Refine execution target mapping helpers and coverage across usecase, HTTP, and LLM

internal/adapter/http/handler.go

@@ -63,18 +63,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	var model *domain.ExecutionTarget
 	if req.Model != nil {
-		model = &domain.ExecutionTarget{
+		model = executionTargetFromModelOverrideDTO(req.Model)
-			Endpoint:        req.Model.Endpoint,
-			Model:           req.Model.Model,
-			Temperature:     req.Model.Temperature,
-			MaxTokens:       req.Model.MaxTokens,
-			TopP:            req.Model.TopP,
-			TimeoutSeconds:  req.Model.TimeoutSeconds,
-			ServiceTier:     req.Model.ServiceTier,
-			ReasoningEffort: req.Model.ReasoningEffort,
-			APIKeyEnv:       req.Model.APIKeyEnv,
-			ExtraParams:     req.Model.ExtraParams,
-		}
 	}
 
 	res, err := h.runner.Run(r.Context(), domain.RunRequest{
@@ -110,19 +99,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			SelectedProfileID:  res.SelectedProfileID,
 			ModelName:          res.ModelName,
 			Endpoint:           res.Endpoint,
-			ModelParams: modelParamsDTO{
+			ModelParams:        modelParamsDTOFromExecutionTarget(res.EffectiveModelParams),
-				Endpoint:        res.EffectiveModelParams.Endpoint,
+			InputHashes:        res.InputHashes,
-				Model:           res.EffectiveModelParams.Model,
-				Temperature:     res.EffectiveModelParams.Temperature,
-				MaxTokens:       res.EffectiveModelParams.MaxTokens,
-				TopP:            res.EffectiveModelParams.TopP,
-				TimeoutSeconds:  res.EffectiveModelParams.TimeoutSeconds,
-				ServiceTier:     res.EffectiveModelParams.ServiceTier,
-				ReasoningEffort: res.EffectiveModelParams.ReasoningEffort,
-				APIKeyEnv:       res.EffectiveModelParams.APIKeyEnv,
-				ExtraParams:     res.EffectiveModelParams.ExtraParams,
-			},
-			InputHashes: res.InputHashes,
 			Usage: tokenUsageDTO{
 				PromptTokens:     res.Usage.PromptTokens,
 				CompletionTokens: res.Usage.CompletionTokens,
@@ -143,6 +121,39 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, resp)
 }
 
+func executionTargetFromModelOverrideDTO(dto *modelOverrideRequestDTO) *domain.ExecutionTarget {
+	if dto == nil {
+		return nil
+	}
+	return &domain.ExecutionTarget{
+		Endpoint:        dto.Endpoint,
+		Model:           dto.Model,
+		Temperature:     dto.Temperature,
+		MaxTokens:       dto.MaxTokens,
+		TopP:            dto.TopP,
+		TimeoutSeconds:  dto.TimeoutSeconds,
+		ServiceTier:     dto.ServiceTier,
+		ReasoningEffort: dto.ReasoningEffort,
+		APIKeyEnv:       dto.APIKeyEnv,
+		ExtraParams:     dto.ExtraParams,
+	}
+}
+
+func modelParamsDTOFromExecutionTarget(target domain.ExecutionTarget) modelParamsDTO {
+	return modelParamsDTO{
+		Endpoint:        target.Endpoint,
+		Model:           target.Model,
+		Temperature:     target.Temperature,
+		MaxTokens:       target.MaxTokens,
+		TopP:            target.TopP,
+		TimeoutSeconds:  target.TimeoutSeconds,
+		ServiceTier:     target.ServiceTier,
+		ReasoningEffort: target.ReasoningEffort,
+		APIKeyEnv:       target.APIKeyEnv,
+		ExtraParams:     target.ExtraParams,
+	}
+}
+
 func mapValidation(v domain.ValidationResult) validationDTO {
 	return validationDTO{
 		Status:         string(v.Status),

internal/adapter/http/handler_test.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"reflect"
 	"strings"
 	"testing"
 	"time"
@@ -173,6 +174,136 @@ func TestHandlerPostRunsSuccessUsingPromptDefaultProfile(t *testing.T) {
 	}
 }
 
