nex/backend/internal/conversion/engine.go

package conversion

import (
	"encoding/json"
	"fmt"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"
)

// HTTPRequestSpec HTTP 请求规格
type HTTPRequestSpec struct {
	URL     string            `json:"url"`
	Method  string            `json:"method"`
	Headers map[string]string `json:"headers"`
	Body    []byte            `json:"body"`
}

// HTTPResponseSpec HTTP 响应规格
type HTTPResponseSpec struct {
	StatusCode int               `json:"status_code"`
	Headers    map[string]string `json:"headers"`
	Body       []byte            `json:"body"`
}

// ConversionEngine 转换引擎门面
type ConversionEngine struct {
	registry        AdapterRegistry
	middlewareChain *MiddlewareChain
	logger          *zap.Logger
}

// NewConversionEngine 创建转换引擎
func NewConversionEngine(registry AdapterRegistry, logger *zap.Logger) *ConversionEngine {
	if logger == nil {
		logger = zap.L()
	}
	return &ConversionEngine{
		registry:        registry,
		middlewareChain: NewMiddlewareChain(),
		logger:          logger,
	}
}

// RegisterAdapter 注册协议适配器
func (e *ConversionEngine) RegisterAdapter(adapter ProtocolAdapter) error {
	return e.registry.Register(adapter)
}

// GetRegistry 返回注册表（供外部使用）
func (e *ConversionEngine) GetRegistry() AdapterRegistry {
	return e.registry
}

// Use 添加中间件
func (e *ConversionEngine) Use(mw ConversionMiddleware) {
	e.middlewareChain.Use(mw)
}

// IsPassthrough 判断是否同协议透传
func (e *ConversionEngine) IsPassthrough(clientProtocol, providerProtocol string) bool {
	if clientProtocol != providerProtocol {
		return false
	}
	adapter, err := e.registry.Get(clientProtocol)
	if err != nil {
		return false
	}
	return adapter.SupportsPassthrough()
}

// ConvertHttpRequest 转换 HTTP 请求
func (e *ConversionEngine) ConvertHttpRequest(spec HTTPRequestSpec, clientProtocol, providerProtocol string, provider *TargetProvider) (*HTTPRequestSpec, error) {
	nativePath := spec.URL

	if e.IsPassthrough(clientProtocol, providerProtocol) {
		providerAdapter, err := e.registry.Get(providerProtocol)
		if err != nil {
			return nil, err
		}

		// Smart Passthrough: 同协议时最小化改写 model 字段
		interfaceType := providerAdapter.DetectInterfaceType(nativePath)
		rewrittenBody := spec.Body

		// 对于 Chat/Embedding/Rerank 接口，改写请求体中的 model 字段
		if interfaceType == InterfaceTypeChat || interfaceType == InterfaceTypeEmbeddings || interfaceType == InterfaceTypeRerank {
			if len(spec.Body) > 0 && provider.ModelName != "" {
				rewrittenBody, err = providerAdapter.RewriteRequestModelName(spec.Body, provider.ModelName, interfaceType)
				if err != nil {
					e.logger.Warn("Smart Passthrough 改写请求失败，使用原始请求体",
						zap.String("error", err.Error()),
						zap.String("interface", string(interfaceType)))
					rewrittenBody = spec.Body
				}
			}
		}

		return &HTTPRequestSpec{
			URL:     provider.BaseURL + nativePath,
			Method:  spec.Method,
			Headers: providerAdapter.BuildHeaders(provider),
			Body:    rewrittenBody,
		}, nil
	}

	clientAdapter, err := e.registry.Get(clientProtocol)
	if err != nil {
		return nil, fmt.Errorf("未找到客户端适配器 %s: %w", clientProtocol, err)
	}
	providerAdapter, err := e.registry.Get(providerProtocol)
	if err != nil {
		return nil, fmt.Errorf("未找到服务端适配器 %s: %w", providerProtocol, err)
	}

	interfaceType := clientAdapter.DetectInterfaceType(nativePath)
	providerUrl := providerAdapter.BuildUrl(nativePath, interfaceType)
	providerHeaders := providerAdapter.BuildHeaders(provider)
	providerBody, err := e.convertBody(interfaceType, clientAdapter, providerAdapter, provider, spec.Body)
	if err != nil {
		return nil, err
	}

	return &HTTPRequestSpec{
		URL:     provider.BaseURL + providerUrl,
		Method:  spec.Method,
		Headers: providerHeaders,
		Body:    providerBody,
	}, nil
}

