import * as Crypto from 'expo-crypto';

/**
 * Handles password hashing (SHA-256) and base64 encoding of account data objects
 */
class CredentialEncryption {
  /**
   * Hash a password with SHA-256 and return a hex digest
   */
  async hashPassword(password) {
    try {
      if (!password) throw new Error('Password is required');
      return await Crypto.digestStringAsync(
        Crypto.CryptoDigestAlgorithm.SHA256,
        password
      );
    } catch (error) {
      console.error('Password hashing error:', error);
      throw new Error('Failed to hash password: ' + error.message);
    }
  }

  /**
   * Compare a plaintext password against a stored hash
   */
  async verifyPassword(password, storedHash) {
    try {
      const hash = await this.hashPassword(password);
      return hash === storedHash;
    } catch (error) {
      console.error('Password verification error:', error);
      throw new Error('Failed to verify password: ' + error.message);
    }
  }

  /**
   * Encode an object as a base64 JSON string for database storage
   */
  encrypt(data) {
    try {
      if (!data) throw new Error('No data provided to encrypt');
      const jsonString = JSON.stringify(data);
      return btoa(unescape(encodeURIComponent(jsonString)));
    } catch (error) {
      console.error('Encryption error:', error);
      throw new Error('Failed to encrypt data: ' + error.message);
    }
  }

  /**
   * Decode a base64 JSON string back to an object
   */
  decrypt(encryptedData) {
    try {
      if (!encryptedData) return null;
      const jsonString = decodeURIComponent(escape(atob(encryptedData)));
      return JSON.parse(jsonString);
    } catch (error) {
      console.error('Decryption error:', error);
      throw new Error('Failed to decrypt data: ' + error.message);
    }
  }
}

export default new CredentialEncryption();