const Message = require('../models/Message');
const ConversationService = require('./ConversationService');
const LLMApiClient = require('./LLMApiClient');
const cacheManager = require('../utils/cache');

class ChatService {
  constructor() {
    this.conversationService = new ConversationService();
    this.llmClient = new LLMApiClient();
    this.cachePrefix = 'chat_service';
  }

  /**
   * 处理用户消息并获取AI回复
   */
  async processMessage(conversationId, userMessage, options = {}) {
    try {
      // 验证输入
      if (!conversationId || isNaN(conversationId)) {
        throw new Error('无效的对话ID');
      }

      if (!userMessage || userMessage.trim().length === 0) {
        throw new Error('消息内容不能为空');
      }

      const trimmedMessage = userMessage.trim();
      
      // 确保对话存在
      const conversation = await this.conversationService.getConversationById(conversationId);
      if (!conversation) {
        throw new Error('对话不存在');
      }

      console.log(`处理消息: 对话${conversationId}, 内容: ${trimmedMessage.substring(0, 50)}...`);

      // 1. 保存用户消息
      const userMsg = await Message.create(conversationId, 'user', trimmedMessage);

      // 2. 获取对话历史作为上下文
      const conversationHistory = await this.getConversationContext(conversationId);

      // 3. 检查缓存
      const cacheKey = this.generateCacheKey(conversationHistory);
      let cachedResponse = cacheManager.getCachedApiResponse(conversationHistory);
      
      let aiResponse;
      if (cachedResponse && !options.skipCache) {
        console.log('使用缓存的AI回复');
        aiResponse = cachedResponse;
      } else {
        // 4. 调用LLM API获取回复
        aiResponse = await this.getLLMResponse(conversationHistory, options);
        
        // 5. 缓存API响应
        if (aiResponse && !options.skipCache) {
          cacheManager.cacheApiResponse(conversationHistory, aiResponse);
        }
      }

      if (!aiResponse || !aiResponse.content) {
        throw new Error('LLM服务返回无效响应');
      }

      // 6. 保存AI回复
      const aiMsg = await Message.create(conversationId, 'assistant', aiResponse.content);

      // 7. 更新对话活动时间
      await this.conversationService.updateLastActivity(conversationId);

      // 8. 如果是对话的第一条消息，自动生成标题
      if (conversation.title === '新对话') {
        await this.conversationService.generateConversationTitle(conversationId);
      }

      // 9. 更新上下文缓存
      this.updateContextCache(conversationId);

      const result = {
        userMessage: {
          id: userMsg.id,
          content: userMsg.content,
          timestamp: userMsg.timestamp
        },
        aiResponse: {
          id: aiMsg.id,
          content: aiMsg.content,
          timestamp: aiMsg.timestamp
        },
        conversationId: conversationId,
        usage: aiResponse.usage
      };

      console.log(`消息处理完成: 对话${conversationId}`);
      return result;

    } catch (error) {
      console.error('ChatService.processMessage错误:', error);
      throw error;
    }
  }

  /**
   * 处理流式消息响应
   */
  async processStreamMessage(conversationId, userMessage, options = {}) {
    try {
      // 验证输入
      if (!conversationId || isNaN(conversationId)) {
        throw new Error('无效的对话ID');
      }

      if (!userMessage || userMessage.trim().length === 0) {
        throw new Error('消息内容不能为空');
      }

      const trimmedMessage = userMessage.trim();

      // 确保对话存在
      const conversation = await this.conversationService.getConversationById(conversationId);
      if (!conversation) {
        throw new Error('对话不存在');
      }

      console.log(`处理流式消息: 对话${conversationId}`);

      // 1. 保存用户消息
      const userMsg = await Message.create(conversationId, 'user', trimmedMessage);

      // 2. 获取对话历史
      const conversationHistory = await this.getConversationContext(conversationId);

      // 3. 获取流式响应
      const stream = await this.llmClient.createStreamChatCompletion(conversationHistory, {
        ...options,
        stream: true
      });

      // 返回流式响应处理函数
      return {
        userMessage: {
          id: userMsg.id,
          content: userMsg.content,
          timestamp: userMsg.timestamp
        },
        stream: stream,
        conversationId: conversationId
      };

    } catch (error) {
      console.error('ChatService.processStreamMessage错误:', error);
      throw error;
    }
  }

  /**
   * 完成流式消息处理（保存完整的AI回复）
   */
  async completeStreamMessage(conversationId, aiContent) {
    try {
      if (!aiContent || aiContent.trim().length === 0) {
        throw new Error('AI回复内容为空');
      }

      // 保存AI回复
      const aiMsg = await Message.create(conversationId, 'assistant', aiContent.trim());

      // 更新对话活动时间
      await this.conversationService.updateLastActivity(conversationId);

      // 更新上下文缓存
      this.updateContextCache(conversationId);

      return {
        id: aiMsg.id,
        content: aiMsg.content,
        timestamp: aiMsg.timestamp
      };

    } catch (error) {
      console.error('ChatService.completeStreamMessage错误:', error);
      throw error;
    }
  }

