Refactor backend options marshaling/unmarshaling

pkg/backends/backend.go

@@ -25,6 +25,12 @@ type backend interface {
 	Validate() error
 }
 
+var backendConstructors = map[BackendType]func() backend{
+	BackendTypeLlamaCpp: func() backend { return &LlamaServerOptions{} },
+	BackendTypeMlxLm:    func() backend { return &MlxServerOptions{} },
+	BackendTypeVllm:     func() backend { return &VllmServerOptions{} },
+}
+
 type Options struct {
 	BackendType    BackendType    `json:"backend_type"`
 	BackendOptions map[string]any `json:"backend_options,omitempty"`
@@ -36,7 +42,6 @@ type Options struct {
 }
 
 func (o *Options) UnmarshalJSON(data []byte) error {
-	// Use anonymous struct to avoid recursion
 	type Alias Options
 	aux := &struct {
 		*Alias
@@ -48,52 +53,31 @@ func (o *Options) UnmarshalJSON(data []byte) error {
 		return err
 	}
 
-	// Parse backend-specific options
-	switch o.BackendType {
-	case BackendTypeLlamaCpp:
-		if o.BackendOptions != nil {
-			// Convert map to JSON and then unmarshal to LlamaServerOptions
-			optionsData, err := json.Marshal(o.BackendOptions)
-			if err != nil {
-				return fmt.Errorf("failed to marshal backend options: %w", err)
-			}
-
-			o.LlamaServerOptions = &LlamaServerOptions{}
-			if err := json.Unmarshal(optionsData, o.LlamaServerOptions); err != nil {
-				return fmt.Errorf("failed to unmarshal llama.cpp options: %w", err)
-			}
+	// Create backend from constructor map
+	if o.BackendOptions != nil {
+		constructor, exists := backendConstructors[o.BackendType]
+		if !exists {
+			return fmt.Errorf("unsupported backend type: %s", o.BackendType)
 		}
-	case BackendTypeMlxLm:
-		if o.BackendOptions != nil {
-			optionsData, err := json.Marshal(o.BackendOptions)
-			if err != nil {
-				return fmt.Errorf("failed to marshal backend options: %w", err)
-			}
 
-			o.MlxServerOptions = &MlxServerOptions{}
-			if err := json.Unmarshal(optionsData, o.MlxServerOptions); err != nil {
-				return fmt.Errorf("failed to unmarshal MLX options: %w", err)
-			}
+		backend := constructor()
+		optionsData, err := json.Marshal(o.BackendOptions)
+		if err != nil {
+			return fmt.Errorf("failed to marshal backend options: %w", err)
 		}
-	case BackendTypeVllm:
-		if o.BackendOptions != nil {
-			optionsData, err := json.Marshal(o.BackendOptions)
-			if err != nil {
-				return fmt.Errorf("failed to marshal backend options: %w", err)
-			}
 
-			o.VllmServerOptions = &VllmServerOptions{}
-			if err := json.Unmarshal(optionsData, o.VllmServerOptions); err != nil {
-				return fmt.Errorf("failed to unmarshal vLLM options: %w", err)
-			}
+		if err := json.Unmarshal(optionsData, backend); err != nil {
+			return fmt.Errorf("failed to unmarshal backend options: %w", err)
 		}
+
+		// Store in the appropriate typed field for backward compatibility
+		o.setBackendOptions(backend)
 	}
 
 	return nil
 }
 
 func (o *Options) MarshalJSON() ([]byte, error) {
-	// Use anonymous struct to avoid recursion
 	type Alias Options
 	aux := &struct {
 		*Alias
@@ -101,48 +85,33 @@ func (o *Options) MarshalJSON() ([]byte, error) {
 		Alias: (*Alias)(o),
 	}
 
-	// Prepare BackendOptions map
-	if o.BackendOptions == nil {
-		o.BackendOptions = make(map[string]any)
-	}
-
-	// Populate BackendOptions based on backend-specific options
-	switch o.BackendType {
-	case BackendTypeLlamaCpp:
-		if o.LlamaServerOptions != nil {
-			optionsData, err := json.Marshal(o.LlamaServerOptions)
-			if err != nil {
-				return nil, fmt.Errorf("failed to marshal llama.cpp options: %w", err)
-			}
-			if err := json.Unmarshal(optionsData, &o.BackendOptions); err != nil {
-				return nil, fmt.Errorf("failed to unmarshal llama.cpp options to map: %w", err)
-			}
+	// Get backend and marshal it
+	backend := o.getBackend()
+	if backend != nil {
+		optionsData, err := json.Marshal(backend)
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal backend options: %w", err)
 		}
-	case BackendTypeMlxLm:
-		if o.MlxServerOptions != nil {
-			optionsData, err := json.Marshal(o.MlxServerOptions)
-			if err != nil {
-				return nil, fmt.Errorf("failed to marshal MLX options: %w", err)
-			}
-			if err := json.Unmarshal(optionsData, &o.BackendOptions); err != nil {
-				return nil, fmt.Errorf("failed to unmarshal MLX options to map: %w", err)
-			}
-		}
-	case BackendTypeVllm:
-		if o.VllmServerOptions != nil {
-			optionsData, err := json.Marshal(o.VllmServerOptions)
-			if err != nil {
-				return nil, fmt.Errorf("failed to marshal vLLM options: %w", err)
-			}
-			if err := json.Unmarshal(optionsData, &o.BackendOptions); err != nil {
-				return nil, fmt.Errorf("failed to unmarshal vLLM options to map: %w", err)
-			}
+		if err := json.Unmarshal(optionsData, &aux.BackendOptions); err != nil {
+			return nil, fmt.Errorf("failed to unmarshal backend options to map: %w", err)
 		}
 	}
 
 	return json.Marshal(aux)
 }
 
+// setBackendOptions stores the backend in the appropriate typed field
+func (o *Options) setBackendOptions(bcknd backend) {
+	switch v := bcknd.(type) {
+	case *LlamaServerOptions:
+		o.LlamaServerOptions = v
+	case *MlxServerOptions:
+		o.MlxServerOptions = v
+	case *VllmServerOptions:
+		o.VllmServerOptions = v
+	}
+}
+
 func (o *Options) getBackendSettings(backendConfig *config.BackendConfig) *config.BackendSettings {
 	switch o.BackendType {
 	case BackendTypeLlamaCpp: