package handler

import (
	"bufio"
	"fmt"
	"net/http"

	"github.com/gin-gonic/gin"

	"nex/backend/internal/config"
	"nex/backend/internal/protocol/openai"
	"nex/backend/internal/provider"
	"nex/backend/internal/router"
)

// OpenAIHandler OpenAI 协议处理器
type OpenAIHandler struct {
	client *provider.Client
	router *router.Router
}

// NewOpenAIHandler 创建 OpenAI 处理器
func NewOpenAIHandler() *OpenAIHandler {
	return &OpenAIHandler{
		client: provider.NewClient(),
		router: router.NewRouter(),
	}
}

// HandleChatCompletions 处理 Chat Completions 请求
func (h *OpenAIHandler) HandleChatCompletions(c *gin.Context) {
	// 解析请求
	var req openai.ChatCompletionRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "无效的请求格式: " + err.Error(),
				Type:    "invalid_request_error",
			},
		})
		return
	}

	// 路由到供应商
	routeResult, err := h.router.Route(req.Model)
	if err != nil {
		h.handleError(c, err)
		return
	}

	// 根据是否流式选择处理方式
	if req.Stream {
		h.handleStreamRequest(c, &req, routeResult)
	} else {
		h.handleNonStreamRequest(c, &req, routeResult)
	}
}

// handleNonStreamRequest 处理非流式请求
func (h *OpenAIHandler) handleNonStreamRequest(c *gin.Context, req *openai.ChatCompletionRequest, routeResult *router.RouteResult) {
	// 发送请求到供应商
	resp, err := h.client.SendRequest(c.Request.Context(), req, routeResult.Provider.APIKey, routeResult.Provider.BaseURL)
	if err != nil {
		c.JSON(http.StatusInternalServerError, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "供应商请求失败: " + err.Error(),
				Type:    "api_error",
			},
		})
		return
	}

	// 记录统计
	go func() {
		_ = config.RecordRequest(routeResult.Provider.ID, req.Model)
	}()

	// 返回响应
	c.JSON(http.StatusOK, resp)
}

// handleStreamRequest 处理流式请求
func (h *OpenAIHandler) handleStreamRequest(c *gin.Context, req *openai.ChatCompletionRequest, routeResult *router.RouteResult) {
	// 发送流式请求到供应商
	eventChan, err := h.client.SendStreamRequest(c.Request.Context(), req, routeResult.Provider.APIKey, routeResult.Provider.BaseURL)
	if err != nil {
		c.JSON(http.StatusInternalServerError, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "供应商请求失败: " + err.Error(),
				Type:    "api_error",
			},
		})
		return
	}

	// 设置 SSE 响应头
	c.Header("Content-Type", "text/event-stream")
	c.Header("Cache-Control", "no-cache")
	c.Header("Connection", "keep-alive")

	// 创建流写入器
	writer := bufio.NewWriter(c.Writer)

	// 流式转发事件
	for event := range eventChan {
		if event.Error != nil {
			// 流错误，记录日志
			fmt.Printf("流错误: %v\n", event.Error)
			break
		}

		if event.Done {
			// 流结束
			writer.WriteString("data: [DONE]\n\n")
			writer.Flush()
			break
		}

		// 写入事件数据
		writer.WriteString("data: ")
		writer.Write(event.Data)
		writer.WriteString("\n\n")
		writer.Flush()
	}

	// 记录统计
	go func() {
		_ = config.RecordRequest(routeResult.Provider.ID, req.Model)
	}()
}

// handleError 处理路由错误
func (h *OpenAIHandler) handleError(c *gin.Context, err error) {
	switch err {
	case router.ErrModelNotFound:
		c.JSON(http.StatusNotFound, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "模型未找到",
				Type:    "invalid_request_error",
				Code:    "model_not_found",
			},
		})
	case router.ErrModelDisabled:
		c.JSON(http.StatusNotFound, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "模型已禁用",
				Type:    "invalid_request_error",
				Code:    "model_disabled",
			},
		})
	case router.ErrProviderDisabled:
		c.JSON(http.StatusNotFound, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "供应商已禁用",
				Type:    "invalid_request_error",
				Code:    "provider_disabled",
			},
		})
	default:
		c.JSON(http.StatusInternalServerError, openai.ErrorResponse{
			Error: openai.ErrorDetail{
				Message: "内部错误: " + err.Error(),
				Type:    "internal_error",
			},
		})
	}
}