/*

 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.UncheckedIOException;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.file.Path;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.NoSuchElementException;

import java.util.Objects;

import java.util.concurrent.ConcurrentLinkedQueue;

import java.util.concurrent.Flow;

import java.util.concurrent.Flow.Publisher;

import java.util.function.Supplier;

import java.net.http.HttpRequest.BodyPublisher;

public final class RequestPublishers {

    private RequestPublishers() { }

    public static class ByteArrayPublisher implements BodyPublisher {

        private volatile Flow.Publisher<ByteBuffer> delegate;

        private final int length;

        private final byte[] content;

        private final int offset;

        private final int bufSize;

        public ByteArrayPublisher(byte[] content) {

            this(content, 0, content.length);

        }

        public ByteArrayPublisher(byte[] content, int offset, int length) {

            this(content, offset, length, Utils.BUFSIZE);

        }

        /* bufSize exposed for testing purposes */

        ByteArrayPublisher(byte[] content, int offset, int length, int bufSize) {

            this.content = content;

            this.offset = offset;

            this.length = length;

            this.bufSize = bufSize;

        }

        List<ByteBuffer> copy(byte[] content, int offset, int length) {

            List<ByteBuffer> bufs = new ArrayList<>();

            while (length > 0) {

                ByteBuffer b = ByteBuffer.allocate(Math.min(bufSize, length));

                int max = b.capacity();

                int tocopy = Math.min(max, length);

                b.put(content, offset, tocopy);

                offset += tocopy;

                length -= tocopy;

                b.flip();

                bufs.add(b);

            }

            return bufs;

        }

        @Override

        public void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            List<ByteBuffer> copy = copy(content, offset, length);

            this.delegate = new PullPublisher<>(copy);

            delegate.subscribe(subscriber);

        }

        @Override

        public long contentLength() {

            return length;

        }

    }

    // This implementation has lots of room for improvement.

    public static class IterablePublisher implements BodyPublisher {

        private volatile Flow.Publisher<ByteBuffer> delegate;

        private final Iterable<byte[]> content;

        private volatile long contentLength;

        public IterablePublisher(Iterable<byte[]> content) {

            this.content = Objects.requireNonNull(content);

        }

        // The ByteBufferIterator will iterate over the byte[] arrays in

        // the content one at the time.

        //

        class ByteBufferIterator implements Iterator<ByteBuffer> {

            final ConcurrentLinkedQueue<ByteBuffer> buffers = new ConcurrentLinkedQueue<>();

            final Iterator<byte[]> iterator = content.iterator();

            @Override

            public boolean hasNext() {

                return !buffers.isEmpty() || iterator.hasNext();

            }

            @Override

            public ByteBuffer next() {

                ByteBuffer buffer = buffers.poll();

                while (buffer == null) {

                    copy();

                    buffer = buffers.poll();

                }

                return buffer;

            }

            ByteBuffer getBuffer() {

                return Utils.getBuffer();

            }

            void copy() {

                byte[] bytes = iterator.next();

                int length = bytes.length;

                if (length == 0 && iterator.hasNext()) {

                    // avoid inserting empty buffers, except

                    // if that's the last.

                    return;

                }

                int offset = 0;

                do {

                    ByteBuffer b = getBuffer();

                    int max = b.capacity();

                    int tocopy = Math.min(max, length);

                    b.put(bytes, offset, tocopy);

                    offset += tocopy;

                    length -= tocopy;

                    b.flip();

                    buffers.add(b);

                } while (length > 0);

            }

        }

        public Iterator<ByteBuffer> iterator() {

            return new ByteBufferIterator();

        }

        @Override

        public void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            Iterable<ByteBuffer> iterable = this::iterator;

            this.delegate = new PullPublisher<>(iterable);

            delegate.subscribe(subscriber);

        }

        static long computeLength(Iterable<byte[]> bytes) {

            long len = 0;

            for (byte[] b : bytes) {

                len = Math.addExact(len, (long)b.length);

            }

            return len;

        }

        @Override

        public long contentLength() {

            if (contentLength == 0) {

                synchronized(this) {

                    if (contentLength == 0) {

                        contentLength = computeLength(content);

                    }

                }

            }

            return contentLength;

        }

    }

    public static class StringPublisher extends ByteArrayPublisher {

        public StringPublisher(String content, Charset charset) {

            super(content.getBytes(charset));

