const express = require('express');
const ChatService = require('../services/ChatService');

const router = express.Router();
const chatService = new ChatService();

/**
 * 发送消息
 * POST /api/chat/send
 */
router.post('/send', async (req, res) => {
  try {
    const { conversationId, message, options = {} } = req.body;
    
    // 验证必需参数
    if (!conversationId || isNaN(conversationId)) {
      return res.status(400).json({
        success: false,
        error: '无效的对话ID',
        message: '参数错误'
      });
    }
    
    if (!message || message.trim().length === 0) {
      return res.status(400).json({
        success: false,
        error: '消息内容不能为空',
        message: '参数错误'
      });
    }
    
    // 限制消息长度
    if (message.length > 10000) {
      return res.status(400).json({
        success: false,
        error: '消息长度不能超过10000个字符',
        message: '参数错误'
      });
    }
    
    // 处理消息
    const result = await chatService.processMessage(
      parseInt(conversationId), 
      message.trim(), 
      options
    );
    
    res.json({
      success: true,
      data: result,
      message: '消息发送成功'
    });
    
  } catch (error) {
    console.error('发送消息API错误:', error);
    
    // 根据错误类型返回不同的HTTP状态码
    let statusCode = 500;
    let errorMessage = '发送消息失败';
    
    if (error.message === '对话不存在') {
      statusCode = 404;
      errorMessage = '对话未找到';
    } else if (error.message.includes('AI服务配置错误')) {
      statusCode = 503;
      errorMessage = 'AI服务配置错误';
    } else if (error.message.includes('请求过于频繁')) {
      statusCode = 429;
      errorMessage = '请求过于频繁';
    } else if (error.message.includes('网络')) {
      statusCode = 503;
      errorMessage = '网络连接异常';
    }
    
    res.status(statusCode).json({
      success: false,
      error: error.message,
      message: errorMessage
    });
  }
});

/**
 * 发送流式消息
 * POST /api/chat/stream
 */
router.post('/stream', async (req, res) => {
  try {
    const { conversationId, message, options = {} } = req.body;
    
    // 验证必需参数
    if (!conversationId || isNaN(conversationId)) {
      return res.status(400).json({
        success: false,
        error: '无效的对话ID',
        message: '参数错误'
      });
    }
    
    if (!message || message.trim().length === 0) {
      return res.status(400).json({
        success: false,
        error: '消息内容不能为空',
        message: '参数错误'
      });
    }
    
    // 设置流式响应头
    res.writeHead(200, {
      'Content-Type': 'text/plain; charset=utf-8',
      'Transfer-Encoding': 'chunked',
      'Cache-Control': 'no-cache',
      'Connection': 'keep-alive'
    });
    
    const streamResult = await chatService.processStreamMessage(
      parseInt(conversationId), 
      message.trim(), 
      options
    );
    
    // 发送用户消息信息
    res.write(JSON.stringify({
      type: 'user_message',
      data: streamResult.userMessage
    }) + '\n');
    
    let fullContent = '';
    
    // 处理流式响应
    streamResult.stream.on('data', (chunk) => {
      const lines = chunk.toString().split('\n');
      
      for (const line of lines) {
        if (line.startsWith('data: ')) {
          const data = line.slice(6);
          
          if (data === '[DONE]') {
            // 流式响应结束
            res.write(JSON.stringify({
              type: 'done',
              data: { content: fullContent }
            }) + '\n');
            res.end();
            
            // 保存完整的AI回复
            chatService.completeStreamMessage(conversationId, fullContent)
              .catch(error => {
                console.error('保存流式消息失败:', error);
              });
            
            return;
          }
          
          try {
            const parsed = JSON.parse(data);
            const delta = parsed.choices?.[0]?.delta;
            
            if (delta?.content) {
              fullContent += delta.content;
              
              // 发送增量内容
              res.write(JSON.stringify({
                type: 'content',
                data: { delta: delta.content, content: fullContent }
              }) + '\n');
            }
            
          } catch (parseError) {
            console.error('解析流式数据失败:', parseError);
          }
        }
      }
    });
    
    streamResult.stream.on('error', (error) => {
      console.error('流式响应错误:', error);
      res.write(JSON.stringify({
        type: 'error',
        data: { error: error.message }
      }) + '\n');
      res.end();
    });
    
