/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.phoenix.iterate;

import static org.apache.phoenix.util.ScanUtil.getDummyTuple;
import static org.apache.phoenix.util.ScanUtil.isDummy;

import java.sql.SQLException;
import java.util.List;
import org.apache.phoenix.compile.ExplainPlanAttributes.ExplainPlanAttributesBuilder;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.util.EnvironmentEdgeManager;

/**
 * Iterates through tuples up to a limit
 * @since 1.2
 */
public class OffsetResultIterator extends DelegateResultIterator {
  private int rowCount;
  private final int offset;
  private Tuple lastScannedTuple;
  private long pageSizeMs = Long.MAX_VALUE;
  private boolean isIncompatibleClient = false;

  public OffsetResultIterator(ResultIterator delegate, Integer offset) {
    super(delegate);
    this.offset = offset == null ? -1 : offset;
    this.lastScannedTuple = null;
  }

  public OffsetResultIterator(ResultIterator delegate, Integer offset, long pageSizeMs,
    boolean isIncompatibleClient) {
    this(delegate, offset);
    this.pageSizeMs = pageSizeMs;
    this.isIncompatibleClient = isIncompatibleClient;
  }

  @Override
  public Tuple next() throws SQLException {
    long startTime = EnvironmentEdgeManager.currentTimeMillis();
    while (rowCount < offset) {
      Tuple tuple = super.next();
      if (tuple == null) {
        return null;
      }
      if (tuple.size() == 0 || isDummy(tuple)) {
        if (!isIncompatibleClient) {
          return tuple;
        }
        // While rowCount < offset absorb the dummy and call next on the underlying scanner.
        // This is applicable to old client.
        continue;
      }
      rowCount++;
      lastScannedTuple = tuple;
      if (!isIncompatibleClient) {
        if (EnvironmentEdgeManager.currentTimeMillis() - startTime >= pageSizeMs) {
          return getDummyTuple(lastScannedTuple);
        }
      }
    }
    Tuple result = super.next();
    if (result != null) {
      lastScannedTuple = result;
    }
    return result;
  }

  @Override
  public void explain(List<String> planSteps) {
    super.explain(planSteps);
    planSteps.add("CLIENT OFFSET " + offset);
  }

  @Override
  public void explain(List<String> planSteps,
    ExplainPlanAttributesBuilder explainPlanAttributesBuilder) {
    super.explain(planSteps, explainPlanAttributesBuilder);
    explainPlanAttributesBuilder.setClientOffset(offset);
    planSteps.add("CLIENT OFFSET " + offset);
  }

  @Override
  public String toString() {
    return "OffsetResultIterator [rowCount=" + rowCount + ", offset=" + offset + "]";
  }

  public Integer getRemainingOffset() {
    return Math.max(offset - rowCount, 0);
  }

  public Tuple getLastScannedTuple() {
    return lastScannedTuple;
  }

  public void setRowCountToOffset() {
    this.rowCount = this.offset;
  }
}
