package handler

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

	"github.com/gin-gonic/gin"

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

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

// NewAnthropicHandler 创建 Anthropic 处理器
func NewAnthropicHandler() *AnthropicHandler {
	return &AnthropicHandler{
		client: provider.NewClient(),
		router: router.NewRouter(),
	}
}

// HandleMessages 处理 Messages 请求
func (h *AnthropicHandler) HandleMessages(c *gin.Context) {
	// 解析 Anthropic 请求
	var req anthropic.MessagesRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "invalid_request_error",
				Message: "无效的请求格式: " + err.Error(),
			},
		})
		return
	}

	// 检查多模态内容
	if err := h.checkMultimodalContent(&req); err != nil {
		c.JSON(http.StatusBadRequest, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "invalid_request_error",
				Message: err.Error(),
			},
		})
		return
	}

	// 转换为 OpenAI 请求
	openaiReq, err := anthropic.ConvertRequest(&req)
	if err != nil {
		c.JSON(http.StatusBadRequest, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "invalid_request_error",
				Message: "请求转换失败: " + err.Error(),
			},
		})
		return
	}

	// 路由到供应商
	routeResult, err := h.router.Route(openaiReq.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, openaiReq, routeResult)
	} else {
		h.handleNonStreamRequest(c, openaiReq, routeResult)
	}
}

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

	// 转换为 Anthropic 响应
	anthropicResp, err := anthropic.ConvertResponse(openaiResp)
	if err != nil {
		c.JSON(http.StatusInternalServerError, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "api_error",
				Message: "响应转换失败: " + err.Error(),
			},
		})
		return
	}

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

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

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

	// 创建流式转换器
	converter := anthropic.NewStreamConverter(
		fmt.Sprintf("msg_%s", routeResult.Provider.ID),
		openaiReq.Model,
	)

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

		if event.Done {
			break
		}

		// 解析 OpenAI 流块
		chunk, err := openai.NewAdapter().ParseStreamChunk(event.Data)
		if err != nil {
			fmt.Printf("解析流块失败: %v\n", err)
			continue
		}

		// 转换为 Anthropic 事件
		anthropicEvents, err := converter.ConvertChunk(chunk)
		if err != nil {
			fmt.Printf("转换事件失败: %v\n", err)
			continue
		}

		// 写入事件
		for _, ae := range anthropicEvents {
			eventStr, err := anthropic.SerializeEvent(ae)
			if err != nil {
				fmt.Printf("序列化事件失败: %v\n", err)
				continue
			}
			writer.WriteString(eventStr)
			writer.Flush()
		}
	}

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

// checkMultimodalContent 检查多模态内容
func (h *AnthropicHandler) checkMultimodalContent(req *anthropic.MessagesRequest) error {
	for _, msg := range req.Messages {
		for _, block := range msg.Content {
			if block.Type == "image" {
				return fmt.Errorf("MVP 不支持多模态内容（图片）")
			}
		}
	}
	return nil
}

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