import * as crypto from 'crypto';
import { logger } from '../utils/logger';
import { FeatureGovernanceService } from '../core/governance/FeatureGovernanceService';

export interface EncryptedStreamMetadata {
  streamId: string;
  sourceNode: string;
  targetNode: string;
  payloadSize: number;
  timestamp: Date;
  hash: string;
  signature: string;
}

/**
 * [CORE_SEC_09] 全链路加密数据流审计 (Encrypted Stream Audit)
 * @description 在不解密数据载荷的情况下，通过元数据分析、流量指纹与统计特性对加密数据流进行合规性与安全性审计。
 */
export class EncryptedStreamAuditService {
  /**
   * 审计加密流元数据
   */
  static async auditStream(metadata: EncryptedStreamMetadata): Promise<{ isCompliant: boolean; reason?: string }> {
    // Feature Flag Check
    if (!(await FeatureGovernanceService.isEnabled('CORE_SEC_STREAM_AUDIT'))) {
      logger.info(`[EncryptedAudit] Service is disabled via Feature Flag.`);
      return { isCompliant: true }; // 默认合规
    }

    logger.info(`[EncryptedAudit] Auditing stream ${metadata.streamId} from ${metadata.sourceNode}`);

    // 1. 签名与哈希校验 (Integrity Check)
    if (!this.verifyIntegrity(metadata)) {
      logger.error(`[EncryptedAudit] Integrity check failed for stream ${metadata.streamId}`);
      return { isCompliant: false, reason: 'Stream integrity or signature invalid' };
    }

    // 2. 流量统计分析 (Statistical Anomaly Detection)
    if (this.detectTrafficAnomaly(metadata)) {
      logger.warn(`[EncryptedAudit] Traffic anomaly detected for stream ${metadata.streamId}`);
      return { isCompliant: false, reason: 'Unusual traffic pattern (potential data exfiltration)' };
    }

    // 3. 租户与节点白名单校验 (Access Control Audit)
    if (!this.isNodeAuthorized(metadata.sourceNode, metadata.targetNode)) {
      logger.error(`[EncryptedAudit] Unauthorized node communication: ${metadata.sourceNode} -> ${metadata.targetNode}`);
      return { isCompliant: false, reason: 'Unauthorized node communication path' };
    }

    return { isCompliant: true };
  }

  /**
   * 验证流的签名与哈希
   */
  private static verifyIntegrity(metadata: EncryptedStreamMetadata): boolean {
    // 模拟基于公钥的签名验证逻辑
    const isValidSignature = metadata.signature.startsWith('sig_');
    const isValidHash = metadata.hash.length === 64; // SHA-256
    return isValidSignature && isValidHash;
  }

  /**
   * 检测流量异常 (如负载过大或频率异常)
   */
  private static detectTrafficAnomaly(metadata: EncryptedStreamMetadata): boolean {
    const MAX_PAYLOAD_SIZE = 10 * 1024 * 1024; // 10MB
    if (metadata.payloadSize > MAX_PAYLOAD_SIZE) {
      return true;
    }
    // 实际场景中会结合 Redis 计数器检测单位时间内的流频率
    return false;
  }

  /**
   * 检查节点间的通讯是否在授权范围内
   */
  private static isNodeAuthorized(source: string, target: string): boolean {
    // 模拟白名单校验
    const allowedNodes = ['node-1', 'node-2', 'edge-gateway-1', 'central-hub'];
    return allowedNodes.includes(source) && allowedNodes.includes(target);
  }

  /**
   * 记录审计日志 (存证)
   */
  static async logAuditResult(metadata: EncryptedStreamMetadata, result: any) {
    logger.debug(`[EncryptedAudit] Audit log saved for ${metadata.streamId}: ${JSON.stringify(result)}`);
    // 实际应存入数据库审计表或区块链溯源服务
  }
}
