/*
 *  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.commons.compress.archivers.zip;

import org.apache.commons.compress.parallel.FileBasedScatterGatherBackingStore;
import org.apache.commons.compress.parallel.InputStreamSupplier;
import org.apache.commons.compress.parallel.ScatterGatherBackingStore;
import org.apache.commons.compress.parallel.ScatterGatherBackingStoreSupplier;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.zip.Deflater;

import static java.util.Collections.synchronizedList;
import static org.apache.commons.compress.archivers.zip.ZipArchiveEntryRequest.createZipArchiveEntryRequest;

Creates a zip in parallel by using multiple threadlocal ScatterZipOutputStream instances. 
 Note that this class generally makes no guarantees about the order of things written to the output file. Things that need to come in a specific order (manifests, directories) must be handled by the client of this class, usually by writing these things to the ZipArchiveOutputStream before calling writeTo on this class.
 The client can supply an ExecutorService, but for reasons of memory model consistency, this will be shut down by this class prior to completion. 
Since:
1.10/**
 * Creates a zip in parallel by using multiple threadlocal {@link ScatterZipOutputStream} instances.
 * <p>
 * Note that this class generally makes no guarantees about the order of things written to
 * the output file. Things that need to come in a specific order (manifests, directories)
 * must be handled by the client of this class, usually by writing these things to the
 * {@link ZipArchiveOutputStream} <em>before</em> calling {@link #writeTo writeTo} on this class.</p>
 * <p>
 * The client can supply an {@link java.util.concurrent.ExecutorService}, but for reasons of
 * memory model consistency, this will be shut down by this class prior to completion.
 * </p>
 * @since 1.10
 */
public class ParallelScatterZipCreator {
    private final List<ScatterZipOutputStream> streams = synchronizedList(new ArrayList<ScatterZipOutputStream>());
    private final ExecutorService es;
    private final ScatterGatherBackingStoreSupplier backingStoreSupplier;
    private final List<Future<Object>> futures = new ArrayList<>();

    private final long startedAt = System.currentTimeMillis();
    private long compressionDoneAt = 0;
    private long scatterDoneAt;

    private static class DefaultBackingStoreSupplier implements ScatterGatherBackingStoreSupplier {
        final AtomicInteger storeNum = new AtomicInteger(0);

        @Override
        public ScatterGatherBackingStore get() throws IOException {
            final File tempFile = File.createTempFile("parallelscatter", "n" + storeNum.incrementAndGet());
            return new FileBasedScatterGatherBackingStore(tempFile);
        }
    }

    private ScatterZipOutputStream createDeferred(final ScatterGatherBackingStoreSupplier scatterGatherBackingStoreSupplier)
            throws IOException {
        final ScatterGatherBackingStore bs = scatterGatherBackingStoreSupplier.get();
        // lifecycle is bound to the ScatterZipOutputStream returned
        final StreamCompressor sc = StreamCompressor.create(Deflater.DEFAULT_COMPRESSION, bs); //NOSONAR
        return new ScatterZipOutputStream(bs, sc);
    }

    private final ThreadLocal<ScatterZipOutputStream> tlScatterStreams = new ThreadLocal<ScatterZipOutputStream>() {
        @Override
        protected ScatterZipOutputStream initialValue() {
            try {
                final ScatterZipOutputStream scatterStream = createDeferred(backingStoreSupplier);
                streams.add(scatterStream);
                return scatterStream;
            } catch (final IOException e) {
                throw new RuntimeException(e); //NOSONAR
            }
        }
    };

    
Create a ParallelScatterZipCreator with default threads, which is set to the number of available processors, as defined by Runtime.availableProcessors /**
     * Create a ParallelScatterZipCreator with default threads, which is set to the number of available
     * processors, as defined by {@link java.lang.Runtime#availableProcessors}
     */
    public ParallelScatterZipCreator() {
        this(Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors()));
    }

    
Create a ParallelScatterZipCreator
Params:
executorService – The executorService to use for parallel scheduling. For technical reasons,
                       this will be shut down by this class./**
     * Create a ParallelScatterZipCreator
     *
     * @param executorService The executorService to use for parallel scheduling. For technical reasons,
     *                        this will be shut down by this class.
     */
    public ParallelScatterZipCreator(final ExecutorService executorService) {
        this(executorService, new DefaultBackingStoreSupplier());
    }

