Added paging methods, closes #538

SpotifyAPI.Web.Tests/Clients/SpotifyClientTest.cs

@@ -0,0 +1,96 @@
+using System.Reflection;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Moq;
+using NUnit.Framework;
+using SpotifyAPI.Web.Http;
+
+namespace SpotifyAPI.Web.Tests
+{
+  [TestFixture]
+  public class SpotifyClientTest
+  {
+    [Test]
+    public async Task NextPageForIPaginatable()
+    {
+      var api = new Mock<IAPIConnector>();
+      var config = SpotifyClientConfig.CreateDefault("FakeToken").WithAPIConnector(api.Object);
+      var spotify = new SpotifyClient(config);
+
+      var response = new SearchResponse
+      {
+        Albums = new Paging<SimpleAlbum, SearchResponse>
+        {
+          Next = "https://next-url",
+        }
+      };
+
+      await spotify.NextPage(response.Albums);
+      api.Verify(a => a.Get<SearchResponse>(new System.Uri("https://next-url")), Times.Once);
+    }
+
+    [Test]
+    public async Task NextPageForCursorPaging()
+    {
+      var api = new Mock<IAPIConnector>();
+      var config = SpotifyClientConfig.CreateDefault("FakeToken").WithAPIConnector(api.Object);
+      var spotify = new SpotifyClient(config);
+
+      var response = new CursorPaging<PlayHistoryItem>
+      {
+        Next = "https://next-url"
+      };
+
+      await spotify.NextPage(response);
+      api.Verify(a => a.Get<CursorPaging<PlayHistoryItem>>(new System.Uri("https://next-url")), Times.Once);
+    }
+
+    [Test]
+    public async Task NextPageForPaging()
+    {
+      var api = new Mock<IAPIConnector>();
+      var config = SpotifyClientConfig.CreateDefault("FakeToken").WithAPIConnector(api.Object);
+      var spotify = new SpotifyClient(config);
+
+      var response = new Paging<PlayHistoryItem>
+      {
+        Next = "https://next-url"
+      };
+
+      await spotify.NextPage(response);
+      api.Verify(a => a.Get<Paging<PlayHistoryItem>>(new System.Uri("https://next-url")), Times.Once);
+    }
+
+    [Test]
+    public async Task PreviousPageForPaging()
+    {
+      var api = new Mock<IAPIConnector>();
+      var config = SpotifyClientConfig.CreateDefault("FakeToken").WithAPIConnector(api.Object);
+      var spotify = new SpotifyClient(config);
+
+      var response = new Paging<PlayHistoryItem>
+      {
+        Previous = "https://previous-url"
+      };
+
+      await spotify.PreviousPage(response);
+      api.Verify(a => a.Get<Paging<PlayHistoryItem>>(new System.Uri("https://previous-url")), Times.Once);
+    }
+
+    [Test]
+    public async Task PreviousPageForCustomPaging()
+    {
+      var api = new Mock<IAPIConnector>();
+      var config = SpotifyClientConfig.CreateDefault("FakeToken").WithAPIConnector(api.Object);
+      var spotify = new SpotifyClient(config);
+
+      var response = new Paging<PlayHistoryItem, SearchResponse>
+      {
+        Previous = "https://previous-url"
+      };
+
+      await spotify.PreviousPage(response);
+      api.Verify(a => a.Get<SearchResponse>(new System.Uri("https://previous-url")), Times.Once);
+    }
+  }
+}

SpotifyAPI.Web/Clients/Interfaces/ISpotifyClient.cs

@@ -167,5 +167,15 @@ namespace SpotifyAPI.Web
     );
 
 #endif
+
+    public Task<Paging<T>> NextPage<T>(Paging<T> paging);
+
+    public Task<CursorPaging<T>> NextPage<T>(CursorPaging<T> cursorPaging);
+
+    public Task<TNext> NextPage<T, TNext>(IPaginatable<T, TNext> paginatable);
+
+    public Task<Paging<T>> PreviousPage<T>(Paging<T> paging);
+
+    public Task<TNext> PreviousPage<T, TNext>(Paging<T, TNext> paging);
   }
 }

