package websocket

import (
	"context"
	"encoding/json"
	"log"
	"net/http"
	"sync"
	"time"

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

	"market-data-service/api"
)

var upgrader = websocket.Upgrader{
	CheckOrigin: func(r *http.Request) bool {
		return true // 允许所有来源，生产环境需要限制
	},
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

// Hub WebSocket连接管理中心
type Hub struct {
	// 已注册的客户端
	clients map[*Client]bool

	// 广播消息通道
	broadcast chan []byte

	// 注册请求通道
	register chan *Client

	// 注销请求通道
	unregister chan *Client

	// 标的订阅映射: symbol -> clients
	subscriptions map[string]map[*Client]bool

	// 保护subscriptions的锁
	subMu sync.RWMutex

	// 最大订阅标的数
	maxSymbolsPerClient int
}

// NewHub 创建Hub
func NewHub() *Hub {
	return &Hub{
		clients:             make(map[*Client]bool),
		broadcast:           make(chan []byte),
		register:            make(chan *Client),
		unregister:          make(chan *Client),
		subscriptions:       make(map[string]map[*Client]bool),
		maxSymbolsPerClient: 100,
	}
}

// Run 启动Hub
func (h *Hub) Run() {
	for {
		select {
		case client := <-h.register:
			h.clients[client] = true
			log.Printf("Client registered, total: %d", len(h.clients))

		case client := <-h.unregister:
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.send)
				// 清理订阅
				h.removeAllSubscriptions(client)
				log.Printf("Client unregistered, total: %d", len(h.clients))
			}

		case message := <-h.broadcast:
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					// 发送缓冲满，关闭连接
					close(client.send)
					delete(h.clients, client)
				}
			}
		}
	}
}

// Subscribe 客户端订阅标的
func (h *Hub) Subscribe(client *Client, symbols []string) error {
	if len(client.subscriptions)+len(symbols) > h.maxSymbolsPerClient {
		return api.ErrRateLimit
	}

	h.subMu.Lock()
	defer h.subMu.Unlock()

	for _, symbol := range symbols {
		if _, ok := h.subscriptions[symbol]; !ok {
			h.subscriptions[symbol] = make(map[*Client]bool)
		}
		h.subscriptions[symbol][client] = true
		client.subscriptions[symbol] = true
	}

	return nil
}

// Unsubscribe 客户端取消订阅
func (h *Hub) Unsubscribe(client *Client, symbols []string) {
	h.subMu.Lock()
	defer h.subMu.Unlock()

	for _, symbol := range symbols {
		if clients, ok := h.subscriptions[symbol]; ok {
			delete(clients, client)
			if len(clients) == 0 {
				delete(h.subscriptions, symbol)
			}
		}
		delete(client.subscriptions, symbol)
	}
}

// removeAllSubscriptions 移除客户端所有订阅
func (h *Hub) removeAllSubscriptions(client *Client) {
	h.subMu.Lock()
	defer h.subMu.Unlock()

	for symbol := range client.subscriptions {
		if clients, ok := h.subscriptions[symbol]; ok {
			delete(clients, client)
			if len(clients) == 0 {
				delete(h.subscriptions, symbol)
			}
		}
	}
}

// BroadcastToSymbol 向订阅了某标的的所有客户端广播
func (h *Hub) BroadcastToSymbol(symbol string, data []byte) {
	h.subMu.RLock()
	clients := h.subscriptions[symbol]
	h.subMu.RUnlock()

	for client := range clients {
		select {
		case client.send <- data:
		default:
			// 发送缓冲满，稍后处理
		}
	}
}

// GetSubscriptionStats 获取订阅统计
func (h *Hub) GetSubscriptionStats() map[string]interface{} {
	h.subMu.RLock()
	defer h.subMu.RUnlock()

	return map[string]interface{}{
		"total_clients":     len(h.clients),
		"total_subscriptions": len(h.subscriptions),
	}
}

// Client WebSocket客户端
type Client struct {
	hub  *Hub
	conn *websocket.Conn
	send chan []byte

	// 已订阅的标的
	subscriptions map[string]bool
	subMu         sync.RWMutex
}

// NewClient 创建客户端
func NewClient(hub *Hub, conn *websocket.Conn) *Client {
	return &Client{
		hub:           hub,
		conn:          conn,
		send:          make(chan []byte, 256),
		subscriptions: make(map[string]bool),
	}
}

