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/*
 * Copyright © 2021-present Arcade Data Ltd ([email protected])
 *
 * 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.
 *
 * SPDX-FileCopyrightText: 2021-present Arcade Data Ltd ([email protected])
 * SPDX-License-Identifier: Apache-2.0
 */
package com.arcadedb.query.sql.executor;

import com.arcadedb.query.sql.parser.Expression;
import com.arcadedb.query.sql.parser.GroupBy;
import com.arcadedb.query.sql.parser.Projection;
import com.arcadedb.query.sql.parser.ProjectionItem;

import java.util.*;

/**
 * Created by luigidellaquila on 12/07/16.
 */
public class AggregateProjectionCalculationStep extends ProjectionCalculationStep {

  private final GroupBy groupBy;
  private final long    timeoutMillis;
  private final long    limit;

  //the key is the GROUP BY key, the value is the (partially) aggregated value
  private final Map aggregateResults = new LinkedHashMap<>();
  private       List      finalResults     = null;

  private int nextItem = 0;

  public AggregateProjectionCalculationStep(final Projection projection, final GroupBy groupBy, final long limit, final CommandContext context,
      final long timeoutMillis, final boolean profilingEnabled) {
    super(projection, context, profilingEnabled);
    this.groupBy = groupBy;
    this.timeoutMillis = timeoutMillis;
    this.limit = limit;
  }

  @Override
  public ResultSet syncPull(final CommandContext context, final int nRecords) {
    if (finalResults == null) {
      executeAggregation(context, nRecords);
    }

    return new ResultSet() {
      int localNext = 0;

      @Override
      public boolean hasNext() {
        return localNext <= nRecords && nextItem < finalResults.size();
      }

      @Override
      public Result next() {
        if (localNext > nRecords || nextItem >= finalResults.size()) {
          throw new NoSuchElementException();
        }
        final Result result = finalResults.get(nextItem);
        nextItem++;
        localNext++;
        return result;
      }
    };
  }

  private void executeAggregation(final CommandContext context, final int nRecords) {
    final long timeoutBegin = System.currentTimeMillis();

    final ExecutionStepInternal prevStep = checkForPrevious("Cannot execute an aggregation or a GROUP BY without a previous result");
    ResultSet lastRs = prevStep.syncPull(context, nRecords);
    while (lastRs.hasNext()) {
      if (timeoutMillis > 0 && timeoutBegin + timeoutMillis < System.currentTimeMillis()) {
        sendTimeout();
      }
      aggregate(lastRs.next(), context);
      if (!lastRs.hasNext()) {
        lastRs = prevStep.syncPull(context, nRecords);
      }
    }
    finalResults = new ArrayList<>(aggregateResults.values());
    aggregateResults.clear();
    for (final ResultInternal item : finalResults) {
      if (timeoutMillis > 0 && timeoutBegin + timeoutMillis < System.currentTimeMillis()) {
        sendTimeout();
      }
      for (final String name : item.getTemporaryProperties()) {
        final Object prevVal = item.getTemporaryProperty(name);
        if (prevVal instanceof AggregationContext) {
          item.setTemporaryProperty(name, ((AggregationContext) prevVal).getFinalValue());
        }
      }
    }
  }

  private void aggregate(final Result next, final CommandContext context) {
    final long begin = profilingEnabled ? System.nanoTime() : 0;
    try {
      final List