Spotify.NET/SpotifyAPI.Web.Auth/SpotifyAuthServer.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using SpotifyAPI.Web.Enums;
using Unosquare.Labs.EmbedIO;
using Unosquare.Labs.EmbedIO.Modules;

namespace SpotifyAPI.Web.Auth
{
  public abstract class SpotifyAuthServer<T>
  {
    public string ClientId { get; set; }
    public string ServerUri { get; set; }
    public string RedirectUri { get; set; }
    public string State { get; set; }
    public Scope Scope { get; set; }
    public bool ShowDialog { get; set; }

    private readonly string _folder;
    private readonly string _type;
    private WebServer _server;
    protected CancellationTokenSource _serverSource;

    public delegate void OnAuthReceived(object sender, T payload);
    public event OnAuthReceived AuthReceived;

    internal static readonly Dictionary<string, SpotifyAuthServer<T>> Instances = new Dictionary<string, SpotifyAuthServer<T>>();

    internal SpotifyAuthServer(string type, string folder, string redirectUri, string serverUri, Scope scope = Scope.None, string state = "")
    {
      _type = type;
      _folder = folder;
      ServerUri = serverUri;
      RedirectUri = redirectUri;
      Scope = scope;
      State = string.IsNullOrEmpty(state) ? string.Join("", Guid.NewGuid().ToString("n").Take(8)) : state;
    }

    public void Start()
    {
      Instances.Add(State, this);
      _serverSource = new CancellationTokenSource();

      _server = WebServer.Create(ServerUri);
      _server.RegisterModule(new WebApiModule());
      AdaptWebServer(_server);
      _server.RegisterModule(new ResourceFilesModule(Assembly.GetExecutingAssembly(), $"SpotifyAPI.Web.Auth.Resources.{_folder}"));
#pragma warning disable 4014
      _server.RunAsync(_serverSource.Token);
#pragma warning restore 4014
    }

    public virtual string GetUri()
    {
      StringBuilder builder = new StringBuilder("https://accounts.spotify.com/authorize/?");
      builder.Append("client_id=" + ClientId);
      builder.Append($"&response_type={_type}");
      builder.Append("&redirect_uri=" + RedirectUri);
      builder.Append("&state=" + State);
      builder.Append("&scope=" + Scope.GetStringAttribute(" "));
      builder.Append("&show_dialog=" + ShowDialog);
      return Uri.EscapeUriString(builder.ToString());
    }

    public void Stop(int delay = 2000)
    {
      if (_serverSource == null) return;
      _serverSource.CancelAfter(delay);
      Instances.Remove(State);
    }

    public void OpenBrowser()
    {
      string uri = GetUri();
      AuthUtil.OpenBrowser(uri);
    }

    internal void TriggerAuth(T payload)
    {
      AuthReceived?.Invoke(this, payload);
    }

    internal static SpotifyAuthServer<T> GetByState(string state)
    {
      return Instances.TryGetValue(state, out SpotifyAuthServer<T> auth) ? auth : null;
    }

    protected abstract void AdaptWebServer(WebServer webServer);
  }
}