package handler

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"

	"github.com/yourname/cyrene-ai/gateway/internal/config"
	"github.com/yourname/cyrene-ai/gateway/internal/middleware"
	"github.com/yourname/cyrene-ai/gateway/internal/ws"
)

// ChatHandler 聊天处理器
type ChatHandler struct {
	cfg      *config.Config
	hub      *ws.Hub
	upgrader websocket.Upgrader
}

// NewChatHandler 创建聊天处理器
func NewChatHandler(cfg *config.Config, hub *ws.Hub) *ChatHandler {
	return &ChatHandler{
		cfg: cfg,
		hub: hub,
		upgrader: websocket.Upgrader{
			ReadBufferSize:  1024,
			WriteBufferSize: 1024,
			CheckOrigin: func(r *http.Request) bool {
				return true // 开发阶段允许所有来源
			},
		},
	}
}

// HandleWebSocket 处理WebSocket升级和消息路由
func (h *ChatHandler) HandleWebSocket(c *gin.Context) {
	// 从query参数获取token和session_id
	token := c.Query("token")
	sessionID := c.Query("session_id")

	if token == "" {
		// 也尝试从Authorization头读取
		authHeader := c.GetHeader("Authorization")
		if len(authHeader) > 7 && authHeader[:7] == "Bearer " {
			token = authHeader[7:]
		}
	}

	if token == "" {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "需要认证令牌"})
		return
	}

	// 验证token
	userID, err := h.cfg.ValidateToken(token)
	if err != nil {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "认证令牌无效"})
		return
	}

	if sessionID == "" {
		sessionID = "session_" + generateID()
	}

	// 升级WebSocket连接
	conn, err := h.upgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		log.Printf("[WS] 升级连接失败: %v", err)
		return
	}

	// 创建客户端
	client := ws.NewClient(h.hub, conn, userID, sessionID)

	// 注册到Hub
	h.hub.Register(client)

	// 启动读写协程
	go client.WritePump()
	go client.ReadPump(func(client *ws.Client, msg ws.ClientMessage) {
		h.handleMessage(client, msg)
	})
}

// handleMessage 处理WebSocket消息
func (h *ChatHandler) handleMessage(client *ws.Client, msg ws.ClientMessage) {
	switch msg.Type {
	case "message":
		h.handleChatMessage(client, msg)
	case "voice_input":
		h.handleVoiceInput(client, msg)
	default:
		log.Printf("[WS] 未知消息类型: %s from user=%s", msg.Type, client.UserID)
	}
}

// handleChatMessage 处理文字聊天消息 - 转发到 AI-Core
func (h *ChatHandler) handleChatMessage(client *ws.Client, msg ws.ClientMessage) {
	mode := msg.Mode
	if mode == "" {
		mode = "text"
	}

	// 记录用户消息
	h.hub.RecordMessage(client.SessionID, "user", msg.Content)

	// 设置会话状态为 thinking
	h.hub.UpdateSessionState(client.SessionID, "thinking")

	// 构建 AI-Core 请求
	aiReq := map[string]string{
		"user_id":    client.UserID,
		"session_id": client.SessionID,
		"message":    msg.Content,
		"mode":       mode,
	}
	reqBody, err := json.Marshal(aiReq)
	if err != nil {
		log.Printf("[chat] 序列化请求失败: %v", err)
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     "内部错误，请稍后重试",
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}

	// 调用 AI-Core
	aiCoreURL := h.cfg.AICoreURL + "/api/v1/chat"
	httpReq, err := http.NewRequest("POST", aiCoreURL, bytes.NewReader(reqBody))
	if err != nil {
		log.Printf("[chat] 创建 AI-Core 请求失败: %v", err)
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     "服务暂不可用",
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}
	httpReq.Header.Set("Content-Type", "application/json")

	httpClient := &http.Client{Timeout: 120 * time.Second}
	resp, err := httpClient.Do(httpReq)
	if err != nil {
		log.Printf("[chat] AI-Core 调用失败: %v", err)
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     fmt.Sprintf("AI-Core 调用失败: %v", err),
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Printf("[chat] 读取 AI-Core 响应失败: %v", err)
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     "读取响应失败",
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}

	if resp.StatusCode != http.StatusOK {
		log.Printf("[chat] AI-Core 返回错误 [%d]: %s", resp.StatusCode, string(body))
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     fmt.Sprintf("AI-Core 错误 (%d)", resp.StatusCode),
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}

	// 解析 AI-Core 响应
	var aiResp struct {
		Text      string `json:"text"`
		Mode      string `json:"mode"`
		MessageID string `json:"message_id"`
	}
	if err := json.Unmarshal(body, &aiResp); err != nil {
		log.Printf("[chat] 解析 AI-Core 响应失败: %v", err)
		h.hub.UpdateSessionState(client.SessionID, "error")
		client.SendMessage(ws.ServerMessage{
			Type:      "error",
			MessageID: "msg_" + generateID(),
			Error:     "解析响应失败",
			Timestamp: time.Now().UnixMilli(),
		})
		return
	}

	// 记录助手响应
	h.hub.RecordMessage(client.SessionID, "assistant", aiResp.Text)

	// 设置会话状态为 idle
	h.hub.UpdateSessionState(client.SessionID, "idle")

	// 发送响应给客户端
	response := ws.ServerMessage{
		Type:         "response",
		MessageID:    aiResp.MessageID,
		Text:         aiResp.Text,
		ResponseMode: mode,
		Timestamp:    time.Now().UnixMilli(),
	}

	if err := client.SendMessage(response); err != nil {
		log.Printf("[WS] 发送响应失败: %v", err)
	}
}

// handleVoiceInput 处理语音输入
func (h *ChatHandler) handleVoiceInput(client *ws.Client, msg ws.ClientMessage) {
	// MVP阶段：返回提示
	response := ws.ServerMessage{
		Type:      "error",
		MessageID: "msg_" + generateID(),
		Error:     "语音处理功能将在后续版本中启用",
		Timestamp: time.Now().UnixMilli(),
	}
	client.SendMessage(response)
}


// SendSystemMessage 向用户发送系统消息（用于主动通知）
func (h *ChatHandler) SendSystemMessage(userID, sessionID, text string) error {
	msg := ws.ServerMessage{
		Type:      "response",
		MessageID: "sys_" + generateID(),
		Text:      text,
		Timestamp: time.Now().UnixMilli(),
	}

	data, err := json.Marshal(msg)
	if err != nil {
		return err
	}

	h.hub.SendToSession(userID, sessionID, data)
	return nil
}

func generateID() string {
	return time.Now().Format("20060102150405") + randomStr(6)
}

func randomStr(n int) string {
	const letters = "abcdefghijklmnopqrstuvwxyz0123456789"
	b := make([]byte, n)
	for i := range b {
		b[i] = letters[time.Now().UnixNano()%int64(len(letters))]
	}
	return string(b)
}

// 确保未使用变量不报错
var _ = middleware.GetUserID