SpotifyAPI.Web/Clients/SpotifyClient.cs

@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
-using System.Threading;
 using System.Threading.Tasks;
 using SpotifyAPI.Web.Http;
 using System.Runtime.CompilerServices;
+using System.Threading;
 
 namespace SpotifyAPI.Web
 {
@@ -29,14 +29,7 @@ namespace SpotifyAPI.Web
 #pragma warning restore CA2208
       }
 
-      _apiConnector = new APIConnector(
-        config.BaseAddress,
-        config.Authenticator,
-        config.JSONSerializer,
-        config.HTTPClient,
-        config.RetryHandler,
-        config.HTTPLogger
-      );
+      _apiConnector = config.BuildAPIConnector();
       _apiConnector.ResponseReceived += (sender, response) =>
       {
         LastResponse = response;
@@ -124,6 +117,79 @@ namespace SpotifyAPI.Web
       return (paginator ?? DefaultPaginator).PaginateAll(firstPage, mapper, _apiConnector);
     }
 
+    private Task<T> FetchPage<T>(string? nextUrl)
+    {
+      if (nextUrl == null)
+      {
+        throw new APIPagingException("The paging object has no next page");
+      }
+
+      return _apiConnector.Get<T>(new Uri(nextUrl, UriKind.Absolute));
+    }
+
+    /// <summary>
+    /// Fetches the next page of the paging object
+    /// </summary>
+    /// <param name="paging">A paging object which has a next page</param>
+    /// <typeparam name="T"></typeparam>
+    /// <returns></returns>
+    public Task<Paging<T>> NextPage<T>(Paging<T> paging)
+    {
+      Ensure.ArgumentNotNull(paging, nameof(paging));
+      return FetchPage<Paging<T>>(paging.Next);
+    }
+
+    /// <summary>
+    /// Fetches the next page of the cursor paging object
+    /// </summary>
+    /// <param name="cursorPaging">A cursor paging object which has a next page</param>
+    /// <typeparam name="T"></typeparam>
+    /// <returns></returns>
+    public Task<CursorPaging<T>> NextPage<T>(CursorPaging<T> cursorPaging)
+    {
+      Ensure.ArgumentNotNull(cursorPaging, nameof(cursorPaging));
+      return FetchPage<CursorPaging<T>>(cursorPaging.Next);
+    }
+
+    /// <summary>
+    /// Fetches the next page of the complex IPaginatable object.
+    /// </summary>
+    /// <param name="paginatable">A complex IPaginatable object with a next page</param>
+    /// <typeparam name="T"></typeparam>
+    /// <typeparam name="TNext">The type of the next page</typeparam>
+    /// <returns></returns>
+    public Task<TNext> NextPage<T, TNext>(IPaginatable<T, TNext> paginatable)
+    {
+      Ensure.ArgumentNotNull(paginatable, nameof(paginatable));
+      return FetchPage<TNext>(paginatable.Next);
+    }
+
+    /// <summary>
+    /// Fetches the previous page of the paging object.
+    /// </summary>
+    /// <param name="paging">A paging object with a previous page</param>
+    /// <typeparam name="T"></typeparam>
+    /// <returns></returns>
+    public Task<Paging<T>> PreviousPage<T>(Paging<T> paging)
+    {
+      Ensure.ArgumentNotNull(paging, nameof(paging));
+      return FetchPage<Paging<T>>(paging.Previous);
+    }
+
+
+    /// <summary>
+    /// Fetches the previous page of the complex paging object.
+    /// </summary>
+    /// <param name="paging">A complex paging object with a previous page</param>
+    /// <typeparam name="T"></typeparam>
+    /// <typeparam name="TNext">The type of the next page</typeparam>
+    /// <returns></returns>
+    public Task<TNext> PreviousPage<T, TNext>(Paging<T, TNext> paging)
+    {
+      Ensure.ArgumentNotNull(paging, nameof(paging));
+      return FetchPage<TNext>(paging.Previous);
+    }
+
 #if NETSTANDARD2_1
 