+func TestHandlerModelOverrideMapsAllSupportedExecutionFields(t *testing.T) {
+	r := &fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte("ok")},
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1"},
+	}}
+	h := NewHandler(r)
+
+	reqBody := `{
+		"prompt_id": "prompt-1",
+		"inputs": {"transcript": {"type": "file", "uri": "./t.md"}},
+		"model": {
+			"endpoint": "http://override/v1",
+			"model": "override-model",
+			"temperature": 0.6,
+			"max_tokens": 250,
+			"top_p": 0.85,
+			"timeout_seconds": 33,
+			"service_tier": "flex",
+			"reasoning_effort": "medium",
+			"api_key_env": "SCRIPTORIUM_API_KEY",
+			"extra_params": {"provider_option":"on"}
+		}
+	}`
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(reqBody))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+	if r.last.Execution == nil {
+		t.Fatalf("expected execution override in run request")
+	}
+	got := r.last.Execution
+	if got.Endpoint != "http://override/v1" ||
+		got.Model != "override-model" ||
+		got.Temperature != 0.6 ||
+		got.MaxTokens != 250 ||
+		got.TopP != 0.85 ||
+		got.TimeoutSeconds != 33 ||
+		got.ServiceTier != "flex" ||
+		got.ReasoningEffort != "medium" ||
+		got.APIKeyEnv != "SCRIPTORIUM_API_KEY" {
+		t.Fatalf("unexpected mapped execution target: %+v", got)
+	}
+	if !reflect.DeepEqual(got.ExtraParams, map[string]string{"provider_option": "on"}) {
+		t.Fatalf("unexpected mapped extra_params: %#v", got.ExtraParams)
+	}
+}
+
+func TestHandlerResponseMetadataModelParamsIncludesAllSupportedFields(t *testing.T) {
+	r := &fakeRunner{result: &domain.RunResult{
+		Artifact: domain.Artifact{
+			Name:        "output",
+			ContentType: "text/plain",
+			Body:        []byte("ok"),
+			Size:        2,
+			Hash:        "abc",
+		},
+		Validation: domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{
+			Endpoint:        "http://llm/v1",
+			Model:           "gpt-test",
+			Temperature:     0.4,
+			MaxTokens:       321,
+			TopP:            0.7,
+			TimeoutSeconds:  45,
+			ServiceTier:     "priority",
+			ReasoningEffort: "high",
+			APIKeyEnv:       "SCRIPTORIUM_API_KEY",
+			ExtraParams: map[string]string{
+				"provider_option": "on",
+			},
+		},
+	}}
+	h := NewHandler(r)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{"prompt_id":"p","inputs":{"x":{"type":"file","uri":"a"}}}`))
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+
+	var resp map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("invalid JSON response: %v", err)
+	}
+	metadata := resp["metadata"].(map[string]any)
+	params := metadata["model_params"].(map[string]any)
+
+	if params["endpoint"] != "http://llm/v1" {
+		t.Fatalf("unexpected endpoint: %#v", params["endpoint"])
+	}
+	if params["model"] != "gpt-test" {
+		t.Fatalf("unexpected model: %#v", params["model"])
+	}
+	if params["temperature"] != 0.4 {
+		t.Fatalf("unexpected temperature: %#v", params["temperature"])
+	}
+	if params["max_tokens"] != float64(321) {
+		t.Fatalf("unexpected max_tokens: %#v", params["max_tokens"])
+	}
+	if params["top_p"] != 0.7 {
+		t.Fatalf("unexpected top_p: %#v", params["top_p"])
+	}
+	if params["timeout_seconds"] != float64(45) {
+		t.Fatalf("unexpected timeout_seconds: %#v", params["timeout_seconds"])
+	}
+	if params["service_tier"] != "priority" {
+		t.Fatalf("unexpected service_tier: %#v", params["service_tier"])
+	}
+	if params["reasoning_effort"] != "high" {
+		t.Fatalf("unexpected reasoning_effort: %#v", params["reasoning_effort"])
+	}
+	if params["api_key_env"] != "SCRIPTORIUM_API_KEY" {
+		t.Fatalf("unexpected api_key_env: %#v", params["api_key_env"])
+	}
+	extraParams, ok := params["extra_params"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected extra_params object, got %#v", params["extra_params"])
+	}
+	if extraParams["provider_option"] != "on" {
+		t.Fatalf("unexpected extra_params.provider_option: %#v", extraParams["provider_option"])
+	}
+}
+
 func TestHandlerInvalidJSON(t *testing.T) {
 	h := NewHandler(&fakeRunner{})
 	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString("{"))

internal/llm/openai_compatible_client.go

@@ -75,14 +75,6 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 		return nil, fmt.Errorf("%w: timeout_seconds must be greater than or equal to 0", ErrInvalidRequest)
 	}
 
