content: /*
   * 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.beam.sdk.transforms.splittabledofn;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkNotNull;
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import java.math.BigDecimal;
  import java.math.MathContext;
  import org.apache.beam.sdk.io.range.OffsetRange;
  import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker.HasProgress;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.MoreObjects;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A {@link RestrictionTracker} for claiming offsets in an {@link OffsetRange} in a monotonically
   * increasing fashion.
   *
   * <p>The smallest offset is {@code Long.MIN_VALUE} and the largest offset is {@code Long.MAX_VALUE
   * - 1}.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class OffsetRangeTracker extends RestrictionTracker<OffsetRange, Long>
      implements HasProgress {
    protected OffsetRange range;
    protected @Nullable Long lastClaimedOffset = null;
    protected @Nullable Long lastAttemptedOffset = null;
  
    public OffsetRangeTracker(OffsetRange range) {
      this.range = checkNotNull(range);
    }
  
    @Override
    public OffsetRange currentRestriction() {
      return range;
    }
  
    @Override
    public SplitResult<OffsetRange> trySplit(double fractionOfRemainder) {
      // Convert to BigDecimal in computation to prevent overflow, which may result in loss of
      // precision.
      BigDecimal cur =
          (lastAttemptedOffset == null)
              ? BigDecimal.valueOf(range.getFrom()).subtract(BigDecimal.ONE, MathContext.DECIMAL128)
              : BigDecimal.valueOf(lastAttemptedOffset);
      // split = cur + max(1, (range.getTo() - cur) * fractionOfRemainder)
      BigDecimal splitPos =
          cur.add(
              BigDecimal.valueOf(range.getTo())
                  .subtract(cur, MathContext.DECIMAL128)
                  .multiply(BigDecimal.valueOf(fractionOfRemainder), MathContext.DECIMAL128)
                  .max(BigDecimal.ONE),
              MathContext.DECIMAL128);
  
      long split = splitPos.longValue();
      if (split >= range.getTo()) {
        return null;
      }
      OffsetRange res = new OffsetRange(split, range.getTo());
      this.range = new OffsetRange(range.getFrom(), split);
      return SplitResult.of(range, res);
    }
  
    /**
     * Attempts to claim the given offset.
     *
     * <p>Must be larger than the last successfully claimed offset.
     *
     * @return {@code true} if the offset was successfully claimed, {@code false} if it is outside the
     *     current {@link OffsetRange} of this tracker (in that case this operation is a no-op).
     */
    @Override
    public boolean tryClaim(Long i) {
      checkArgument(
          lastAttemptedOffset == null || i > lastAttemptedOffset,
          "Trying to claim offset %s while last attempted was %s",
          i,
          lastAttemptedOffset);
      checkArgument(
          i >= range.getFrom(), "Trying to claim offset %s before start of the range %s", i, range);
      lastAttemptedOffset = i;
      // No respective checkArgument for i < range.to() - it's ok to try claiming offsets beyond it.
      if (i >= range.getTo()) {
        return false;
      }
      lastClaimedOffset = i;
      return true;
    }
  
    @Override
    public void checkDone() throws IllegalStateException {
      if (range.getFrom() == range.getTo()) {
        return;
      }
      checkState(
          lastAttemptedOffset != null,
          "Last attempted offset should not be null. No work was claimed in non-empty range %s.",
          range);
      checkState(
          lastAttemptedOffset >= range.getTo() - 1,
          "Last attempted offset was %s in range %s, claiming work in [%s, %s) was not attempted",
          lastAttemptedOffset,
          range,
          lastAttemptedOffset + 1,
          range.getTo());
    }
  
    @Override
    public IsBounded isBounded() {
      return IsBounded.BOUNDED;
    }
  
    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("range", range)
          .add("lastClaimedOffset", lastClaimedOffset)
          .add("lastAttemptedOffset", lastAttemptedOffset)
          .toString();
    }
  
    @Override
    public Progress getProgress() {
      // If we have never attempted an offset, we return the length of the entire range as work
      // remaining.
      // Convert to BigDecimal in computation to prevent overflow, which may result in loss of
      // precision.
      if (lastAttemptedOffset == null) {
        return Progress.from(
            0,
            BigDecimal.valueOf(range.getTo())
                .subtract(BigDecimal.valueOf(range.getFrom()), MathContext.DECIMAL128)
                .doubleValue());
      }
  
      // Compute the amount of work remaining from where we are to where we are attempting to get to
      // with a minimum of zero in case we have claimed beyond the end of the range.
      BigDecimal workRemaining =
          BigDecimal.valueOf(range.getTo())
              .subtract(BigDecimal.valueOf(lastAttemptedOffset), MathContext.DECIMAL128)
              .max(BigDecimal.ZERO);
      BigDecimal totalWork =
          BigDecimal.valueOf(range.getTo())
              .subtract(BigDecimal.valueOf(range.getFrom()), MathContext.DECIMAL128);
      return Progress.from(
          totalWork.subtract(workRemaining, MathContext.DECIMAL128).doubleValue(),
          workRemaining.doubleValue());
    }
  }
  