package openai

import (
	"encoding/json"
	"fmt"
	"strings"

	"nex/backend/internal/conversion"
	"nex/backend/internal/conversion/canonical"
)

// Adapter OpenAI 协议适配器
type Adapter struct{}

// NewAdapter 创建 OpenAI 适配器
func NewAdapter() *Adapter {
	return &Adapter{}
}

// ProtocolName 返回协议名称
func (a *Adapter) ProtocolName() string { return "openai" }

// ProtocolVersion 返回协议版本
func (a *Adapter) ProtocolVersion() string { return "" }

// SupportsPassthrough 支持同协议透传
func (a *Adapter) SupportsPassthrough() bool { return true }

// DetectInterfaceType 根据路径检测接口类型
func (a *Adapter) DetectInterfaceType(nativePath string) conversion.InterfaceType {
	switch {
	case nativePath == "/chat/completions":
		return conversion.InterfaceTypeChat
	case nativePath == "/models":
		return conversion.InterfaceTypeModels
	case isModelInfoPath(nativePath):
		return conversion.InterfaceTypeModelInfo
	case nativePath == "/embeddings":
		return conversion.InterfaceTypeEmbeddings
	case nativePath == "/rerank":
		return conversion.InterfaceTypeRerank
	default:
		return conversion.InterfaceTypePassthrough
	}
}

// isModelInfoPath 判断是否为模型详情路径（/models/{id}，允许 id 含 /）
func isModelInfoPath(path string) bool {
	if !strings.HasPrefix(path, "/models/") {
		return false
	}
	suffix := path[len("/models/"):]
	return suffix != ""
}

// BuildUrl 根据接口类型构建 URL
func (a *Adapter) BuildUrl(nativePath string, interfaceType conversion.InterfaceType) string {
	switch interfaceType {
	case conversion.InterfaceTypeChat:
		return "/chat/completions"
	case conversion.InterfaceTypeModels:
		return "/models"
	case conversion.InterfaceTypeEmbeddings:
		return "/embeddings"
	case conversion.InterfaceTypeRerank:
		return "/rerank"
	default:
		return nativePath
	}
}

// BuildHeaders 构建请求头
func (a *Adapter) BuildHeaders(provider *conversion.TargetProvider) map[string]string {
	headers := map[string]string{
		"Authorization": "Bearer " + provider.APIKey,
		"Content-Type":  "application/json",
	}
	if org, ok := provider.AdapterConfig["organization"].(string); ok && org != "" {
		headers["OpenAI-Organization"] = org
	}
	return headers
}

// SupportsInterface 检查是否支持接口类型
func (a *Adapter) SupportsInterface(interfaceType conversion.InterfaceType) bool {
	switch interfaceType {
	case conversion.InterfaceTypeChat,
		conversion.InterfaceTypeModels,
		conversion.InterfaceTypeModelInfo,
		conversion.InterfaceTypeEmbeddings,
		conversion.InterfaceTypeRerank:
		return true
	default:
		return false
	}
}

// DecodeRequest 解码请求
func (a *Adapter) DecodeRequest(raw []byte) (*canonical.CanonicalRequest, error) {
	return decodeRequest(raw)
}

// EncodeRequest 编码请求
func (a *Adapter) EncodeRequest(req *canonical.CanonicalRequest, provider *conversion.TargetProvider) ([]byte, error) {
	return encodeRequest(req, provider)
}

// DecodeResponse 解码响应
func (a *Adapter) DecodeResponse(raw []byte) (*canonical.CanonicalResponse, error) {
	return decodeResponse(raw)
}

// EncodeResponse 编码响应
func (a *Adapter) EncodeResponse(resp *canonical.CanonicalResponse) ([]byte, error) {
	return encodeResponse(resp)
}

// CreateStreamDecoder 创建流式解码器
func (a *Adapter) CreateStreamDecoder() conversion.StreamDecoder {
	return NewStreamDecoder()
}

// CreateStreamEncoder 创建流式编码器
func (a *Adapter) CreateStreamEncoder() conversion.StreamEncoder {
	return NewStreamEncoder()
}

// EncodeError 编码错误
func (a *Adapter) EncodeError(err *conversion.ConversionError) ([]byte, int) {
	errType := mapErrorCode(err.Code)
	statusCode := 500

	errMsg := ErrorResponse{
		Error: ErrorDetail{
			Message: err.Message,
			Type:    errType,
			Param:   nil,
			Code:    string(err.Code),
		},
	}
	body, _ := json.Marshal(errMsg)
	return body, statusCode
}

// mapErrorCode 映射错误码到 OpenAI 错误类型
func mapErrorCode(code conversion.ErrorCode) string {
	switch code {
	case conversion.ErrorCodeInvalidInput,
		conversion.ErrorCodeMissingRequiredField,
		conversion.ErrorCodeIncompatibleFeature,
		conversion.ErrorCodeToolCallParseError,
		conversion.ErrorCodeJSONParseError,
		conversion.ErrorCodeProtocolConstraint,
		conversion.ErrorCodeFieldMappingFailure:
		return "invalid_request_error"
	default:
		return "server_error"
	}
}

// DecodeModelsResponse 解码模型列表响应
func (a *Adapter) DecodeModelsResponse(raw []byte) (*canonical.CanonicalModelList, error) {
	return decodeModelsResponse(raw)
}

// EncodeModelsResponse 编码模型列表响应
func (a *Adapter) EncodeModelsResponse(list *canonical.CanonicalModelList) ([]byte, error) {
	return encodeModelsResponse(list)
}

