wether site caching is on or off.</param>
		/// <param name="uiIsoLangugageName">Two letter ISO language name.</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="viewService">View service to close page.</param>
		public AgbViewModel(
			string hostName,
			bool isSiteCachingOn,
			Func<string, string> resourceProvider,
			IViewService viewService)
		{
			HostName = hostName;
			IsSiteCachingOn = isSiteCachingOn;

			ViewService = viewService
				?? throw new ArgumentException($"Can not instantiate {typeof(WhatsNewViewModel)}-object. No view available.");

			ResourceProvider = resourceProvider
				?? throw new ArgumentException($"Can not instantiate {typeof(WhatsNewViewModel)}-object. No ressource provider availalbe.");
		}

		/// <summary> Gets the platfrom specific prefix. </summary>
		private Func<string, string> ResourceProvider { get; set; }

		/// <summary> Agb information text.</summary>
		private HtmlWebViewSource infoAgb;

		/// <summary> Agb information text.</summary>
		public HtmlWebViewSource InfoAgb
		{
			get => infoAgb;
			set
			{
				infoAgb = value;
				PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(InfoAgb)));
			}
		}

		/// <summary> Called when page is shown. </summary>
		public async Task OnAppearing()
		{
			InfoAgb = await InfoPageViewModel.GetAgb(HostName, "agbResourcePath", IsSiteCachingOn);
		}

		/// <summary> User clicks OK button.</summary>
		public ICommand OnOk
		{
			get
			{
				return new Command(async () => await ViewService.PopModalAsync());
			}
		}

		/// <summary> Reference to view service object.</summary>
		private IViewService ViewService;
	}
}