package handler

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

	"github.com/gin-gonic/gin"

	appErrors "nex/backend/pkg/errors"

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

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

// NewOpenAIHandler 创建 OpenAI 处理器
func NewOpenAIHandler(client provider.ProviderClient, routingService service.RoutingService, statsService service.StatsService) *OpenAIHandler {
	return &OpenAIHandler{
		client:         client,
		routingService: routingService,
		statsService:   statsService,
	}
}

// HandleChatCompletions 处理 Chat Completions 请求
func (h *OpenAIHandler) HandleChatCompletions(c *gin.Context) {
	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
	}

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

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

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

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

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

	c.JSON(http.StatusOK, resp)
}

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

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

	writer := bufio.NewWriter(c.Writer)

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

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

		writer.WriteString("data: ")
		writer.Write(event.Data)
		writer.WriteString("\n\n")
		writer.Flush()
	}

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

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

// formatValidationErrors 将验证错误 map 格式化为字符串
func formatValidationErrors(errors map[string]string) string {
	parts := make([]string, 0, len(errors))
	for field, msg := range errors {
		parts = append(parts, fmt.Sprintf("%s: %s", field, msg))
	}
	return "请求验证失败: " + strings.Join(parts, "; ")
}