/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.flink.streaming.connectors.elasticsearch;

import org.apache.flink.api.common.functions.Function;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.elasticsearch.action.ActionRequest;

import java.io.Serializable;

/**
 * Creates multiple {@link ActionRequest ActionRequests} from an element in a stream.
 *
 * <p>
 * This is used by sinks to prepare elements for sending them to Elasticsearch.
 *
 * <p>
 * Example:
 *
 * <pre>{@code
 *					private static class TestElasticSearchSinkFunction implements
 *						ElasticsearchSinkFunction<Tuple2<Integer, String>> {
 *
 *					public IndexRequest createIndexRequest(Tuple2<Integer, String> element) {
 *						Map<String, Object> json = new HashMap<>();
 *						json.put("data", element.f1);
 *
 *						return Requests.indexRequest()
 *							.index("my-index")
 *							.type("my-type")
 *							.id(element.f0.toString())
 *							.source(json);
 *						}
 *
 *				public void process(Tuple2<Integer, String> element, RuntimeContext ctx, RequestIndexer indexer) {
 *					indexer.add(createIndexRequest(element));
 *				}
 *		}
 *
 * }</pre>
 *
 * @param <T> The type of the element handled by this {@code ElasticsearchSinkFunction}
 */
public interface ElasticsearchSinkFunction<T> extends Serializable, Function {

	/**
	 * Process the incoming element to produce multiple {@link ActionRequest ActionsRequests}.
	 * The produced requests should be added to the provided {@link RequestIndexer}.
	 *
	 * @param element incoming element to process
	 * @param ctx     runtime context containing information about the sink instance
	 * @param indexer request indexer that {@code ActionRequest} should be added to
	 */
	void process(T element, RuntimeContext ctx, RequestIndexer indexer);
}