        }

    }

    public static class EmptyPublisher implements BodyPublisher {

        private final Flow.Publisher<ByteBuffer> delegate =

                new PullPublisher<ByteBuffer>(Collections.emptyList(), null);

        @Override

        public long contentLength() {

            return 0;

        }

        @Override

        public void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            delegate.subscribe(subscriber);

        }

    }

    public static class FilePublisher implements BodyPublisher  {

        private final File file;

        private volatile AccessControlContext acc;

        public FilePublisher(Path name) {

            file = name.toFile();

        }

        void setAccessControlContext(AccessControlContext acc) {

            this.acc = acc;

        }

        @Override

        public void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            if (System.getSecurityManager() != null && acc == null)

                throw new InternalError(

                        "Unexpected null acc when security manager has been installed");

            InputStream is;

            try {

                PrivilegedExceptionAction<FileInputStream> pa =

                        () -> new FileInputStream(file);

                is = AccessController.doPrivileged(pa, acc);

            } catch (PrivilegedActionException pae) {

                throw new UncheckedIOException((IOException)pae.getCause());

            }

            PullPublisher<ByteBuffer> publisher =

                    new PullPublisher<>(() -> new StreamIterator(is));

            publisher.subscribe(subscriber);

        }

        @Override

        public long contentLength() {

            assert System.getSecurityManager() != null ? acc != null: true;

            PrivilegedAction<Long> pa = () -> file.length();

            return AccessController.doPrivileged(pa, acc);

        }

    }

    /**

     * Reads one buffer ahead all the time, blocking in hasNext()

     */

    public static class StreamIterator implements Iterator<ByteBuffer> {

        final InputStream is;

        final Supplier<? extends ByteBuffer> bufSupplier;

        volatile ByteBuffer nextBuffer;

        volatile boolean need2Read = true;

        volatile boolean haveNext;

        StreamIterator(InputStream is) {

            this(is, Utils::getBuffer);

        }

        StreamIterator(InputStream is, Supplier<? extends ByteBuffer> bufSupplier) {

            this.is = is;

            this.bufSupplier = bufSupplier;

        }

//        Throwable error() {

//            return error;

//        }

        private int read() {

            nextBuffer = bufSupplier.get();

            nextBuffer.clear();

            byte[] buf = nextBuffer.array();

            int offset = nextBuffer.arrayOffset();

            int cap = nextBuffer.capacity();

            try {

                int n = is.read(buf, offset, cap);

                if (n == -1) {

                    is.close();

                    return -1;

                }

                //flip

                nextBuffer.limit(n);

                nextBuffer.position(0);

                return n;

            } catch (IOException ex) {

                return -1;

            }

        }

        @Override

        public synchronized boolean hasNext() {

            if (need2Read) {

                haveNext = read() != -1;

                if (haveNext) {

                    need2Read = false;

                }

                return haveNext;

            }

            return haveNext;

        }

        @Override

        public synchronized ByteBuffer next() {

            if (!hasNext()) {

                throw new NoSuchElementException();

            }

            need2Read = true;

            return nextBuffer;

        }

    }

    public static class InputStreamPublisher implements BodyPublisher {

        private final Supplier<? extends InputStream> streamSupplier;

        public InputStreamPublisher(Supplier<? extends InputStream> streamSupplier) {

            this.streamSupplier = Objects.requireNonNull(streamSupplier);

        }

        @Override

        public void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            PullPublisher<ByteBuffer> publisher;

            InputStream is = streamSupplier.get();

            if (is == null) {

                Throwable t = new IOException("streamSupplier returned null");

                publisher = new PullPublisher<>(null, t);

            } else  {

                publisher = new PullPublisher<>(iterableOf(is), null);

            }

            publisher.subscribe(subscriber);

        }

        protected Iterable<ByteBuffer> iterableOf(InputStream is) {

            return () -> new StreamIterator(is);

        }

        @Override

        public long contentLength() {

            return -1;

        }

    }

    public static final class PublisherAdapter implements BodyPublisher {

        private final Publisher<? extends ByteBuffer> publisher;

        private final long contentLength;

        public PublisherAdapter(Publisher<? extends ByteBuffer> publisher,

                         long contentLength) {

            this.publisher = Objects.requireNonNull(publisher);

            this.contentLength = contentLength;

        }

        @Override

        public final long contentLength() {

            return contentLength;

        }

        @Override

        public final void subscribe(Flow.Subscriber<? super ByteBuffer> subscriber) {

            publisher.subscribe(subscriber);

        }

    }

}