-	model := strings.TrimSpace(req.Target.Model)
-	if model == "" {
-		model = strings.TrimSpace(c.defaultModel)
-	}
-	if model == "" {
-		return nil, fmt.Errorf("%w: model is required", ErrInvalidRequest)
-	}
-
 	endpoint := strings.TrimSpace(req.Target.Endpoint)
 	if endpoint == "" {
 		endpoint = c.baseURL
@@ -92,36 +84,9 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 	}
 	endpoint = strings.TrimRight(endpoint, "/") + defaults.OpenAIChatCompletionsPath
 
-	wireReq := openAIChatRequest{
+	wireReq, err := openAIChatRequestFromGenerateRequest(req, c.defaultModel)
-		Model: model,
+	if err != nil {
-	}
+		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
-
-	wireReq.Messages = make([]openAIChatMessage, 0, len(req.Prompt.Messages))
-	for _, msg := range req.Prompt.Messages {
-		wireReq.Messages = append(wireReq.Messages, openAIChatMessage{
-			Role:    msg.Role,
-			Content: msg.Content,
-		})
-	}
-
-	if req.Target.Temperature != 0 {
-		wireReq.Temperature = &req.Target.Temperature
-	}
-	if req.Target.MaxTokens != 0 {
-		wireReq.MaxTokens = &req.Target.MaxTokens
-	}
-	if req.Target.TopP != 0 {
-		wireReq.TopP = &req.Target.TopP
-	}
-	if strings.TrimSpace(req.Target.ServiceTier) != "" {
-		wireReq.ServiceTier = req.Target.ServiceTier
-	}
-	if req.StructuredOutput != nil {
-		responseFormat, err := toOpenAIResponseFormat(req.StructuredOutput)
-		if err != nil {
-			return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
-		}
-		wireReq.ResponseFormat = responseFormat
 	}
 
 	payload, err := json.Marshal(wireReq)
@@ -190,6 +155,50 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 	}, nil
 }
 
+func openAIChatRequestFromGenerateRequest(req domain.GenerateRequest, defaultModel string) (openAIChatRequest, error) {
+	model := strings.TrimSpace(req.Target.Model)
+	if model == "" {
+		model = strings.TrimSpace(defaultModel)
+	}
+	if model == "" {
+		return openAIChatRequest{}, errors.New("model is required")
+	}
+
+	wireReq := openAIChatRequest{
+		Model: model,
+	}
+
+	wireReq.Messages = make([]openAIChatMessage, 0, len(req.Prompt.Messages))
+	for _, msg := range req.Prompt.Messages {
+		wireReq.Messages = append(wireReq.Messages, openAIChatMessage{
+			Role:    msg.Role,
+			Content: msg.Content,
+		})
+	}
+
+	if req.Target.Temperature != 0 {
+		wireReq.Temperature = &req.Target.Temperature
+	}
+	if req.Target.MaxTokens != 0 {
+		wireReq.MaxTokens = &req.Target.MaxTokens
+	}
+	if req.Target.TopP != 0 {
+		wireReq.TopP = &req.Target.TopP
+	}
+	if strings.TrimSpace(req.Target.ServiceTier) != "" {
+		wireReq.ServiceTier = req.Target.ServiceTier
+	}
+	if req.StructuredOutput != nil {
+		responseFormat, err := toOpenAIResponseFormat(req.StructuredOutput)
+		if err != nil {
+			return openAIChatRequest{}, err
+		}
+		wireReq.ResponseFormat = responseFormat
+	}
+
+	return wireReq, nil
+}
+
 type openAIChatRequest struct {
 	Model          string                `json:"model"`
 	Messages       []openAIChatMessage   `json:"messages"`

internal/llm/openai_compatible_client_test.go

@@ -96,6 +96,15 @@ func TestOpenAICompatibleClientGenerateSuccess(t *testing.T) {
 	if got, ok := obs.Body["model"].(string); !ok || got != "gpt-test" {
 		t.Fatalf("unexpected model payload: %#v", obs.Body["model"])
 	}
+	if got, ok := obs.Body["temperature"].(float64); !ok || got != 0.4 {
+		t.Fatalf("unexpected temperature payload: %#v", obs.Body["temperature"])
+	}
+	if got, ok := obs.Body["max_tokens"].(float64); !ok || got != 123 {
+		t.Fatalf("unexpected max_tokens payload: %#v", obs.Body["max_tokens"])
+	}
+	if got, ok := obs.Body["top_p"].(float64); !ok || got != 0.7 {
+		t.Fatalf("unexpected top_p payload: %#v", obs.Body["top_p"])
+	}
 	if got, ok := obs.Body["service_tier"].(string); !ok || got != "priority" {
 		t.Fatalf("unexpected service_tier payload: %#v", obs.Body["service_tier"])
 	}
@@ -166,6 +175,43 @@ func TestOpenAICompatibleClientOmitsResponseFormatWhenNoStructuredOutput(t *test
 	}
 }
 
