MeWeb/src/MeWeb.Android/AndroidPlatform.cs

using Android.Content;
using Android.Net;
using Android.Net.Wifi;

using MeWeb.Core.Net;

namespace MeWeb.Android;

public class AndroidPlatform : SystemPlatform
{
  static Context Context => global::Android.App.Application.Context;

  public override DeviceKind Device => DeviceKind.Phone;

  public override string Name => "android";

  public override bool? HasBattery => true;

  public override bool ShareLink(string url, string title)
  {
    var send = new Intent(Intent.ActionSend);
    send.SetType("text/plain");
    send.PutExtra(Intent.ExtraText, url);
    send.PutExtra(Intent.ExtraSubject, title);
    var chooser = Intent.CreateChooser(send, title);
    if (chooser is null) return false;
    chooser.AddFlags(ActivityFlags.NewTask);
    Context.StartActivity(chooser);
    return true;
  }

  public override IDisposable AllowMulticast()
  {
    if (Context.GetSystemService(Context.WifiService) is not WifiManager wifi) return base.AllowMulticast();
    var multicast = wifi.CreateMulticastLock("meweb");
    multicast.SetReferenceCounted(false);
    multicast.Acquire();
    return new Held(multicast);
  }

  public override LocalSnapshot ReadNetwork()
  {
    var snapshot = new LocalSnapshot();
    if (Context.GetSystemService(Context.ConnectivityService) is not ConnectivityManager connectivity) return base.ReadNetwork();
    var network = connectivity.ActiveNetwork;
    if (network is null) return snapshot;
    var link = connectivity.GetLinkProperties(network);
    var capabilities = connectivity.GetNetworkCapabilities(network);
    if (link is null) return base.ReadNetwork();

    var item = new LocalInterface
    {
      Name = link.InterfaceName,
      Kind = capabilities switch
      {
        not null when capabilities.HasTransport(TransportType.Wifi) => LinkKind.Wifi,
        not null when capabilities.HasTransport(TransportType.Cellular) => LinkKind.Mobile,
        not null when capabilities.HasTransport(TransportType.Ethernet) => LinkKind.Cable,
        _ => LinkKind.Unknown,
      },
    };
    foreach (var address in link.LinkAddresses)
    {
      var text = Usable(address.Address?.HostAddress);
      if (text is not null) item.Addresses.Add(text);
    }
    foreach (var route in link.Routes)
    {
      var gateway = route.Gateway?.HostAddress;
      if (!route.IsDefaultRoute || gateway is null || gateway is "0.0.0.0" or "::") continue;
      if (!item.Gateways.Contains(gateway)) item.Gateways.Add(gateway);
    }
    item.Gateways = item.Gateways.OrderBy(g => g.Contains(':') ? 1 : 0).ToList();
    if (item.Kind == LinkKind.Wifi) item.SpeedMbps = WifiSpeed(capabilities);
    snapshot.Interfaces.Add(item);
    snapshot.Dns = link.DnsServers.Select(d => d.HostAddress).Where(d => d is not null).Distinct().ToList();
    return snapshot;
  }

  static string Usable(string text)
  {
    var address = Addresses.Parse(text?.Split('%')[0]);
    if (address is null) return null;
    return Addresses.Classify(address) is AddressKind.Loopback or AddressKind.LinkLocal or AddressKind.Unspecified ? null : address.ToString();
  }

  static long WifiSpeed(NetworkCapabilities capabilities)
  {
    if (!OperatingSystem.IsAndroidVersionAtLeast(29))
      return Context.GetSystemService(Context.WifiService) is WifiManager wifi ? Math.Max(0, wifi.ConnectionInfo?.LinkSpeed ?? 0) : 0;
    return capabilities?.TransportInfo is WifiInfo info ? Math.Max(0, info.LinkSpeed) : 0;
  }

  sealed class Held(WifiManager.MulticastLock multicast) : IDisposable
  {
    public void Dispose()
    {
      if (multicast.IsHeld) multicast.Release();
    }
  }
}