/**
 * 消息状态管理器
 * 纯状态管理类，不包含业务逻辑
 * 负责管理所有消息相关的内存状态
 */

import type {
  ConversationResponse,
  MessageResponse,
} from '../../types/dto';
import type {
  MessageManagerState,
  MessageSubscriber,
  MessageEvent,
  IMessageStateManager,
} from './types';

export class MessageStateManager implements IMessageStateManager {
  private state: MessageManagerState;

  constructor() {
    this.state = {
      conversations: new Map(),
      conversationList: [],
      messagesMap: new Map(),
      totalUnreadCount: 0,
      systemUnreadCount: 0,
      isWSConnected: false,
      currentConversationId: null,
      isLoadingConversations: false,
      loadingMessagesSet: new Set(),
      isInitialized: false,
      subscribers: new Set(),
      typingUsersMap: new Map(),
      mutedStatusMap: new Map(),
    };
  }

  // ==================== 获取状态 ====================

  getState(): MessageManagerState {
    return this.state;
  }

  getConversations(): ConversationResponse[] {
    return this.state.conversationList;
  }

  getConversation(conversationId: string): ConversationResponse | null {
    const normalizedId = this.normalizeConversationId(conversationId);
    return this.state.conversations.get(normalizedId) || null;
  }

  getMessages(conversationId: string): MessageResponse[] {
    const normalizedId = this.normalizeConversationId(conversationId);
    return this.state.messagesMap.get(normalizedId) || [];
  }

  getUnreadCount(): { total: number; system: number } {
    return {
      total: this.state.totalUnreadCount,
      system: this.state.systemUnreadCount,
    };
  }

  isConnected(): boolean {
    return this.state.isWSConnected;
  }

  isLoading(): boolean {
    return this.state.isLoadingConversations;
  }

  isLoadingMessages(conversationId: string): boolean {
    const normalizedId = this.normalizeConversationId(conversationId);
    return this.state.loadingMessagesSet.has(normalizedId);
  }

  getTypingUsers(groupId: string): string[] {
    return this.state.typingUsersMap.get(groupId) || [];
  }

  isMuted(groupId: string): boolean {
    return this.state.mutedStatusMap.get(groupId) || false;
  }

  getActiveConversation(): string | null {
    return this.state.currentConversationId;
  }

  // ==================== 设置状态 ====================

  setConversations(conversations: Map<string, ConversationResponse>): void {
    this.state.conversations = conversations;
    this.updateConversationList();
  }

  updateConversation(conversation: ConversationResponse): void {
    const id = this.normalizeConversationId(conversation.id);
    this.state.conversations.set(id, { ...conversation, id });
    this.updateConversationList();
  }

  removeConversation(conversationId: string): void {
    const normalizedId = this.normalizeConversationId(conversationId);
    const target = this.state.conversations.get(normalizedId);
    const removedUnread = target?.unread_count || 0;

    this.state.conversations.delete(normalizedId);
    this.state.messagesMap.delete(normalizedId);
    this.state.totalUnreadCount = Math.max(0, this.state.totalUnreadCount - removedUnread);
    
    if (this.state.currentConversationId === normalizedId) {
      this.state.currentConversationId = null;
    }
    
    this.updateConversationList();
  }

  setMessages(conversationId: string, messages: MessageResponse[]): void {
    const normalizedId = this.normalizeConversationId(conversationId);
    this.state.messagesMap.set(normalizedId, messages);
  }

  addMessage(conversationId: string, message: MessageResponse): void {
    const normalizedId = this.normalizeConversationId(conversationId);
    const existing = this.state.messagesMap.get(normalizedId) || [];
    const exists = existing.some(m => String(m.id) === String(message.id));
    
    if (!exists) {
      const updated = this.mergeMessagesById(existing, [message]);
      this.state.messagesMap.set(normalizedId, updated);
    }
  }

