package ws

import (
	"fmt"
	"log"
	"sync"
	"time"
)

// SessionState 会话状态
type SessionState struct {
	SessionID      string           `json:"session_id"`
	UserID         string           `json:"user_id"`
	State          string           `json:"state"` // idle, thinking, streaming, error
	ConnectedAt    time.Time        `json:"connected_at"`
	LastActivity   time.Time        `json:"last_activity"`
	MessageCount   int              `json:"message_count"`
	RecentMessages []SessionMessage `json:"recent_messages,omitempty"`
}

// SessionMessage 会话消息记录
type SessionMessage struct {
	Role      string `json:"role"`      // user, assistant, system
	Content   string `json:"content"`   // 截断到 100 字符
	Timestamp int64  `json:"timestamp"`
}

// Message 完整对话消息（用于缓存）
type Message struct {
	Role      string `json:"role"`
	Content   string `json:"content"`
	Timestamp int64  `json:"timestamp"`
}

const maxRecentMessages = 20

// Hub WebSocket连接池
type Hub struct {
	mu         sync.RWMutex
	clients    map[*Client]bool
	broadcast  chan []byte
	register   chan *Client
	unregister chan *Client

	// 按用户ID索引的客户端映射
	userClients map[string]map[*Client]bool

	// 会话状态追踪 (sessionID -> SessionState)
	sessions map[string]*SessionState

	// 对话缓存：key = "userID:sessionID", value = []Message
	conversationCache sync.Map
	convCacheMu       sync.Mutex
}

// NewHub 创建WebSocket Hub
func NewHub() *Hub {
	return &Hub{
		clients:     make(map[*Client]bool),
		broadcast:   make(chan []byte, 256),
		register:    make(chan *Client),
		unregister:  make(chan *Client),
		userClients: make(map[string]map[*Client]bool),
		sessions:    make(map[string]*SessionState),
	}
}

// Run 启动Hub主循环
func (h *Hub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = true

			// 用户索引
			if h.userClients[client.UserID] == nil {
				h.userClients[client.UserID] = make(map[*Client]bool)
			}
			h.userClients[client.UserID][client] = true

			// 会话状态追踪：如果该session尚未存在则创建
			if _, exists := h.sessions[client.SessionID]; !exists {
				h.sessions[client.SessionID] = &SessionState{
					SessionID:    client.SessionID,
					UserID:       client.UserID,
					State:        "idle",
					ConnectedAt:  time.Now(),
					LastActivity: time.Now(),
					MessageCount: 0,
				}
			}
			h.mu.Unlock()

			log.Printf("[WS] 客户端连接: user=%s session=%s (当前连接数: %d)",
				client.UserID, client.SessionID, len(h.clients))

		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.Send)

				// 清理用户索引
				if h.userClients[client.UserID] != nil {
					delete(h.userClients[client.UserID], client)
					if len(h.userClients[client.UserID]) == 0 {
						delete(h.userClients, client.UserID)
					}
				}

				// 检查该session是否还有其他连接，没有则移除会话状态
				hasOtherConn := false
				if clients, ok := h.userClients[client.UserID]; ok {
					for c := range clients {
						if c.SessionID == client.SessionID {
							hasOtherConn = true
							break
						}
					}
				}
				if !hasOtherConn {
					delete(h.sessions, client.SessionID)
				}
			}
			h.mu.Unlock()

			log.Printf("[WS] 客户端断开: user=%s session=%s (当前连接数: %d)",
				client.UserID, client.SessionID, len(h.clients))

		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.Send <- message:
				default:
					// 客户端发送通道已满，跳过
					close(client.Send)
					delete(h.clients, client)
				}
			}
			h.mu.RUnlock()
		}
	}
}

// Register 注册客户端到Hub（供外部包使用）
func (h *Hub) Register(client *Client) {
	h.register <- client
}

// SendToUser 向指定用户的所有连接发送消息
func (h *Hub) SendToUser(userID string, message []byte) {
	h.mu.RLock()
	defer h.mu.RUnlock()

	if clients, ok := h.userClients[userID]; ok {
		for client := range clients {
			select {
			case client.Send <- message:
			default:
				// 跳过阻塞的客户端
			}
		}
	}
}

// SendToSession 向指定会话的连接发送消息
func (h *Hub) SendToSession(userID, sessionID string, message []byte) {
	h.mu.RLock()
	defer h.mu.RUnlock()

	if clients, ok := h.userClients[userID]; ok {
		for client := range clients {
			if client.SessionID == sessionID {
				select {
				case client.Send <- message:
				default:
				}
			}
		}
	}
}

// ClientCount 获取当前连接数
func (h *Hub) ClientCount() int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return len(h.clients)
}

