feat: implement GetModelAsync method

src/AnthropicClient/AnthropicApiClient.cs

@@ -49,6 +49,13 @@ public interface IAnthropicApiClient
   /// <returns>An asynchronous enumerable that yields the response as an <see cref="AnthropicResult{T}"/> where T is <see cref="Page{T}"/> where T is <see cref="AnthropicModel"/>.</returns>
   /// 
   IAsyncEnumerable<AnthropicResult<Page<AnthropicModel>>> ListAllModelsAsync(int limit = 20);
+
+  /// <summary>
+  /// Gets a model by its ID asynchronously.
+  /// </summary>
+  /// <param name="modelId">The ID of the model to get.</param>
+  /// <returns>A task that represents the asynchronous operation. The task result contains the response as an <see cref="AnthropicResult{T}"/> where T is <see cref="AnthropicModel"/>.</returns>
+  Task<AnthropicResult<AnthropicModel>> GetModelAsync(string modelId);
 }
 
 /// <inheritdoc cref="IAnthropicApiClient"/>
@@ -352,6 +359,24 @@ public class AnthropicApiClient : IAnthropicApiClient
     } while (hasMore);
   }
 
+  /// <inheritdoc/>
+  public async Task<AnthropicResult<AnthropicModel>> GetModelAsync(string modelId)
+  {
+    var endpoint = $"{ModelsEndpoint}/{modelId}";
+    var response = await SendRequestAsync(endpoint);
+    var anthropicHeaders = new AnthropicHeaders(response.Headers);
+    var responseContent = await response.Content.ReadAsStringAsync();
+
+    if (response.IsSuccessStatusCode is false)
+    {
+      var error = Deserialize<AnthropicError>(responseContent) ?? new AnthropicError();
+      return AnthropicResult<AnthropicModel>.Failure(error, anthropicHeaders);
+    }
+
+    var model = Deserialize<AnthropicModel>(responseContent) ?? new AnthropicModel();
+    return AnthropicResult<AnthropicModel>.Success(model, anthropicHeaders);
+  }
+
   private ToolCall? GetToolCall(MessageResponse response, List<Tool> tools)
   {
     var toolUse = response.Content.OfType<ToolUseContent>().FirstOrDefault();

tests/AnthropicClient.Tests/EndToEnd/AnthropicApiClientTests.cs

@@ -331,4 +331,14 @@ public class ClientTests(ConfigurationFixture configFixture) : EndToEndTest(conf
 
     responses.Should().HaveCountGreaterThan(0);
   }
+
+  [Fact]
+  public async Task GetModelAsync_WhenCalled_ItShouldReturnResponse()
+  {
+    var result = await _client.GetModelAsync(AnthropicModels.Claude3Haiku);
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<AnthropicModel>();
+    result.Value.Id.Should().Be(AnthropicModels.Claude3Haiku);
+  }
 }

tests/AnthropicClient.Tests/Integration/AnthropicApiClientTests.cs

@@ -479,7 +479,7 @@ public class AnthropicApiClientTests : IntegrationTest
   }
 
   [Fact]
-  public async Task CountMessageTokensAsync_WhenCalledRequestFailsAndCanNotSerializeError_ItShouldReturnUnknownError()
+  public async Task CountMessageTokensAsync_WhenCalledRequestFailsAndCanNotDeserializeError_ItShouldReturnUnknownError()
   {
     _mockHttpMessageHandler
       .WhenCountMessageTokensRequest()
@@ -647,7 +647,7 @@ public class AnthropicApiClientTests : IntegrationTest
   }
 
   [Fact]
-  public async Task ListModelsAsync_WhenCalledRequestFailsAndCanNotSerializeError_ItShouldReturnUnknownError()
+  public async Task ListModelsAsync_WhenCalledRequestFailsAndCanNotDeserializeError_ItShouldReturnUnknownError()
   {
     _mockHttpMessageHandler
       .WhenListModelsRequest()
@@ -794,7 +794,7 @@ public class AnthropicApiClientTests : IntegrationTest
   }
 
