package handler

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

	"github.com/gin-gonic/gin"

	appErrors "nex/backend/pkg/errors"

	"nex/backend/internal/domain"
	"nex/backend/internal/protocol/anthropic"
	"nex/backend/internal/protocol/openai"
	"nex/backend/internal/provider"
	"nex/backend/internal/service"
)

// AnthropicHandler Anthropic 协议处理器
type AnthropicHandler struct {
	client         provider.ProviderClient
	routingService service.RoutingService
	statsService   service.StatsService
}

// NewAnthropicHandler 创建 Anthropic 处理器
func NewAnthropicHandler(client provider.ProviderClient, routingService service.RoutingService, statsService service.StatsService) *AnthropicHandler {
	return &AnthropicHandler{
		client:         client,
		routingService: routingService,
		statsService:   statsService,
	}
}

// HandleMessages 处理 Messages 请求
func (h *AnthropicHandler) HandleMessages(c *gin.Context) {
	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
	}

	// 请求验证
	if validationErrors := anthropic.ValidateRequest(&req); validationErrors != nil {
		errMsg := formatValidationErrors(validationErrors)
		c.JSON(http.StatusBadRequest, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "invalid_request_error",
				Message: errMsg,
			},
		})
		return
	}

	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
	}

	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
	}

	routeResult, err := h.routingService.Route(openaiReq.Model)
	if err != nil {
		h.handleError(c, err)
		return
	}

	if req.Stream {
		h.handleStreamRequest(c, openaiReq, routeResult)
	} else {
		h.handleNonStreamRequest(c, openaiReq, routeResult)
	}
}

func (h *AnthropicHandler) handleNonStreamRequest(c *gin.Context, openaiReq *openai.ChatCompletionRequest, routeResult *domain.RouteResult) {
	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
	}

	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
	}

	go func() {
		_ = h.statsService.Record(routeResult.Provider.ID, openaiReq.Model)
	}()

	c.JSON(http.StatusOK, anthropicResp)
}

func (h *AnthropicHandler) handleStreamRequest(c *gin.Context, openaiReq *openai.ChatCompletionRequest, routeResult *domain.RouteResult) {
	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
	}

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

	writer := bufio.NewWriter(c.Writer)

	converter := anthropic.NewStreamConverter(
		fmt.Sprintf("msg_%s", routeResult.Provider.ID),
		openaiReq.Model,
	)

	for event := range eventChan {
		if event.Error != nil {
			break
		}

		if event.Done {
			break
		}

		chunk, err := openai.NewAdapter().ParseStreamChunk(event.Data)
		if err != nil {
			continue
		}

		anthropicEvents, err := converter.ConvertChunk(chunk)
		if err != nil {
			continue
		}

		for _, ae := range anthropicEvents {
			eventStr, err := anthropic.SerializeEvent(ae)
			if err != nil {
				continue
			}
			writer.WriteString(eventStr)
			writer.Flush()
		}
	}

	go func() {
		_ = h.statsService.Record(routeResult.Provider.ID, openaiReq.Model)
	}()
}

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
}

func (h *AnthropicHandler) handleError(c *gin.Context, err error) {
	if appErr, ok := appErrors.AsAppError(err); ok {
		c.JSON(appErr.HTTPStatus, anthropic.ErrorResponse{
			Type: "error",
			Error: anthropic.ErrorDetail{
				Type:    "not_found_error",
				Message: appErr.Message,
			},
		})
		return
	}
	c.JSON(http.StatusInternalServerError, anthropic.ErrorResponse{
		Type: "error",
		Error: anthropic.ErrorDetail{
			Type:    "internal_error",
			Message: "内部错误: " + err.Error(),
		},
	})
}