const axios = require('axios');

/**
 * Coze 智能体对话服务
 * 通过 Coze v3 Chat API 与已配置知识库的 Bot 进行对话
 * 支持流式和非流式两种模式，Coze 内部管理会话历史
 */
class CozeChatService {
  constructor() {
    this.baseUrl = (process.env.COZE_BASE_URL || 'https://api.coze.cn') + '/v3';
  }

  _getHeaders() {
    return {
      'Content-Type': 'application/json',
      'Authorization': `Bearer ${process.env.COZE_API_TOKEN}`,
    };
  }

  _getBotId() {
    return process.env.COZE_BOT_ID;
  }

  isConfigured() {
    const token = process.env.COZE_API_TOKEN;
    const botId = process.env.COZE_BOT_ID;
    return token && token !== 'your_coze_api_token' && botId && botId !== 'your_coze_bot_id';
  }

  /**
   * 非流式对话
   * @param {string} userId - 用户标识
   * @param {string} message - 用户消息
   * @param {string|null} conversationId - Coze 会话 ID（续接对话时传入）
   * @param {Array} extraMessages - 额外上下文消息（如语音字幕历史）
   * @returns {{ content: string, conversationId: string }}
   */
  async chat(userId, message, conversationId = null, extraMessages = []) {
    const additionalMessages = [
      ...extraMessages.map(m => ({
        role: m.role,
        content: m.content || m.text,
        content_type: 'text',
      })),
      {
        role: 'user',
        content: message,
        content_type: 'text',
      },
    ];

    const body = {
      bot_id: this._getBotId(),
      user_id: userId,
      additional_messages: additionalMessages,
      stream: false,
      auto_save_history: true,
    };

    if (conversationId) {
      body.conversation_id = conversationId;
    }

    console.log(`[CozeChat] Sending non-stream chat, userId=${userId}, convId=${conversationId || 'new'}`);

    const chatRes = await axios.post(`${this.baseUrl}/chat`, body, {
      headers: this._getHeaders(),
      timeout: 15000,
    });

    const chatData = chatRes.data?.data;
    if (!chatData?.id || !chatData?.conversation_id) {
      throw new Error('Coze chat creation failed: ' + JSON.stringify(chatRes.data));
    }

    const chatId = chatData.id;
    const convId = chatData.conversation_id;

    // 轮询等待完成（最多 60 秒）
    const maxAttempts = 30;
    for (let i = 0; i < maxAttempts; i++) {
      await new Promise(r => setTimeout(r, 2000));

      const statusRes = await axios.get(
        `${this.baseUrl}/chat/retrieve?chat_id=${chatId}&conversation_id=${convId}`,
        { headers: this._getHeaders(), timeout: 10000 }
      );

      const status = statusRes.data?.data?.status;
      if (status === 'completed') break;
      if (status === 'failed' || status === 'requires_action') {
        throw new Error(`Coze chat ended with status: ${status}`);
      }
    }

    // 获取消息列表
    const msgRes = await axios.get(
      `${this.baseUrl}/chat/message/list?chat_id=${chatId}&conversation_id=${convId}`,
      { headers: this._getHeaders(), timeout: 10000 }
    );

    const messages = msgRes.data?.data || [];
    const answerMsg = messages.find(m => m.role === 'assistant' && m.type === 'answer');

    return {
      content: answerMsg?.content || '',
      conversationId: convId,
    };
  }

  /**
   * 流式对话
   * @param {string} userId - 用户标识
   * @param {string} message - 用户消息
   * @param {string|null} conversationId - Coze 会话 ID
   * @param {Array} extraMessages - 额外上下文消息
   * @param {{ onChunk, onDone }} callbacks - 流式回调
   * @returns {{ content: string, conversationId: string }}
   */
  async chatStream(userId, message, conversationId = null, extraMessages = [], { onChunk, onDone }) {
    const additionalMessages = [
      ...extraMessages.map(m => ({
        role: m.role,
        content: m.content || m.text,
        content_type: 'text',
      })),
      {
        role: 'user',
        content: message,
        content_type: 'text',
      },
    ];

    const body = {
      bot_id: this._getBotId(),
      user_id: userId,
      additional_messages: additionalMessages,
      stream: true,
      auto_save_history: true,
    };

    if (conversationId) {
      body.conversation_id = conversationId;
    }

    console.log(`[CozeChat] Sending stream chat, userId=${userId}, convId=${conversationId || 'new'}`);

    const response = await axios.post(`${this.baseUrl}/chat`, body, {
      headers: this._getHeaders(),
      timeout: 60000,
      responseType: 'stream',
    });

    return new Promise((resolve, reject) => {
      let fullContent = '';
      let resultConvId = conversationId;
      let buffer = '';

      response.data.on('data', (chunk) => {
        buffer += chunk.toString();
        const lines = buffer.split('\n');
        buffer = lines.pop() || '';

        let currentEvent = '';

        for (const line of lines) {
          const trimmed = line.trim();

          if (trimmed.startsWith('event:')) {
            currentEvent = trimmed.slice(6).trim();
            continue;
          }

          if (!trimmed.startsWith('data:')) continue;
          const data = trimmed.slice(5).trim();
          if (data === '"[DONE]"' || data === '[DONE]') continue;

          try {
            const parsed = JSON.parse(data);

            if (currentEvent === 'conversation.chat.created') {
              resultConvId = parsed.conversation_id || resultConvId;
            }

            if (currentEvent === 'conversation.message.delta') {
              if (parsed.role === 'assistant' && parsed.type === 'answer') {
                const content = parsed.content || '';
                fullContent += content;
                onChunk?.(content);
              }
            }
          } catch (e) {
            // skip malformed SSE lines
          }
        }
      });

      response.data.on('end', () => {
        onDone?.(fullContent);
        resolve({ content: fullContent, conversationId: resultConvId });
      });

      response.data.on('error', (err) => {
        console.error('[CozeChat] Stream error:', err.message);
        reject(err);
      });
    });
  }
}

module.exports = new CozeChatService();