package com.atlassian.asap.core.client.http;
   
   import com.atlassian.asap.api.Jwt;
   import com.atlassian.asap.api.client.http.AuthorizationHeaderGenerator;
   import com.atlassian.asap.api.exception.CannotRetrieveKeyException;
   import com.atlassian.asap.api.exception.InvalidTokenException;
   import com.atlassian.asap.core.JwtConstants;
   import com.atlassian.asap.core.keys.KeyProvider;
   import com.atlassian.asap.core.keys.privatekey.PrivateKeyProviderFactory;
  import com.atlassian.asap.core.serializer.JwtSerializer;
  import com.atlassian.asap.core.validator.ValidatedKeyId;
  import com.atlassian.asap.nimbus.serializer.NimbusJwtSerializer;
  
  import java.net.URI;
  import java.security.PrivateKey;
  import java.util.Objects;
  
  public class AuthorizationHeaderGeneratorImpl implements AuthorizationHeaderGenerator {
      private final JwtSerializer jwtSerializer;
      private final KeyProvider<PrivateKey> privateKeyProvider;
  
      /**
       * Creates a new instance of {@link AuthorizationHeaderGeneratorImpl}.
       *
       * @param jwtSerializer      the serializer to use for signing and serializing a JWT object
       * @param privateKeyProvider the key provider to use for retrieving private keys used in signing
       */
      public AuthorizationHeaderGeneratorImpl(JwtSerializer jwtSerializer, KeyProvider<PrivateKey> privateKeyProvider) {
          this.jwtSerializer = Objects.requireNonNull(jwtSerializer);
          this.privateKeyProvider = Objects.requireNonNull(privateKeyProvider);
      }
  
      /**
       * Constructs a default instance for the given private key path.
       *
       * @param privateKeyPath location of the private keys
       * @return a new instance of the header generator
       */
      public static AuthorizationHeaderGenerator createDefault(URI privateKeyPath) {
          KeyProvider<PrivateKey> keyProvider = PrivateKeyProviderFactory.createPrivateKeyProvider(privateKeyPath);
          return new AuthorizationHeaderGeneratorImpl(new NimbusJwtSerializer(), keyProvider);
      }
  
      @Override
      public String generateAuthorizationHeader(Jwt jwt) throws InvalidTokenException, CannotRetrieveKeyException {
          ValidatedKeyId validatedKeyId = ValidatedKeyId.validate(jwt.getHeader().getKeyId());
  
          PrivateKey privateKey = privateKeyProvider.getKey(validatedKeyId);
  
          return JwtConstants.HTTP_AUTHORIZATION_HEADER_VALUE_PREFIX + jwtSerializer.serialize(jwt, privateKey);
      }
  }