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

using System;
using System.Collections.Generic;
using System.Linq;
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;
        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();
            WebServer server = AdaptWebServer(WebServer.Create(ServerUri));
            server.RegisterModule(new ResourceFilesModule(typeof(ImplictGrantAuth).Assembly, $"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 WebServer AdaptWebServer(WebServer webServer);
    }
}