package com.atlassian.asap.core.client;
   
   import com.atlassian.asap.api.Jwt;
   import com.atlassian.asap.api.JwtBuilder;
   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.client.http.AuthorizationHeaderGeneratorImpl;
   import org.apache.commons.io.IOUtils;
  import org.apache.http.client.methods.CloseableHttpResponse;
  import org.apache.http.client.methods.HttpGet;
  import org.apache.http.impl.client.CloseableHttpClient;
  import org.apache.http.impl.client.HttpClientBuilder;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.net.URI;
  import java.nio.charset.StandardCharsets;
  
  /**
   * A simple client for demonstration purposes. It makes a single GET request to a URL with a JWT access token.
   */
  public class SimpleClient {
      private static final Logger logger = LoggerFactory.getLogger(SimpleClient.class);
  
      private final String issuer;
      private final String keyId;
      private final String audience;
      private final AuthorizationHeaderGenerator authorizationHeaderGenerator;
  
      /**
       * @param issuer         identification of this client
       * @param keyId          key ID used to sign the outgoing requests
       * @param audience       audience of this client
       * @param privateKeyPath location of the private keys
       */
      public SimpleClient(String issuer, String keyId, String audience, URI privateKeyPath) {
          this.issuer = issuer;
          this.keyId = keyId;
          this.audience = audience;
          this.authorizationHeaderGenerator = AuthorizationHeaderGeneratorImpl.createDefault(privateKeyPath);
      }
  
      /**
       * Makes an authenticated request to get a resource.
       *
       * @param resourceServerUrl URL of the resource
       * @throws CannotRetrieveKeyException the private identified by keyId cannot be found
       * @throws InvalidTokenException      some other problem when signing the token
       */
      public void execute(URI resourceServerUrl) throws CannotRetrieveKeyException, InvalidTokenException {
          Jwt jwt = JwtBuilder.newJwt()
                  .keyId(keyId)
                  .audience(audience)
                  .issuer(issuer)
                  .build();
  
          logger.info("Making a GET request to {} using access token {}", resourceServerUrl, jwt);
          HttpGet httpGet = new HttpGet(resourceServerUrl);
          httpGet.setHeader("Authorization", authorizationHeaderGenerator.generateAuthorizationHeader(jwt));
  
          try (CloseableHttpClient httpClient = HttpClientBuilder.create().build();
               CloseableHttpResponse response = httpClient.execute(httpGet);
               InputStreamReader reader = new InputStreamReader(response.getEntity().getContent(), StandardCharsets.UTF_8)) {
              logger.info("Request completed status={} -- response body: {}",
                      response.getStatusLine().getStatusCode(), IOUtils.toString(reader));
          } catch (IOException ex) {
              logger.error("Error accessing resource server", ex);
          }
      }
  }