/*
 * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
 *
 * 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 org.gradoop.flink.model.impl.operators.fusion.functions;

import org.apache.flink.api.java.functions.FunctionAnnotation;
import org.apache.flink.api.java.functions.KeySelector;
import org.apache.flink.api.java.tuple.Tuple2;
import org.gradoop.common.model.api.entities.Element;
import org.gradoop.common.model.impl.id.GradoopId;

/**
 * Left projection with id obtained.
 * @param <K> Element where the id is extracted
 *
 */
@FunctionAnnotation.ForwardedFieldsFirst("id -> *")
public class LeftElementId<K extends Element>
  implements KeySelector<Tuple2<K, GradoopId>, GradoopId> {
  @Override
  public GradoopId getKey(Tuple2<K, GradoopId> value) throws Exception {
    return value.f0.getId();
  }
}
