OPIK-610 removed unnecessary interface

apps/opik-backend/src/main/java/com/comet/opik/domain/ChatCompletionService.java

@@ -1,7 +1,7 @@
 package com.comet.opik.domain;
 
-import com.comet.opik.domain.llmproviders.DefaultLlmProviderStreamHandler;
 import com.comet.opik.domain.llmproviders.LlmProviderFactory;
+import com.comet.opik.domain.llmproviders.LlmProviderStreamHandler;
 import dev.ai4j.openai4j.chat.ChatCompletionRequest;
 import dev.ai4j.openai4j.chat.ChatCompletionResponse;
 import jakarta.inject.Inject;
@@ -14,13 +14,12 @@
 @Slf4j
 public class ChatCompletionService {
     private final LlmProviderFactory llmProviderFactory;
-    private final DefaultLlmProviderStreamHandler defaultStreamHandler;
+    private final LlmProviderStreamHandler streamHandler;
 
     @Inject
-    public ChatCompletionService(LlmProviderFactory llmProviderFactory,
-            DefaultLlmProviderStreamHandler defaultStreamHandler) {
+    public ChatCompletionService(LlmProviderFactory llmProviderFactory, LlmProviderStreamHandler streamHandler) {
         this.llmProviderFactory = llmProviderFactory;
-        this.defaultStreamHandler = defaultStreamHandler;
+        this.streamHandler = streamHandler;
     }
 
     public ChatCompletionResponse create(@NonNull ChatCompletionRequest request, @NonNull String workspaceId) {
@@ -35,7 +34,7 @@ public ChunkedOutput<String> createAndStreamResponse(
             @NonNull ChatCompletionRequest request, @NonNull String workspaceId) {
         log.info("Creating and streaming chat completions, workspaceId '{}', model '{}'", workspaceId, request.model());
         var llmProviderClient = llmProviderFactory.getService(workspaceId, request.model());
-        var chunkedOutput = llmProviderClient.generateStream(request, workspaceId, defaultStreamHandler);
+        var chunkedOutput = llmProviderClient.generateStream(request, workspaceId, streamHandler);
         log.info("Created and streaming chat completions, workspaceId '{}', model '{}'", workspaceId, request.model());
         return chunkedOutput;
     }

apps/opik-backend/src/main/java/com/comet/opik/domain/llmproviders/LlmProviderStreamHandler.java

@@ -1,9 +1,49 @@
 package com.comet.opik.domain.llmproviders;
 
+import com.comet.opik.utils.JsonUtils;
+import dev.ai4j.openai4j.OpenAiHttpException;
+import io.dropwizard.jersey.errors.ErrorMessage;
+import lombok.extern.slf4j.Slf4j;
 import org.glassfish.jersey.server.ChunkedOutput;
 
-public interface LlmProviderStreamHandler {
-    void handleMessage(Object item, ChunkedOutput<String> chunkedOutput);
-    void handleClose(ChunkedOutput<String> chunkedOutput);
-    void handleError(Throwable throwable, ChunkedOutput<String> chunkedOutput);
+import java.io.IOException;
+import java.io.UncheckedIOException;
+
+@Slf4j
+public class LlmProviderStreamHandler {
+    private static final String UNEXPECTED_ERROR_CALLING_LLM_PROVIDER = "Unexpected error calling LLM provider";
+
+    public void handleMessage(Object item, ChunkedOutput<String> chunkedOutput) {
+        if (chunkedOutput.isClosed()) {
+            log.warn("Output stream is already closed");
+            return;
+        }
+        try {
+            chunkedOutput.write(JsonUtils.writeValueAsString(item));
+        } catch (IOException ioException) {
+            throw new UncheckedIOException(ioException);
+        }
+    }
+
+    public void handleClose(ChunkedOutput<String> chunkedOutput) {
+        try {
+            chunkedOutput.close();
+        } catch (IOException ioException) {
+            log.error("Failed to close output stream", ioException);
+        }
+    }
+
+    public void handleError(Throwable throwable, ChunkedOutput<String> chunkedOutput) {
+        log.error(UNEXPECTED_ERROR_CALLING_LLM_PROVIDER, throwable);
+        var errorMessage = new ErrorMessage(UNEXPECTED_ERROR_CALLING_LLM_PROVIDER);
+        if (throwable instanceof OpenAiHttpException openAiHttpException) {
+            errorMessage = new ErrorMessage(openAiHttpException.code(), openAiHttpException.getMessage());
+        }
+        try {
+            handleMessage(errorMessage, chunkedOutput);
+        } catch (UncheckedIOException uncheckedIOException) {
+            log.error("Failed to stream error message to client", uncheckedIOException);
+        }
+        handleClose(chunkedOutput);
+    }
 }