  updateMessage(conversationId: string, messageId: string, updates: Partial<MessageResponse>): void {
    const normalizedId = this.normalizeConversationId(conversationId);
    const messages = this.state.messagesMap.get(normalizedId);
    if (!messages) return;

    const updated = messages.map(m => 
      String(m.id) === String(messageId) ? { ...m, ...updates } : m
    );
    this.state.messagesMap.set(normalizedId, updated);
  }

  setUnreadCount(total: number, system: number): void {
    this.state.totalUnreadCount = total;
    this.state.systemUnreadCount = system;
  }

  setSSEConnected(connected: boolean): void {
    this.state.isWSConnected = connected;
  }

  setCurrentConversation(conversationId: string | null): void {
    this.state.currentConversationId = conversationId;
  }

  setLoading(loading: boolean): void {
    this.state.isLoadingConversations = loading;
  }

  setLoadingMessages(conversationId: string, loading: boolean): void {
    const normalizedId = this.normalizeConversationId(conversationId);
    if (loading) {
      this.state.loadingMessagesSet.add(normalizedId);
    } else {
      this.state.loadingMessagesSet.delete(normalizedId);
    }
  }

  setTypingUsers(groupId: string, users: string[]): void {
    this.state.typingUsersMap.set(groupId, users);
  }

  setMutedStatus(groupId: string, isMuted: boolean): void {
    this.state.mutedStatusMap.set(groupId, isMuted);
  }

  setInitialized(initialized: boolean): void {
    this.state.isInitialized = initialized;
  }

  // ==================== 订阅机制 ====================

  subscribe(subscriber: MessageSubscriber): () => void {
    this.state.subscribers.add(subscriber);
    return () => {
      this.state.subscribers.delete(subscriber);
    };
  }

  notifySubscribers(event: MessageEvent): void {
    this.state.subscribers.forEach(subscriber => {
      try {
        subscriber(event);
      } catch (error) {
        console.error('[MessageStateManager] 订阅者执行失败:', error);
      }
    });
  }

  // ==================== 工具方法 ====================

  private normalizeConversationId(conversationId: string | number | null | undefined): string {
    return conversationId == null ? '' : String(conversationId);
  }

  /**
   * 更新会话列表排序
   * 排序规则：置顶优先，再按最后消息时间排序
   */
  private updateConversationList(): void {
    const list = Array.from(this.state.conversations.values()).sort((a, b) => {
      const aPinned = a.is_pinned ? 1 : 0;
      const bPinned = b.is_pinned ? 1 : 0;
      if (aPinned !== bPinned) {
        return bPinned - aPinned;
      }
      const aTime = new Date(a.last_message_at || a.updated_at || 0).getTime();
      const bTime = new Date(b.last_message_at || b.updated_at || 0).getTime();
      return bTime - aTime;
    });
    this.state.conversationList = list;
  }

  /**
   * 按 message_id 合并消息并按 seq 排序
   * 后者覆盖前者，可用来吸收更完整的同 ID 消息体
   */
  private mergeMessagesById(base: MessageResponse[], incoming: MessageResponse[]): MessageResponse[] {
    if (incoming.length === 0) return base;
    const merged = new Map<string, MessageResponse>();
    [...base, ...incoming].forEach(msg => {
      merged.set(String(msg.id), msg);
    });
    return Array.from(merged.values()).sort((a, b) => a.seq - b.seq);
  }

  // ==================== 重置 ====================

  reset(): void {
    this.state.conversations.clear();
    this.state.conversationList = [];
    this.state.messagesMap.clear();
    this.state.totalUnreadCount = 0;
    this.state.systemUnreadCount = 0;
    this.state.isWSConnected = false;
    this.state.currentConversationId = null;
    this.state.isLoadingConversations = false;
    this.state.loadingMessagesSet.clear();
    this.state.isInitialized = false;
    this.state.typingUsersMap.clear();
    this.state.mutedStatusMap.clear();
  }
}

// 单例导出
export const messageStateManager = new MessageStateManager();