/*
 * Copyright 1999-2006 University of Chicago
 * 
 * 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.dcache.ftp.client;

import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * Thread safe reference implementation of DataSink and DataSource.
 * Implements reading and writing data to a local file.
 * <b>Note: Does not work with {@link Session#MODE_STREAM Session.STREAM}
 * transfer mode, only with {@link GridFTPSession#MODE_EBLOCK
 * GridFTPSession.EBLOCK} mode.</b>
 */
public class FileRandomIO
        implements DataSink, DataSource
{

    public static final int DEFAULT_BUFFER_SIZE = 16384;

    protected final int bufferSize;
    protected final RandomAccessFile file;
    protected long offset;

    /**
     * Behave like FileRandomIO(file, DEFAULT_BUFFER_SIZE)
     *
     * @param file local file that will be be used as data source or
     *             destination
     */
    public FileRandomIO(RandomAccessFile file)
    {
        this(file, DEFAULT_BUFFER_SIZE);
    }

    /**
     * @param file       local file that will be be used as data source or
     *                   destination
     * @param bufferSize size of the buffer returned during single
     *                   read operation
     */
    public FileRandomIO(RandomAccessFile file, int bufferSize)
    {
        this.file = file;
        this.bufferSize = bufferSize;
    }

    @Override
    public synchronized void write(Buffer buffer)
            throws IOException
    {
        long bufOffset = buffer.getOffset();

        if (bufOffset == -1) {
            if (file.getFilePointer() != this.offset) {
                throw new IOException("Invalid offset: " + bufOffset);
            }
        } else {
            file.seek(bufOffset);
        }

        file.write(buffer.getBuffer(), 0, buffer.getLength());
        this.offset += buffer.getLength();
    }

    /**
     * In this implementation, each read() returns data sequentially.
     */
    @Override
    public synchronized Buffer read()
            throws IOException
    {
        long offset = file.getFilePointer();
        byte[] buf = new byte[bufferSize];
        int read = file.read(buf);
        if (read == -1) {
            return null;
        } else {
            return new Buffer(buf, read, offset);
        }
    }

    /**
     * Closes the underlying file
     */
    @Override
    public synchronized void close()
            throws IOException
    {
        file.close();
    }


    @Override
    public long totalSize()
            throws IOException
    {
        return file.length();
    }
}