Added Credentials Authenticator

SpotifyAPI.Web/Clients/OAuthClient.cs

@@ -16,8 +16,16 @@ namespace SpotifyAPI.Web
     public OAuthClient(SpotifyClientConfig config) : base(ValidateConfig(config)) { }
 
     public Task<TokenResponse> RequestToken(ClientCredentialsRequest request)
+    {
+      return RequestToken(request, API);
+    }
+
+    public static Task<TokenResponse> RequestToken(
+        ClientCredentialsRequest request, IAPIConnector apiConnector
+      )
     {
       Ensure.ArgumentNotNull(request, nameof(request));
+      Ensure.ArgumentNotNull(apiConnector, nameof(apiConnector));
 
       var form = new List<KeyValuePair<string, string>>
       {
@@ -30,7 +38,7 @@ namespace SpotifyAPI.Web
         { "Authorization", $"Basic {base64}"}
       };
 
-      return API.Post<TokenResponse>(SpotifyUrls.OAuthToken, null, new FormUrlEncodedContent(form), headers);
+      return apiConnector.Post<TokenResponse>(SpotifyUrls.OAuthToken, null, new FormUrlEncodedContent(form), headers);
     }
 
     private static APIConnector ValidateConfig(SpotifyClientConfig config)

SpotifyAPI.Web/Http/APIConnector.cs

@@ -192,10 +192,7 @@ namespace SpotifyAPI.Web.Http
 
     private async Task<IResponse> DoRequest(IRequest request)
     {
-      if (_authenticator != null)
-      {
-        await _authenticator.Apply(request, this).ConfigureAwait(false);
-      }
+      await ApplyAuthenticator(request).ConfigureAwait(false);
       _httpLogger?.OnRequest(request);
       IResponse response = await _httpClient.DoRequest(request).ConfigureAwait(false);
       _httpLogger?.OnResponse(response);
@@ -203,10 +200,7 @@ namespace SpotifyAPI.Web.Http
       {
         response = await _retryHandler.HandleRetry(request, response, async (newRequest) =>
         {
-          if (_authenticator != null)
-          {
-            await _authenticator.Apply(request, this).ConfigureAwait(false);
-          }
+          await ApplyAuthenticator(request).ConfigureAwait(false);
           var newResponse = await _httpClient.DoRequest(request).ConfigureAwait(false);
           _httpLogger?.OnResponse(newResponse);
           return newResponse;
@@ -216,6 +210,14 @@ namespace SpotifyAPI.Web.Http
       return response;
     }
 
+    private async Task ApplyAuthenticator(IRequest request)
+    {
+      if (_authenticator != null && !request.Endpoint.IsAbsoluteUri)
+      {
+        await _authenticator.Apply(request, this).ConfigureAwait(false);
+      }
+    }
+
     public Task<IResponse> SendRawRequest(
         Uri uri,
         HttpMethod method,

SpotifyAPI.Web/Http/Authenticators/CredentialsAuthenticator.cs

@@ -0,0 +1,54 @@
+using System.Threading.Tasks;
+
+namespace SpotifyAPI.Web.Http
+{
+  /// <summary>
+  ///   This Authenticator requests new credentials token on demand and stores them into memory.
+  ///   It is unable to query user specifc details.
+  /// </summary>
+  public class CredentialsAuthenticator : IAuthenticator
+  {
+    private TokenResponse _token;
+
+    /// <summary>
+    ///   Initiate a new instance. The first token will be fetched when the first API call occurs
+    /// </summary>
+    /// <param name="clientId">
+    ///   The ClientID, defined in a spotify application in your Spotify Developer Dashboard
+    /// </param>
+    /// <param name="clientSecret">
+    ///   The ClientID, defined in a spotify application in your Spotify Developer Dashboard
+    /// </param>
+    public CredentialsAuthenticator(string clientId, string clientSecret)
+    {
+      Ensure.ArgumentNotNullOrEmptyString(clientId, nameof(clientId));
+      Ensure.ArgumentNotNullOrEmptyString(clientSecret, nameof(clientSecret));
+
+      ClientId = clientId;
+      ClientSecret = clientSecret;
+    }
+
+    /// <summary>
+    ///   The ClientID, defined in a spotify application in your Spotify Developer Dashboard
+    /// </summary>
+    public string ClientId { get; }
+
+    /// <summary>
+    ///   The ClientID, defined in a spotify application in your Spotify Developer Dashboard
+    /// </summary>
+    public string ClientSecret { get; set; }
+
+    public async Task Apply(IRequest request, IAPIConnector apiConnector)
+    {
+      Ensure.ArgumentNotNull(request, nameof(request));
+
+      if (_token == null || _token.IsExpired)
+      {
+        var tokenRequest = new ClientCredentialsRequest(ClientId, ClientSecret);
+        _token = await OAuthClient.RequestToken(tokenRequest, apiConnector).ConfigureAwait(false);
+      }
+
+      request.Headers["Authorization"] = $"{_token.TokenType} {_token.AccessToken}";
+    }
+  }
+}

SpotifyAPI.Web/Models/Response/Token.cs

@@ -1,3 +1,4 @@
+using System;
 namespace SpotifyAPI.Web
 {
   public class TokenResponse
@@ -5,5 +6,13 @@ namespace SpotifyAPI.Web
     public string AccessToken { get; set; }
     public string TokenType { get; set; }
     public int ExpiresIn { get; set; }
+
+    /// <summary>
+    ///   Auto-Initalized to UTC Now
+    /// </summary>
+    /// <value></value>
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+    public bool IsExpired { get => CreatedAt.AddSeconds(ExpiresIn) <= DateTime.UtcNow; }
   }
 }