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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.adapter.enumerable.EnumerableRel;
import org.apache.calcite.adapter.enumerable.EnumerableRelImplementor;
import org.apache.calcite.adapter.enumerable.JavaRowFormat;
import org.apache.calcite.adapter.enumerable.PhysType;
import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
import org.apache.calcite.linq4j.tree.BlockBuilder;
import org.apache.calcite.linq4j.tree.Expression;
import org.apache.calcite.linq4j.tree.Expressions;
import org.apache.calcite.linq4j.tree.MethodCallExpression;
import org.apache.calcite.plan.ConventionTraitDef;
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.RelNode;
import org.apache.calcite.rel.convert.ConverterImpl;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.Pair;

import java.util.AbstractList;
import java.util.List;
import java.util.stream.Collectors;

/**
 * Relational expression representing a scan of a table in an Elasticsearch data source.
 */
public class ElasticsearchToEnumerableConverter extends ConverterImpl implements EnumerableRel {
  ElasticsearchToEnumerableConverter(RelOptCluster cluster, RelTraitSet traits,
      RelNode input) {
    super(cluster, ConventionTraitDef.INSTANCE, traits, input);
  }

  @Override public RelNode copy(RelTraitSet traitSet, List inputs) {
    return new ElasticsearchToEnumerableConverter(getCluster(), traitSet, sole(inputs));
  }

  @Override public RelOptCost computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {
    return super.computeSelfCost(planner, mq).multiplyBy(.1);
  }

  @Override public Result implement(EnumerableRelImplementor relImplementor, Prefer prefer) {
    final BlockBuilder block = new BlockBuilder();
    final ElasticsearchRel.Implementor implementor = new ElasticsearchRel.Implementor();
    implementor.visitChild(0, getInput());

    final RelDataType rowType = getRowType();
    final PhysType physType = PhysTypeImpl.of(relImplementor.getTypeFactory(), rowType,
        prefer.prefer(JavaRowFormat.ARRAY));
    final Expression fields = block.append("fields",
        constantArrayList(
            Pair.zip(ElasticsearchRules.elasticsearchFieldNames(rowType),
                new AbstractList() {
                  @Override public Class get(int index) {
                    return physType.fieldClass(index);
                  }

                  @Override public int size() {
                    return rowType.getFieldCount();
                  }
                }),
            Pair.class));
    final Expression table = block.append("table",
        implementor.table
            .getExpression(ElasticsearchTable.ElasticsearchQueryable.class));
    final Expression ops = block.append("ops", Expressions.constant(implementor.list));
    final Expression sort = block.append("sort", constantArrayList(implementor.sort, Pair.class));
    final Expression groupBy = block.append("groupBy", Expressions.constant(implementor.groupBy));
    final Expression aggregations = block.append("aggregations",
        constantArrayList(implementor.aggregations, Pair.class));

    final Expression mappings = block.append("mappings",
        Expressions.constant(implementor.expressionItemMap));

    final Expression offset = block.append("offset", Expressions.constant(implementor.offset));
    final Expression fetch = block.append("fetch", Expressions.constant(implementor.fetch));

    Expression enumerable = block.append("enumerable",
        Expressions.call(table, ElasticsearchMethod.ELASTICSEARCH_QUERYABLE_FIND.method, ops,
            fields, sort, groupBy, aggregations, mappings, offset, fetch));
    block.add(Expressions.return_(null, enumerable));
    return relImplementor.result(physType, block.toBlock());
  }

  /** E.g. {@code constantArrayList("x", "y")} returns
   * "Arrays.asList('x', 'y')".
   * @param values list of values
   * @param clazz runtime class representing each element in the list
   * @param  type of elements in the list
   * @return method call which creates a list
   */
  private static  MethodCallExpression constantArrayList(List values, Class clazz) {
    return Expressions.call(BuiltInMethod.ARRAYS_AS_LIST.method,
        Expressions.newArrayInit(clazz, constantList(values)));
  }

  /** E.g. {@code constantList("x", "y")} returns
   * {@code {ConstantExpression("x"), ConstantExpression("y")}}.
   * @param values list of elements
   * @param  type of elements inside this list
   * @return list of constant expressions
   */
  private static  List constantList(List values) {
    return values.stream().map(Expressions::constant).collect(Collectors.toList());
  }
}

// End ElasticsearchToEnumerableConverter.java