// ConvertHttpResponse 转换 HTTP 响应，modelOverride 用于跨协议场景覆写 model 字段
func (e *ConversionEngine) ConvertHttpResponse(spec HTTPResponseSpec, clientProtocol, providerProtocol string, interfaceType InterfaceType, modelOverride string) (*HTTPResponseSpec, error) {
	if e.IsPassthrough(clientProtocol, providerProtocol) {
		// Smart Passthrough: 同协议时最小化改写 model 字段
		if modelOverride != "" && len(spec.Body) > 0 {
			adapter, err := e.registry.Get(clientProtocol)
			if err != nil {
				return &spec, nil
			}

			rewrittenBody, err := adapter.RewriteResponseModelName(spec.Body, modelOverride, interfaceType)
			if err != nil {
				e.logger.Warn("Smart Passthrough 改写响应失败，使用原始响应体",
					zap.String("error", err.Error()),
					zap.String("interface", string(interfaceType)))
				return &spec, nil
			}

			return &HTTPResponseSpec{
				StatusCode: spec.StatusCode,
				Headers:    spec.Headers,
				Body:       rewrittenBody,
			}, nil
		}
		return &spec, nil
	}

	clientAdapter, err := e.registry.Get(clientProtocol)
	if err != nil {
		return nil, err
	}
	providerAdapter, err := e.registry.Get(providerProtocol)
	if err != nil {
		return nil, err
	}

	convertedBody, err := e.convertResponseBody(interfaceType, clientAdapter, providerAdapter, spec.Body, modelOverride)
	if err != nil {
		return nil, err
	}

	return &HTTPResponseSpec{
		StatusCode: spec.StatusCode,
		Headers:    spec.Headers,
		Body:       convertedBody,
	}, nil
}

// CreateStreamConverter 创建流式转换器，modelOverride 用于跨协议场景覆写 model 字段
func (e *ConversionEngine) CreateStreamConverter(clientProtocol, providerProtocol string, modelOverride string, interfaceType InterfaceType) (StreamConverter, error) {
	if e.IsPassthrough(clientProtocol, providerProtocol) {
		// Smart Passthrough: 同协议流式场景需要逐 chunk 改写 model 字段
		if modelOverride != "" {
			adapter, err := e.registry.Get(clientProtocol)
			if err != nil {
				return NewPassthroughStreamConverter(), nil
			}
			return NewSmartPassthroughStreamConverter(adapter, modelOverride, interfaceType), nil
		}
		return NewPassthroughStreamConverter(), nil
	}

	providerAdapter, err := e.registry.Get(providerProtocol)
	if err != nil {
		return nil, err
	}
	clientAdapter, err := e.registry.Get(clientProtocol)
	if err != nil {
		return nil, err
	}

	ctx := ConversionContext{
		ConversionID:   uuid.New().String(),
		InterfaceType:  InterfaceTypeChat,
		Timestamp:      time.Now(),
	}

	return NewCanonicalStreamConverterWithMiddleware(
		providerAdapter.CreateStreamDecoder(),
		clientAdapter.CreateStreamEncoder(),
		e.middlewareChain,
		ctx,
		clientProtocol,
		providerProtocol,
		modelOverride,
	), nil
}

// convertBody 转换请求体
func (e *ConversionEngine) convertBody(interfaceType InterfaceType, clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
	switch interfaceType {
	case InterfaceTypeChat:
		return e.convertChatBody(clientAdapter, providerAdapter, provider, body)
	case InterfaceTypeModels, InterfaceTypeModelInfo:
		return body, nil
	case InterfaceTypeEmbeddings:
		if !clientAdapter.SupportsInterface(InterfaceTypeEmbeddings) || !providerAdapter.SupportsInterface(InterfaceTypeEmbeddings) {
			return body, nil
		}
		return e.convertEmbeddingBody(clientAdapter, providerAdapter, provider, body)
	case InterfaceTypeRerank:
		if !clientAdapter.SupportsInterface(InterfaceTypeRerank) || !providerAdapter.SupportsInterface(InterfaceTypeRerank) {
			return body, nil
		}
		return e.convertRerankBody(clientAdapter, providerAdapter, provider, body)
	default:
		return body, nil
	}
}

// convertResponseBody 转换响应体，modelOverride 非空时在 canonical 层面覆写 Model 字段
func (e *ConversionEngine) convertResponseBody(interfaceType InterfaceType, clientAdapter, providerAdapter ProtocolAdapter, body []byte, modelOverride string) ([]byte, error) {
	switch interfaceType {
	case InterfaceTypeChat:
		return e.convertChatResponseBody(clientAdapter, providerAdapter, body, modelOverride)
	case InterfaceTypeModels:
		if !clientAdapter.SupportsInterface(InterfaceTypeModels) || !providerAdapter.SupportsInterface(InterfaceTypeModels) {
			return body, nil
		}
		return e.convertModelsResponseBody(clientAdapter, providerAdapter, body)
	case InterfaceTypeModelInfo:
		if !clientAdapter.SupportsInterface(InterfaceTypeModelInfo) || !providerAdapter.SupportsInterface(InterfaceTypeModelInfo) {
			return body, nil
		}
		return e.convertModelInfoResponseBody(clientAdapter, providerAdapter, body)
	case InterfaceTypeEmbeddings:
		if !clientAdapter.SupportsInterface(InterfaceTypeEmbeddings) || !providerAdapter.SupportsInterface(InterfaceTypeEmbeddings) {
			return body, nil
		}
		return e.convertEmbeddingResponseBody(clientAdapter, providerAdapter, body, modelOverride)
	case InterfaceTypeRerank:
		if !clientAdapter.SupportsInterface(InterfaceTypeRerank) || !providerAdapter.SupportsInterface(InterfaceTypeRerank) {
			return body, nil
		}
		return e.convertRerankResponseBody(clientAdapter, providerAdapter, body, modelOverride)
	default:
		return body, nil
	}
}

