const express = require('express');
const router = express.Router();
const db = require('../db');

/**
 * GET /api/session/list
 * 获取会话列表（按更新时间倒序，带最后一条消息预览）
 */
router.get('/list', async (req, res) => {
  try {
    const userId = req.query.userId || null;
    const limit = parseInt(req.query.limit) || 50;
    const sessions = await db.getSessionList(userId, limit);
    res.json({
      success: true,
      data: sessions.map((s) => ({
        id: s.id,
        userId: s.user_id,
        mode: s.mode,
        createdAt: s.created_at,
        updatedAt: s.updated_at,
        lastMessage: s.last_message ? (s.last_message.length > 60 ? s.last_message.slice(0, 60) + '...' : s.last_message) : null,
        messageCount: parseInt(s.message_count) || 0,
      })),
    });
  } catch (err) {
    console.error('[Session] List failed:', err.message);
    res.status(500).json({ success: false, error: err.message });
  }
});

/**
 * DELETE /api/session/:id
 * 删除会话及其所有消息
 */
router.delete('/:id', async (req, res) => {
  try {
    const { id } = req.params;
    await db.deleteSession(id);
    res.json({ success: true });
  } catch (err) {
    console.error('[Session] Delete failed:', err.message);
    res.status(500).json({ success: false, error: err.message });
  }
});

/**
 * GET /api/session/:id/history
 * 获取会话完整历史（用于文字↔语音切换时加载上下文）
 */
router.get('/:id/history', async (req, res) => {
  try {
    const { id } = req.params;
    const limit = parseInt(req.query.limit) || 20;
    const format = req.query.format || 'llm'; // 'llm' | 'full'

    let messages;
    if (format === 'full') {
      messages = await db.getRecentMessages(id, limit);
    } else {
      messages = await db.getHistoryForLLM(id, limit);
    }

    const session = await db.getSession(id);

    res.json({
      success: true,
      data: {
        sessionId: id,
        mode: session?.mode || null,
        messages,
        count: messages.length,
      },
    });
  } catch (err) {
    console.error('[Session] Get history failed:', err.message);
    res.status(500).json({ success: false, error: err.message });
  }
});

/**
 * POST /api/session/:id/switch
 * 切换会话模式（voice ↔ chat），返回上下文历史
 */
router.post('/:id/switch', async (req, res) => {
  try {
    const { id } = req.params;
    const { targetMode } = req.body; // 'voice' | 'chat'

    if (!targetMode || !['voice', 'chat'].includes(targetMode)) {
      return res.status(400).json({ success: false, error: 'targetMode must be "voice" or "chat"' });
    }

    // 更新会话模式
    await db.updateSessionMode(id, targetMode);

    // 返回最近的对话历史供新模式使用
    const history = await db.getHistoryForLLM(id, 20);

    console.log(`[Session] Switched ${id} to ${targetMode}, history: ${history.length} messages`);

    res.json({
      success: true,
      data: {
        sessionId: id,
        mode: targetMode,
        history,
        count: history.length,
      },
    });
  } catch (err) {
    console.error('[Session] Switch failed:', err.message);
    res.status(500).json({ success: false, error: err.message });
  }
});

module.exports = router;