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Criteria support for ElasticSearch
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/*
 * Copyright 2019 Immutables Authors and Contributors
 *
 * Licensed 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.immutables.criteria.elasticsearch;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import org.immutables.criteria.backend.PathNaming;
import org.immutables.criteria.expression.AbstractExpressionVisitor;
import org.immutables.criteria.expression.Call;
import org.immutables.criteria.expression.ComparableOperators;
import org.immutables.criteria.expression.Expression;
import org.immutables.criteria.expression.Operator;
import org.immutables.criteria.expression.Operators;
import org.immutables.criteria.expression.OptionalOperators;
import org.immutables.criteria.expression.Path;
import org.immutables.criteria.expression.StringOperators;
import org.immutables.criteria.expression.Visitors;

import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.function.Predicate;
import java.util.regex.Pattern;

/**
 * Evaluating expression into Elastic Query DSL
 */
class ElasticsearchQueryVisitor extends AbstractExpressionVisitor {

  private final PathNaming pathNaming;
  private final Predicate idPredicate;

  ElasticsearchQueryVisitor(PathNaming pathNaming, Predicate idPredicate) {
    super(e -> { throw new UnsupportedOperationException(); });
    this.pathNaming = Objects.requireNonNull(pathNaming, "pathNaming");
    this.idPredicate = Objects.requireNonNull(idPredicate, "idPredicate");
  }

  @Override
  public QueryBuilders.QueryBuilder visit(Call call) {
    final Operator op = call.operator();
    final List args = call.arguments();

    if (op == OptionalOperators.IS_PRESENT || op == OptionalOperators.IS_ABSENT) {
      final String field = pathNaming.name(Visitors.toPath(args.get(0)));

      QueryBuilders.QueryBuilder builder = QueryBuilders.existsQuery(field);

      if (op == OptionalOperators.IS_ABSENT) {
        builder = QueryBuilders.boolQuery().mustNot(builder);
      }

      return builder;
    }

    if (op == Operators.AND || op == Operators.OR) {
      Preconditions.checkArgument(!args.isEmpty(), "Size should be >=1 for %s but was %s", op, args.size());

      final QueryBuilders.BoolQueryBuilder builder = args.stream()
              .map(a -> a.accept(this))
              .reduce(QueryBuilders.boolQuery(), (a, b) -> op == Operators.AND ? a.must(b) : a.should(b), (a, b) -> b);

      return builder;
    }

    if (op == Operators.NOT) {
      Preconditions.checkArgument(args.size() == 1, "Size should be 1 for %s but was %s", op, args.size());
      final QueryBuilders.QueryBuilder builder = args.get(0).accept(this);
      return QueryBuilders.boolQuery().mustNot(builder);
    }

    if (op.arity() == Operator.Arity.BINARY) {
      return binaryCall(call);
    }

    throw new UnsupportedOperationException("Don't know how to handle " + call);
  }

  private QueryBuilders.QueryBuilder binaryCall(Call call) {
    final List arguments = call.arguments();
    Preconditions.checkArgument(arguments.size() == 2, "Size should be 2 for %s but was %s",
            call.operator(), arguments.size());
    final Operator op = call.operator();
    final Path path = Visitors.toPath(arguments.get(0));
    final String field = pathNaming.name(path);
    final Object value = Visitors.toConstant(arguments.get(1)).value();

    if (op == Operators.EQUAL || op == Operators.NOT_EQUAL) {
      QueryBuilders.QueryBuilder builder;
      if (idPredicate.test(path)) {
        // use more efficient ids query for keys
        builder = QueryBuilders.idsQuery(Collections.singleton(value));
      } else {
        builder = QueryBuilders.termQuery(field, value);
      }

      if (op == Operators.NOT_EQUAL) {
        QueryBuilders.BoolQueryBuilder bool = QueryBuilders.boolQuery().mustNot(builder);
        if ("".equals(value)) {
          // string is not empty (should also exists)
          bool = bool.should(QueryBuilders.existsQuery(field));
        }
        builder = bool;
      }

      return builder;
    }

    if (op == Operators.IN || op == Operators.NOT_IN) {
      final Collection