/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.io.output;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

A Proxy stream which acts as expected, that is it passes the method
calls on to the proxied stream and doesn't change which methods are
being called. It is an alternative base class to FilterOutputStream
to increase reusability.

See the protected methods for ways in which a subclass can easily decorate
a stream with custom pre-, post- or error processing functionality.
/**
 * A Proxy stream which acts as expected, that is it passes the method
 * calls on to the proxied stream and doesn't change which methods are
 * being called. It is an alternative base class to FilterOutputStream
 * to increase reusability.
 * <p>
 * See the protected methods for ways in which a subclass can easily decorate
 * a stream with custom pre-, post- or error processing functionality.
 *
 */
public class ProxyOutputStream extends FilterOutputStream {

    
Constructs a new ProxyOutputStream.
Params:
proxy –  the OutputStream to delegate to/**
     * Constructs a new ProxyOutputStream.
     *
     * @param proxy  the OutputStream to delegate to
     */
    public ProxyOutputStream(final OutputStream proxy) {
        super(proxy);
        // the proxy is stored in a protected superclass variable named 'out'
    }

    
Invokes the delegate's write(int) method.
Params:
idx – the byte to write
Throws:
IOException – if an I/O error occurs/**
     * Invokes the delegate's <code>write(int)</code> method.
     * @param idx the byte to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(final int idx) throws IOException {
        try {
            beforeWrite(1);
            out.write(idx);
            afterWrite(1);
        } catch (final IOException e) {
            handleIOException(e);
        }
    }

    
Invokes the delegate's write(byte[]) method.
Params:
bts – the bytes to write
Throws:
IOException – if an I/O error occurs/**
     * Invokes the delegate's <code>write(byte[])</code> method.
     * @param bts the bytes to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(final byte[] bts) throws IOException {
        try {
            final int len = bts != null ? bts.length : 0;
            beforeWrite(len);
            out.write(bts);
            afterWrite(len);
        } catch (final IOException e) {
            handleIOException(e);
        }
    }

    
Invokes the delegate's write(byte[]) method.
Params:
bts – the bytes to write
st – The start offset
end – The number of bytes to write
Throws:
IOException – if an I/O error occurs/**
     * Invokes the delegate's <code>write(byte[])</code> method.
     * @param bts the bytes to write
     * @param st The start offset
     * @param end The number of bytes to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(final byte[] bts, final int st, final int end) throws IOException {
        try {
            beforeWrite(end);
            out.write(bts, st, end);
            afterWrite(end);
        } catch (final IOException e) {
            handleIOException(e);
        }
    }

    
Invokes the delegate's flush() method.
Throws:
IOException – if an I/O error occurs/**
     * Invokes the delegate's <code>flush()</code> method.
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void flush() throws IOException {
        try {
            out.flush();
        } catch (final IOException e) {
            handleIOException(e);
        }
    }

    
Invokes the delegate's close() method.
Throws:
IOException – if an I/O error occurs/**
     * Invokes the delegate's <code>close()</code> method.
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void close() throws IOException {
        try {
            out.close();
        } catch (final IOException e) {
            handleIOException(e);
        }
    }

    
Invoked by the write methods before the call is proxied. The number of bytes to be written (1 for the write(int) method, buffer length for write(byte[]), etc.) is given as an argument. 

Subclasses can override this method to add common pre-processing
functionality without having to override all the write methods.
The default implementation does nothing.
Params:
n – number of bytes to be written
Throws:
IOException – if the pre-processing fails
Since:
2.0/**
     * Invoked by the write methods before the call is proxied. The number
     * of bytes to be written (1 for the {@link #write(int)} method, buffer
     * length for {@link #write(byte[])}, etc.) is given as an argument.
     * <p>
     * Subclasses can override this method to add common pre-processing
     * functionality without having to override all the write methods.
     * The default implementation does nothing.
     *
     * @since 2.0
     * @param n number of bytes to be written
     * @throws IOException if the pre-processing fails
     */
    protected void beforeWrite(final int n) throws IOException {
    }

    
Invoked by the write methods after the proxied call has returned successfully. The number of bytes written (1 for the write(int) method, buffer length for write(byte[]), etc.) is given as an argument. 

Subclasses can override this method to add common post-processing
functionality without having to override all the write methods.
The default implementation does nothing.
Params:
n – number of bytes written
Throws:
IOException – if the post-processing fails
Since:
2.0/**
     * Invoked by the write methods after the proxied call has returned
     * successfully. The number of bytes written (1 for the
     * {@link #write(int)} method, buffer length for {@link #write(byte[])},
     * etc.) is given as an argument.
     * <p>
     * Subclasses can override this method to add common post-processing
     * functionality without having to override all the write methods.
     * The default implementation does nothing.
     *
     * @since 2.0
     * @param n number of bytes written
     * @throws IOException if the post-processing fails
     */
    protected void afterWrite(final int n) throws IOException {
    }

    
Handle any IOExceptions thrown.

This method provides a point to implement custom exception
handling. The default behaviour is to re-throw the exception.
Params:
e – The IOException thrown
Throws:
IOException – if an I/O error occurs
Since:
2.0/**
     * Handle any IOExceptions thrown.
     * <p>
     * This method provides a point to implement custom exception
     * handling. The default behaviour is to re-throw the exception.
     * @param e The IOException thrown
     * @throws IOException if an I/O error occurs
     * @since 2.0
     */
    protected void handleIOException(final IOException e) throws IOException {
        throw e;
    }

}