  /**
   * 获取对话上下文
   */
  async getConversationContext(conversationId, maxTokens = 4000) {
    try {
      // 先尝试从缓存获取
      let context = cacheManager.getConversationContext(conversationId);
      if (context) {
        console.log(`从缓存获取对话上下文: ${conversationId}`);
        return context;
      }

      // 从数据库获取
      context = await Message.getConversationHistory(conversationId, maxTokens);
      
      // 缓存上下文
      cacheManager.cacheConversationContext(conversationId, context);
      
      console.log(`获取对话上下文: ${conversationId}, ${context.length}条消息`);
      return context;

    } catch (error) {
      console.error('ChatService.getConversationContext错误:', error);
      throw new Error('获取对话上下文失败');
    }
  }

  /**
   * 调用LLM API获取回复
   */
  async getLLMResponse(messages, options = {}) {
    try {
      const llmOptions = {
        temperature: options.temperature,
        max_tokens: options.max_tokens,
        top_p: options.top_p,
        frequency_penalty: options.frequency_penalty,
        presence_penalty: options.presence_penalty,
        model: options.model
      };

      // 移除undefined值
      Object.keys(llmOptions).forEach(key => {
        if (llmOptions[key] === undefined) {
          delete llmOptions[key];
        }
      });

      console.log('调用LLM API:', JSON.stringify(llmOptions, null, 2));

      const response = await this.llmClient.createChatCompletion(messages, llmOptions);
      
      console.log('LLM API响应:', {
        model: response.model,
        usage: response.usage,
        contentLength: response.content?.length || 0
      });

      return response;

    } catch (error) {
      console.error('ChatService.getLLMResponse错误:', error);
      
      // 根据错误类型返回更友好的错误信息
      if (error.message.includes('API密钥')) {
        throw new Error('AI服务配置错误，请联系管理员');
      } else if (error.message.includes('请求频率')) {
        throw new Error('请求过于频繁，请稍后再试');
      } else if (error.message.includes('网络')) {
        throw new Error('网络连接异常，请检查网络设置');
      } else {
        throw new Error('AI服务暂时不可用，请稍后重试');
      }
    }
  }

  /**
   * 生成缓存键
   */
  generateCacheKey(messages) {
    const messageString = JSON.stringify(messages);
    return cacheManager.generateKey('chat_completion', messageString);
  }

  /**
   * 更新上下文缓存
   */
  updateContextCache(conversationId) {
    try {
      // 删除旧的上下文缓存，强制下次重新获取
      cacheManager.deleteConversationContext(conversationId);
      
      // 清除相关的消息缓存
      this.conversationService.clearConversationCache(conversationId);
      
    } catch (error) {
      console.error('更新上下文缓存失败:', error);
    }
  }

  /**
   * 重新生成AI回复
   */
  async regenerateResponse(conversationId, options = {}) {
    try {
      // 获取最后一条用户消息
      const messages = await Message.getRecentMessages(conversationId, 10);
      const lastUserMessage = messages.reverse().find(msg => msg.role === 'user');
      
      if (!lastUserMessage) {
        throw new Error('没有找到用户消息');
      }

      // 删除最后一条AI回复（如果存在）
      const lastMessage = messages[messages.length - 1];
      if (lastMessage && lastMessage.role === 'assistant') {
        await Message.delete(lastMessage.id);
        console.log('删除上一条AI回复');
      }

      // 获取更新后的对话历史
      const conversationHistory = await this.getConversationContext(conversationId);

      // 强制跳过缓存，重新生成回复
      const aiResponse = await this.getLLMResponse(conversationHistory, {
        ...options,
        skipCache: true
      });

      if (!aiResponse || !aiResponse.content) {
        throw new Error('重新生成回复失败');
      }

      // 保存新的AI回复
      const aiMsg = await Message.create(conversationId, 'assistant', aiResponse.content);

      // 更新对话活动时间
      await this.conversationService.updateLastActivity(conversationId);

      // 更新上下文缓存
      this.updateContextCache(conversationId);

      const result = {
        id: aiMsg.id,
        content: aiMsg.content,
        timestamp: aiMsg.timestamp,
        usage: aiResponse.usage
      };

      console.log(`重新生成回复完成: 对话${conversationId}`);
      return result;

    } catch (error) {
      console.error('ChatService.regenerateResponse错误:', error);
      throw error;
    }
  }

  /**
   * 检查LLM服务状态
   */
  async checkLLMStatus() {
    try {
      const status = await this.llmClient.checkConnection();
      return status;
    } catch (error) {
      console.error('检查LLM状态失败:', error);
      return {
        status: 'error',
        message: '无法连接到LLM服务'
      };
    }
  }

  /**
   * 获取聊天统计信息
   */
  async getChatStats() {
    try {
      // 这里可以添加更多统计信息
      const cacheStats = cacheManager.getStats();
      
      return {
        cache: cacheStats,
        llm: {
          connected: (await this.checkLLMStatus()).status === 'connected'
        }
      };
    } catch (error) {
      console.error('获取聊天统计信息失败:', error);
      return {
        error: error.message
      };
    }
  }
}

module.exports = ChatService;