package com.srv4pos.server.api.activation;
   
   import com.srv4pos.commons.io.BytesUtils;
   import com.srv4pos.server.api.infrastructure.SignService;
   import org.apache.commons.codec.binary.Base64;
   
   import java.io.IOException;
   import java.security.InvalidKeyException;
   import java.security.NoSuchAlgorithmException;
  import java.security.SignatureException;
  import java.security.spec.InvalidKeySpecException;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * Helper to work with digital signatures. For instance verification.
   * <p>User: Kirill, Date: 31.03.14 0:46</p>
   */
  public class SignatureHelper {
  
      private Map<String, byte[]> pubKeys = new HashMap<String, byte[]>();
  
      public SignatureHelper() {
      }
  
      /**
       * Make sure ActivationCode signed correctly.
       *
       * @param activationCodeInfo to check
       * @return true if correctly
       * @throws java.security.NoSuchAlgorithmException
       * @throws java.security.spec.InvalidKeySpecException
       * @throws java.security.InvalidKeyException
       * @throws java.security.SignatureException
       * @throws java.io.IOException
       */
      public boolean verifySignature(ActivationCodeInfo activationCodeInfo) throws NoSuchAlgorithmException, InvalidKeySpecException,
              InvalidKeyException, SignatureException, IOException {
  
          final String publicKeyFileName = activationCodeInfo.getPublicKeyFileName();
  
          if (publicKeyFileName == null) {
              return false;
          }
  
          byte[] pubKeyBytes = pubKeys.get(publicKeyFileName);
  
          if (pubKeyBytes == null) {
              pubKeyBytes = BytesUtils.readResource(publicKeyFileName, getClass());
              pubKeys.put(publicKeyFileName, pubKeyBytes);
          }
  
          final byte[] signature = Base64.decodeBase64(activationCodeInfo.getSignature().getBytes(ActivationServiceSample.SIGNATURE_CHARSET));
          final String activationDescriptorInfoJson = activationCodeInfo.getActivationDescriptorInfo();
          return SignService.verifySignature(activationDescriptorInfoJson.getBytes(ActivationServiceSample.SIGNATURE_CHARSET), pubKeyBytes, signature);
      }
  
      /**
       * Get file name of a public key, which should be used to verify signature. It's used for ActivationCode.set
       *
       * @param isProductionHost for procution
       * @return the file name for host's public key
       */
      public static String getPublicKeyFileName(boolean isProductionHost) {
          return isProductionHost ? "production.pub.der" : "development.pub.der";
      }
  }