content: /*
   * 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.mongodb;
  
  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.RelCollation;
  import org.apache.calcite.rel.RelFieldCollation;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Sort;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rel.type.RelDataTypeField;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.util.Util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
  * Implementation of {@link org.apache.calcite.rel.core.Sort}
  * relational expression in MongoDB.
  */
  public class MongoSort extends Sort implements MongoRel {
    public MongoSort(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode child, RelCollation collation, RexNode offset, RexNode fetch) {
      super(cluster, traitSet, child, collation, offset, fetch);
      assert getConvention() == MongoRel.CONVENTION;
      assert getConvention() == child.getConvention();
    }
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      return super.computeSelfCost(planner, mq).multiplyBy(0.05);
    }
  
    @Override public Sort copy(RelTraitSet traitSet, RelNode input,
        RelCollation newCollation, RexNode offset, RexNode fetch) {
      return new MongoSort(getCluster(), traitSet, input, collation, offset,
          fetch);
    }
  
    @Override public void implement(Implementor implementor) {
      implementor.visitChild(0, getInput());
      if (!collation.getFieldCollations().isEmpty()) {
        final List<String> keys = new ArrayList<>();
        final List<RelDataTypeField> fields = getRowType().getFieldList();
        for (RelFieldCollation fieldCollation : collation.getFieldCollations()) {
          final String name =
              fields.get(fieldCollation.getFieldIndex()).getName();
          keys.add(MongoRules.maybeQuote(name) + ": " + direction(fieldCollation));
          if (false) {
            // TODO: NULLS FIRST and NULLS LAST
            switch (fieldCollation.nullDirection) {
            case FIRST:
              break;
            case LAST:
              break;
            default:
              break;
            }
          }
        }
        implementor.add(null,
            "{$sort: " + Util.toString(keys, "{", ", ", "}") + "}");
      }
      if (offset != null) {
        implementor.add(null,
            "{$skip: " + ((RexLiteral) offset).getValue() + "}");
      }
      if (fetch != null) {
        implementor.add(null,
            "{$limit: " + ((RexLiteral) fetch).getValue() + "}");
      }
    }
  
    private static int direction(RelFieldCollation fieldCollation) {
      switch (fieldCollation.getDirection()) {
      case DESCENDING:
      case STRICTLY_DESCENDING:
        return -1;
      case ASCENDING:
      case STRICTLY_ASCENDING:
      default:
        return 1;
      }
    }
  }
  