  } catch (error) {
    console.error('流式消息API错误:', error);
    
    if (!res.headersSent) {
      res.status(500).json({
        success: false,
        error: error.message,
        message: '流式消息发送失败'
      });
    } else {
      res.write(JSON.stringify({
        type: 'error',
        data: { error: error.message }
      }) + '\n');
      res.end();
    }
  }
});

/**
 * 重新生成回复
 * POST /api/chat/regenerate
 */
router.post('/regenerate', async (req, res) => {
  try {
    const { conversationId, options = {} } = req.body;
    
    if (!conversationId || isNaN(conversationId)) {
      return res.status(400).json({
        success: false,
        error: '无效的对话ID',
        message: '参数错误'
      });
    }
    
    const result = await chatService.regenerateResponse(
      parseInt(conversationId), 
      options
    );
    
    res.json({
      success: true,
      data: result,
      message: '重新生成回复成功'
    });
    
  } catch (error) {
    console.error('重新生成回复API错误:', error);
    
    let statusCode = 500;
    let errorMessage = '重新生成回复失败';
    
    if (error.message === '对话不存在') {
      statusCode = 404;
      errorMessage = '对话未找到';
    } else if (error.message === '没有找到用户消息') {
      statusCode = 400;
      errorMessage = '没有可重新生成的消息';
    }
    
    res.status(statusCode).json({
      success: false,
      error: error.message,
      message: errorMessage
    });
  }
});

/**
 * 检查LLM服务状态
 * GET /api/chat/status
 */
router.get('/status', async (req, res) => {
  try {
    const status = await chatService.checkLLMStatus();
    
    res.json({
      success: true,
      data: status,
      message: 'LLM服务状态检查完成'
    });
    
  } catch (error) {
    console.error('检查LLM状态API错误:', error);
    res.status(500).json({
      success: false,
      error: error.message,
      message: '检查LLM状态失败'
    });
  }
});

/**
 * 获取聊天统计信息
 * GET /api/chat/stats
 */
router.get('/stats', async (req, res) => {
  try {
    const stats = await chatService.getChatStats();
    
    res.json({
      success: true,
      data: stats,
      message: '获取聊天统计成功'
    });
    
  } catch (error) {
    console.error('获取聊天统计API错误:', error);
    res.status(500).json({
      success: false,
      error: error.message,
      message: '获取聊天统计失败'
    });
  }
});

/**
 * 清除缓存
 * POST /api/chat/clear-cache
 */
router.post('/clear-cache', async (req, res) => {
  try {
    const { type = 'all' } = req.body;
    
    const cacheManager = require('../utils/cache');
    
    if (type === 'all') {
      cacheManager.clearAll();
    } else {
      cacheManager.clear(type);
    }
    
    res.json({
      success: true,
      message: `${type}缓存清理成功`
    });
    
  } catch (error) {
    console.error('清除缓存API错误:', error);
    res.status(500).json({
      success: false,
      error: error.message,
      message: '清除缓存失败'
    });
  }
});

/**
 * 获取对话上下文
 * GET /api/chat/context/:conversationId
 */
router.get('/context/:conversationId', async (req, res) => {
  try {
    const { conversationId } = req.params;
    const { maxTokens = 4000 } = req.query;
    
    if (!conversationId || isNaN(conversationId)) {
      return res.status(400).json({
        success: false,
        error: '无效的对话ID',
        message: '参数错误'
      });
    }
    
    const context = await chatService.getConversationContext(
      parseInt(conversationId), 
      parseInt(maxTokens)
    );
    
    res.json({
      success: true,
      data: {
        context,
        messageCount: context.length,
        estimatedTokens: context.reduce((sum, msg) => 
          sum + (msg.content?.length || 0), 0
        )
      },
      message: '获取对话上下文成功'
    });
    
  } catch (error) {
    console.error('获取对话上下文API错误:', error);
    res.status(500).json({
      success: false,
      error: error.message,
      message: '获取对话上下文失败'
    });
  }
});

module.exports = router;