import { logger } from '../../utils/logger';
import { FederatedNode, FederatedNodeService } from './FederatedNodeService';
import { RedisService } from '../../utils/RedisService';

export interface P2PMessage {
  from: string;
  to: string;
  type: string;
  payload: any;
  signature: string;
  timestamp: number;
}

/**
 * [SOV_NET_06] 基于 Libp2p/WebRTC 的节点直连通信 (P2P Connectivity)
 * @description 核心逻辑：建立并管理 Hub 节点间的双向加密流。
 * 在联邦网络中支持低延迟、高可靠的 P2P 直连通信，绕过中心化中继。
 * 遵循 Autocomplete-First (V31.5) 规范。
 */
export class P2PConnectionService {
  private static readonly CONNECTION_CACHE_PREFIX = 'sov_net:p2p:conn:';
  private static readonly PEER_STORE_KEY = 'sov_net:p2p:peers';

  /**
   * 初始化 P2P 连接监听 (DHT Discovery & PeerStore)
   */
  static async init() {
    logger.info(`[SovNet] Initializing P2P connection listener (Libp2p/DHT mode)...`);
    
    // 1. 启动 DHT 发现循环 (模拟)
    setInterval(async () => {
      await this.discoverPeersViaDHT();
    }, 60000); // 每分钟发现一次
  }

  /**
   * 对接 DHT 发现节点并同步 PeerStore (DHT Discovery)
   * @private
   */
  private static async discoverPeersViaDHT() {
    logger.info(`[SovNet] Scanning DHT for new Hub nodes...`);
    
    // 模拟从分布式哈希表发现新节点
    const activeNodes = await FederatedNodeService.getActiveNodes();
    const peerIds = activeNodes.map(n => n.nodeId);
    
    await RedisService.set(this.PEER_STORE_KEY, JSON.stringify(peerIds));
    logger.info(`[SovNet] PeerStore synchronized. ${peerIds.length} peers discovered.`);
  }

  /**
   * 建立与远程节点的 P2P 连接 (Noise/TLS 1.3 Handshake)
   * @param targetNodeId 目标节点 ID
   */
  static async connectToNode(targetNodeId: string): Promise<boolean> {
    logger.info(`[SovNet] Attempting P2P connection to node: ${targetNodeId}`);

    const nodes = await FederatedNodeService.getActiveNodes();
    const targetNode = nodes.find(n => n.nodeId === targetNodeId);

    if (!targetNode) {
      logger.error(`[SovNet] Target node ${targetNodeId} not found or offline.`);
      return false;
    }

    try {
      // 1. 模拟 Noise Protocol / TLS 1.3 双向加密握手 (Noise-IK)
      const handshakeSuccess = await this.performP2PHandshake(targetNode);
      if (!handshakeSuccess) {
        logger.warn(`[SovNet] Handshake failed with node ${targetNodeId}. Connection rejected.`);
        return false;
      }

      // 2. 建立多路复用流 (Stream Multiplexing)
      await this.establishMplexStream(targetNodeId);

      // 3. 缓存连接状态
      await RedisService.set(`${this.CONNECTION_CACHE_PREFIX}${targetNodeId}`, 'ESTABLISHED', 300);

      logger.info(`[SovNet] P2P (Noise/TLS 1.3) connection established with node ${targetNodeId}`);
      return true;
    } catch (err: any) {
      logger.error(`[SovNet] P2P connection failed: ${err.message}`);
      return false;
    }
  }

  /**
   * 建立流复用 (Stream Multiplexing)
   * @private
   */
  private static async establishMplexStream(nodeId: string) {
    // 模拟 mplex / yamux 流复用建立
    logger.info(`[SovNet] Mplex stream multiplexing initialized for ${nodeId}`);
  }

  /**
   * 发送 P2P 消息 (Life-cycle Management)
   * @param message 消息对象
   */
  static async sendMessage(message: P2PMessage): Promise<boolean> {
    logger.info(`[SovNet] Sending P2P message to ${message.to} (Type: ${message.type})`);

    const connectionStatus = await RedisService.get(`${this.CONNECTION_CACHE_PREFIX}${message.to}`);
    if (connectionStatus !== 'ESTABLISHED') {
      const reconnected = await this.connectToNode(message.to);
      if (!reconnected) return false;
    }

    // 实际生产中通过 libp2p.pubsub 或 stream 发送
    // 模拟发送成功并更新最后活动时间
    await RedisService.set(`${this.CONNECTION_CACHE_PREFIX}${message.to}`, 'ESTABLISHED', 300);
    return true;
  }

  /**
   * 模拟 Noise/TLS 1.3 握手逻辑 (Noise-IK)
   * @private
   */
  private static async performP2PHandshake(node: FederatedNode): Promise<boolean> {
    logger.info(`[SovNet] Performing Noise-IK handshake with DID: ${node.did}`);
    // 模拟验证远程节点 DID 签名与证书链
    // 生产环境中会使用 node.publicKey 进行加密挑战响应
    return node.trustScore > 0.4; // 降低一点门槛以兼容更多节点
  }
}
