/*
 * Copyright © 2015-2019 Cask Data, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package io.cdap.cdap.etl.api;

import io.cdap.cdap.api.annotation.Beta;
import io.cdap.cdap.api.data.schema.Schema;
import javax.annotation.Nullable;

/**
 * This stores the input schema that is passed to this stage from other stages in the pipeline and
 * the output schema that could be sent to the next stages from this stage.
 */
@Beta
public interface StageConfigurer {

  /**
   * get the input schema for this stage, or null if its unknown
   *
   * @return input schema
   */
  @Nullable
  Schema getInputSchema();

  /**
   * set the output schema for this stage, or null if its unknown
   *
   * @param outputSchema output schema for this stage
   */
  void setOutputSchema(@Nullable Schema outputSchema);

  /**
   * set the error schema for this stage, or null if its unknown. If no error schema is set, it will
   * default to the input schema for the stage. Note that since source plugins do not have an input
   * schema, it will default to null for sources.
   *
   * @param errorSchema error schema for this stage
   */
  void setErrorSchema(@Nullable Schema errorSchema);

  /**
   * Returns a failure collector for the stage.
   *
   * @return a failure collector
   * @throws UnsupportedOperationException if the implementation does not override this method
   */
  default FailureCollector getFailureCollector() {
    throw new UnsupportedOperationException("Getting failure collector is not supported.");
  }
}
