content: package lambda.process.internal.orderchange.stepfunctions;
  
  import com.amazonaws.services.lambda.runtime.Context;
  import com.amazonaws.services.lambda.runtime.LambdaLogger;
  import com.amazonaws.services.lambda.runtime.RequestHandler;
  import com.google.gson.Gson;
  import lambda.common.ClientCredentials;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import static lambda.common.Constants.*;
  
  /**
   * A sample Lambda handler used in a Step Functions workflow to simulate user notifications
   * based on order-related events (e.g., ORDER_CHANGE).
   *
   * This class extracts relevant information (e.g., subject, message, recipient) from the Step Functions
   * payload and logs it as if an email or message were being sent.
   *
   * <p>Note: In this sample implementation, no actual email or messaging service is invoked.
   * This is intentional to keep the solution lightweight and free of service-specific setup,
   * such as verified SES email identities or SNS/Webhook configurations.
   *
   * <p>In a production-grade implementation, {@link #invokeNotificationToUser(ClientCredentials, String, String, LambdaLogger)}
   * should be extended to perform actual delivery via services like Amazon SES, SNS, or external webhooks.
   */
  public class SendNotificationHandler implements RequestHandler<Map<String, Object>, Map<String, Object>> {
  
      private static final Gson gson = new Gson();
  
      public Map<String, Object> handleRequest(Map<String, Object> input, Context context) {
          LambdaLogger logger = context.getLogger();
  
          logger.log(gson.toJson(input));
  
          String subject = (String) input.get(STEP_FUNCTION_INPUT_KEY_SUBJECT);
          String messageBody = (String) input.get(STEP_FUNCTION_INPUT_KEY_MESSAGE);
          ClientCredentials credential =
                  gson.fromJson(gson.toJsonTree(input.get(STEP_FUNCTION_INPUT_KEY_CREDENTIAL)), ClientCredentials.class);
  
          invokeNotificationToUser(credential, subject, messageBody, logger);
          logger.log("Notification invoked successfully.");
  ;
          return new HashMap<>(input);
      }
  
      /**
       * In a production environment, this method is intended to send a notification to the user,
       * such as sending an email via Amazon SES or posting to a messaging service (e.g., SNS, webhook).
       *
       * However, in this sample solution, to keep things simple and avoid the need for additional setup
       * like verified email addresses or service subscriptions, the implementation is intentionally left empty.
       * The actual sending logic should be implemented here when used in a real-world context.
       */
      private void invokeNotificationToUser(ClientCredentials credential, String subject, String messageBody, LambdaLogger logger) {
          logger.log("Sending email...\nTo: " + credential.getMail() + "\nSubject: " + subject + "\nSubject: " + messageBody);
      }
  }
  