/*
 * 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.gearpump.sql.rel;

import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Filter;
import org.apache.calcite.rex.RexNode;
import org.apache.gearpump.DefaultMessage;
import org.apache.gearpump.Message;
import org.apache.gearpump.cluster.UserConfig;
import org.apache.gearpump.sql.table.SampleString;
import org.apache.gearpump.streaming.dsl.javaapi.JavaStream;
import org.apache.gearpump.streaming.dsl.javaapi.JavaStreamApp;
import org.apache.gearpump.streaming.dsl.javaapi.functions.FlatMapFunction;
import org.apache.gearpump.streaming.source.DataSource;
import org.apache.gearpump.streaming.source.Watermark;
import org.apache.gearpump.streaming.task.TaskContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.Tuple2;

import java.time.Instant;
import java.util.Arrays;
import java.util.Iterator;

public class GearFlatMapRel extends Filter implements GearRelNode {

  private static final Logger LOG = LoggerFactory.getLogger(GearFlatMapRel.class);

  public GearFlatMapRel(RelOptCluster cluster, RelTraitSet traits, RelNode child, RexNode condition) {
    super(cluster, traits, child, condition);
  }

  public GearFlatMapRel() {
    super(null, null, null, null);
  }

  @Override
  public Filter copy(RelTraitSet traitSet, RelNode input, RexNode condition) {
    return new GearFlatMapRel(getCluster(), traitSet, input, condition);
  }

  @Override
  public JavaStream<Tuple2<String, Integer>> buildGearPipeline(JavaStreamApp app,
                                                               JavaStream<Tuple2<String, Integer>> javaStream) throws Exception {
    LOG.debug("Adding Source");
    JavaStream<String> sentence = app.source(new StringSource(SampleString.Stream.getKV()),
      1, UserConfig.empty(), "source");
    LOG.debug("Adding flatMap");
    SampleString.WORDS = sentence.flatMap(new Split(), "flatMap");
    return null;
  }

  private static class StringSource implements DataSource {
    private final String str;
    private boolean hasNext = true;

    StringSource(String str) {
      this.str = str;
    }

    @Override
    public void open(TaskContext context, Instant startTime) {
    }

    @Override
    public Message read() {
      Message msg = new DefaultMessage(str, Instant.now());
      hasNext = false;
      return msg;
    }

    @Override
    public void close() {
    }

    @Override
    public Instant getWatermark() {
      if (hasNext) {
        return Instant.now();
      } else {
        return Watermark.MAX();
      }
    }
  }

  private static class Split extends FlatMapFunction<String, String> {
    @Override
    public Iterator<String> flatMap(String s) {
      return Arrays.asList(s.split("\\s+")).iterator();
    }
  }

}