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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.CommandExecutionException;
import com.arcadedb.query.sql.parser.SimpleExecStatement;

import java.util.*;

/**
 * @author Luigi Dell'Aquila (luigi.dellaquila-(at)-gmail.com)
 */
public class SingleOpExecutionPlan implements InternalExecutionPlan {
  protected final SimpleExecStatement statement;
  final           CommandContext      context;
  boolean executed = false;
  private ResultSet result;

  public SingleOpExecutionPlan(final CommandContext context, final SimpleExecStatement stm) {
    this.context = context;
    this.statement = stm;
  }

  @Override
  public ResultSet fetchNext(final int n) {
    if (executed && result == null)
      return new InternalResultSet();

    if (!executed) {
      executed = true;
      result = statement.executeSimple(this.context);
      if (result instanceof InternalResultSet) {
        ((InternalResultSet) result).plan = this;
      }
    }
    return new ResultSet() {
      int fetched = 0;

      @Override
      public boolean hasNext() {
        return fetched < n && result.hasNext();
      }

      @Override
      public Result next() {
        if (fetched >= n) {
          throw new NoSuchElementException();
        }
        fetched++;
        return result.next();
      }

      @Override
      public void close() {
        result.close();
      }

    };
  }

  public void reset(final CommandContext context) {
    executed = false;
  }

  @Override
  public boolean canBeCached() {
    return false;
  }

  public ResultSet executeInternal() throws CommandExecutionException {
    if (executed) {
      throw new CommandExecutionException("Trying to execute a result-set twice. Please use reset()");
    }
    executed = true;
    result = statement.executeSimple(this.context);
    if (result instanceof InternalResultSet) {
      ((InternalResultSet) result).plan = this;
    }
    return result;
  }

  @Override
  public List getSteps() {
    return Collections.emptyList();
  }

  @Override
  public String prettyPrint(final int depth, final int indent) {
    final String spaces = ExecutionStepInternal.getIndent(depth, indent);
    return spaces + "+ " + statement.toString();
  }

  @Override
  public Result toResult() {
    final ResultInternal result = new ResultInternal();
    result.setProperty("type", "QueryExecutionPlan");
    result.setProperty("javaType", getClass().getName());
    result.setProperty("stmText", statement.toString());
    result.setProperty("cost", getCost());
    result.setProperty("prettyPrint", prettyPrint(0, 2));
    result.setProperty("steps", null);
    return result;
  }
}