/*
 * 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.flink.fs.s3.common;

import org.apache.flink.core.fs.EntropyInjectingFileSystem;
import org.apache.flink.core.fs.FileSystemKind;
import org.apache.flink.core.fs.RecoverableWriter;
import org.apache.flink.fs.s3.common.utils.RefCountedFile;
import org.apache.flink.fs.s3.common.utils.RefCountedTmpFileCreator;
import org.apache.flink.fs.s3.common.writer.S3AccessHelper;
import org.apache.flink.fs.s3.common.writer.S3RecoverableWriter;
import org.apache.flink.runtime.fs.hdfs.HadoopFileSystem;
import org.apache.flink.util.Preconditions;
import org.apache.flink.util.StringUtils;
import org.apache.flink.util.function.FunctionWithException;

import javax.annotation.Nullable;

import java.io.File;
import java.io.IOException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Implementation of the Flink {@link org.apache.flink.core.fs.FileSystem} interface for S3.
 * This class implements the common behavior implemented directly by Flink and delegates
 * common calls to an implementation of Hadoop's filesystem abstraction.
 */
public class FlinkS3FileSystem extends HadoopFileSystem implements EntropyInjectingFileSystem {

	@Nullable
	private final String entropyInjectionKey;

	private final int entropyLength;

	// ------------------- Recoverable Writer Parameters -------------------

	/** The minimum size of a part in the multipart upload, except for the last part: 5 MIBytes. */
	public static final long S3_MULTIPART_MIN_PART_SIZE = 5L << 20;

	private final String localTmpDir;

	private final FunctionWithException<File, RefCountedFile, IOException> tmpFileCreator;

	@Nullable
	private final S3AccessHelper s3AccessHelper;

	private final Executor uploadThreadPool;

	private final long s3uploadPartSize;

	private final int maxConcurrentUploadsPerStream;

	/**
	 * Creates a FlinkS3FileSystem based on the given Hadoop S3 file system.
	 * The given Hadoop file system object is expected to be initialized already.
	 *
	 * <p>This constructor additionally configures the entropy injection for the file system.
	 *
	 * @param hadoopS3FileSystem The Hadoop FileSystem that will be used under the hood.
	 * @param entropyInjectionKey The substring that will be replaced by entropy or removed.
	 * @param entropyLength The number of random alphanumeric characters to inject as entropy.
	 */
	public FlinkS3FileSystem(
			org.apache.hadoop.fs.FileSystem hadoopS3FileSystem,
			String localTmpDirectory,
			@Nullable String entropyInjectionKey,
			int entropyLength,
			@Nullable S3AccessHelper s3UploadHelper,
			long s3uploadPartSize,
			int maxConcurrentUploadsPerStream) {

		super(hadoopS3FileSystem);

		if (entropyInjectionKey != null && entropyLength <= 0) {
			throw new IllegalArgumentException("Entropy length must be >= 0 when entropy injection key is set");
		}

		this.entropyInjectionKey = entropyInjectionKey;
		this.entropyLength = entropyLength;

		// recoverable writer parameter configuration initialization
		this.localTmpDir = Preconditions.checkNotNull(localTmpDirectory);
		this.tmpFileCreator = RefCountedTmpFileCreator.inDirectories(new File(localTmpDirectory));
		this.s3AccessHelper = s3UploadHelper;
		this.uploadThreadPool = Executors.newCachedThreadPool();

		Preconditions.checkArgument(s3uploadPartSize >= S3_MULTIPART_MIN_PART_SIZE);
		this.s3uploadPartSize = s3uploadPartSize;
		this.maxConcurrentUploadsPerStream = maxConcurrentUploadsPerStream;
	}

	// ------------------------------------------------------------------------

	@Nullable
	@Override
	public String getEntropyInjectionKey() {
		return entropyInjectionKey;
	}

	@Override
	public String generateEntropy() {
		return StringUtils.generateRandomAlphanumericString(ThreadLocalRandom.current(), entropyLength);
	}

	@Override
	public FileSystemKind getKind() {
		return FileSystemKind.OBJECT_STORE;
	}

	public String getLocalTmpDir() {
		return localTmpDir;
	}

	@Override
	public RecoverableWriter createRecoverableWriter() throws IOException {
		if (s3AccessHelper == null) {
			// this is the case for Presto
			throw new UnsupportedOperationException("This s3 file system implementation does not support recoverable writers.");
		}

		return S3RecoverableWriter.writer(
				getHadoopFileSystem(),
				tmpFileCreator,
				s3AccessHelper,
				uploadThreadPool,
				s3uploadPartSize,
				maxConcurrentUploadsPerStream);
	}
}