const Redis = require('ioredis');

// ============ 配置 ============
const REDIS_URL = process.env.REDIS_URL || 'redis://127.0.0.1:6379';
const REDIS_PASSWORD = process.env.REDIS_PASSWORD || '';
const REDIS_DB = parseInt(process.env.REDIS_DB) || 0;
const KEY_PREFIX = process.env.REDIS_KEY_PREFIX || 'bigwo:';

const HISTORY_MAX_LEN = 10; // 5轮 × 2条/轮
const HISTORY_TTL_S = 1800; // 30分钟
const KB_CACHE_HIT_TTL_S = 300; // 5分钟
const KB_CACHE_NOHIT_TTL_S = 120; // 2分钟

// ============ 连接管理 ============
let client = null;
let isReady = false;

function createClient() {
  if (client) return client;

  const opts = {
    db: REDIS_DB,
    keyPrefix: KEY_PREFIX,
    retryStrategy(times) {
      if (times > 10) {
        console.error('[Redis] max retries reached, giving up');
        return null;
      }
      return Math.min(times * 200, 3000);
    },
    reconnectOnError(err) {
      const targetErrors = ['READONLY', 'ECONNRESET'];
      return targetErrors.some(e => err.message.includes(e));
    },
    lazyConnect: true,
    maxRetriesPerRequest: 2,
    connectTimeout: 5000,
    commandTimeout: 3000,
  };

  if (REDIS_PASSWORD) {
    opts.password = REDIS_PASSWORD;
  }

  client = new Redis(REDIS_URL, opts);

  client.on('ready', () => {
    isReady = true;
    console.log('[Redis] connected and ready');
  });
  client.on('error', (err) => {
    console.warn('[Redis] error:', err.message);
  });
  client.on('close', () => {
    isReady = false;
    console.warn('[Redis] connection closed');
  });
  client.on('reconnecting', () => {
    console.log('[Redis] reconnecting...');
  });

  client.connect().catch((err) => {
    console.warn('[Redis] initial connect failed:', err.message);
  });

  return client;
}

function getClient() {
  if (!client) createClient();
  return client;
}

function isAvailable() {
  return isReady && client && client.status === 'ready';
}

// ============ 对话历史 ============
const historyKey = (sessionId) => `voice:history:${sessionId}`;

async function pushMessage(sessionId, msg) {
  if (!isAvailable()) return false;
  try {
    const key = historyKey(sessionId);
    const value = JSON.stringify({
      role: msg.role,
      content: msg.content,
      source: msg.source || '',
      ts: Date.now(),
    });
    await client.lpush(key, value);
    await client.ltrim(key, 0, HISTORY_MAX_LEN - 1);
    await client.expire(key, HISTORY_TTL_S);
    return true;
  } catch (err) {
    console.warn('[Redis] pushMessage failed:', err.message);
    return false;
  }
}

async function getRecentHistory(sessionId, maxRounds = 5) {
  if (!isAvailable()) return null;
  try {
    const key = historyKey(sessionId);
    const items = await client.lrange(key, 0, maxRounds * 2 - 1);
    if (!items || items.length === 0) return [];
    // lpush 是倒序插入，lrange 取出的也是最新在前，需要 reverse 恢复时间顺序
    return items
      .map((item) => {
        try { return JSON.parse(item); } catch { return null; }
      })
      .filter(Boolean)
      .reverse();
  } catch (err) {
    console.warn('[Redis] getRecentHistory failed:', err.message);
    return null;
  }
}

async function clearSession(sessionId) {
  if (!isAvailable()) return false;
  try {
    await client.del(historyKey(sessionId));
    return true;
  } catch (err) {
    console.warn('[Redis] clearSession failed:', err.message);
    return false;
  }
}

// ============ KB 缓存 ============
const kbCacheKey = (cacheKey) => `kb_cache:${cacheKey}`;

async function setKbCache(cacheKey, result) {
  // 只缓存 hit 结果；no-hit 不写入 Redis，避免阻止后续 retry
  if (!isAvailable() || !result.hit) return false;
  try {
    const key = kbCacheKey(cacheKey);
    await client.set(key, JSON.stringify(result), 'EX', KB_CACHE_HIT_TTL_S);
    return true;
  } catch (err) {
    console.warn('[Redis] setKbCache failed:', err.message);
    return false;
  }
}

async function getKbCache(cacheKey) {
  if (!isAvailable()) return null;
  try {
    const key = kbCacheKey(cacheKey);
    const data = await client.get(key);
    if (!data) return null;
    return JSON.parse(data);
  } catch (err) {
    console.warn('[Redis] getKbCache failed:', err.message);
    return null;
  }
}

// ============ 优雅关闭 ============
async function disconnect() {
  if (client) {
    try {
      await client.quit();
    } catch {
      client.disconnect();
    }
    client = null;
    isReady = false;
    console.log('[Redis] disconnected');
  }
}

module.exports = {
  createClient,
  getClient,
  isAvailable,
  pushMessage,
  getRecentHistory,
  clearSession,
  setKbCache,
  getKbCache,
  disconnect,
};