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/*
 * Copyright 2020, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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 com.querydsl.core.group;

import static com.querydsl.core.util.TupleUtils.toTuple;

import com.querydsl.core.FetchableQuery;
import com.querydsl.core.Tuple;
import com.querydsl.core.types.Expression;
import com.querydsl.core.types.FactoryExpression;
import com.querydsl.core.types.FactoryExpressionUtils;
import com.querydsl.core.types.Projections;
import java.util.Map;
import java.util.function.Supplier;

/**
 * Provides aggregated results as a map
 *
 * @param  Map key type
 * @param  Map value type
 * @param  Resulting map type
 * @author Jan-Willem Gmelig Meyling
 */
public class GroupByGenericMap>
    extends AbstractGroupByTransformer {

  private final Supplier mapFactory;

  GroupByGenericMap(Supplier mapFactory, Expression key, Expression... expressions) {
    super(key, expressions);
    this.mapFactory = mapFactory;
  }

  @Override
  public RES transform(FetchableQuery query) {
    Map groups = (Map) mapFactory.get();

    // create groups
    FactoryExpression expr = FactoryExpressionUtils.wrap(Projections.tuple(expressions));
    var hasGroups = false;
    for (Expression e : expr.getArgs()) {
      hasGroups |= e instanceof GroupExpression;
    }
    if (hasGroups) {
      expr = withoutGroupExpressions(expr);
    }
    try (var iter = query.select(expr).iterate()) {
      while (iter.hasNext()) {
        var tuple = toTuple(iter.next(), expressions);
        @SuppressWarnings("unchecked") // This type is mandated by the key type
        var row = (K[]) tuple.toArray();
        var groupId = row[0];
        var group = (GroupImpl) groups.get(groupId);
        if (group == null) {
          group = new GroupImpl(groupExpressions, maps);
          groups.put(groupId, group);
        }
        group.add(row);
      }
    }

    // transform groups
    return transform(groups);
  }

  @SuppressWarnings("unchecked")
  protected RES transform(Map groups) {
    return (RES) groups;
  }
}