feat: Add CachedApiResponse and modify GET /Tags endpoint in SDK

BuildingBlocks/src/BuildingBlocks.SDK/Endpoints/Common/EndpointClient.cs

@@ -17,6 +17,8 @@ public class EndpointClient
                                         }
                                         """;
 
+    private const string EMPTY_CACHED_RESULT = "{}";
+
     private const string EMPTY_VALUE = """
                                        {
                                            "value": {}
@@ -67,6 +69,18 @@ public async Task<ApiResponse<T>> GetUnauthenticated<T>(string url, NameValueCol
             .Execute();
     }
 
+    public async Task<CachedApiResponse<T>> GetCachedUnauthenticated<T>(string url, NameValueCollection? queryParameters = null, PaginationFilter? pagination = null, CacheControl? cacheControl = null)
+    {
+        var builder = Request<T>(HttpMethod.Get, url)
+            .WithPagination(pagination)
+            .AddQueryParameters(queryParameters);
+
+        if (cacheControl != null)
+            builder.AddExtraHeader("If-None-Match", cacheControl.ETag);
+
+        return await builder.ExecuteCached();
+    }
+
     public async Task<ApiResponse<T>> Put<T>(string url, object? requestContent = null)
     {
         return await Request<T>(HttpMethod.Put, url)
@@ -117,6 +131,28 @@ private async Task<ApiResponse<T>> Execute<T>(HttpRequestMessage request)
         return deserializedResponseContent;
     }
 
+    private async Task<CachedApiResponse<T>> ExecuteCached<T>(HttpRequestMessage request)
+    {
+        var response = await _httpClient.SendAsync(request);
+        var responseContent = await response.Content.ReadAsStreamAsync();
+        var statusCode = response.StatusCode;
+
+        if (statusCode == HttpStatusCode.NotModified || responseContent.Length == 0)
+        {
+            responseContent.Close();
+            responseContent = new MemoryStream(Encoding.UTF8.GetBytes(EMPTY_CACHED_RESULT));
+        }
+
+        var deserializedResponseContent = JsonSerializer.Deserialize<CachedApiResponse<T>>(responseContent, _jsonSerializerOptions);
+
+        deserializedResponseContent!.Status = statusCode;
+        deserializedResponseContent.RawContent = await response.Content.ReadAsStringAsync();
+        deserializedResponseContent.ContentType = response.Content.Headers.ContentType?.MediaType;
+        deserializedResponseContent.ETag = response.Headers.ETag!.Tag; //TODO: Timo (Is it safe to assume that the ETag is non-null?)
+
+        return deserializedResponseContent;
+    }
+
     private async Task<ApiResponse<T>> ExecuteOData<T>(HttpRequestMessage request)
     {
         var response = await _httpClient.SendAsync(request);
@@ -279,6 +315,11 @@ public async Task<RawApiResponse> ExecuteRaw()
             return await _client.ExecuteRaw(await CreateRequestMessage());
         }
 
+        public async Task<CachedApiResponse<T>> ExecuteCached()
+        {
+            return await _client.ExecuteCached<T>(await CreateRequestMessage());
+        }
+
         private async Task<HttpRequestMessage> CreateRequestMessage()
         {
             var request = new HttpRequestMessage(_method, EncodeParametersInUrl())

BuildingBlocks/src/BuildingBlocks.SDK/Endpoints/Common/Types/CacheControl.cs

@@ -0,0 +1,6 @@
+namespace Backbone.BuildingBlocks.SDK.Endpoints.Common.Types;
+
+public class CacheControl
+{
+    public required string ETag { get; set; }
+}

BuildingBlocks/src/BuildingBlocks.SDK/Endpoints/Common/Types/CachedApiResponse.cs

@@ -0,0 +1,8 @@
+namespace Backbone.BuildingBlocks.SDK.Endpoints.Common.Types;
+
+public class CachedApiResponse<TResult> : ApiResponse<TResult>
+{
+    public bool NotModified => Result == null;
+
+    public string ETag { get; set; } = string.Empty;
+}

Sdks/ConsumerApi.Sdk/src/Endpoints/Tags/TagsEndpoint.cs

@@ -6,8 +6,8 @@ namespace Backbone.ConsumerApi.Sdk.Endpoints.Tags;
 
 public class TagsEndpoint(EndpointClient client) : ConsumerApiEndpoint(client)
 {
-    public async Task<ApiResponse<ListTagsResponse>> ListTags()
+    public async Task<CachedApiResponse<ListTagsResponse>> ListTags(CacheControl? cacheControl = null)
     {
-        return await _client.GetUnauthenticated<ListTagsResponse>($"api/{API_VERSION}/Tags");
+        return await _client.GetCachedUnauthenticated<ListTagsResponse>($"api/{API_VERSION}/Tags", null, null, cacheControl);
     }
 }