Added UserCredential override with TokenUpdated event

Added Success code parser
Updated packages versions

YouTube.API/Authorization/AuthorizationHelpers.cs

@@ -5,6 +5,7 @@ using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
 using System.Net.Http;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
 namespace YouTube.Authorization
@@ -12,9 +13,9 @@ namespace YouTube.Authorization
 	public static class AuthorizationHelpers
 	{
 		public static Uri Endpoint => "https://accounts.google.com/o/oauth2/approval".ToUri();
-        const string refreshEndpoint = "https://oauth2.googleapis.com/token";
+		private const string refreshEndpoint = "https://oauth2.googleapis.com/token";
-        const string tokenEndpoint = "https://www.googleapis.com/oauth2/v4/token";
+		private const string tokenEndpoint = "https://www.googleapis.com/oauth2/v4/token";
-        const string redirectUrl = "urn:ietf:wg:oauth:2.0:oob";
+		private const string redirectUrl = "urn:ietf:wg:oauth:2.0:oob";
 
 		public static Uri FormQueryString(ClientSecrets clientSecrets, params string[] scopes)
 		{
@@ -24,6 +25,9 @@ namespace YouTube.Authorization
 			return $"https://accounts.google.com/o/oauth2/auth?client_id={clientId}&redirect_uri={redirectUrl}&response_type=code&scope={scopeStr}".ToUri();
 		}
 
+		public static string ParseSuccessCode(string responseData) =>
+			new Regex(@"(?<=code=)(.*?)(?=&)").Match(responseData).Value;
+
 		public static async Task<UserCredential> ExchangeToken(ClientSecrets clientSecrets, string responseToken)
 		{
 			using HttpClient client = new HttpClient();

YouTube.API/Authorization/UserCredential.cs

@@ -0,0 +1,61 @@
+using Google.Apis.Auth.OAuth2.Flows;
+using Google.Apis.Auth.OAuth2.Responses;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace YouTube.Authorization
+{
+	public class UserCredential : Google.Apis.Auth.OAuth2.UserCredential
+	{
+		/// <summary>
+		/// Event is fired when new refresh token is recieved and the old one is no loger valid
+		/// </summary>
+		public event EventHandler RefreshTokenUpdated;
+
+		/// <summary>Constructs a new credential instance.</summary>
+		/// <param name="flow">Authorization code flow.</param>
+		/// <param name="userId">User identifier.</param>
+		/// <param name="token">An initial token for the user.</param>
+		public UserCredential(IAuthorizationCodeFlow flow, string userId, TokenResponse token) : base(flow, userId, token) { }
+
+		/// <summary>Constructs a new credential instance.</summary>
+		/// <param name="flow">Authorization code flow.</param>
+		/// <param name="userId">User identifier.</param>
+		/// <param name="token">An initial token for the user.</param>
+		/// <param name="quotaProjectId">The ID of the project associated 
+		/// to this credential for the purposes of quota calculation and billing. Can be null.</param>
+		public UserCredential(IAuthorizationCodeFlow flow, string userId, TokenResponse token, string quotaProjectId) : base(flow, userId, token, quotaProjectId) { }
+
+		/// <summary>
+		/// Refreshes the token by calling to
+		/// <see cref="Google.Apis.Auth.OAuth2.Flows.IAuthorizationCodeFlow.RefreshTokenAsync"/>.
+		/// Then it updates the <see cref="TokenResponse"/> with the new token instance.
+		/// </summary>
+		/// <param name="taskCancellationToken">Cancellation token to cancel an operation.</param>
+		/// <returns><c>true</c> if the token was refreshed.</returns>
+		public new async Task<bool> RefreshTokenAsync(CancellationToken taskCancellationToken)
+		{
+			if (Token.RefreshToken == null)
+			{
+				Logger.Warning("Refresh token is null, can't refresh the token!");
+				return false;
+			}
+
+			// It's possible that two concurrent calls will be made to refresh the token, in that case the last one 
+			// will win.
+			var newToken = await Flow.RefreshTokenAsync(UserId, Token.RefreshToken, taskCancellationToken)
+				.ConfigureAwait(false);
+
+			Logger.Info("Access token was refreshed successfully");
+
+			if (newToken.RefreshToken == null)
+				newToken.RefreshToken = Token.RefreshToken;
+
+			Token = newToken;
+
+			RefreshTokenUpdated?.Invoke(this, null);
+			return true;
+		}
+	}
+}

YouTube.API/YouTube.API.csproj

@@ -21,15 +21,15 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="AngleSharp" Version="0.13.0" />
+    <PackageReference Include="AngleSharp" Version="0.14.0" />
-    <PackageReference Include="Google.Apis" Version="1.42.0" />
+    <PackageReference Include="Google.Apis" Version="1.45.0" />
-    <PackageReference Include="Google.Apis.Auth" Version="1.42.0" />
+    <PackageReference Include="Google.Apis.Auth" Version="1.45.0" />
-    <PackageReference Include="Google.Apis.Core" Version="1.42.0" />
+    <PackageReference Include="Google.Apis.Core" Version="1.45.0" />
-    <PackageReference Include="Google.Apis.Oauth2.v2" Version="1.42.0.1602" />
+    <PackageReference Include="Google.Apis.Oauth2.v2" Version="1.45.0.1869" />
-    <PackageReference Include="Google.Apis.YouTube.v3" Version="1.42.0.1758" />
+    <PackageReference Include="Google.Apis.YouTube.v3" Version="1.45.0.1918" />
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0" PrivateAssets="all" />
-    <PackageReference Include="YoutubeExplode" Version="4.7.10" />
+    <PackageReference Include="YoutubeExplode" Version="4.7.16" />
   </ItemGroup>
 
   <ItemGroup>