sharee.bike-App/TINKLib/ViewModel/Info/InfoPageViewModel.cs

using System;
using System.ComponentModel;
using System.Threading.Tasks;
using TINK.Model.Device;
using TINK.Services.CopriApi.ServerUris;
using Xamarin.Essentials;
using Xamarin.Forms;

namespace TINK.ViewModel.Info
{
    /// <summary> Manges the tabbed info page. </summary>
    public class InfoPageViewModel : 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; }

        private string AgbResourcePath { get; }

        private string PrivacyResourcePath { get; }

        private string ImpressResourcePath { get; }

        /// <summary> Constructs Info 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>
        public InfoPageViewModel(
            string hostName,
            string agbResourcePath,
            string privacyResourcePath,
            string impressResourcePath,
            bool isSiteCachingOn,
            Func<string, string> resourceProvider)
        {
            HostName = hostName;
            AgbResourcePath = agbResourcePath;
            PrivacyResourcePath = privacyResourcePath;  
            ImpressResourcePath = impressResourcePath;  
            IsSiteCachingOn = isSiteCachingOn;

            InfoAgb = new HtmlWebViewSource { Html = "<html>Loading...</html>" };

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

        /// <summary> Called when page is shown. </summary>
        public async void OnAppearing()
        {
            InfoAgb = await GetAgb(HostName, AgbResourcePath, IsSiteCachingOn);
                
            InfoPrivacy = new HtmlWebViewSource
            {
                Html = !string.IsNullOrEmpty(PrivacyResourcePath) 
                    ? await ViewModelHelper.GetSource(
                        $"https://{HostName}/{PrivacyResourcePath}", // "site/privacy.html"
                        IsSiteCachingOn)
                    : await Task.FromResult(ViewModelHelper.FromBody("No privacy resource available. Resource path is null or empty."))
            };

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

        /// <summary> Gets the AGBs</summary>
        /// <param name="resourceProvider"></param>
        /// <returns> AGBs</returns>
        public static async Task<HtmlWebViewSource> GetAgb(
            string hostName,
            string agbResourcePath,
            bool isSiteCachingOn)
        {
            return new HtmlWebViewSource
            {
                Html = !string.IsNullOrEmpty(agbResourcePath)
                    ? await ViewModelHelper.GetSource(
                            $"https://{hostName}/{agbResourcePath}", // "agb.html"
                            isSiteCachingOn)
                    : await Task.FromResult(ViewModelHelper.FromBody("No terms resource available. Resource path is null or empty."))
            };
        }

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

        /// <summary> Gets the app related information (app version and licenses). </summary>
        public HtmlWebViewSource InfoLicenses => new HtmlWebViewSource
        {
            Html = ResourceProvider("HtmlResouces.V02.InfoLicenses.html")
                .Replace("CURRENT_VERSION_TINKAPP", DependencyService.Get<IAppInfo>().Version.ToString())
                .Replace("ACTIVE_APPNAME", AppInfo.Name)
        };

        /// <summary> Privacy text.</summary>
        private HtmlWebViewSource infoImpress;
        /// <summary> Gets the privacy related information. </summary>
        public  HtmlWebViewSource InfoImpressum
        {
            get => infoImpress;
            set
            {
                infoImpress = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(InfoImpressum)));
            }
        }

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

        /// <summary> Privacy text.</summary>
        private HtmlWebViewSource infoPrivacy;

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

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