import { v4 as uuidv4 } from 'uuid';
import type { DPoPProof } from './types';

// Note: This requires a custom Native Module (NativeCryptoModule) capable of 
// generating ECC keys in the Secure Enclave and signing data with them.
// This is a placeholder implementation that would need native module integration.

const DPOP_KEY_ALIAS = 'lynkedup.dpop.key.v1';

/**
 * DPoP (Demonstrating Proof-of-Possession) Service
 * Implements RFC 9449 for sender-constrained access tokens
 * 
 * Features:
 * - Hardware-backed ECC key generation
 * - JWT signing with private key in secure enclave
 * - Request binding via HTTP method and URI
 */
export class DPoPService {
  private publicKey: string | null = null;

  /**
   * Initialize DPoP key pair in secure enclave
   * Returns the public key JWK
   */
  async initializeKeyPair(): Promise<string> {
    if (this.publicKey) return this.publicKey;

    // Check if key exists natively using the alias, otherwise generate it
    // This would call into a native module
    let pubKey = await this.getPublicKeyFromNative(DPOP_KEY_ALIAS);
    
    if (!pubKey) {
      pubKey = await this.generateHardwareECCKeyPair(DPOP_KEY_ALIAS);
    }
    
    this.publicKey = pubKey;
    return pubKey;
  }

  /**
   * Sign a DPoP proof for HTTP request
   * @param method HTTP method (GET, POST, etc.)
   * @param uri Full request URI
   * @param accessToken Optional access token to bind to request
   */
  async signProof(method: string, uri: string, accessToken?: string): Promise<string> {
    if (!this.publicKey) {
      await this.initializeKeyPair();
    }

    // Construct the DPoP JWT payload (htu, htm, jti, ath)
    const payload = {
      htm: method, // HTTP Method
      htu: uri,    // HTTP URI
      jti: uuidv4(), // Unique identifier for this proof
      iat: Math.floor(Date.now() / 1000), // Issued at time
      // Include hash of access token (ath) if present
      ath: accessToken ? this.base64url(this.sha256(accessToken)) : undefined,
    };

    // Sign the JWT using the hardware-backed private key via the native module
    const signedJwt = await this.signJWTWithNative(payload, DPOP_KEY_ALIAS);
    
    return signedJwt;
  }

  /**
   * Sign arbitrary data with DPoP key
   */
  async signData(data: string): Promise<string> {
    if (!this.publicKey) {
      await this.initializeKeyPair();
    }

    const signaturePayload = {
      data,
      timestamp: Date.now(),
      nonce: uuidv4()
    };

    return this.signJWTWithNative(signaturePayload, DPOP_KEY_ALIAS);
  }

  /**
   * Get the current public key
   */
  getPublicKey(): string | null {
    return this.publicKey;
  }

  // Native module integration methods (would be implemented via bridge)
  private async getPublicKeyFromNative(keyAlias: string): Promise<string | null> {
    // This would call into a native module
    // Example: return NativeCryptoModule.getPublicKey(keyAlias);
    console.warn('Native module integration required for getPublicKeyFromNative');
    return null;
  }

  private async generateHardwareECCKeyPair(keyAlias: string): Promise<string> {
    // This would call into a native module to generate ECC key in secure enclave
    // Example: return NativeCryptoModule.generateHardwareECCKeyPair(keyAlias);
    console.warn('Native module integration required for generateHardwareECCKeyPair');
    
    // Mock implementation for development
    return JSON.stringify({
      kty: 'EC',
      crv: 'P-256',
      x: 'mock-x-coordinate',
      y: 'mock-y-coordinate',
      use: 'sig',
      kid: keyAlias
    });
  }

  private async signJWTWithNative(payload: any, keyAlias: string): Promise<string> {
    // This would call into a native module to sign JWT with hardware key
    // Example: return NativeCryptoModule.signJWT(payload, keyAlias);
    console.warn('Native module integration required for signJWTWithNative');
    
    // Mock implementation for development
    const header = { alg: 'ES256', typ: 'dpop+jwt', jwk: JSON.parse(this.publicKey!) };
    const encodedHeader = this.base64url(JSON.stringify(header));
    const encodedPayload = this.base64url(JSON.stringify(payload));
    const signature = 'mock-signature'; // Would be actual signature from secure enclave
    
    return `${encodedHeader}.${encodedPayload}.${signature}`;
  }

  // Utility methods
  private base64url(str: string): string {
    return Buffer.from(str)
      .toString('base64')
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/=/g, '');
  }

  private sha256(str: string): string {
    // This would use a proper crypto library
    console.warn('Proper SHA256 implementation required');
    return 'mock-hash';
  }
}