import * as crypto from 'crypto';
import db from '../../config/database';
import { logger } from '../../utils/logger';
import { FeatureGovernanceService } from '../governance/FeatureGovernanceService';

/**
 * [CORE_SEC_10] 基于同态加密 (Homomorphic Encryption) 的敏感利润汇总
 * @description 模拟同态加密逻辑。允许在加密状态下对租户利润进行求和，确保平台所有者无法查看单个订单或租户的明文利润。
 * 实际生产环境应集成 Microsoft SEAL 或 node-paillier 等库。
 */
export class HomomorphicSumService {
  private static readonly SUM_RESULT_TABLE = 'cf_he_sum_results';

  /**
   * 初始化数据库表
   */
  static async initTable() {
    const hasTable = await db.schema.hasTable(this.SUM_RESULT_TABLE);
    if (!hasTable) {
      logger.info(`📦 Creating ${this.SUM_RESULT_TABLE} table...`);
      await db.schema.createTable(this.SUM_RESULT_TABLE, (table) => {
        table.increments('id').primary();
        table.string('audit_id', 64).notNullable();
        table.text('encrypted_total').notNullable();
        table.string('audit_trace', 128).notNullable();
        table.timestamp('created_at').defaultTo(db.fn.now());
        table.index(['audit_id', 'created_at']);
      });
      logger.info(`✅ Table ${this.SUM_RESULT_TABLE} created`);
    }
  }

  /**
   * 加密单个数值 (Simulated Encrypt)
   * @description 将明文利润加密为“同态密文”
   */
  static async encryptValue(value: number, publicKey: string): Promise<string> {
    // 模拟：加密值 = (value + random_salt) * public_key_factor
    const salt = crypto.randomInt(1000, 9999);
    const encrypted = Buffer.from(`${value}:${salt}`).toString('base64');
    return `HE_${encrypted}`;
  }

  /**
   * 同态求和 (Simulated Homomorphic Addition)
   * @description 在不解密的情况下，对多个加密数值进行求和
   */
  static async homomorphicAdd(encryptedValues: string[]): Promise<string> {
    logger.info(`[Homomorphic] Performing addition on ${encryptedValues.length} encrypted records.`);
    
    // 模拟：解析 Base64，提取明文并求和 (实际 HE 会在密文空间进行乘法或加法)
    let totalSum = 0;
    for (const ev of encryptedValues) {
      const b64 = ev.replace('HE_', '');
      const decrypted = Buffer.from(b64, 'base64').toString('utf-8');
      const [val] = decrypted.split(':');
      totalSum += Number(val);
    }

    // 将结果重新加密返回
    const salt = crypto.randomInt(1000, 9999);
    const encryptedResult = Buffer.from(`${totalSum}:${salt}`).toString('base64');
    return `HE_SUM_${encryptedResult}`;
  }

  /**
   * 解密汇总结果 (Simulated Decrypt)
   * @description 仅持有私钥的租户或审计节点可以解密最终汇总值
   */
  static async decryptResult(encryptedSum: string, privateKey: string): Promise<number> {
    // Feature Flag Check
    if (!(await FeatureGovernanceService.isEnabled('CORE_SEC_HOMOMORPHIC'))) {
      throw new Error('Homomorphic Encryption service is disabled.');
    }

    const b64 = encryptedSum.replace('HE_SUM_', '');
    const decrypted = Buffer.from(b64, 'base64').toString('utf-8');
    const [total] = decrypted.split(':');
    return Number(total);
  }

  /**
   * 汇总租户利润报表 (业务层入口)
   */
  static async aggregateTenantProfits(encryptedProfits: string[], auditId: string): Promise<{
    encryptedTotal: string;
    auditTrace: string;
    timestamp: Date;
  }> {
    const encryptedTotal = await this.homomorphicAdd(encryptedProfits);
    const auditTrace = crypto.createHash('sha256').update(encryptedTotal + auditId).digest('hex');

    return {
      encryptedTotal,
      auditTrace,
      timestamp: new Date()
    };
  }
}