// UserClientCount 获取指定用户的连接数
func (h *Hub) UserClientCount(userID string) int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	if clients, ok := h.userClients[userID]; ok {
		return len(clients)
	}
	return 0
}

// GetActiveSessions 返回所有活跃会话的列表
func (h *Hub) GetActiveSessions() []*SessionState {
	h.mu.RLock()
	defer h.mu.RUnlock()

	result := make([]*SessionState, 0, len(h.sessions))
	for _, s := range h.sessions {
		// 返回副本避免外部修改
		cp := *s
		// 不包含 recent_messages 在列表接口中
		cp.RecentMessages = nil
		result = append(result, &cp)
	}
	return result
}

// GetActiveSessionsByUser 返回按用户分组的活跃会话列表
func (h *Hub) GetActiveSessionsByUser() map[string][]*SessionState {
	h.mu.RLock()
	defer h.mu.RUnlock()

	result := make(map[string][]*SessionState)
	for _, s := range h.sessions {
		cp := *s
		cp.RecentMessages = nil
		result[s.UserID] = append(result[s.UserID], &cp)
	}
	return result
}

// GetUserSessions 获取某用户的所有活跃会话
func (h *Hub) GetUserSessions(userID string) []*SessionState {
	h.mu.RLock()
	defer h.mu.RUnlock()

	var result []*SessionState
	if clients, ok := h.userClients[userID]; ok {
		seen := make(map[string]bool)
		for c := range clients {
			if !seen[c.SessionID] {
				if s, ok := h.sessions[c.SessionID]; ok {
					cp := *s
					cp.RecentMessages = nil
					result = append(result, &cp)
					seen[c.SessionID] = true
				}
			}
		}
	}
	return result
}

// GetSession 返回指定会话的详细信息（含最近消息）
func (h *Hub) GetSession(sessionID string) *SessionState {
	h.mu.RLock()
	defer h.mu.RUnlock()

	s, ok := h.sessions[sessionID]
	if !ok {
		return nil
	}

	// 返回副本
	cp := *s
	if s.RecentMessages != nil {
		cp.RecentMessages = make([]SessionMessage, len(s.RecentMessages))
		copy(cp.RecentMessages, s.RecentMessages)
	}
	return &cp
}

// UpdateSessionState 更新会话状态
func (h *Hub) UpdateSessionState(sessionID, state string) {
	h.mu.Lock()
	defer h.mu.Unlock()

	if s, ok := h.sessions[sessionID]; ok {
		s.State = state
		s.LastActivity = time.Now()
	}
}

// RecordMessage 记录消息到会话
func (h *Hub) RecordMessage(sessionID, role, content string) {
	h.mu.Lock()
	defer h.mu.Unlock()

	s, ok := h.sessions[sessionID]
	if !ok {
		return
	}

	s.MessageCount++
	s.LastActivity = time.Now()

	// 截断内容到 100 字符
	runes := []rune(content)
	if len(runes) > 100 {
		content = string(runes[:100]) + "..."
	}

	s.RecentMessages = append(s.RecentMessages, SessionMessage{
		Role:      role,
		Content:   content,
		Timestamp: time.Now().UnixMilli(),
	})

	// 只保留最近 N 条消息
	if len(s.RecentMessages) > maxRecentMessages {
		s.RecentMessages = s.RecentMessages[len(s.RecentMessages)-maxRecentMessages:]
	}
}

// ========== 对话缓存方法 ==========

// cacheKey 生成对话缓存 key
func cacheKey(userID, sessionID string) string {
	return fmt.Sprintf("%s:%s", userID, sessionID)
}

// CacheMessage 缓存单条消息到对话历史
func (h *Hub) CacheMessage(userID, sessionID string, msg Message) {
	key := cacheKey(userID, sessionID)

	h.convCacheMu.Lock()
	defer h.convCacheMu.Unlock()

	existing, _ := h.conversationCache.Load(key)
	var messages []Message
	if existing != nil {
		messages = existing.([]Message)
	}
	messages = append(messages, msg)
	h.conversationCache.Store(key, messages)
}

// GetConversation 获取完整对话历史
func (h *Hub) GetConversation(userID, sessionID string) []Message {
	key := cacheKey(userID, sessionID)

	val, ok := h.conversationCache.Load(key)
	if !ok {
		return []Message{}
	}

	messages, ok := val.([]Message)
	if !ok {
		return []Message{}
	}
	return messages
}

// DeleteConversation 删除对话缓存
func (h *Hub) DeleteConversation(userID, sessionID string) {
	key := cacheKey(userID, sessionID)
	h.conversationCache.Delete(key)
}