/*
 * TransportSender.java February 2007
 *
 * Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
 *
 * 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.simpleframework.transport;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * The <code>TransportSender</code> object is used to send bytes to and
 * underlying transport. This is essentially an adapter between an
 * <code>OutputStream</code> and the underlying transport. Each byte array
 * segment written to the underlying transport is wrapped in a bytes buffer so
 * that it can be sent by the transport layer.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.transport.Transport
 */
public class TransportSender implements Sender {

    /**
     * This is the underlying transport to write the bytes to.
     */
    private Transport transport;

    /**
     * This is used to determine if the transport has been closed.
     */
    private volatile boolean closed;

    /**
     * Constructor for the <code>TransportSender</code> object. This is used to
     * create an adapter for the transport such that a byte array can be used to
     * write bytes to the array.
     * 
     * @param transport
     *            the underlying transport to send bytes to
     */
    public TransportSender(Transport transport) {
        this.transport = transport;
    }

    /**
     * This method is used to deliver the provided array of bytes to the
     * underlying transport. Depending on the connection type the array may be
     * encoded for SSL transport or send directly. Any implementation may choose
     * to buffer the bytes for performance.
     * 
     * @param array
     *            this is the array of bytes to send to the client
     */
    @Override
    public void send(byte[] array) throws IOException {
        this.send(array, 0, array.length);
    }

    /**
     * This method is used to deliver the provided array of bytes to the
     * underlying transport. Depending on the connection type the array may be
     * encoded for SSL transport or send directly. Any implementation may choose
     * to buffer the bytes for performance.
     * 
     * @param array
     *            this is the array of bytes to send to the client
     * @param off
     *            this is the offset within the array to send from
     * @param len
     *            this is the number of bytes that are to be sent
     */
    @Override
    public void send(byte[] array, int off, int len) throws IOException {
        ByteBuffer buffer = ByteBuffer.wrap(array, off, len);

        if (len > 0) {
            this.send(buffer);
        }
    }

    /**
     * This method is used to deliver the provided buffer of bytes to the
     * underlying transport. Depending on the connection type the array may be
     * encoded for SSL transport or send directly. Any implementation may choose
     * to buffer the bytes for performance.
     * 
     * @param buffer
     *            this is the buffer of bytes to send to the client
     */
    @Override
    public void send(ByteBuffer buffer) throws IOException {
        int mark = buffer.position();
        int size = buffer.limit();

        if (mark > size)
            throw new IOException("Buffer position greater than limit");
        this.send(buffer, 0, size - mark);
    }

    /**
     * This method is used to deliver the provided buffer of bytes to the
     * underlying transport. Depending on the connection type the array may be
     * encoded for SSL transport or send directly. Any implementation may choose
     * to buffer the bytes for performance.
     * 
     * @param buffer
     *            this is the buffer of bytes to send to the client
     * @param off
     *            this is the offset within the buffer to send from
     * @param len
     *            this is the number of bytes that are to be sent
     */
    @Override
    public void send(ByteBuffer buffer, int off, int len) throws IOException {
        int mark = buffer.position();
        int limit = buffer.limit();

        if ((limit - mark) > len) {
            buffer.limit(mark + len); // reduce usable size
        }
        this.transport.write(buffer);
        buffer.limit(limit);
    }

    /**
     * This method is used to flush the contents of the buffer to the client.
     * This method will block until such time as all of the data has been sent
     * to the client. If at any point there is an error sending the content an
     * exception is thrown.
     */
    @Override
    public void flush() throws IOException {
        this.transport.flush();
    }

    /**
     * This is used to close the sender and the underlying transport. If a close
     * is performed on the sender then no more bytes can be read from or written
     * to the transport and the client will received a connection close on their
     * side.
     */
    @Override
    public void close() throws IOException {
        if (!this.closed) {
            this.transport.close();
            this.closed = true;
        }
    }
}