feat: add ResolveReferenceMetadata utility function (#15663)

Add `ResolveReferenceMetadata` to parse `include_metadata` /
`metadata_fields` from request and config payloads.

### Changes
- **New**: `internal/common/reference_metadata.go` — pure function, zero
dependencies
- **New**: `internal/common/reference_metadata_test.go` — 8 test cases

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

internal/common/reference_metadata.go

@@ -0,0 +1,64 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package common
+
+// ResolveReferenceMetadata resolves metadata include/fields from request and
+// optional config. Request values take precedence over config values.
+// Supports legacy request keys: include_metadata / metadata_fields.
+// Python equivalent: api/utils/reference_metadata_utils.py::resolve_reference_metadata_preferences()
+func ResolveReferenceMetadata(requestPayload, configPayload map[string]interface{}) (bool, []string) {
+	resolved := make(map[string]interface{})
+
+	// Config reference_metadata
+	if configPayload != nil {
+		if cfg, ok := configPayload["reference_metadata"].(map[string]interface{}); ok {
+			for k, v := range cfg {
+				resolved[k] = v
+			}
+		}
+	}
+
+	// Request reference_metadata (overrides config)
+	if requestPayload != nil {
+		if req, ok := requestPayload["reference_metadata"].(map[string]interface{}); ok {
+			for k, v := range req {
+				resolved[k] = v
+			}
+		}
+		// Legacy keys
+		if v, ok := requestPayload["include_metadata"]; ok {
+			resolved["include"] = v
+		}
+		if v, ok := requestPayload["metadata_fields"]; ok {
+			resolved["fields"] = v
+		}
+	}
+
+	include, _ := resolved["include"].(bool)
+
+	rawFields, ok := resolved["fields"].([]interface{})
+	if !ok {
+		return include, nil
+	}
+	var fields []string
+	for _, f := range rawFields {
+		if s, ok := f.(string); ok {
+			fields = append(fields, s)
+		}
+	}
+	return include, fields
+}

internal/common/reference_metadata_test.go

@@ -0,0 +1,142 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package common
+
+import (
+	"testing"
+)
+
+func TestResolveReferenceMetadata_NilInputs(t *testing.T) {
+	include, fields := ResolveReferenceMetadata(nil, nil)
+	if include {
+		t.Error("expected include=false")
+	}
+	if fields != nil {
+		t.Errorf("expected nil fields, got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_EmptyInputs(t *testing.T) {
+	include, fields := ResolveReferenceMetadata(map[string]interface{}{}, map[string]interface{}{})
+	if include {
+		t.Error("expected include=false")
+	}
+	if fields != nil {
+		t.Errorf("expected nil fields, got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_FromConfig(t *testing.T) {
+	config := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": true,
+			"fields":  []interface{}{"author", "date"},
+		},
+	}
+	include, fields := ResolveReferenceMetadata(nil, config)
+	if !include {
+		t.Error("expected include=true")
+	}
+	if len(fields) != 2 || fields[0] != "author" || fields[1] != "date" {
+		t.Errorf("expected [author date], got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_RequestOverridesConfig(t *testing.T) {
+	config := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": true,
+			"fields":  []interface{}{"config_field"},
+		},
+	}
+	request := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": false,
+			"fields":  []interface{}{"request_field"},
+		},
+	}
+	include, fields := ResolveReferenceMetadata(request, config)
+	if include {
+		t.Error("expected include=false (request overrides)")
+	}
+	if len(fields) != 1 || fields[0] != "request_field" {
+		t.Errorf("expected [request_field], got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_LegacyKeys(t *testing.T) {
+	request := map[string]interface{}{
+		"include_metadata": true,
+		"metadata_fields":  []interface{}{"author", "category"},
+	}
+	include, fields := ResolveReferenceMetadata(request, nil)
+	if !include {
+		t.Error("expected include=true from legacy key")
+	}
+	if len(fields) != 2 || fields[0] != "author" {
+		t.Errorf("expected [author category], got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_LegacyIncludeFalse(t *testing.T) {
+	request := map[string]interface{}{
+		"include_metadata": false,
+	}
+	include, fields := ResolveReferenceMetadata(request, nil)
+	if include {
+		t.Error("expected include=false")
+	}
+	if fields != nil {
+		t.Errorf("expected nil fields, got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_NoFields(t *testing.T) {
+	config := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": true,
+		},
+	}
+	include, fields := ResolveReferenceMetadata(nil, config)
+	if !include {
+		t.Error("expected include=true")
+	}
+	if fields != nil {
+		t.Errorf("expected nil fields, got %v", fields)
+	}
+}
+
+func TestResolveReferenceMetadata_PartialOverride(t *testing.T) {
+	config := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": true,
+			"fields":  []interface{}{"from_config"},
+		},
+	}
+	request := map[string]interface{}{
+		"reference_metadata": map[string]interface{}{
+			"include": false, // override include only, fields stays from config
+		},
+	}
+	include, fields := ResolveReferenceMetadata(request, config)
+	if include {
+		t.Error("expected include=false (request overrides)")
+	}
+	if len(fields) != 1 || fields[0] != "from_config" {
+		t.Errorf("expected [from_config], got %v", fields)
+	}
+}