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/*
 * 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.iceberg.aws.s3;

import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import org.apache.iceberg.aws.AwsProperties;
import org.apache.iceberg.io.SeekableInputStream;
import org.apache.iceberg.relocated.com.google.common.base.Joiner;
import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
import org.apache.iceberg.relocated.com.google.common.io.ByteStreams;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.awssdk.core.sync.ResponseTransformer;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.GetObjectRequest;

class S3InputStream extends SeekableInputStream {
  private static final Logger LOG = LoggerFactory.getLogger(S3InputStream.class);

  private final StackTraceElement[] createStack;
  private final S3Client s3;
  private final S3URI location;
  private final AwsProperties awsProperties;

  private InputStream stream;
  private long pos = 0;
  private long next = 0;
  private boolean closed = false;

  private int skipSize = 1024 * 1024;

  S3InputStream(S3Client s3, S3URI location) {
    this(s3, location, new AwsProperties());
  }

  S3InputStream(S3Client s3, S3URI location, AwsProperties awsProperties) {
    this.s3 = s3;
    this.location = location;
    this.awsProperties = awsProperties;

    createStack = Thread.currentThread().getStackTrace();
  }

  @Override
  public long getPos() {
    return next;
  }

  @Override
  public void seek(long newPos) {
    Preconditions.checkState(!closed, "already closed");
    Preconditions.checkArgument(newPos >= 0, "position is negative: %s", newPos);

    // this allows a seek beyond the end of the stream but the next read will fail
    next = newPos;
  }

  @Override
  public int read() throws IOException {
    Preconditions.checkState(!closed, "Cannot read: already closed");
    positionStream();

    pos += 1;
    next += 1;

    return stream.read();
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    Preconditions.checkState(!closed, "Cannot read: already closed");
    positionStream();

    int bytesRead = stream.read(b, off, len);
    pos += bytesRead;
    next += bytesRead;

    return bytesRead;
  }

  @Override
  public void close() throws IOException {
    super.close();
    closed = true;
    closeStream();
  }

  private void positionStream() throws IOException {
    if ((stream != null) && (next == pos)) {
      // already at specified position
      return;
    }

    if ((stream != null) && (next > pos)) {
      // seeking forwards
      long skip = next - pos;
      if (skip <= Math.max(stream.available(), skipSize)) {
        // already buffered or seek is small enough
        LOG.debug("Read-through seek for {} to offset {}", location, next);
        try {
          ByteStreams.skipFully(stream, skip);
          pos = next;
          return;
        } catch (IOException ignored) {
          // will retry by re-opening the stream
        }
      }
    }

    // close the stream and open at desired position
    LOG.debug("Seek with new stream for {} to offset {}", location, next);
    pos = next;
    openStream();
  }

  private void openStream() throws IOException {
    GetObjectRequest.Builder requestBuilder = GetObjectRequest.builder()
        .bucket(location.bucket())
        .key(location.key())
        .range(String.format("bytes=%s-", pos));

    S3RequestUtil.configureEncryption(awsProperties, requestBuilder);

    closeStream();
    stream = s3.getObject(requestBuilder.build(), ResponseTransformer.toInputStream());
  }

  private void closeStream() throws IOException {
    if (stream != null) {
      stream.close();
    }
  }

  public void setSkipSize(int skipSize) {
    this.skipSize = skipSize;
  }

  @SuppressWarnings("checkstyle:NoFinalizer")
  @Override
  protected void finalize() throws Throwable {
    super.finalize();
    if (!closed) {
      close(); // releasing resources is more important than printing the warning
      String trace = Joiner.on("\n\t").join(
          Arrays.copyOfRange(createStack, 1, createStack.length));
      LOG.warn("Unclosed input stream created by:\n\t{}", trace);
    }
  }
}