func (e *ConversionEngine) convertChatBody(clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
	canonicalReq, err := clientAdapter.DecodeRequest(body)
	if err != nil {
		return nil, NewConversionError(ErrorCodeJSONParseError, "解码请求失败").WithCause(err)
	}

	ctx := NewConversionContext(InterfaceTypeChat)
	canonicalReq, err = e.middlewareChain.Apply(canonicalReq, clientAdapter.ProtocolName(), providerAdapter.ProtocolName(), ctx)
	if err != nil {
		return nil, err
	}

	encoded, err := providerAdapter.EncodeRequest(canonicalReq, provider)
	if err != nil {
		return nil, NewConversionError(ErrorCodeEncodingFailure, "编码请求失败").WithCause(err)
	}
	return encoded, nil
}

func (e *ConversionEngine) convertChatResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte, modelOverride string) ([]byte, error) {
	canonicalResp, err := providerAdapter.DecodeResponse(body)
	if err != nil {
		return nil, NewConversionError(ErrorCodeJSONParseError, "解码响应失败").WithCause(err)
	}
	if modelOverride != "" {
		canonicalResp.Model = modelOverride
	}
	encoded, err := clientAdapter.EncodeResponse(canonicalResp)
	if err != nil {
		return nil, NewConversionError(ErrorCodeEncodingFailure, "编码响应失败").WithCause(err)
	}
	return encoded, nil
}

func (e *ConversionEngine) convertModelsResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte) ([]byte, error) {
	models, err := providerAdapter.DecodeModelsResponse(body)
	if err != nil {
		e.logger.Warn("解码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
		return body, nil
	}
	encoded, err := clientAdapter.EncodeModelsResponse(models)
	if err != nil {
		e.logger.Warn("编码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
		return body, nil
	}
	return encoded, nil
}

func (e *ConversionEngine) convertModelInfoResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte) ([]byte, error) {
	info, err := providerAdapter.DecodeModelInfoResponse(body)
	if err != nil {
		e.logger.Warn("解码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
		return body, nil
	}
	encoded, err := clientAdapter.EncodeModelInfoResponse(info)
	if err != nil {
		e.logger.Warn("编码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
		return body, nil
	}
	return encoded, nil
}

func (e *ConversionEngine) convertEmbeddingBody(clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
	req, err := clientAdapter.DecodeEmbeddingRequest(body)
	if err != nil {
		e.logger.Warn("解码 Embedding 请求失败，返回原始请求", zap.String("error", err.Error()))
		return body, nil
	}
	return providerAdapter.EncodeEmbeddingRequest(req, provider)
}

func (e *ConversionEngine) convertEmbeddingResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte, modelOverride string) ([]byte, error) {
	resp, err := providerAdapter.DecodeEmbeddingResponse(body)
	if err != nil {
		e.logger.Warn("解码 Embedding 响应失败，返回原始响应", zap.String("error", err.Error()))
		return body, nil
	}
	if modelOverride != "" {
		resp.Model = modelOverride
	}
	return clientAdapter.EncodeEmbeddingResponse(resp)
}

func (e *ConversionEngine) convertRerankBody(clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
	req, err := clientAdapter.DecodeRerankRequest(body)
	if err != nil {
		e.logger.Warn("解码 Rerank 请求失败，返回原始请求", zap.String("error", err.Error()))
		return body, nil
	}
	return providerAdapter.EncodeRerankRequest(req, provider)
}

func (e *ConversionEngine) convertRerankResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte, modelOverride string) ([]byte, error) {
	resp, err := providerAdapter.DecodeRerankResponse(body)
	if err != nil {
		return body, nil
	}
	if modelOverride != "" {
		resp.Model = modelOverride
	}
	return clientAdapter.EncodeRerankResponse(resp)
}

// DetectInterfaceType 检测接口类型
func (e *ConversionEngine) DetectInterfaceType(nativePath, clientProtocol string) (InterfaceType, error) {
	adapter, err := e.registry.Get(clientProtocol)
	if err != nil {
		return InterfaceTypePassthrough, err
	}
	return adapter.DetectInterfaceType(nativePath), nil
}

// EncodeError 使用客户端适配器编码错误
func (e *ConversionEngine) EncodeError(err *ConversionError, clientProtocol string) ([]byte, int, error) {
	adapter, adapterErr := e.registry.Get(clientProtocol)
	if adapterErr != nil {
		fallback := map[string]any{
			"error": map[string]string{
				"message": err.Error(),
				"type":    "internal_error",
			},
		}
		body, _ := json.Marshal(fallback)
		return body, 500, nil
	}
	body, statusCode := adapter.EncodeError(err)
	return body, statusCode, nil
}