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

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="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="p_oViewService">View service to close page.</param>
        public AgbViewModel(
            string hostName,
            bool isSiteCachingOn,
            Func<string, string> resourceProvider,
            IViewService p_oViewService)
        {
            HostName = hostName;

            IsSiteCachingOn = isSiteCachingOn;

            ViewService = p_oViewService
                ?? 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 InfoViewModel.GetAgb(HostName, IsSiteCachingOn, ResourceProvider);
        }

        /// <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;
    }
}