feat: update image generation translator constructor for tracing support

- Update NewImageGenerationOpenAIToOpenAITranslator constructor to accept tracing.ImageGenerationSpan parameter
- Change modelNameOverride parameter type from string to internalapi.ModelNameOverride for type consistency
- Add span field to openAIToOpenAIImageGenerationTranslator struct for tracing support
- Update all test calls to pass nil span parameter to maintain compatibility

Signed-off-by: Hrushikesh Patil <[email protected]>

Author: nutanix-Hrushikesh

internal/extproc/translator/imagegeneration_openai_openai.go

@@ -10,25 +10,29 @@ import (
 	"fmt"
 	"io"
 	"path"
+	"strconv"
 
 	corev3 "github.com/envoyproxy/go-control-plane/envoy/config/core/v3"
 	extprocv3 "github.com/envoyproxy/go-control-plane/envoy/service/ext_proc/v3"
 	"github.com/tidwall/sjson"
 
+	"github.com/envoyproxy/ai-gateway/internal/internalapi"
 	tracing "github.com/envoyproxy/ai-gateway/internal/tracing/api"
 	openaisdk "github.com/openai/openai-go/v2"
 )
 
 // NewImageGenerationOpenAIToOpenAITranslator implements [Factory] for OpenAI to OpenAI image generation translation.
-func NewImageGenerationOpenAIToOpenAITranslator(apiVersion string, modelNameOverride string) ImageGenerationTranslator {
-	return &openAIToOpenAIImageGenerationTranslator{modelNameOverride: modelNameOverride, path: path.Join("/", apiVersion, "images/generations")}
+func NewImageGenerationOpenAIToOpenAITranslator(apiVersion string, modelNameOverride internalapi.ModelNameOverride, span tracing.ImageGenerationSpan) ImageGenerationTranslator {
+	return &openAIToOpenAIImageGenerationTranslator{modelNameOverride: modelNameOverride, path: path.Join("/", apiVersion, "images/generations"), span: span}
 }
 
 // openAIToOpenAIImageGenerationTranslator implements [ImageGenerationTranslator] for /v1/images/generations.
 type openAIToOpenAIImageGenerationTranslator struct {
-	modelNameOverride string
+	modelNameOverride internalapi.ModelNameOverride
 	// The path of the images generations endpoint to be used for the request. It is prefixed with the OpenAI path prefix.
 	path string
+	// span is the tracing span for this request, inherited from the router filter.
+	span tracing.ImageGenerationSpan
 }
 
 // RequestBody implements [ImageGenerationTranslator.RequestBody].
@@ -62,8 +66,10 @@ func (o *openAIToOpenAIImageGenerationTranslator) RequestBody(original []byte, r
 		bodyMutation = &extprocv3.BodyMutation{
 			Mutation: &extprocv3.BodyMutation_Body{Body: newBody},
 		}
-		// Note: content-length header is set via dynamic metadata in the processor
-		// to avoid conflicts with Envoy's REPLACE_AND_CONTINUE processing mode
+		headerMutation.SetHeaders = append(headerMutation.SetHeaders, &corev3.HeaderValueOption{Header: &corev3.HeaderValue{
+			Key:      "content-length",
+			RawValue: []byte(strconv.Itoa(len(newBody))),
+		}})
 	}
 	return
 }

internal/extproc/translator/imagegeneration_openai_openai_test.go

@@ -16,7 +16,7 @@ import (
 )
 
 func TestOpenAIToOpenAIImageTranslator_RequestBody_ModelOverrideAndPath(t *testing.T) {
-	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "gpt-image-1")
+	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "gpt-image-1", nil)
 	req := &openaisdk.ImageGenerateParams{Model: openaisdk.ImageModelDallE3, Prompt: "a cat"}
 	original, _ := json.Marshal(req)
 
@@ -36,7 +36,7 @@ func TestOpenAIToOpenAIImageTranslator_RequestBody_ModelOverrideAndPath(t *testi
 }
 
 func TestOpenAIToOpenAIImageTranslator_RequestBody_ForceMutation(t *testing.T) {
-	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "")
+	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "", nil)
 	req := &openaisdk.ImageGenerateParams{Model: openaisdk.ImageModelDallE2, Prompt: "a cat"}
 	original, _ := json.Marshal(req)
 
@@ -57,7 +57,7 @@ func TestOpenAIToOpenAIImageTranslator_RequestBody_ForceMutation(t *testing.T) {
 }
 
 func TestOpenAIToOpenAIImageTranslator_ResponseError_NonJSON(t *testing.T) {
-	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "")
+	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "", nil)
 	headers := map[string]string{contentTypeHeaderName: "text/plain", statusHeaderName: "503"}
 	hm, bm, err := tr.ResponseError(headers, bytes.NewReader([]byte("backend error")))
 	require.NoError(t, err)
@@ -71,7 +71,7 @@ func TestOpenAIToOpenAIImageTranslator_ResponseError_NonJSON(t *testing.T) {
 }
 
 func TestOpenAIToOpenAIImageTranslator_ResponseBody_OK(t *testing.T) {
-	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "")
+	tr := NewImageGenerationOpenAIToOpenAITranslator("v1", "", nil)
 	resp := &openaisdk.ImagesResponse{Size: openaisdk.ImagesResponseSize1024x1024}
 	buf, _ := json.Marshal(resp)
 	hm, bm, usage, metadata, err := tr.ResponseBody(map[string]string{}, bytes.NewReader(buf), true)