+func TestOpenAICompatibleClientOmitsReasoningEffortAndExtraParams(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{
+			Model:           "model",
+			ReasoningEffort: "high",
+			ExtraParams: map[string]string{
+				"provider_option": "on",
+			},
+		},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if _, exists := observedBody["reasoning_effort"]; exists {
+		t.Fatalf("expected reasoning_effort omitted, got %#v", observedBody["reasoning_effort"])
+	}
+	if _, exists := observedBody["extra_params"]; exists {
+		t.Fatalf("expected extra_params omitted, got %#v", observedBody["extra_params"])
+	}
+}
+
 func TestOpenAICompatibleClientNoAuthorizationHeaderWhenNoAPIKey(t *testing.T) {
 	hadAuth := false
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

internal/usecase/runner_test.go

@@ -1122,6 +1122,174 @@ func TestRunnerRunJSONSchemaRepairCarriesStructuredOutputSpec(t *testing.T) {
 	}
 }
 
+func TestExecutionProfileToTargetPopulatesAllFieldsAndCopiesExtraParams(t *testing.T) {
+	src := &domain.ExecutionProfile{
+		ID:              "exec",
+		Endpoint:        "http://profile/v1",
+		Model:           "profile-model",
+		Temperature:     0.2,
+		MaxTokens:       123,
+		TopP:            0.75,
+		TimeoutSeconds:  90,
+		ServiceTier:     "priority",
+		ReasoningEffort: "medium",
+		APIKeyEnv:       "SCRIPTORIUM_API_KEY",
+		ExtraParams: map[string]string{
+			"provider_option": "on",
+		},
+	}
+
+	target := executionProfileToTarget(src)
+	if target.Endpoint != src.Endpoint ||
+		target.Model != src.Model ||
+		target.Temperature != src.Temperature ||
+		target.MaxTokens != src.MaxTokens ||
+		target.TopP != src.TopP ||
+		target.TimeoutSeconds != src.TimeoutSeconds ||
+		target.ServiceTier != src.ServiceTier ||
+		target.ReasoningEffort != src.ReasoningEffort ||
+		target.APIKeyEnv != src.APIKeyEnv {
+		t.Fatalf("expected all profile fields to populate target, got %+v", target)
+	}
+	if !reflect.DeepEqual(target.ExtraParams, src.ExtraParams) {
+		t.Fatalf("expected extra_params to match, got %#v", target.ExtraParams)
+	}
+
+	src.ExtraParams["provider_option"] = "changed"
+	if target.ExtraParams["provider_option"] != "on" {
+		t.Fatalf("expected extra_params copy to be independent, got %#v", target.ExtraParams)
+	}
+}
+
+func TestResolveExecutionTargetProfileValuesPopulateAllSupportedFields(t *testing.T) {
+	profileValue := &domain.ExecutionProfile{
+		ID:              "exec",
+		Endpoint:        "http://profile/v1",
+		Model:           "profile-model",
+		Temperature:     0.3,
+		MaxTokens:       222,
+		TopP:            0.6,
+		TimeoutSeconds:  77,
+		ServiceTier:     "priority",
+		ReasoningEffort: "low",
+		APIKeyEnv:       "PROFILE_KEY",
+		ExtraParams: map[string]string{
+			"profile_option": "enabled",
+		},
+	}
+
+	target := resolveExecutionTarget(profileValue, nil)
+	if target.Endpoint != profileValue.Endpoint ||
+		target.Model != profileValue.Model ||
+		target.Temperature != profileValue.Temperature ||
+		target.MaxTokens != profileValue.MaxTokens ||
+		target.TopP != profileValue.TopP ||
+		target.TimeoutSeconds != profileValue.TimeoutSeconds ||
+		target.ServiceTier != profileValue.ServiceTier ||
+		target.ReasoningEffort != profileValue.ReasoningEffort ||
+		target.APIKeyEnv != profileValue.APIKeyEnv {
+		t.Fatalf("expected profile values to populate target, got %+v", target)
+	}
+	if !reflect.DeepEqual(target.ExtraParams, profileValue.ExtraParams) {