    
Create a ParallelScatterZipCreator
Params:
executorService – The executorService to use. For technical reasons, this will be shut down
                       by this class.
backingStoreSupplier – The supplier of backing store which shall be used/**
     * Create a ParallelScatterZipCreator
     *
     * @param executorService The executorService to use. For technical reasons, this will be shut down
     *                        by this class.
     * @param backingStoreSupplier The supplier of backing store which shall be used
     */
    public ParallelScatterZipCreator(final ExecutorService executorService,
                                     final ScatterGatherBackingStoreSupplier backingStoreSupplier) {
        this.backingStoreSupplier = backingStoreSupplier;
        es = executorService;
    }

    
Adds an archive entry to this archive.

This method is expected to be called from a single client thread

Params:
zipArchiveEntry – The entry to add.
source –          The source input stream supplier/**
     * Adds an archive entry to this archive.
     * <p>
     * This method is expected to be called from a single client thread
     * </p>
     *
     * @param zipArchiveEntry The entry to add.
     * @param source          The source input stream supplier
     */

    public void addArchiveEntry(final ZipArchiveEntry zipArchiveEntry, final InputStreamSupplier source) {
        submit(createCallable(zipArchiveEntry, source));
    }

    
Adds an archive entry to this archive.

This method is expected to be called from a single client thread

Params:
zipArchiveEntryRequestSupplier – Should supply the entry to be added.
Since:
1.13/**
     * Adds an archive entry to this archive.
     * <p>
     * This method is expected to be called from a single client thread
     * </p>
     *
     * @param zipArchiveEntryRequestSupplier Should supply the entry to be added.
     * @since 1.13
     */
    public void addArchiveEntry(final ZipArchiveEntryRequestSupplier zipArchiveEntryRequestSupplier) {
        submit(createCallable(zipArchiveEntryRequestSupplier));
    }

    
Submit a callable for compression.
Params:
callable – The callable to run, created by createCallable, possibly wrapped by caller.
See Also:
for details of if/when to use this./**
     * Submit a callable for compression.
     *
     * @see ParallelScatterZipCreator#createCallable for details of if/when to use this.
     *
     * @param callable The callable to run, created by {@link #createCallable createCallable}, possibly wrapped by caller.
     */
    public final void submit(final Callable<Object> callable) {
        futures.add(es.submit(callable));
    }

    
Create a callable that will compress the given archive entry.
This method is expected to be called from a single client thread.
 Consider using addArchiveEntry, which wraps this method and submit. The most common use case for using createCallable and submit from a client is if you want to wrap the callable in something that can be prioritized by the supplied ExecutorService, for instance to process large or slow files first. Since the creation of the ExecutorService is handled by the client, all of this is up to the client. 
Params:
zipArchiveEntry – The entry to add.
source –          The source input stream supplier
Returns:
A callable that should subsequently passed to #submit, possibly in a wrapped/adapted from. The
value of this callable is not used, but any exceptions happening inside the compression
will be propagated through the callable./**
     * Create a callable that will compress the given archive entry.
     *
     * <p>This method is expected to be called from a single client thread.</p>
     *
     * Consider using {@link #addArchiveEntry addArchiveEntry}, which wraps this method and {@link #submit submit}.
     * The most common use case for using {@link #createCallable createCallable} and {@link #submit submit} from a
     * client is if you want to wrap the callable in something that can be prioritized by the supplied
     * {@link ExecutorService}, for instance to process large or slow files first.
     * Since the creation of the {@link ExecutorService} is handled by the client, all of this is up to the client.
     *
     * @param zipArchiveEntry The entry to add.
     * @param source          The source input stream supplier
     * @return A callable that should subsequently passed to #submit, possibly in a wrapped/adapted from. The
     * value of this callable is not used, but any exceptions happening inside the compression
     * will be propagated through the callable.
     */

    public final Callable<Object> createCallable(final ZipArchiveEntry zipArchiveEntry, final InputStreamSupplier source) {
        final int method = zipArchiveEntry.getMethod();
        if (method == ZipMethod.UNKNOWN_CODE) {
            throw new IllegalArgumentException("Method must be set on zipArchiveEntry: " + zipArchiveEntry);
        }
        final ZipArchiveEntryRequest zipArchiveEntryRequest = createZipArchiveEntryRequest(zipArchiveEntry, source);
        return new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                tlScatterStreams.get().addArchiveEntry(zipArchiveEntryRequest);
                return null;
            }
        };
    }