// ReadPump 读取客户端消息
func (c *Client) ReadPump() {
	defer func() {
		c.hub.unregister <- c
		c.conn.Close()
	}()

	c.conn.SetReadLimit(512 * 1024) // 512KB
	c.conn.SetReadDeadline(time.Now().Add(60 * time.Second))
	c.conn.SetPongHandler(func(string) error {
		c.conn.SetReadDeadline(time.Now().Add(60 * time.Second))
		return nil
	})

	for {
		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("WebSocket error: %v", err)
			}
			break
		}

		// 处理客户端消息
		c.handleMessage(message)
	}
}

// WritePump 向客户端写入消息
func (c *Client) WritePump() {
	ticker := time.NewTicker(30 * time.Second)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()

	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
			if !ok {
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			c.conn.WriteMessage(websocket.TextMessage, message)

		case <-ticker.C:
			c.conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

// handleMessage 处理客户端消息
func (c *Client) handleMessage(data []byte) {
	var msg ClientMessage
	if err := json.Unmarshal(data, &msg); err != nil {
		c.sendError(1000, "Invalid message format")
		return
	}

	switch msg.Action {
	case "subscribe":
		c.handleSubscribe(msg.Symbols)
	case "unsubscribe":
		c.handleUnsubscribe(msg.Symbols)
	default:
		c.sendError(1001, "Unknown action")
	}
}

// handleSubscribe 处理订阅请求
func (c *Client) handleSubscribe(symbols []string) {
	if len(symbols) == 0 {
		c.sendError(1002, "Symbols cannot be empty")
		return
	}

	if err := c.hub.Subscribe(c, symbols); err != nil {
		c.sendError(1003, err.Error())
		return
	}

	// 发送确认
	ack := map[string]interface{}{
		"type":    "ack",
		"action":  "subscribe",
		"symbols": symbols,
		"ts":      time.Now().Format(time.RFC3339),
	}
	data, _ := json.Marshal(ack)
	c.send <- data
}

// handleUnsubscribe 处理取消订阅请求
func (c *Client) handleUnsubscribe(symbols []string) {
	c.hub.Unsubscribe(c, symbols)

	ack := map[string]interface{}{
		"type":    "ack",
		"action":  "unsubscribe",
		"symbols": symbols,
		"ts":      time.Now().Format(time.RFC3339),
	}
	data, _ := json.Marshal(ack)
	c.send <- data
}

// sendError 发送错误消息
func (c *Client) sendError(code int, message string) {
	err := map[string]interface{}{
		"type":    "error",
		"code":    code,
		"message": message,
		"ts":      time.Now().Format(time.RFC3339),
	}
	data, _ := json.Marshal(err)
	c.send <- data
}

// ClientMessage 客户端消息结构
type ClientMessage struct {
	Action  string   `json:"action"`
	Symbols []string `json:"symbols"`
}

// Server WebSocket服务器
type Server struct {
	hub *Hub
}

// NewServer 创建WebSocket服务器
func NewServer(hub *Hub) *Server {
	return &Server{hub: hub}
}

// HandleWebSocket 处理WebSocket连接
func (s *Server) HandleWebSocket(c *gin.Context) {
	// 认证检查
	apiKey := c.GetHeader("X-API-Key")
	if apiKey == "" {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "Missing API Key"})
		return
	}

	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		log.Printf("WebSocket upgrade failed: %v", err)
		return
	}

	client := NewClient(s.hub, conn)
	s.hub.register <- client

	go client.WritePump()
	go client.ReadPump()
}

// BroadcastTick 广播Tick数据
func (s *Server) BroadcastTick(symbol string, tick map[string]interface{}) {
	data, err := json.Marshal(tick)
	if err != nil {
		return
	}
	s.hub.BroadcastToSymbol(symbol, data)
}

// BroadcastKLine 广播K线闭合数据
func (s *Server) BroadcastKLine(symbol string, freq string, kline map[string]interface{}) {
	msg := map[string]interface{}{
		"type":   "klines",
		"symbol": symbol,
		"freq":   freq,
		"data":   kline,
		"ts":     time.Now().Format(time.RFC3339),
	}
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}
	s.hub.BroadcastToSymbol(symbol, data)
}