     /// <summary>

SpotifyAPI.Web/Clients/SpotifyClientConfig.cs

@@ -13,6 +13,7 @@ namespace SpotifyAPI.Web
     public IHTTPLogger? HTTPLogger { get; private set; }
     public IRetryHandler? RetryHandler { get; private set; }
     public IPaginator DefaultPaginator { get; private set; }
+    public IAPIConnector? APIConnector { get; private set; }
 
     /// <summary>
     ///   This config spefies the internal parts of the SpotifyClient.
@@ -24,6 +25,7 @@ namespace SpotifyAPI.Web
     /// <param name="retryHandler"></param>
     /// <param name="httpLogger"></param>
     /// <param name="defaultPaginator"></param>
+    /// <param name="apiConnector"></param>
     public SpotifyClientConfig(
       Uri baseAddress,
       IAuthenticator? authenticator,
@@ -31,7 +33,8 @@ namespace SpotifyAPI.Web
       IHTTPClient httpClient,
       IRetryHandler? retryHandler,
       IHTTPLogger? httpLogger,
-      IPaginator defaultPaginator
+      IPaginator defaultPaginator,
+      IAPIConnector? apiConnector = null
     )
     {
       BaseAddress = baseAddress;
@@ -41,6 +44,7 @@ namespace SpotifyAPI.Web
       RetryHandler = retryHandler;
       HTTPLogger = httpLogger;
       DefaultPaginator = defaultPaginator;
+      APIConnector = apiConnector;
     }
 
     public SpotifyClientConfig WithToken(string token, string tokenType = "Bearer")
@@ -145,6 +149,34 @@ namespace SpotifyAPI.Web
       );
     }
 
+    public SpotifyClientConfig WithAPIConnector(IAPIConnector apiConnector)
+    {
+      Ensure.ArgumentNotNull(apiConnector, nameof(apiConnector));
+
+      return new SpotifyClientConfig(
+        BaseAddress,
+        Authenticator,
+        JSONSerializer,
+        HTTPClient,
+        RetryHandler,
+        HTTPLogger,
+        DefaultPaginator,
+        apiConnector
+      );
+    }
+
+    public IAPIConnector BuildAPIConnector()
+    {
+      return APIConnector ?? new APIConnector(
+        BaseAddress,
+        Authenticator,
+        JSONSerializer,
+        HTTPClient,
+        RetryHandler,
+        HTTPLogger
+      );
+    }
+
     public static SpotifyClientConfig CreateDefault(string token, string tokenType = "Bearer")
     {
       return CreateDefault().WithAuthenticator(new TokenAuthenticator(token, tokenType));

SpotifyAPI.Web/Exceptions/APIPagingException.cs

@@ -0,0 +1,31 @@
+using System.Globalization;
+using System.Runtime.Serialization;
+using System;
+using SpotifyAPI.Web.Http;
+
+namespace SpotifyAPI.Web
+{
+  [Serializable]
+  public class APIPagingException : APIException
+  {
+    public TimeSpan RetryAfter { get; }
+
+    public APIPagingException(IResponse response) : base(response)
+    {
+      Ensure.ArgumentNotNull(response, nameof(response));
+
+      if (response.Headers.TryGetValue("Retry-After", out string? retryAfter))
+      {
+        RetryAfter = TimeSpan.FromSeconds(int.Parse(retryAfter, CultureInfo.InvariantCulture));
+      }
+    }
+
+    public APIPagingException() { }
+
+    public APIPagingException(string message) : base(message) { }
+
+    public APIPagingException(string message, Exception innerException) : base(message, innerException) { }
+
+    protected APIPagingException(SerializationInfo info, StreamingContext context) : base(info, context) { }
+  }
+}