   [Fact]
-  public async Task ListAllModelsAsync_WhenCalledRequestFailsAndCanNotSerializeError_ItShouldReturnUnknownError()
+  public async Task ListAllModelsAsync_WhenCalledRequestFailsAndCanNotDeserializeError_ItShouldReturnUnknownError()
   {
     _mockHttpMessageHandler
       .WhenListModelsRequest()
@@ -886,4 +886,97 @@ public class AnthropicApiClientTests : IntegrationTest
 
     count.Should().Be(2);
   }
+
+  [Fact]
+  public async Task GetModelAsync_WhenCalled_ItShouldReturnModel()
+  {
+    var modelId = "claude-3-5-sonnet-20241022";
+
+    _mockHttpMessageHandler
+      .WhenGetModelRequest(modelId)
+      .Respond(
+        HttpStatusCode.OK,
+        "application/json",
+        @"{
+            ""type"": ""model"",
+            ""id"": ""claude-3-5-sonnet-20241022"",
+            ""display_name"": ""Claude 3.5 Sonnet (New)"",
+            ""created_at"": ""2024-10-22T00:00:00Z""
+          }"
+      );
+
+    var result = await Client.GetModelAsync(modelId);
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<AnthropicModel>();
+    result.Value.Type.Should().Be("model");
+    result.Value.Id.Should().Be("claude-3-5-sonnet-20241022");
+    result.Value.DisplayName.Should().Be("Claude 3.5 Sonnet (New)");
+    result.Value.CreatedAt.Should().Be(DateTimeOffset.Parse("2024-10-22T00:00:00Z"));
+  }
+
+  [Fact]
+  public async Task GetModelAsync_WhenCalledAndErrorReturned_ItShouldHandleError()
+  {
+    var modelId = "claude-3-5-sonnet-20241022";
+
+    _mockHttpMessageHandler
+      .WhenGetModelRequest(modelId)
+      .Respond(
+        HttpStatusCode.BadRequest,
+        "application/json",
+        @"{
+            ""type"": ""error"",
+            ""error"": {
+              ""type"": ""invalid_request_error"",
+              ""message"": ""messages: roles must alternate between user and assistant, but found multiple user roles in a row""
+            }
+          }"
+      );
+
+    var result = await Client.GetModelAsync(modelId);
+
+    result.IsSuccess.Should().BeFalse();
+    result.Error.Should().BeOfType<AnthropicError>();
+    result.Error.Error.Should().BeOfType<InvalidRequestError>();
+  }
+
+  [Fact]
+  public async Task GetModelAsync_WhenCalledRequestFailsAndCanNotDeserializeError_ItShouldReturnUnknownError()
+  {
+    var modelId = "claude-3-5-sonnet-20241022";
+
+    _mockHttpMessageHandler
+      .WhenGetModelRequest(modelId)
+      .Respond(
+        HttpStatusCode.BadRequest,
+        "application/json",
+        @"{}"
+      );
+
+    var result = await Client.GetModelAsync(modelId);
+
+    result.IsSuccess.Should().BeFalse();
+    result.Error.Should().BeOfType<AnthropicError>();
+    result.Error.Error.Should().BeOfType<ApiError>();
+  }
+
+  [Fact]
+  public async Task GetModelAsync_WhenCalledAndCanNotDeserializeModel_ItShouldReturnEmptyModel()
+  {
+    var modelId = "claude-3-5-sonnet-20241022";
+
+    _mockHttpMessageHandler
+      .WhenGetModelRequest(modelId)
+      .Respond(
+        HttpStatusCode.OK,
+        "application/json",
+        @"{}"
+      );
+
+    var result = await Client.GetModelAsync(modelId);
+
+    result.IsSuccess.Should().BeFalse();
+    result.Error.Should().BeOfType<AnthropicModel>();
+  }
 }

tests/AnthropicClient.Tests/Integration/IntegrationTest.cs

@@ -58,4 +58,10 @@ public static class MockHttpMessageHandlerExtensions
     return mockHttpMessageHandler
       .SetupBaseRequest(HttpMethod.Get, ModelsEndpoint);
   }
+
+  public static MockedRequest WhenGetModelRequest(this MockHttpMessageHandler mockHttpMessageHandler, string modelId)
+  {
+    return mockHttpMessageHandler
+      .SetupBaseRequest(HttpMethod.Get, $"{ModelsEndpoint}/{modelId}");
+  }
 }