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

export interface AuthEvent {
  nodeId: string;
  ip: string;
  behaviorScore: number; // 0-1
  lastVerifiedAt: Date;
  status: 'VERIFIED' | 'SUSPICIOUS' | 'REVOKED';
}

/**
 * [CORE_SEC_11] 零信任节点身份连续认证 (Continuous Auth)
 * @description 核心逻辑：基于节点行为特征（请求频率、地理位置、业务模式）进行持续安全校验，而非仅在登录时校验。
 */
export class ContinuousAuthService {
  private static readonly AUTH_PREFIX = 'sec:auth:node:';

  /**
   * 持续身份校验 (Continuous Validation)
   */
  static async validateNode(nodeId: string, context: { ip: string; action: string; metadata?: any }): Promise<boolean> {
    // Feature Flag Check
    if (!(await FeatureGovernanceService.isEnabled('CORE_SEC_CONTINUOUS_AUTH'))) {
      return true; // 如果关闭，则回退到基础 JWT 校验
    }

    const authKey = `${this.AUTH_PREFIX}${nodeId}`;
    const cachedAuth = await RedisService.get(authKey);
    let event: AuthEvent;

    if (cachedAuth) {
      event = JSON.parse(cachedAuth);
    } else {
      event = {
        nodeId,
        ip: context.ip,
        behaviorScore: 1.0,
        lastVerifiedAt: new Date(),
        status: 'VERIFIED'
      };
    }

    // 行为风险评估算法 (Behavioral Risk Assessment)
    const riskScore = this.calculateRisk(event, context);
    event.behaviorScore = Math.max(0, event.behaviorScore - riskScore);
    event.lastVerifiedAt = new Date();

    // 如果评分低于阈值，标记为 SUSPICIOUS 或 REVOKED
    if (event.behaviorScore < 0.3) {
      event.status = 'REVOKED';
      logger.error(`[ContinuousAuth] Security Breach! Node ${nodeId} status REVOKED. Score: ${event.behaviorScore}`);
    } else if (event.behaviorScore < 0.7) {
      event.status = 'SUSPICIOUS';
      logger.warn(`[ContinuousAuth] Suspicious behavior from Node ${nodeId}. Score: ${event.behaviorScore}`);
    }

    await RedisService.set(authKey, JSON.stringify(event), 3600);
    return event.status !== 'REVOKED';
  }

  /**
   * 风险计算逻辑
   */
  private static calculateRisk(event: AuthEvent, context: { ip: string; action: string }): number {
    let risk = 0;
    
    // 1. IP 变更风险
    if (event.ip !== context.ip) risk += 0.3;
    
    // 2. 异常动作风险 (如短时间内大量删除)
    if (context.action === 'MASS_DELETE') risk += 0.5;
    
    // 3. 时间窗口频率检查 (模拟)
    const isLateNight = new Date().getHours() < 5;
    if (isLateNight) risk += 0.1;

    return risk;
  }

  /**
   * 生成动态行为令牌
   */
  static async generateBehaviorToken(nodeId: string): Promise<string> {
    const salt = crypto.randomBytes(16).toString('hex');
    return crypto.createHash('sha256').update(nodeId + salt + Date.now()).digest('hex');
  }
}
