NetworkService.cs

using System.Net;
using System.Runtime.CompilerServices;
using System.Runtime.ExceptionServices;
using NeuroAccessMaui.Exceptions;
using NeuroAccessMaui.Extensions;
using NeuroAccessMaui.Resources.Languages;
using Waher.Networking.DNS;
using Waher.Networking.DNS.ResourceRecords;
using Waher.Networking.XMPP;
using Waher.Runtime.Inventory;
 
namespace NeuroAccessMaui.Services.Network
{
    [Singleton]
    internal class NetworkService : LoadableService, INetworkService
    {
        private const int defaultXmppPortNumber = 5222;
 
        public event EventHandler<ConnectivityChangedEventArgs>? ConnectivityChanged;
 
        public NetworkService()
        {
        }
 
        public override Task Load(bool IsResuming, CancellationToken CancellationToken)
        {
            if (this.BeginLoad(IsResuming, CancellationToken))
            {
                if (DeviceInfo.Platform != DevicePlatform.Unknown && !DesignMode.IsDesignModeEnabled) // Need to check this, as Xamarin.Essentials doesn't work in unit tests. It has no effect when running on a real phone.
                    Connectivity.ConnectivityChanged += this.Connectivity_ConnectivityChanged;
 
                this.EndLoad(true);
            }
 
            return Task.CompletedTask;
        }
 
        public override Task Unload()
        {
            if (this.BeginUnload())
            {
                if (DeviceInfo.Platform != DevicePlatform.Unknown)
                    Connectivity.ConnectivityChanged -= this.Connectivity_ConnectivityChanged;
 
                this.EndUnload();
            }
 
            return Task.CompletedTask;
        }
 
        private void Connectivity_ConnectivityChanged(object? Sender, ConnectivityChangedEventArgs e)
        {
            this.ConnectivityChanged?.Invoke(this, e);
        }
 
        public virtual bool IsOnline =>
            Connectivity.NetworkAccess == NetworkAccess.Internet ||
            Connectivity.NetworkAccess == NetworkAccess.ConstrainedInternet;
 
        public async Task<(string HostName, int Port, bool IsIpAddress)> LookupXmppHostnameAndPort(string DomainName)
        {
            if (IPAddress.TryParse(DomainName, out IPAddress? _))
                return (DomainName, defaultXmppPortNumber, true);
 
            try
            {
                SRV endpoint = await DnsResolver.LookupServiceEndpoint(DomainName, "xmpp-client", "tcp");
 
                if (endpoint is not null && !string.IsNullOrWhiteSpace(endpoint.TargetHost) && endpoint.Port > 0)
                    return (endpoint.TargetHost, endpoint.Port, false);
            }
            catch (Exception)
            {
                // No service endpoint registered
            }
 
            return (DomainName, defaultXmppPortNumber, false);
        }
 
        public async Task<bool> TryRequest(Func<Task> func, bool rethrowException = false, bool displayAlert = true,
            [CallerMemberName] string memberName = "")
        {
            (bool succeeded, bool _) = await this.PerformRequestInner(async () =>
            {
                await func();
                return true;
            }, memberName, rethrowException, displayAlert);
 
            return succeeded;
        }
 
        public Task<(bool Succeeded, TReturn? ReturnValue)> TryRequest<TReturn>(Func<Task<TReturn>> func, bool rethrowException = false, bool displayAlert = true, [CallerMemberName] string memberName = "")
        {
            return this.PerformRequestInner(async () => await func(), memberName, rethrowException, displayAlert);
        }
 
        private async Task<(bool Succeeded, TReturn? ReturnValue)> PerformRequestInner<TReturn>(Func<Task<TReturn>> func, string memberName, bool rethrowException = false, bool displayAlert = true)
        {
            Exception thrownException;
            try
            {
                if (!this.IsOnline)
                {
                    thrownException = new MissingNetworkException(ServiceRef.Localizer[nameof(AppResources.ThereIsNoNetwork)]);
                    ServiceRef.LogService.LogException(thrownException, GetParameter(memberName));
 
                    if (displayAlert)
                    {
                        await ServiceRef.UiService.DisplayAlert(
                            ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                            ServiceRef.Localizer[nameof(AppResources.ThereIsNoNetwork)]);
                    }
                }
                else
                {
                    TReturn t = await func().TimeoutAfter(Constants.Timeouts.GenericRequest);
                    return (true, t);
                }
            }
            catch (AggregateException ae)
            {
                thrownException = ae;
 
                if (ae.InnerException is TimeoutException te)
                {
                    ServiceRef.LogService.LogException(te, GetParameter(memberName));
 
                    if (displayAlert)
                    {
                        await ServiceRef.UiService.DisplayAlert(
                            ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                            ServiceRef.Localizer[nameof(AppResources.RequestTimedOut)]);
                    }
                }
                else if (ae.InnerException is TaskCanceledException tce)
                {
                    ServiceRef.LogService.LogException(tce, GetParameter(memberName));
 
                    if (displayAlert)
                    {
                        await ServiceRef.UiService.DisplayAlert(
                            ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                            ServiceRef.Localizer[nameof(AppResources.RequestWasCancelled)]);
                    }
                }
                else if (ae.InnerException is not null)
                {
                    ServiceRef.LogService.LogException(ae.InnerException, GetParameter(memberName));
 
                    if (displayAlert)
                    {
                        await ServiceRef.UiService.DisplayAlert(
                            ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                            ae.InnerException.Message);
                    }
                }
                else
                {
                    ServiceRef.LogService.LogException(ae, GetParameter(memberName));
 
                    if (displayAlert)
                    {
                        await ServiceRef.UiService.DisplayAlert(
                            ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                            ae.Message);
                    }
                }
            }
            catch (TimeoutException te)
            {
                thrownException = te;
                ServiceRef.LogService.LogException(te, GetParameter(memberName));
 
                if (displayAlert)
                {
                    await ServiceRef.UiService.DisplayAlert(
                        ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                        ServiceRef.Localizer[nameof(AppResources.RequestTimedOut)]);
                }
            }
            catch (TaskCanceledException tce)
            {
                thrownException = tce;
                ServiceRef.LogService.LogException(tce, GetParameter(memberName));
 
                if (displayAlert)
                {
                    await ServiceRef.UiService.DisplayAlert(
                        ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                        ServiceRef.Localizer[nameof(AppResources.RequestWasCancelled)]);
                }
            }
            catch (Exception ex)
            {
                string message;
 
                thrownException = ex;
 
                if (ex is XmppException xe && xe.Stanza is not null)
                    message = xe.Stanza.InnerText;
                else
                    message = ex.Message;
 
                ServiceRef.LogService.LogException(ex, GetParameter(memberName));
 
                if (displayAlert)
                {
                    await ServiceRef.UiService.DisplayAlert(
                        ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                        message);
                }
            }
 
            if (rethrowException)
                ExceptionDispatchInfo.Capture(thrownException).Throw();
 
            return (false, default);
        }
 
        private static KeyValuePair<string, object?>[] GetParameter(string MemberName)
        {
            if (!string.IsNullOrWhiteSpace(MemberName))
            {
                return
                [
                    new KeyValuePair<string, object?>("Caller", MemberName)
                ];
            }
 
            return [];
        }
    }
}