/*
 *
 *    OPEN-XCHANGE legal information
 *
 *    All intellectual property rights in the Software are protected by
 *    international copyright laws.
 *
 *
 *    In some countries OX, OX Open-Xchange, open xchange and OXtender
 *    as well as the corresponding Logos OX Open-Xchange and OX are registered
 *    trademarks of the Open-Xchange, Inc. group of companies.
 *    The use of the Logos is not covered by the GNU General Public License.
 *    Instead, you are allowed to use these Logos according to the terms and
 *    conditions of the Creative Commons License, Version 2.5, Attribution,
 *    Non-commercial, ShareAlike, and the interpretation of the term
 *    Non-commercial applicable to the aforementioned license is published
 *    on the web site http://www.open-xchange.com/EN/legal/index.html.
 *
 *    Please make sure that third-party modules and libraries are used
 *    according to their respective licenses.
 *
 *    Any modifications to this package must retain all copyright notices
 *    of the original copyright holder(s) for the original code used.
 *
 *    After any such modifications, the original and derivative code shall remain
 *    under the copyright of the copyright holder(s) and/or original author(s)per
 *    the Attribution and Assignment Agreement that can be located at
 *    http://www.open-xchange.com/EN/developer/. The contributing author shall be
 *    given Attribution for the derivative code and a license granting use.
 *
 *     Copyright (C) 2004-2010 Open-Xchange, Inc.
 *     Mail: info@open-xchange.com
 *
 *
 *     This program is free software; you can redistribute it and/or modify it
 *     under the terms of the GNU General Public License, Version 2 as published
 *     by the Free Software Foundation.
 *
 *     This program 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
 *     for more details.
 *
 *     You should have received a copy of the GNU General Public License along
 *     with this program; if not, write to the Free Software Foundation, Inc., 59
 *     Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

package com.openexchange.filemanagement.internal;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import com.openexchange.filemanagement.ManagedFileException;
import com.openexchange.filemanagement.ManagedFileExceptionErrorMessage;
import com.openexchange.filemanagement.ManagedFileExceptionFactory;
import com.openexchange.filemanagement.ManagedFileManagement;
import com.openexchange.tools.stream.UnsynchronizedByteArrayInputStream;
import com.openexchange.tools.stream.UnsynchronizedByteArrayOutputStream;

/**
 * {@link ManagedInputStream} - A managed input stream which spools data to disk if necessary.
 * 
 * @author <a href="mailto:thorben.betten@open-xchange.com">Thorben Betten</a>
 */
public final class ManagedInputStream extends InputStream {

    private static final org.apache.commons.logging.Log LOG = org.apache.commons.logging.LogFactory.getLog(ManagedInputStream.class);

    private static final int SIZE_LIMIT = 1048576; // 1MB

    /*-
     * ###################### MEMBER SECTION ############################
     */

    private final InputStream delegate;

    /**
     * Initializes a new {@link ManagedInputStream} from specified bytes with default capacity of <code>1048576</code> (1 MB).
     * 
     * @param bytes The bytes held by this input stream
     * @param management The file management possibly used
     * @throws ManagedFileException If size exceeds memory limit and an appropriate managed file cannot be created.
     */
    public ManagedInputStream(final byte[] bytes, final ManagedFileManagement management) throws ManagedFileException {
        this(bytes, SIZE_LIMIT, management);
    }

    /**
     * Initializes a new {@link ManagedInputStream} from specified bytes.
     * 
     * @param bytes The bytes held by this input stream
     * @param capacity The number of bytes allowed being kept in memory rather than being spooled to disk.
     * @param management The file management possibly used
     * @throws ManagedFileException If size exceeds memory limit and an appropriate managed file cannot be created.
     */
    public ManagedInputStream(final byte[] bytes, final int capacity, final ManagedFileManagement management) throws ManagedFileException {
        super();
        if (bytes.length <= capacity) {
            // keep in memory
            delegate = new UnsynchronizedByteArrayInputStream(bytes);
        } else {
            // write to disk;
            delegate = management.createManagedFile(bytes).getInputStream();
        }
    }

    /**
     * Initializes a new {@link ManagedInputStream} from specified input stream with default capacity of <code>1048576</code> (1 MB) and
     * unknown stream size.
     * 
     * @param in The input stream to manage
     * @param management The file management possibly used
     * @throws ManagedFileException If an appropriate managed file cannot be created.
     */
    public ManagedInputStream(final InputStream in, final ManagedFileManagement management) throws ManagedFileException {
        this(in, -1, SIZE_LIMIT, management);
    }