// DecodeModelInfoResponse 解码模型详情响应
func (a *Adapter) DecodeModelInfoResponse(raw []byte) (*canonical.CanonicalModelInfo, error) {
	return decodeModelInfoResponse(raw)
}

// EncodeModelInfoResponse 编码模型详情响应
func (a *Adapter) EncodeModelInfoResponse(info *canonical.CanonicalModelInfo) ([]byte, error) {
	return encodeModelInfoResponse(info)
}

// DecodeEmbeddingRequest 解码嵌入请求
func (a *Adapter) DecodeEmbeddingRequest(raw []byte) (*canonical.CanonicalEmbeddingRequest, error) {
	return decodeEmbeddingRequest(raw)
}

// EncodeEmbeddingRequest 编码嵌入请求
func (a *Adapter) EncodeEmbeddingRequest(req *canonical.CanonicalEmbeddingRequest, provider *conversion.TargetProvider) ([]byte, error) {
	return encodeEmbeddingRequest(req, provider)
}

// DecodeEmbeddingResponse 解码嵌入响应
func (a *Adapter) DecodeEmbeddingResponse(raw []byte) (*canonical.CanonicalEmbeddingResponse, error) {
	return decodeEmbeddingResponse(raw)
}

// EncodeEmbeddingResponse 编码嵌入响应
func (a *Adapter) EncodeEmbeddingResponse(resp *canonical.CanonicalEmbeddingResponse) ([]byte, error) {
	return encodeEmbeddingResponse(resp)
}

// DecodeRerankRequest 解码重排序请求
func (a *Adapter) DecodeRerankRequest(raw []byte) (*canonical.CanonicalRerankRequest, error) {
	return decodeRerankRequest(raw)
}

// EncodeRerankRequest 编码重排序请求
func (a *Adapter) EncodeRerankRequest(req *canonical.CanonicalRerankRequest, provider *conversion.TargetProvider) ([]byte, error) {
	return encodeRerankRequest(req, provider)
}

// DecodeRerankResponse 解码重排序响应
func (a *Adapter) DecodeRerankResponse(raw []byte) (*canonical.CanonicalRerankResponse, error) {
	return decodeRerankResponse(raw)
}

// EncodeRerankResponse 编码重排序响应
func (a *Adapter) EncodeRerankResponse(resp *canonical.CanonicalRerankResponse) ([]byte, error) {
	return encodeRerankResponse(resp)
}

// ExtractUnifiedModelID 从路径中提取统一模型 ID（/models/{provider_id}/{model_name}）
func (a *Adapter) ExtractUnifiedModelID(nativePath string) (string, error) {
	if !strings.HasPrefix(nativePath, "/models/") {
		return "", fmt.Errorf("不是模型详情路径: %s", nativePath)
	}
	suffix := nativePath[len("/models/"):]
	if suffix == "" {
		return "", fmt.Errorf("路径缺少模型 ID")
	}
	return suffix, nil
}

// locateModelFieldInRequest 定位请求体中 model 字段的值并提供改写函数
func locateModelFieldInRequest(body []byte, ifaceType conversion.InterfaceType) (string, func(string) ([]byte, error), error) {
	var m map[string]json.RawMessage
	if err := json.Unmarshal(body, &m); err != nil {
		return "", nil, err
	}

	switch ifaceType {
	case conversion.InterfaceTypeChat, conversion.InterfaceTypeEmbeddings, conversion.InterfaceTypeRerank:
		raw, exists := m["model"]
		if !exists {
			return "", nil, fmt.Errorf("请求体中缺少 model 字段")
		}
		var current string
		if err := json.Unmarshal(raw, &current); err != nil {
			return "", nil, err
		}
		rewriteFunc := func(newModel string) ([]byte, error) {
			m["model"], _ = json.Marshal(newModel)
			return json.Marshal(m)
		}
		return current, rewriteFunc, nil
	default:
		return "", nil, fmt.Errorf("不支持的接口类型: %s", ifaceType)
	}
}

// ExtractModelName 从请求体中提取 model 值
func (a *Adapter) ExtractModelName(body []byte, ifaceType conversion.InterfaceType) (string, error) {
	model, _, err := locateModelFieldInRequest(body, ifaceType)
	return model, err
}

// RewriteRequestModelName 最小化改写请求体中的 model 字段
func (a *Adapter) RewriteRequestModelName(body []byte, newModel string, ifaceType conversion.InterfaceType) ([]byte, error) {
	_, rewriteFunc, err := locateModelFieldInRequest(body, ifaceType)
	if err != nil {
		return nil, err
	}
	return rewriteFunc(newModel)
}

// RewriteResponseModelName 最小化改写响应体中的 model 字段
func (a *Adapter) RewriteResponseModelName(body []byte, newModel string, ifaceType conversion.InterfaceType) ([]byte, error) {
	var m map[string]json.RawMessage
	if err := json.Unmarshal(body, &m); err != nil {
		return nil, err
	}

	switch ifaceType {
	case conversion.InterfaceTypeChat, conversion.InterfaceTypeEmbeddings:
		// Chat/Embedding 响应必须有 model 字段（协议要求），存在则改写，不存在则添加
		m["model"], _ = json.Marshal(newModel)
		return json.Marshal(m)
	case conversion.InterfaceTypeRerank:
		// Rerank 响应：存在 model 字段则改写，不存在则不添加
		if _, exists := m["model"]; exists {
			m["model"], _ = json.Marshal(newModel)
		}
		return json.Marshal(m)
	default:
		return body, nil
	}
}