/**
 * Java Web Archive Toolkit - Software to read and validate ARC, WARC
 * and GZip files. (http://jwat.org/)
 * Copyright 2011-2012 Netarkivet.dk (http://netarkivet.dk/)
 *
 * Licensed 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.jwat.common;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.concurrent.Semaphore;

/**
 * Simple class to allow the use of an in-memory buffer as an alternate input or output stream.
 *
 * @author nicl
 */
public class ByteArrayIOStream {

    /** Default buffer size if none specified. */
    public static final int DEFAULT_BUFFER_SIZE = 10*1024*1024;

    /** Buffer lock. */
    protected Semaphore lock = new Semaphore(1);

    /** Internal byte array. */
    protected byte[] bytes;

    /** Internal <code>ByteBuffer</code> wrapper of internal byte array. */
    protected ByteBuffer byteBuffer;

    /** Current <code>ByteBuffer</code> limit. */
    protected int limit = 0;

    /**
     * Construct object with default buffer size.
     */
    public ByteArrayIOStream() {
        this(DEFAULT_BUFFER_SIZE);
    }

    /**
     * Construct object with supplied buffer size.
     * @param bufferSize buffer size to use
     */
    public ByteArrayIOStream(int bufferSize) {
        bytes = new byte[bufferSize];
        byteBuffer = ByteBuffer.wrap(bytes);
    }

    /**
     * Return <code>OutputStream</code> and lock this buffer
     * @return <code>OutputStream</code> wrapper of this buffer
     */
    public OutputStream getOutputStream() {
        if (!lock.tryAcquire()) {
            throw new IllegalStateException();
        }
        byteBuffer.clear();
        limit = 0;
        return new OutputStreamImpl(this);
    }

    /**
     * Return internal byte array.
     * @return internal byte array
     */
    public byte[] getBytes() {
        return bytes;
    }

    /**
     * Return allocated length of internal buffer.
     * @return allocated length of internal buffer
     */
    public int getLength() {
        return bytes.length;
    }

    /**
     * Return internal <code>ByteBuffer</code> limit.
     * @return internal <code>ByteBuffer</code> limit
     */
    public int getLimit() {
        return limit;
    }

    /**
     * Return internal byte array wrapped in a new <code>ByteBuffer</code> object.
     * @return internal byte array wrapped in a new <code>ByteBuffer</code> object
     */
    public ByteBuffer getByteBuffer() {
        ByteBuffer buffer = ByteBuffer.wrap(bytes);
        buffer.position(0);
        buffer.limit(limit);
        return buffer;
    }

    /**
     * Return <code>InputStream</code> and lock this buffer
     * @return <code>InputStream</code> wrapper of this buffer
     */
    public InputStream getInputStream() {
        if (!lock.tryAcquire()) {
            throw new IllegalStateException();
        }
        byteBuffer.clear();
        byteBuffer.limit(limit);
        return new InputStreamImpl(this);
    }

    /**
     * Release lock, called when input/output stream is closed.
     */
    protected void release() {
        lock = null;
        byteBuffer = null;
        bytes = null;
        limit = 0;
    }

    /**
     * Byte array OutputStream.
     */
    public static class OutputStreamImpl extends OutputStream {

        /** Owning <code>ByteArrayIOStream</code>. */
        protected ByteArrayIOStream baios;
        /** <code>ByteArrayIOStream</code>'s <code>ByteBuffer</code>. */
        protected ByteBuffer byteBuffer;

        /**
         * Construct <code>OutputStream</code> object.
         * @param baios owning <code>ByteArrayIOStream</code>
         */
        protected OutputStreamImpl(ByteArrayIOStream baios) {
            this.baios = baios;
            this.byteBuffer = baios.byteBuffer;
        }

        @Override
        public void close() {
            if (baios != null) {
                baios.limit = baios.byteBuffer.position();
                baios.lock.release();
                baios = null;
                byteBuffer = null;
            }
        }

        @Override
        public void flush() throws IOException {
        }

        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            byteBuffer.put(b, off, len);
        }

        @Override
        public void write(byte[] b) throws IOException {
            byteBuffer.put(b);
        }

        @Override
        public void write(int b) throws IOException {
            byteBuffer.put((byte)b);
        }

    }

    /**
     * Byte array InputStream.
     */
    public static class InputStreamImpl extends InputStream {

        /** Owning <code>ByteArrayIOStream</code>. */
        protected ByteArrayIOStream baios;
        /** <code>ByteArrayIOStream</code>'s <code>ByteBuffer</code>. */
        protected ByteBuffer byteBuffer;

        /**
         * Construct <code>InputStream</code> object.
         * @param baios owning <code>ByteArrayIOStream</code>
         */
        protected InputStreamImpl(ByteArrayIOStream baios) {
            this.baios = baios;
            this.byteBuffer = baios.byteBuffer;
        }

        @Override
        public void close() {
            if (baios != null) {
                baios.lock.release();
                baios = null;
                byteBuffer = null;
            }
        }

        @Override
        public int available() throws IOException {
            return byteBuffer.limit() - byteBuffer.position();
        }

        @Override
        public boolean markSupported() {
            return false;
        }

        @Override
        public synchronized void mark(int readlimit) {
            throw new UnsupportedOperationException();
        }

        @Override
        public synchronized void reset() throws IOException {
            throw new UnsupportedOperationException();
        }

        @Override
        public int read() throws IOException {
            if (byteBuffer.remaining() > 0) {
                return byteBuffer.get();
            } else {
                return -1;
            }
        }

        @Override
        public int read(byte[] b, int off, int len) throws IOException {
            if (len == 0) {
                return 0;
            }
            int remaining = byteBuffer.remaining();
            if (len > remaining) {
                len = remaining;
            }
            if (len > 0) {
                byteBuffer.get(b, off, len);
                return len;
            } else {
                return -1;
            }
        }

        @Override
        public int read(byte[] b) throws IOException {
            int len = b.length;
            if (len == 0) {
                return 0;
            }
            int remaining = byteBuffer.remaining();
            if (len > remaining) {
                len = remaining;
            }
            if (len > 0) {
                byteBuffer.get(b, 0, len);
                return len;
            } else {
                return -1;
            }
        }

        @Override
        public long skip(long n) throws IOException {
            int remaining = byteBuffer.remaining();
            if (n > remaining) {
                n = remaining;
            }
            if (n > 0) {
                byteBuffer.position(byteBuffer.position() + (int)n);
            }
            return n;
        }

    }

}