    /**
     * Initializes a new {@link ManagedInputStream} from specified input stream with unknown stream size.
     * 
     * @param in The input stream to manage
     * @param capacity The number of bytes allowed being kept in memory rather than being spooled to disk.
     * @param management The file management possibly used
     * @throws ManagedFileException If an appropriate managed file cannot be created.
     */
    public ManagedInputStream(final InputStream in, final int capacity, final ManagedFileManagement management) throws ManagedFileException {
        this(in, -1, capacity, management);
    }

    /**
     * Initializes a new {@link ManagedInputStream} from specified input stream.
     * 
     * @param in The input stream to manage
     * @param size The stream's size; leave to <code>-1</code> if unknown
     * @param capacity The number of bytes allowed being kept in memory rather than being spooled to disk.
     * @param management The file management possibly used
     * @throws ManagedFileException If size exceeds memory limit and an appropriate managed file cannot be created.
     */
    public ManagedInputStream(final InputStream in, final int size, final int capacity, final ManagedFileManagement management) throws ManagedFileException {
        super();
        if (size >= 0 && size <= capacity) {
            // keep in memory
            delegate = in;
        } else {
            // write to disk if necessary
            try {
                final ByteArrayOutputStream tmp = new UnsynchronizedByteArrayOutputStream(8192);
                final byte[] buf = new byte[2048];
                int len = -1;
                int nob = 0;
                // read up to SIZE_LIMIT bytes
                while (nob < capacity && (len = in.read(buf, 0, buf.length)) != -1) {
                    tmp.write(buf, 0, len);
                    nob += len;
                }
                if (nob >= capacity) {
                    delegate = management.createManagedFile(new CombinedInputStream(tmp.toByteArray(), in)).getInputStream();
                } else {
                    delegate = new UnsynchronizedByteArrayInputStream(tmp.toByteArray());
                    // Input stream completely copied to memory, so close it
                    in.close();
                }
            } catch (final IOException e) {
                throw ManagedFileExceptionFactory.getInstance().create(ManagedFileExceptionErrorMessage.IO_ERROR, e, e.getMessage());
            } finally {
                try {
                    in.close();
                } catch (final IOException e) {
                    LOG.error(e.getMessage(), e);
                }
            }
        }
    }

    @Override
    public int available() throws IOException {
        return delegate.available();
    }

    @Override
    public void close() throws IOException {
        delegate.close();
    }

    @Override
    public void mark(final int readAheadLimit) {
        delegate.mark(readAheadLimit);
    }

    @Override
    public boolean markSupported() {
        return delegate.markSupported();
    }

    @Override
    public int read() throws IOException {
        return delegate.read();
    }

    @Override
    public int read(final byte b[], final int off, final int len) throws IOException {
        return delegate.read(b, off, len);
    }

    @Override
    public void reset() throws IOException {
        delegate.reset();
    }

    @Override
    public long skip(final long n) throws IOException {
        return delegate.skip(n);
    }

    /*-
     * ###################### INNER CLASS ############################
     */

    private static final class CombinedInputStream extends InputStream {

        private final byte[] consumed;

        private final InputStream remaining;

        private int count;

        /**
         * Initializes a new {@link CombinedInputStream}.
         * 
         * @param consumed The bytes already consumed from <code>remaining</code> input stream
         * @param remaining The remaining stream
         */
        public CombinedInputStream(final byte[] consumed, final InputStream remaining) {
            super();
            this.consumed = consumed;
            this.remaining = remaining;
            count = 0;
        }

        @Override
        public int read() throws IOException {
            if (count < consumed.length) {
                return consumed[count++];
            }
            return remaining.read();
        }

        @Override
        public int read(final byte b[]) throws IOException {
            return read(b, 0, b.length);
        }

        @Override
        public int read(final byte b[], final int off, final int len) throws IOException {
            if (b == null) {
                throw new NullPointerException();
            }
            if ((off < 0) || (off > b.length) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0)) {
                throw new IndexOutOfBoundsException();
            }
            if (len == 0) {
                return 0;
            }
            if (count < consumed.length) {
                final int buffered = consumed.length - count;
                if (buffered >= len) {
                    // Buffered content offers up to len bytes.
                    final int retval = (buffered <= len) ? buffered : len; // Math.min(int a, int b)
                    System.arraycopy(consumed, count, b, off, retval);
                    count += retval;
                    return retval;
                }
                // Buffered content does NOT offer up to len bytes.
                System.arraycopy(consumed, count, b, off, buffered);
                count += buffered;
                return buffered + remaining.read(b, off + buffered, len - buffered);
            }
            return remaining.read(b, off, len);
        }
    } // End of CombinedInputStream class

}