+		t.Fatalf("expected profile extra_params in target, got %#v", target.ExtraParams)
+	}
+}
+
+func TestResolveExecutionTargetRuntimeOverridesBeatProfileForAllOverrideableFields(t *testing.T) {
+	profileValue := &domain.ExecutionProfile{
+		ID:              "exec",
+		Endpoint:        "http://profile/v1",
+		Model:           "profile-model",
+		Temperature:     0.2,
+		MaxTokens:       200,
+		TopP:            0.8,
+		TimeoutSeconds:  90,
+		ServiceTier:     "priority",
+		ReasoningEffort: "medium",
+		APIKeyEnv:       "PROFILE_KEY",
+		ExtraParams: map[string]string{
+			"profile_only": "yes",
+		},
+	}
+	override := &domain.ExecutionTarget{
+		Endpoint:        "http://override/v1",
+		Model:           "override-model",
+		Temperature:     0.9,
+		MaxTokens:       111,
+		TopP:            0.5,
+		TimeoutSeconds:  30,
+		ServiceTier:     "flex",
+		ReasoningEffort: "high",
+		APIKeyEnv:       "RUNTIME_KEY",
+		ExtraParams: map[string]string{
+			"runtime_only": "yes",
+		},
+	}
+
+	target := resolveExecutionTarget(profileValue, override)
+	if target.Endpoint != override.Endpoint ||
+		target.Model != override.Model ||
+		target.Temperature != override.Temperature ||
+		target.MaxTokens != override.MaxTokens ||
+		target.TopP != override.TopP ||
+		target.TimeoutSeconds != override.TimeoutSeconds ||
+		target.ServiceTier != override.ServiceTier ||
+		target.ReasoningEffort != override.ReasoningEffort ||
+		target.APIKeyEnv != override.APIKeyEnv {
+		t.Fatalf("expected runtime overrides to win for all fields, got %+v", target)
+	}
+	if !reflect.DeepEqual(target.ExtraParams, override.ExtraParams) {
+		t.Fatalf("expected runtime extra_params to replace profile extra_params, got %#v", target.ExtraParams)
+	}
+}
+
+func TestMergeExecutionTargetEmptyStringOverridesDoNotErase(t *testing.T) {
+	base := domain.ExecutionTarget{
+		Endpoint:        "http://base/v1",
+		Model:           "base-model",
+		ServiceTier:     "priority",
+		ReasoningEffort: "medium",
+		APIKeyEnv:       "BASE_KEY",
+	}
+	override := domain.ExecutionTarget{
+		Endpoint:        "http://override/v1",
+		Model:           "override-model",
+		ServiceTier:     "   ",
+		ReasoningEffort: "  ",
+		APIKeyEnv:       "",
+	}
+
+	merged := mergeExecutionTarget(base, override)
+	if merged.Endpoint != "http://override/v1" || merged.Model != "override-model" {
+		t.Fatalf("expected endpoint/model to override, got %+v", merged)
+	}
+	if merged.ServiceTier != "priority" {
+		t.Fatalf("expected empty service_tier override to be ignored, got %q", merged.ServiceTier)
+	}
+	if merged.ReasoningEffort != "medium" {
+		t.Fatalf("expected empty reasoning_effort override to be ignored, got %q", merged.ReasoningEffort)
+	}
+	if merged.APIKeyEnv != "BASE_KEY" {
+		t.Fatalf("expected empty api_key_env override to be ignored, got %q", merged.APIKeyEnv)
+	}
+}
+
+func TestMergeExecutionTargetEmptyExtraParamsDoesNotErase(t *testing.T) {
+	base := domain.ExecutionTarget{
+		ExtraParams: map[string]string{
+			"keep": "value",
+		},
+	}
+	override := domain.ExecutionTarget{
+		ExtraParams: map[string]string{},
+	}
+
+	merged := mergeExecutionTarget(base, override)
+	if !reflect.DeepEqual(merged.ExtraParams, base.ExtraParams) {
+		t.Fatalf("expected empty extra_params override not to erase base values, got %#v", merged.ExtraParams)
+	}
+}
+
 func TestBuildOutputArtifactDefaults(t *testing.T) {
 	tests := []struct {
 		name        string