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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.exception.TimeoutException;
import com.arcadedb.index.Index;
import com.arcadedb.query.sql.parser.IndexIdentifier;

import java.util.*;

/**
 * Returns the number of records contained in an index
 *
 * @author Luigi Dell'Aquila (luigi.dellaquila - at - gmail.com)
 */
public class CountFromIndexStep extends AbstractExecutionStep {
  private final IndexIdentifier target;
  private final String          alias;

  private boolean executed = false;
  private long    cost     = -1;

  /**
   * @param targetIndex      the index name as it is parsed by the SQL parsed
   * @param alias            the name of the property returned in the result-set
   * @param context          the query context
   * @param profilingEnabled true to enable the profiling of the execution (for SQL PROFILE)
   */
  public CountFromIndexStep(final IndexIdentifier targetIndex, final String alias, final CommandContext context, final boolean profilingEnabled) {
    super(context, profilingEnabled);
    this.target = targetIndex;
    this.alias = alias;
  }

  @Override
  public ResultSet syncPull(final CommandContext context, final int nRecords) throws TimeoutException {
    pullPrevious(context, nRecords);

    return new ResultSet() {
      @Override
      public boolean hasNext() {
        return !executed;
      }

      @Override
      public Result next() {
        if (executed) {
          throw new NoSuchElementException();
        }
        final long begin = profilingEnabled ? System.nanoTime() : 0;
        try {
          final Index idx = context.getDatabase().getSchema().getIndexByName(target.getIndexName());
          final long size = idx.countEntries();
          executed = true;
          final ResultInternal result = new ResultInternal();
          result.setProperty(alias, size);
          return result;
        } finally {
          cost += (System.nanoTime() - begin);
        }
      }

      @Override
      public void reset() {
        CountFromIndexStep.this.reset();
      }
    };
  }

  @Override
  public void reset() {
    executed = false;
  }

  @Override
  public String prettyPrint(final int depth, final int indent) {
    final String spaces = ExecutionStepInternal.getIndent(depth, indent);
    return spaces + "+ CALCULATE INDEX SIZE: " + target;
  }
}