/*
 * 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.util.serialization;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.apache.flink.api.common.typeinfo.TypeInformation;

import java.io.IOException;

import static org.apache.flink.api.java.typeutils.TypeExtractor.getForClass;

/**
 * DeserializationSchema that deserializes a JSON String into an ObjectNode.
 * <p>
 * Key fields can be accessed by calling objectNode.get("key").get(<name>).as(<type>)
 * <p>
 * Value fields can be accessed by calling objectNode.get("value").get(<name>).as(<type>)
 * <p>
 * Metadata fields can be accessed by calling objectNode.get("metadata").get(<name>).as(<type>) and include
 * the "offset" (long), "topic" (String) and "partition" (int).
 */
public class JSONKeyValueDeserializationSchema implements KeyedDeserializationSchema<ObjectNode> {
	private final boolean includeMetadata;
	private ObjectMapper mapper;

	public JSONKeyValueDeserializationSchema(boolean includeMetadata) {
		this.includeMetadata = includeMetadata;
	}

	@Override
	public ObjectNode deserialize(byte[] messageKey, byte[] message, String topic, int partition, long offset) throws IOException {
		if (mapper == null) {
			mapper = new ObjectMapper();
		}
		ObjectNode node = mapper.createObjectNode();
		node.set("key", mapper.readValue(messageKey, JsonNode.class));
		node.set("value", mapper.readValue(message, JsonNode.class));
		if (includeMetadata) {
			node.putObject("metadata")
				.put("offset", offset)
				.put("topic", topic)
				.put("partition", partition);
		}
		return node;
	}

	@Override
	public boolean isEndOfStream(ObjectNode nextElement) {
		return false;
	}

	@Override
	public TypeInformation<ObjectNode> getProducedType() {
		return getForClass(ObjectNode.class);
	}
}