    
Create a callable that will compress archive entry supplied by ZipArchiveEntryRequestSupplier. 
This method is expected to be called from a single client thread.
 The same as createCallable(ZipArchiveEntry, InputStreamSupplier), but the archive entry to be added is supplied by a ZipArchiveEntryRequestSupplier. 
Params:
zipArchiveEntryRequestSupplier – Should supply the entry to be added.
See Also:
createCallable(ZipArchiveEntry, InputStreamSupplier)
Returns:
A callable that should subsequently passed to #submit, possibly in a wrapped/adapted from. The
value of this callable is not used, but any exceptions happening inside the compression
will be propagated through the callable.
Since:
1.13/**
     * Create a callable that will compress archive entry supplied by {@link ZipArchiveEntryRequestSupplier}.
     *
     * <p>This method is expected to be called from a single client thread.</p>
     *
     * The same as {@link #createCallable(ZipArchiveEntry, InputStreamSupplier)}, but the archive entry
     * to be added is supplied by a {@link ZipArchiveEntryRequestSupplier}.
     *
     * @see #createCallable(ZipArchiveEntry, InputStreamSupplier)
     *
     * @param zipArchiveEntryRequestSupplier Should supply the entry to be added.
     * @return A callable that should subsequently passed to #submit, possibly in a wrapped/adapted from. The
     * value of this callable is not used, but any exceptions happening inside the compression
     * will be propagated through the callable.
     * @since 1.13
     */
    public final Callable<Object> createCallable(final ZipArchiveEntryRequestSupplier zipArchiveEntryRequestSupplier) {
        return new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                tlScatterStreams.get().addArchiveEntry(zipArchiveEntryRequestSupplier.get());
                return null;
            }
        };
    }

    
Write the contents this to the target ZipArchiveOutputStream. 

It may be beneficial to write things like directories and manifest files to the targetStream
before calling this method.

Calling this method will shut down the ExecutorService used by this class. If any of the Callables submitted to this instance throws an exception, the archive can not be created properly and this method will throw an exception.
Params:
targetStream – The ZipArchiveOutputStream to receive the contents of the scatter streams
Throws:
IOException –          If writing fails
InterruptedException – If we get interrupted
ExecutionException –   If something happens in the parallel execution/**
     * Write the contents this to the target {@link ZipArchiveOutputStream}.
     * <p>
     * It may be beneficial to write things like directories and manifest files to the targetStream
     * before calling this method.
     * </p>
     *
     * <p>Calling this method will shut down the {@link ExecutorService} used by this class. If any of the {@link
     * Callable}s {@link #submit}ted to this instance throws an exception, the archive can not be created properly and
     * this method will throw an exception.</p>
     *
     * @param targetStream The {@link ZipArchiveOutputStream} to receive the contents of the scatter streams
     * @throws IOException          If writing fails
     * @throws InterruptedException If we get interrupted
     * @throws ExecutionException   If something happens in the parallel execution
     */
    public void writeTo(final ZipArchiveOutputStream targetStream)
            throws IOException, InterruptedException, ExecutionException {

        // Make sure we catch any exceptions from parallel phase
        try {
            for (final Future<?> future : futures) {
                future.get();
            }
        } finally {
            es.shutdown();
        }

        es.awaitTermination(1000 * 60L, TimeUnit.SECONDS);  // == Infinity. We really *must* wait for this to complete

        // It is important that all threads terminate before we go on, ensure happens-before relationship
        compressionDoneAt = System.currentTimeMillis();

        synchronized (streams) {
            for (final ScatterZipOutputStream scatterStream : streams) {
                scatterStream.writeTo(targetStream);
                scatterStream.close();
            }
        }

        scatterDoneAt = System.currentTimeMillis();
    }

    
Returns a message describing the overall statistics of the compression run
Returns:
A string/**
     * Returns a message describing the overall statistics of the compression run
     *
     * @return A string
     */
    public ScatterStatistics getStatisticsMessage() {
        return new ScatterStatistics(compressionDoneAt - startedAt, scatterDoneAt - compressionDoneAt);
    }
}