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/*
 * 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.calcite.adapter.elasticsearch;

import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptCost;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.InvalidRelException;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Aggregate;
import org.apache.calcite.rel.core.AggregateCall;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeField;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.fun.SqlStdOperatorTable;
import org.apache.calcite.util.ImmutableBitSet;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;
import java.util.Locale;
import java.util.Set;

/**
 * Implementation of
 * {@link org.apache.calcite.rel.core.Aggregate} relational expression
 * for ElasticSearch.
 */
public class ElasticsearchAggregate extends Aggregate implements ElasticsearchRel {

  private static final Set SUPPORTED_AGGREGATIONS =
      EnumSet.of(SqlKind.COUNT, SqlKind.MAX, SqlKind.MIN, SqlKind.AVG,
          SqlKind.SUM, SqlKind.ANY_VALUE);

  /** Creates an ElasticsearchAggregate. */
  ElasticsearchAggregate(RelOptCluster cluster,
      RelTraitSet traitSet,
      RelNode input,
      ImmutableBitSet groupSet,
      List groupSets,
      List aggCalls) throws InvalidRelException  {
    super(cluster, traitSet, input, groupSet, groupSets, aggCalls);

    if (getConvention() != input.getConvention()) {
      String message = String.format(Locale.ROOT, "%s != %s", getConvention(),
          input.getConvention());
      throw new AssertionError(message);
    }

    assert getConvention() == input.getConvention();
    assert getConvention() == ElasticsearchRel.CONVENTION;
    assert this.groupSets.size() == 1 : "Grouping sets not supported";

    for (AggregateCall aggCall : aggCalls) {
      if (aggCall.isDistinct() && !aggCall.isApproximate()) {
        final String message = String.format(Locale.ROOT, "Only approximate distinct "
            + "aggregations are supported in Elastic (cardinality aggregation). Use %s function",
            SqlStdOperatorTable.APPROX_COUNT_DISTINCT.getName());
        throw new InvalidRelException(message);
      }

      final SqlKind kind = aggCall.getAggregation().getKind();
      if (!SUPPORTED_AGGREGATIONS.contains(kind)) {
        final String message = String.format(Locale.ROOT,
            "Aggregation %s not supported (use one of %s)", kind, SUPPORTED_AGGREGATIONS);
        throw new InvalidRelException(message);
      }
    }

    if (getGroupType() != Group.SIMPLE) {
      final String message = String.format(Locale.ROOT, "Only %s grouping is supported. "
              + "Yours is %s", Group.SIMPLE, getGroupType());
      throw new InvalidRelException(message);
    }
  }

  @Deprecated // to be removed before 2.0
  ElasticsearchAggregate(RelOptCluster cluster,
      RelTraitSet traitSet,
      RelNode input,
      boolean indicator,
      ImmutableBitSet groupSet,
      List groupSets,
      List aggCalls) throws InvalidRelException {
    this(cluster, traitSet, input, groupSet, groupSets, aggCalls);
    checkIndicator(indicator);
  }

  @Override public Aggregate copy(RelTraitSet traitSet, RelNode input,
      ImmutableBitSet groupSet, List groupSets,
      List aggCalls) {
    try {
      return new ElasticsearchAggregate(getCluster(), traitSet, input,
          groupSet, groupSets, aggCalls);
    } catch (InvalidRelException e) {
      throw new AssertionError(e);
    }
  }

  @Override public RelOptCost computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {
    return super.computeSelfCost(planner, mq).multiplyBy(0.1);
  }

  @Override public void implement(Implementor implementor) {
    implementor.visitChild(0, getInput());
    final List inputFields = fieldNames(getInput().getRowType());
    for (int group : groupSet) {
      final String name = inputFields.get(group);
      implementor.addGroupBy(implementor.expressionItemMap.getOrDefault(name, name));
    }

    final ObjectMapper mapper = implementor.elasticsearchTable.mapper;

    for (AggregateCall aggCall : aggCalls) {
      final List names = new ArrayList<>();
      for (int i : aggCall.getArgList()) {
        names.add(inputFields.get(i));
      }

      final ObjectNode aggregation = mapper.createObjectNode();
      final ObjectNode field = aggregation.withObject("/" + toElasticAggregate(aggCall));

      final String name = names.isEmpty() ? ElasticsearchConstants.ID : names.get(0);
      field.put("field", implementor.expressionItemMap.getOrDefault(name, name));
      if (aggCall.getAggregation().getKind() == SqlKind.ANY_VALUE) {
        field.put("size", 1);
      }

      implementor.addAggregation(aggCall.getName(), aggregation.toString());
    }
  }

  /**
   * Most of the aggregations can be retrieved with single
   * stats
   * function. But currently only one-to-one mapping is supported between sql agg and elastic
   * aggregation.
   */
  private static String toElasticAggregate(AggregateCall call) {
    final SqlKind kind = call.getAggregation().getKind();
    switch (kind) {
    case COUNT:
      // approx_count_distinct() vs count()
      return call.isDistinct() && call.isApproximate() ? "cardinality" : "value_count";
    case SUM:
      return "sum";
    case MIN:
      return "min";
    case MAX:
      return "max";
    case AVG:
      return "avg";
    case ANY_VALUE:
      return "terms";
    default:
      throw new IllegalArgumentException("Unknown aggregation kind " + kind + " for " + call);
    }
  }

  private List fieldNames(RelDataType relDataType) {
    List names = new ArrayList<>();

    for (RelDataTypeField rdtf : relDataType.getFieldList()) {
      names.add(rdtf.getName());
    }
    return names;
  }

}

// End ElasticsearchAggregate.java