// Quantum-Safe Cryptography Service
// Hybrid signature generation (ECC-521 + PQC), key management

import { v4 as uuidv4 } from 'uuid';
import prisma from '@/shared/database/prisma';

export interface HybridSignature {
  eccSignature: string;
  pqcSignature: string;
  combinedSignature: string;
}

export interface KeyPair {
  publicKey: string;
  privateKeyRef: string;
  algorithm: string;
}

/**
 * PQC Algorithm Interfaces
 * Implementations can be added later with actual PQC libraries
 */
export interface PQCAlgorithm {
  generateKeyPair(): Promise<KeyPair>;
  sign(message: string, privateKey: string): Promise<string>;
  verify(message: string, signature: string, publicKey: string): Promise<boolean>;
}

export class QuantumCryptoService {
  /**
   * Generate hybrid signature (ECC-521 + PQC)
   */
  async generateHybridSignature(
    message: string,
    eccKeyId: string,
    pqcKeyId: string
  ): Promise<HybridSignature> {
    // Get keys
    const eccKey = await prisma.cryptographic_keys.findUnique({
      where: { keyId: eccKeyId },
    });

    const pqcKey = await prisma.cryptographic_keys.findUnique({
      where: { keyId: pqcKeyId },
    });

    if (!eccKey || !pqcKey) {
      throw new Error('One or both keys not found');
    }

    // In production, this would use actual cryptographic libraries
    // For now, generate mock signatures
    const eccSignature = await this.signWithECC(message, eccKey.privateKeyRef || '');
    const pqcSignature = await this.signWithPQC(message, pqcKey.privateKeyRef || '');

    // Combine signatures
    const combinedSignature = `${eccSignature}:${pqcSignature}`;

    return {
      eccSignature,
      pqcSignature,
      combinedSignature,
    };
  }

  /**
   * Verify hybrid signature
   */
  async verifyHybridSignature(
    message: string,
    signature: HybridSignature,
    eccKeyId: string,
    pqcKeyId: string
  ): Promise<boolean> {
    const eccKey = await prisma.cryptographic_keys.findUnique({
      where: { keyId: eccKeyId },
    });

    const pqcKey = await prisma.cryptographic_keys.findUnique({
      where: { keyId: pqcKeyId },
    });

    if (!eccKey || !pqcKey) {
      return false;
    }

    // Verify both signatures
    const eccValid = await this.verifyECC(message, signature.eccSignature, eccKey.publicKey);
    const pqcValid = await this.verifyPQC(message, signature.pqcSignature, pqcKey.publicKey);

    return eccValid && pqcValid;
  }

  /**
   * Generate ECC-521 key pair
   */
  async generateECCKeyPair(keyPurpose: string): Promise<{ keyId: string; publicKey: string }> {
    // In production, this would use actual ECC-521 library
    const keyId = uuidv4();
    const publicKey = `ecc_521_public_${keyId}`;
    const privateKeyRef = `hsm_ecc_521_${keyId}`;

    await prisma.cryptographic_keys.create({
      data: {
        id: uuidv4(),
        keyId,
        keyType: 'ecc_521',
        keyPurpose,
        publicKey,
        privateKeyRef,
        algorithm: 'ECC-521',
        keySize: 521,
        status: 'active',
      },
    });

    return { keyId, publicKey };
  }

  /**
   * Generate PQC key pair (CRYSTALS-Kyber or CRYSTALS-Dilithium)
   */
  async generatePQCKeyPair(
    algorithm: 'CRYSTALS-Kyber' | 'CRYSTALS-Dilithium',
    keyPurpose: string
  ): Promise<{ keyId: string; publicKey: string }> {
    const keyId = uuidv4();
    const publicKey = `${algorithm.toLowerCase()}_public_${keyId}`;
    const privateKeyRef = `hsm_${algorithm.toLowerCase()}_${keyId}`;

    const keyType = algorithm === 'CRYSTALS-Kyber' ? 'pqc_kyber' : 'pqc_dilithium';

    await prisma.cryptographic_keys.create({
      data: {
        id: uuidv4(),
        keyId,
        keyType,
        keyPurpose,
        publicKey,
        privateKeyRef,
        algorithm,
        keySize: algorithm === 'CRYSTALS-Kyber' ? 800 : 1952, // Approximate key sizes
        status: 'active',
      },
    });

    return { keyId, publicKey };
  }

  /**
   * Generate hybrid key pair (ECC + PQC)
   */
  async generateHybridKeyPair(keyPurpose: string): Promise<{
    eccKeyId: string;
    pqcKeyId: string;
    eccPublicKey: string;
    pqcPublicKey: string;
  }> {
    const ecc = await this.generateECCKeyPair(keyPurpose);
    const pqc = await this.generatePQCKeyPair('CRYSTALS-Dilithium', keyPurpose);

    return {
      eccKeyId: ecc.keyId,
      pqcKeyId: pqc.keyId,
      eccPublicKey: ecc.publicKey,
      pqcPublicKey: pqc.publicKey,
    };
  }

  /**
   * Rotate key
   */
  async rotateKey(oldKeyId: string, newKeyPurpose?: string): Promise<string> {
    const oldKey = await prisma.cryptographic_keys.findUnique({
      where: { keyId: oldKeyId },
    });

    if (!oldKey) {
      throw new Error(`Key not found: ${oldKeyId}`);
    }

    // Mark old key as rotated
    await prisma.cryptographic_keys.update({
      where: { keyId: oldKeyId },
      data: {
        status: 'rotated',
        rotatedAt: new Date(),
      },
    });

    // Generate new key
    let newKeyId: string;
    if (oldKey.keyType === 'ecc_521') {
      const newKey = await this.generateECCKeyPair(newKeyPurpose || oldKey.keyPurpose);
      newKeyId = newKey.keyId;
    } else if (oldKey.keyType === 'pqc_kyber') {
      const newKey = await this.generatePQCKeyPair('CRYSTALS-Kyber', newKeyPurpose || oldKey.keyPurpose);
      newKeyId = newKey.keyId;
    } else if (oldKey.keyType === 'pqc_dilithium') {
      const newKey = await this.generatePQCKeyPair('CRYSTALS-Dilithium', newKeyPurpose || oldKey.keyPurpose);
      newKeyId = newKey.keyId;
    } else {
      throw new Error(`Unsupported key type for rotation: ${oldKey.keyType}`);
    }

    return newKeyId;
  }

  // Mock implementations - in production, these would use actual crypto libraries
  private async signWithECC(message: string, privateKeyRef: string): Promise<string> {
    // In production: use ECC-521 library to sign
    return `ecc_signature_${Buffer.from(message).toString('base64').substring(0, 64)}`;
  }

  private async signWithPQC(message: string, privateKeyRef: string): Promise<string> {
    // In production: use PQC library (CRYSTALS-Dilithium) to sign
    return `pqc_signature_${Buffer.from(message).toString('base64').substring(0, 64)}`;
  }

  private async verifyECC(message: string, signature: string, publicKey: string): Promise<boolean> {
    // In production: use ECC-521 library to verify
    return signature.startsWith('ecc_signature_');
  }

  private async verifyPQC(message: string, signature: string, publicKey: string): Promise<boolean> {
    // In production: use PQC library to verify
    return signature.startsWith('pqc_signature_');
  }
}

export const quantumCryptoService = new QuantumCryptoService();

