/*
 * 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 com.dataartisans;

import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.java.typeutils.TypeExtractor;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.source.SourceFunction;
import org.apache.flink.streaming.connectors.kafka.KafkaSink;
import org.apache.flink.streaming.util.serialization.DeserializationSchema;
import org.apache.flink.streaming.util.serialization.SerializationSchema;
import org.apache.flink.streaming.util.serialization.SimpleStringSchema;


/**
 * Simple example for writing data into Kafka.
 *
 * The following arguments are required:
 *
 *  - "bootstrap.servers" (comma separated list of kafka brokers)
 *  - "topic" the name of the topic to write data to.
 *
 * This is an example command line argument:
 *  "--topic test --bootstrap.servers localhost:9092"
 */
public class WriteIntoKafka {
	public static void main(String[] args) throws Exception {
		// create execution environment
		StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

		// parse user parameters
		ParameterTool parameterTool = ParameterTool.fromArgs(args);

		// add a simple source which is writing some strings
		DataStream<String> messageStream = env.addSource(new SimpleStringGenerator());

		// write stream to Kafka
		messageStream.addSink(new KafkaSink<>(parameterTool.getRequired("bootstrap.servers"),
				parameterTool.getRequired("topic"),
				new SimpleStringSchema()));

		env.execute();
	}

	public static class SimpleStringGenerator implements SourceFunction<String> {
		private static final long serialVersionUID = 2174904787118597072L;
		boolean running = true;
		long i = 0;
		@Override
		public void run(SourceContext<String> ctx) throws Exception {
			while(running) {
				ctx.collect("element-"+ (i++));
				Thread.sleep(10);
			}
		}

		@Override
		public void cancel() {
			running = false;
		}
	}


	public static class SimpleStringSchema implements DeserializationSchema<String>, SerializationSchema<String, byte[]> {
		private static final long serialVersionUID = 1L;

		public SimpleStringSchema() {
		}

		public String deserialize(byte[] message) {
			return new String(message);
		}

		public boolean isEndOfStream(String nextElement) {
			return false;
		}

		public byte[] serialize(String element) {
			return element.getBytes();
		}

		public TypeInformation<String> getProducedType() {
			return TypeExtractor.getForClass(String.class);
		}
	}
}